Van's Air Force
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Lycoming Superiority
- Thread starter BruceMe
- Start date
Jconard said:
Let's just remember that the Sube is 2.2 or 2.5 or 3L depending on model and the Lyco is 6L. I can run with an 0-360 at 12,000 feet in my 2.2 turbo pulling only 30 inches and 4600 rpm, hardly taxing it.
I agree with your basic points about Delta T and water/ air cooled differences however more drag is not necessarily the result. There is a huge difference in the efficiency of a heat exchanger vs. a finned cylinder for instance which can easily offset the large difference in temperature between the two approaches. There is also a difference in the resistance to flow or drag between the two and the possible recovery of pressure on the inlet and exit of a rad duct vs. a conventional RV cowling. There have been no studies done to date which can shed light on this. I would go as far to say that cheek mounted rads and the belly exit used on most liquid cooled RVs offers higher drag than a typical Lyco setup which is reasonably efficient for an air cooled engine.
While it would be relatively easy to instrument an RV cowling with a manometer and attach a big blower to the cowling exit to determine pressure drop (drag) offered by each setup, this is only part of the equation. We need to be able to measure the exit speed of the air in flight as well.
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Had to put my 2 cents in to
The cost of lycoming and lyclone parts are not due to some profit monster it is due to the insurance that has to be paid for every part and engine to feed the hungry lawyers.
take a look at rotax look up some of the part prices and you will be shocked unless you own one of these little gas guzzling hand grenades
then call a skidoo dealer and ket a price on the same part without the lawyer food these are the same parts from the same assembly line but much cheaper.
If mazda or suburu had to pay the price of admission to the aviation market the cost would be passed on to the customers.
I would like to point out the reason all the GA manufactures stopped producing small aircraft long ago, it was because of the cost of the insurance bond that had to be purchased for every plane.
car manufacture's only have to build a product that can make it past the warranty period. look at some of the automakers junk that was dumped on unsuspecting customers, aluminum chevy vega, chevy odd fire V6, 5.7 litr diesel, or ford's head cracking escort and head cracking 4 cyl tortus engine
chevys 454 diesel conversion for trucks. this list gous on and on how long would lycoming be in bussiness with product lines like the auto manufactures and no liability.
My daughter had a toyota camery it blew the water pump before she new it it had overheated and cracked the head which in a way is OK since you have to pull the timing belt to change the water pump any ways. I would also like to point out that the reason water cooling makes sense for cars is because cars dont run LOP the run just rich of detonation for fuel economy.
next another of my opinions an engine at the beginning of life has a finite number of revolutions before it dies if you run an engine at 20,000 rpm's it will make huge HP numbers but for how long? look at the crotch rocket market a 20,000 mike bike is worn out and this is cutting edge formula one technology
180 HP from a liquid cooled carberated 16 valve double overhead cam 1.3 litr motor at about 12,000 rpm's. to quote an old proverb "there is no replacement for displacement" you can run an engine at 6000 rpm's but for how long?
but this debate on EI i believe this is the here and now so i will be running 2 P-Mags on my Lyclone
another thing since these car engines are half the size of a lycoming why arent they half the weight? that way you could run reduntant engines and answer the liability question once and forall.
Also I looked at the alternative engine options before deciding to go with superior, these auto conversion prices almost made me pass out from sticker shock, another option is to spend a couple of addional years fabing my own car engine package and a few more perfecting it or just use what works a proven bolt in kit that is proven to work every time LYCLONE.
My last question is how reliable would cars be if the driver had to control the fuel mixture? I have seen so many EFI pumps go out on cars along with MAP and O2 sensors wiring issues throttle position sensors fuel flow meters ruptured fuel pressure regulators pouring fuel directlu into the intake manafold at full fuel pressure and so on this last failure would deplete about 20 gal's of fuel in about 15 minutes. this i have seen fuel pourin out of the exaust with eye and nose burning fumes. EFI is a nice thought except it adds many points of failure.
The cost of lycoming and lyclone parts are not due to some profit monster it is due to the insurance that has to be paid for every part and engine to feed the hungry lawyers.
take a look at rotax look up some of the part prices and you will be shocked unless you own one of these little gas guzzling hand grenades
then call a skidoo dealer and ket a price on the same part without the lawyer food these are the same parts from the same assembly line but much cheaper.
If mazda or suburu had to pay the price of admission to the aviation market the cost would be passed on to the customers.
I would like to point out the reason all the GA manufactures stopped producing small aircraft long ago, it was because of the cost of the insurance bond that had to be purchased for every plane.
car manufacture's only have to build a product that can make it past the warranty period. look at some of the automakers junk that was dumped on unsuspecting customers, aluminum chevy vega, chevy odd fire V6, 5.7 litr diesel, or ford's head cracking escort and head cracking 4 cyl tortus engine
chevys 454 diesel conversion for trucks. this list gous on and on how long would lycoming be in bussiness with product lines like the auto manufactures and no liability.
My daughter had a toyota camery it blew the water pump before she new it it had overheated and cracked the head which in a way is OK since you have to pull the timing belt to change the water pump any ways. I would also like to point out that the reason water cooling makes sense for cars is because cars dont run LOP the run just rich of detonation for fuel economy.
next another of my opinions an engine at the beginning of life has a finite number of revolutions before it dies if you run an engine at 20,000 rpm's it will make huge HP numbers but for how long? look at the crotch rocket market a 20,000 mike bike is worn out and this is cutting edge formula one technology
180 HP from a liquid cooled carberated 16 valve double overhead cam 1.3 litr motor at about 12,000 rpm's. to quote an old proverb "there is no replacement for displacement" you can run an engine at 6000 rpm's but for how long?
but this debate on EI i believe this is the here and now so i will be running 2 P-Mags on my Lyclone
another thing since these car engines are half the size of a lycoming why arent they half the weight? that way you could run reduntant engines and answer the liability question once and forall.
Also I looked at the alternative engine options before deciding to go with superior, these auto conversion prices almost made me pass out from sticker shock, another option is to spend a couple of addional years fabing my own car engine package and a few more perfecting it or just use what works a proven bolt in kit that is proven to work every time LYCLONE.
My last question is how reliable would cars be if the driver had to control the fuel mixture? I have seen so many EFI pumps go out on cars along with MAP and O2 sensors wiring issues throttle position sensors fuel flow meters ruptured fuel pressure regulators pouring fuel directlu into the intake manafold at full fuel pressure and so on this last failure would deplete about 20 gal's of fuel in about 15 minutes. this i have seen fuel pourin out of the exaust with eye and nose burning fumes. EFI is a nice thought except it adds many points of failure.
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jbDC9
Well Known Member
dserratt said:
Umm, not necessarily... I have a crotch rocket Honda CBR 600 F4 with almost 49,000 miles while my brother rides a Yamaha YZF 600 with 75,000+ miles; neither of them are even close to being worn out. We don't race 'em but ride fairly aggressively. Redline is around 12,000 rpm; as long as you don't run 'em at redline all day these engines will last a loooong time.
JMHO
John
Interesting Lycoming information
In reading these posts, I note that someone talked about 100s of thousands of Lycomings flying out there today.
Interestingly enough, as of 2005 (Based on an article by Richard Collins http://www.flyingmag.com/article.asp?section_id=12&article_id=555) lycoming has only produced 325,000 aircraft engines, of which they estimate 170,000 are active today. (Seems I remember reading not too long ago that Lycomig announced building their 350,000th engine.)
I would have thought there were a lot more than that, but that's probably one reason prices are high, compared to car engines, which are built by the millions.
In reading these posts, I note that someone talked about 100s of thousands of Lycomings flying out there today.
Interestingly enough, as of 2005 (Based on an article by Richard Collins http://www.flyingmag.com/article.asp?section_id=12&article_id=555) lycoming has only produced 325,000 aircraft engines, of which they estimate 170,000 are active today. (Seems I remember reading not too long ago that Lycomig announced building their 350,000th engine.)
I would have thought there were a lot more than that, but that's probably one reason prices are high, compared to car engines, which are built by the millions.
David-aviator
Well Known Member
dserratt said:
But the cool thing is they almost never fail.
My RV/Subaru H6 ECU has many redundant features to keep it running. If there is fuel, air, and electric, it runs.
Lycoming is a fine engine, I've had 'em. But after all these years, they DO need to come up with a way to build a crank shaft that will not fail.
dd
frankh
Well Known Member
Good point
and that is precisely the argument to use modern day electronics in airplanes.
i.e sure your relying on electrical gadgets but if these gadgets are as reliable as the mechanical components they serve then why not?
It is intersting to me to look at the development path of the new EGGS and the Lyc's. The Lycs are evolving slowly but they are evolving. I don't think there are many Lycs running without electronic ignition these days. Very few however have electric fuel pumps only (mine is one of very few) even though the mechanical pump is in the Hydraulically incorrect place...I don't know of any modern car engines that DO have a mechanical fuel pump...and a pump that is positioned right next to or IN the tank as well. As to FADEC brand new budding technology thats old hat for car engines.
I think the problem comes down to adapting a car engine for a different purpose. ...I mean does your "limp home" failure mode keep the plane flying?? Soobs seem to work pretty well and one day there will be a bolt on P51 style scoop that will improve cooling drag. Gee you can even throw any fuel in there you like and forget it...To do that with a LYC means being careful with CHTS and knowing how to use the mixture control.
Mind you...Why did Honda come come up with a flat four direct drive engine for its airplane engine for the 21st century...You can bet your life they wer'nt just following convention.
Frank
RV7a Matt IO360, electric fuel pumps
Zodiac EA 81 Soob...400 hours and loved it
and that is precisely the argument to use modern day electronics in airplanes.
i.e sure your relying on electrical gadgets but if these gadgets are as reliable as the mechanical components they serve then why not?
It is intersting to me to look at the development path of the new EGGS and the Lyc's. The Lycs are evolving slowly but they are evolving. I don't think there are many Lycs running without electronic ignition these days. Very few however have electric fuel pumps only (mine is one of very few) even though the mechanical pump is in the Hydraulically incorrect place...I don't know of any modern car engines that DO have a mechanical fuel pump...and a pump that is positioned right next to or IN the tank as well. As to FADEC brand new budding technology thats old hat for car engines.
I think the problem comes down to adapting a car engine for a different purpose. ...I mean does your "limp home" failure mode keep the plane flying?? Soobs seem to work pretty well and one day there will be a bolt on P51 style scoop that will improve cooling drag. Gee you can even throw any fuel in there you like and forget it...To do that with a LYC means being careful with CHTS and knowing how to use the mixture control.
Mind you...Why did Honda come come up with a flat four direct drive engine for its airplane engine for the 21st century...You can bet your life they wer'nt just following convention.
Frank
RV7a Matt IO360, electric fuel pumps
Zodiac EA 81 Soob...400 hours and loved it
frankh said:
Technology needs to serve a purpose. In a GA aircraft that needs to either mean more efficiency or more reliability.
So far, when you consider the operating conditions - basically pedal to the medal, the old adage cited earlier, "there is no replacement for displacement" still rings true. There is surprisingly little efficiency gain with automotive engines in aircraft (essentially autobahn) operations. In some cases, there is a net loss.
On the flip side, with equivelent manufacturing tolerances, complexity virtually always increases rates of failure. I'm not sure what you mean by Lycomings running electronic ignition, there is little incentive to give up on good ol' mags as long as the timing is fixed. An ECU would create single points of failure (ex. regulator, alternator, etc.) on what is otherwise a wholly redundant system.
And, like most things in an 'old fashioned' aircraft engine, even the redundancy itself serves a second purpose. Both points firing shortens the cyl distance and results in more complete mixture burns.
We may have to add complexity for other reasons, like adjustabile timing to get rid or lead in the fuel we use, but adding complexity just to feel modern is silly.
It usually takes progress on multiple fronts for technology to make sense. Consider the migration to glass. Vaccuum pumps have always been a headache. But simply powering existing technologies electrically did not make a lot of sense. In order to realize a legitimate improvement in reliability, electrical systems had to increase in complexity, meaning more weight. It was only with the emergence of new sensing technologies that it really started to make real sense.
Now, you can add reasonable backup (batteries, duel electrical) go to electric instrumentation (eliminating the evil vaccum pump) and not pay a price on payload.
Where Lycoming could really benefit is improvement in manufacturing processes and some materials changes at the top of the engine. Add better injectors and do a better job of balancing AFR at the factor (so factory installs can run WOP/LOP for cruise) and they can squeeze some more life out of existing designs still. Put in higher compression cyls and use the improved injection systems to take advantage of ethenol's improved dillution properties and the same 'old' engines of the 50's may well be the new 'green' GA engines of the near future...
-jjf
Walter Atkinson
Well Known Member
We use these old technology TCM and Lycoming engines really for only ONE reason.
Nothing else has ever been invented that is as efficient as a Lycoming or TCM piston enigne. Nothing in the automotive world in 2006 (gasoline) has a BSFC(min) in the .385 range like our "old technology" engines. Nothing.
When something better comes along, I'll be in line to buy one.
Walter
Nothing else has ever been invented that is as efficient as a Lycoming or TCM piston enigne. Nothing in the automotive world in 2006 (gasoline) has a BSFC(min) in the .385 range like our "old technology" engines. Nothing.
When something better comes along, I'll be in line to buy one.
Walter
gmcjetpilot
Well Known Member
If a new engine was designed today it would look like a Lycoming
The materials, processes, QC and tolerances are as modern and tight any engine or as needed in a low RPM engine. The materials are of class 1A castings and steel. I am not sure where you are going with NEW materials. ECI, Superior and Lycoming have different cylinder walls and ring materials and coatings. I still get a chuckle out of the thought of "50 year old engines" being antiquated. It is just inaccurate and miss leading. The Lyc is made the way it is, with the materials it uses and the tolerances, by design. It is not that it's 50 year old.
The "crude" part of the Lyc, I gather is the fact is in the fact a Lyc is a large bore/displacement, low rpm, direct drive, air-cooled engine. I understand precision aluminum castings of the case or cylinder heads have a rough finish, but that is the beauty. If it where hogged out of a forged block it would look pretty but weigh more.
I understand the wishful thinking of a 8,000 rpm Lexus engine with dual overhead cam's and 22 valves per cylinder
, but it would not hack it in a plane. You don't need overhead cam auto technology in a plane engine that lives between 2700-2300 rpm at state RPM 98% of the flight, e.g. takeoff, climb, cruise and decent/approach. Occasionally idle we need to taxi at idle (800-1000 rpm) and 1800-2000 rpm for approach.
Most of the "technology" in car engines that makes them BETTER? has been around for over 50 years. If Lyc wanted or needed to include it, they would have. Power, weight, simplicity, reliability and application are well balanced in an air cooled aircraft engine. It's this way on purpose.
The effort and talent that was put into air cooled aircraft engine research and design, for its day, was like the efforts of putting a man on the moon or the space shuttle of there time. Meaning it was top prority of the the US leading engineering and NACA (now NASA).
There is a lot of technology in a Lycoming. Yes most of it was done over 50 years ago, but as was said it has been refined of the years. The technology used today in making a Lyc is top notch. Actually, when Lyc and also TCM messed up their cranks, is when they tried to change to a "Better modern" method of forging steel. "If it ain't broke don't fix it."
I am going to go out on a limb and say if you built a blank sheet air cooled horz opposed engined today, it would look just like a Lyc or TCM does now. BUT YOU SAY WATER COOLING IS BETTER. Water cooling is the "hi tech" part of car engines, but that has been done for over 100 years on cars and planes. In fact the first plane was water cooled. Some guys named Wright Bros or something like that. If Lyc wanted to go water cooled they could. In fact Lyc has some aftermarket "cool jugs" available. If you hear it in the test stand it sounds like a Subaru. It also cost $9,000 for the jugs and really does nothing more, except add drag from a radiator.
The fastest piston planes (Reno, unlimited gold) are powered by air cooled engines. Water cooling is cool for cars and needed. Water cooling in a plane is a burden. There is a prolific amount of air available in an AIR plane; therefore AIR cooled engines are, dare I say, better suited for planes. The exception is of course the P-51, but that airframe was designed around the plane.
So when you go into it a design and say we want air cooling and no reduction gear box, low frontal profile, you will lock your self into a Lycoming configuration. In-line (cylinder) is fine, but you have a longer crank for the same number of cylinders. Also cooling the back just is a challenge (but doable).
I'll even be so bold as to say the Lycoming is a technological marvel. A light, powerful, simple, reliable power plant that in my opinions, correct me if I am wrong, is still the gold standard all other alternative engines are judged by. I'll even say I can't see improving it. The add on's like, roller cams, FADEC, electronic ignition, composite oil sumps, port/polish/high compression are all great, but the basic design, materials and manufacture is as good as it gets. Please don't bring up cost. The Lyc is cheaper than all off the shelf alternatives. A LS1 chevy quote, just engine and drive was $40,000!
You don't get cheaper with an alternative, and not by much, unless you pound it out like a black smith yourself. I mean a total 100% do it yourself, weld up an engine mount and make all the parts to adapt that Chevy, Ford, Buick, Mazda, Subaru or what ever. The VW and Corvair make good engines below 100 HP, which is too small for our needs, but than again they are air cooled.
I am pretty sure I can say with out challenge , typical Lyc powered RV's are lighter, faster and more efficient (ie lower fuel burn) than the typical hi-tech alternative auto powered RV.
So to say the Lyc is antiquated is kind of a slam on all the new technology, that still can't match the performance of the OLD Lyc. If you want FADEC on a Lyc you can have it. WOW a whole 4% better or what ever. You want better or balanced Injectors, that is doable today. I reject any idea that mixture control is a burden or some how beyond even the lowest common denominator pilot. If you want one lever, state of the art fly a Jet.
This is all in fun and for entertainment purpose. I am not slamming alternative engines or anti-do it your self automotive engine. I am just dispelling the idea that Lycs are antiquated or inferior because the age of the desgin. Hey they just freaking got it right the first time.
I have seen some very nice car engine set-ups, in fact better than anything I could do. That is why I went the KISS method, the Lyc that Van told me to use. I know it is easy to install, and I know what I have when I am done. I will not have to "FINE TUNE" an experimental set-up, no worries. I also know they (ECI/Superior/Textron Lyc) will be around to make parts for a long time and parts are found nation or world wide.
What new material or manufacture process are we talking about? Not that you think this, but I think people see Lycs as being made by a black smith, pounded out like a horse shoe with a hammer and red hot coals.Fitz said:
The materials, processes, QC and tolerances are as modern and tight any engine or as needed in a low RPM engine. The materials are of class 1A castings and steel. I am not sure where you are going with NEW materials. ECI, Superior and Lycoming have different cylinder walls and ring materials and coatings. I still get a chuckle out of the thought of "50 year old engines" being antiquated. It is just inaccurate and miss leading. The Lyc is made the way it is, with the materials it uses and the tolerances, by design. It is not that it's 50 year old.
The "crude" part of the Lyc, I gather is the fact is in the fact a Lyc is a large bore/displacement, low rpm, direct drive, air-cooled engine. I understand precision aluminum castings of the case or cylinder heads have a rough finish, but that is the beauty. If it where hogged out of a forged block it would look pretty but weigh more.
I understand the wishful thinking of a 8,000 rpm Lexus engine with dual overhead cam's and 22 valves per cylinder
, but it would not hack it in a plane. You don't need overhead cam auto technology in a plane engine that lives between 2700-2300 rpm at state RPM 98% of the flight, e.g. takeoff, climb, cruise and decent/approach. Occasionally idle we need to taxi at idle (800-1000 rpm) and 1800-2000 rpm for approach. Most of the "technology" in car engines that makes them BETTER? has been around for over 50 years. If Lyc wanted or needed to include it, they would have. Power, weight, simplicity, reliability and application are well balanced in an air cooled aircraft engine. It's this way on purpose.
The effort and talent that was put into air cooled aircraft engine research and design, for its day, was like the efforts of putting a man on the moon or the space shuttle of there time. Meaning it was top prority of the the US leading engineering and NACA (now NASA).
There is a lot of technology in a Lycoming. Yes most of it was done over 50 years ago, but as was said it has been refined of the years. The technology used today in making a Lyc is top notch. Actually, when Lyc and also TCM messed up their cranks, is when they tried to change to a "Better modern" method of forging steel. "If it ain't broke don't fix it."
I am going to go out on a limb and say if you built a blank sheet air cooled horz opposed engined today, it would look just like a Lyc or TCM does now. BUT YOU SAY WATER COOLING IS BETTER. Water cooling is the "hi tech" part of car engines, but that has been done for over 100 years on cars and planes. In fact the first plane was water cooled. Some guys named Wright Bros or something like that. If Lyc wanted to go water cooled they could. In fact Lyc has some aftermarket "cool jugs" available. If you hear it in the test stand it sounds like a Subaru. It also cost $9,000 for the jugs and really does nothing more, except add drag from a radiator.
The fastest piston planes (Reno, unlimited gold) are powered by air cooled engines. Water cooling is cool for cars and needed. Water cooling in a plane is a burden. There is a prolific amount of air available in an AIR plane; therefore AIR cooled engines are, dare I say, better suited for planes. The exception is of course the P-51, but that airframe was designed around the plane.
So when you go into it a design and say we want air cooling and no reduction gear box, low frontal profile, you will lock your self into a Lycoming configuration. In-line (cylinder) is fine, but you have a longer crank for the same number of cylinders. Also cooling the back just is a challenge (but doable).
I'll even be so bold as to say the Lycoming is a technological marvel. A light, powerful, simple, reliable power plant that in my opinions, correct me if I am wrong, is still the gold standard all other alternative engines are judged by. I'll even say I can't see improving it. The add on's like, roller cams, FADEC, electronic ignition, composite oil sumps, port/polish/high compression are all great, but the basic design, materials and manufacture is as good as it gets. Please don't bring up cost. The Lyc is cheaper than all off the shelf alternatives. A LS1 chevy quote, just engine and drive was $40,000!
You don't get cheaper with an alternative, and not by much, unless you pound it out like a black smith yourself. I mean a total 100% do it yourself, weld up an engine mount and make all the parts to adapt that Chevy, Ford, Buick, Mazda, Subaru or what ever. The VW and Corvair make good engines below 100 HP, which is too small for our needs, but than again they are air cooled.
I am pretty sure I can say with out challenge
, typical Lyc powered RV's are lighter, faster and more efficient (ie lower fuel burn) than the typical hi-tech alternative auto powered RV. So to say the Lyc is antiquated is kind of a slam on all the new technology, that still can't match the performance of the OLD Lyc. If you want FADEC on a Lyc you can have it. WOW a whole 4% better or what ever. You want better or balanced Injectors, that is doable today. I reject any idea that mixture control is a burden or some how beyond even the lowest common denominator pilot. If you want one lever, state of the art fly a Jet.
This is all in fun and for entertainment purpose. I am not slamming alternative engines or anti-do it your self automotive engine. I am just dispelling the idea that Lycs are antiquated or inferior because the age of the desgin. Hey they just freaking got it right the first time.
I have seen some very nice car engine set-ups, in fact better than anything I could do. That is why I went the KISS method, the Lyc that Van told me to use. I know it is easy to install, and I know what I have when I am done. I will not have to "FINE TUNE" an experimental set-up, no worries. I also know they (ECI/Superior/Textron Lyc) will be around to make parts for a long time and parts are found nation or world wide.
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Kevin Horton
Well Known Member
added firewall-forward, ready to fly qualifier
Just curious - are there any alternative engines that have all of the following attributes?
Just curious - are there any alternative engines that have all of the following attributes?
- firewall-forward, ready to fly weight equal to, or less than, an O-360 + Sensenich prop,
- lower cost than an O-360 + Sensenich prop, and
- lower specific fuel consumption than an O-360
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Walter Atkinson said:
I beg to differ.
The turbo compound Wrights were around .37-.38 LOP (remarkable for the era and low CRs run) and the LS1-LS2 have shown figures of .375 running in closed loop in cruise in aircraft. The Honda HE engines were around .36 in cruise at 20 to 1 AFRs quite a number of years ago. Over 20 years ago, the Toyota 5MGE engine was capable of .425 WOT at 2800 rpm. I think you will find that many of the current 10.5 to 11 CR automotive engines running in closed loop like the BMW sixes with direct injection with lean targeted AFRs and the latest 3 way catalysts are well below .40, around the same as the Thielert Diesels currently flying. You cannot compete with a high CR engine, designed with very low friction, CFA derived chamber and port design, fully synthetic light oils, variable valve timing and lift, variable inlet length, direct cylinder injection, computer controlled, high energy ignition, running way LOP with old tech stuff.
The old Lycos and Contis are pretty good for what they are but the door is slowly but surely closing on them in the experimental world. The tremendous upsurge of the numbers installing automotive based alternatives compared to 10 years ago makes that clear.
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David-aviator
Well Known Member
Jconard said:
Yea, a few have gone down, including one I was flying, but I am not aware of the minor sensor failure event. I know of 2 vapor locks, one super charger belt jumping a pulley and wiping out the timing belt (mine), one very experimental PSRU failure, one with 2 dead batteries, one with one dead battery and probably a couple by a guy in California who is pushing the envelope all the time. Stuff happens, this is an experimental effort.
I've done 2 airplanes with Lycoming, both were fine. The third is Subaru- mostly to be doing something different. It's been interesting and fun - well most of it.. It has not been boring.
I am not going as fast as some RV's, nor is the specific fuel consumtion as good as Lycoming, but we are getting better in both areas every day. There is a 2:1 PSRU going into flight test this week end and a new ECU will be coming along also. The effort is not standing still. Some ideas work, some don't. That's what the Egg effort is all about. That's what EAA is all about.
What the heck, anyone can hang a Lycoming and go fly.
dd
RV-7A N707DD
Flyin' the turbine smooth H6, the sound and feel of a mini Merlin!
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Jconard
Well Known Member
I wonder about the 2:1 PSRU, my understanding was that the ratio is generally kept at an odd number to prevent repetitive stress. What I mean is that the same teeth will contact each other repeatedly in an even ratio...I guess the reding I have done on PSRU's suggested that such a ratio was bad for that reason...
Comment?
By the way, I would love to see an alternative, but, I keep hearing about all the variable this and that which is allowed by car technology...I really appreciated those advances, as a driver, when I used to race.
But, why do I want the complexity of variable valve, and such, when I only run in an RPM range of 2000-2700 RPM? Even with ignition, the move away from fixed ignition does not gain all that much.
In short, I understand that with small displacement engines, the RPM range is larger, because they must be spun to produce power. But, the small displacement high rpm choice is what necessitates the extended RPM range, hence necessitating, to some extent the other complexity. But why not simply choose a larger displacement, relatively static rpm range design from the start which would allow simple fixed systems to work...reducing complexity. It sure seem like it results in great performance, and light weight to go that route...
Again, technology is only technology if it serves a need...extra complexity without improved performance seems like change for its own sake.
P.S. I will grant the limited value of subjective smoothness, and the convenience of not having to learn how to use a red knob.
Comment?
By the way, I would love to see an alternative, but, I keep hearing about all the variable this and that which is allowed by car technology...I really appreciated those advances, as a driver, when I used to race.
But, why do I want the complexity of variable valve, and such, when I only run in an RPM range of 2000-2700 RPM? Even with ignition, the move away from fixed ignition does not gain all that much.
In short, I understand that with small displacement engines, the RPM range is larger, because they must be spun to produce power. But, the small displacement high rpm choice is what necessitates the extended RPM range, hence necessitating, to some extent the other complexity. But why not simply choose a larger displacement, relatively static rpm range design from the start which would allow simple fixed systems to work...reducing complexity. It sure seem like it results in great performance, and light weight to go that route...
Again, technology is only technology if it serves a need...extra complexity without improved performance seems like change for its own sake.
P.S. I will grant the limited value of subjective smoothness, and the convenience of not having to learn how to use a red knob.
Jconard said:
The automotive world is usually not driven by change for the sake of change when it comes to engine technology. Emissions regs and fuel economy not to mention power are all driving factors. The new BMW Valvetronic and spray guided GDI technologies have allowed them to increase power output while remaining well under EU4 and LEV emissions standards while both technologies have demonstrated drops in fuel consumption of around 10%- significant indeed.
Mazda, Audi and Toyota have also released GDI engines lately. The Lexus 2GR-FSE combines port and GDI technology impressively in their 306hp 3.5 liter V6. Microprocessor controlled electric water pumps and electrically assisted power steering are now being fitted to some OE engines as well to lower parasitic losses. These advances have given the latest gasoline engines comparable SFCs to older light diesels.
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David-aviator
Well Known Member
H6 Economy Run
I've been installing an irrigation system in our property for 3 weeks, some 3400' of it, and just dropped everything this morning to go flying. What a pleasant break from pure labor.
Local flying is in an economy mode. No sense wasting fuel, its just as enjoyable at 120 knots as a 150. The technique is get airborne, set prop to 2300, climb a bit and haul it back to 1700, all ASAP. Fuel flow drops right off to 5-6 gph with a little throttle back as the engine shifts into closed loop, like cruisin' down the hiway at 55 mph.
Stopped at 2 airports, talked with friends, cut the grass at our EAA Chapter Hangar, had lunch, and flew home. Logged 1.2 hours and 6.2 gallons of fuel was missing - 83 mogas at that - $2.16 at the local Walmart.
dd
Not to be biased - I used to do that with my 0360 also. The only difference is the cost of the fuel. Mogas has really dropped around here recently, but 100LL is still over $4.
I've been installing an irrigation system in our property for 3 weeks, some 3400' of it, and just dropped everything this morning to go flying. What a pleasant break from pure labor.
Local flying is in an economy mode. No sense wasting fuel, its just as enjoyable at 120 knots as a 150. The technique is get airborne, set prop to 2300, climb a bit and haul it back to 1700, all ASAP. Fuel flow drops right off to 5-6 gph with a little throttle back as the engine shifts into closed loop, like cruisin' down the hiway at 55 mph.
Stopped at 2 airports, talked with friends, cut the grass at our EAA Chapter Hangar, had lunch, and flew home. Logged 1.2 hours and 6.2 gallons of fuel was missing - 83 mogas at that - $2.16 at the local Walmart.
dd
Not to be biased - I used to do that with my 0360 also. The only difference is the cost of the fuel. Mogas has really dropped around here recently, but 100LL is still over $4.
Jconard
Well Known Member
EJGUY,
Yes! the technology is wonderful in cars, where throttle response/modulation and smoothness is hugely important, and the engines must operate over a 6000 rpm range...
My question was why the same approach is useful for a constant speed engine with which really operates in a 300 rpm range at cruise.
Yes! the technology is wonderful in cars, where throttle response/modulation and smoothness is hugely important, and the engines must operate over a 6000 rpm range...
My question was why the same approach is useful for a constant speed engine with which really operates in a 300 rpm range at cruise.
I don't think a lot of this technology would be especially useful or applicable to a Lyco but with a clean sheet design, there is no doubt in my mind that something better can be designed today, drawing on the 50+ years of progress in the automotive field.
To replace the O-360 class engines, I'd envision a geared, liquid cooled, 4L flat six turning about 4500 rpm for takeoff, 4000 for climb and around 3500 for cruise. Probably use 4 valves per cylinder actuated by pushrods and roller rockers. Exhaust cam below the crank, intake cam above the crank, gear driven. Compression ratio around 11 to 1. Single plug per cylinder with individual coil on plug ignition. Direct injection also controlled by FADEC. Twin alternators for backup. This would take some serious dough to develop obviously. In the meantime work proceeds on the EG33 for our -10, which is something I can afford.
To replace the O-360 class engines, I'd envision a geared, liquid cooled, 4L flat six turning about 4500 rpm for takeoff, 4000 for climb and around 3500 for cruise. Probably use 4 valves per cylinder actuated by pushrods and roller rockers. Exhaust cam below the crank, intake cam above the crank, gear driven. Compression ratio around 11 to 1. Single plug per cylinder with individual coil on plug ignition. Direct injection also controlled by FADEC. Twin alternators for backup. This would take some serious dough to develop obviously. In the meantime work proceeds on the EG33 for our -10, which is something I can afford.
Jconard
Well Known Member
Why?
I think such an engine would be cool to look at, but there are many bits of complexity that are unnecesary....
1. You choose 4L in order to spin it faster...why?
2. Individual coilpacks have not proven terribly reliable in the field, often failing without advance notice...ask the 500,000 VW 1.8T, 2.8 24V, W8, owners who had coil pack failures, in a relatively cool underhood car, with packs built by Bosch...not just incidence of failure is important, but fair warning is nice...mags fail, but they give you plenty of notice.
3. Why direct injection? requires high pressure pumps, and is great in the VW/Audis that have it, but at a given, narrow rpm range seems to give little improvement for alot of complexity.
4. If the theory is that smaller package is less weight, hence spin it faster to save weight overall, this just does not seem to make sense, in that it has not been born out by some pretty sophisticated car engines.
5. You do not say it, but I assume water cooled. I await the results of your scoop installation...I will admit to have been following your website. If it works, it may make the drag issue less of a burden, and WC certainly requires less pilot skill to operate, but adds weight, and complexity, and seems to require coolant lines in the cockpit.
You should check out what is required to install a truly redundant FADEC system...I have seem the wiring diagram and install of one....holy smoke are there alot of extra wires.
The highest evolution of the modern, spin it fast approach seems to be trying to replace the 5L Lyc, with the 2.5L Sube, modern everything....in fact it seems that those installs would get alot better if they reduced technology, replacing the sube ECU with a more simple Haltech, or SDS system...map out all the points on a dyno and do some tuning in the air with perhaps a trim control. Find some reliable way to have a mechanical fuel pump, and PSRU/CS prop, and you would be in business.
Sort of like the old injection on the VW buses...bone simple, and robust, with no single sensor failures that can crash it. You may loose the small advantage of colsed loop runing, but the high CR engine has greater thermal efficiency, and it would be simple.
Or even build a balance manifold and go to TBI..two redundant injectors in one spot...clean sheet the thing from block up.
I think such an engine would be cool to look at, but there are many bits of complexity that are unnecesary....
1. You choose 4L in order to spin it faster...why?
2. Individual coilpacks have not proven terribly reliable in the field, often failing without advance notice...ask the 500,000 VW 1.8T, 2.8 24V, W8, owners who had coil pack failures, in a relatively cool underhood car, with packs built by Bosch...not just incidence of failure is important, but fair warning is nice...mags fail, but they give you plenty of notice.
3. Why direct injection? requires high pressure pumps, and is great in the VW/Audis that have it, but at a given, narrow rpm range seems to give little improvement for alot of complexity.
4. If the theory is that smaller package is less weight, hence spin it faster to save weight overall, this just does not seem to make sense, in that it has not been born out by some pretty sophisticated car engines.
5. You do not say it, but I assume water cooled. I await the results of your scoop installation...I will admit to have been following your website. If it works, it may make the drag issue less of a burden, and WC certainly requires less pilot skill to operate, but adds weight, and complexity, and seems to require coolant lines in the cockpit.
You should check out what is required to install a truly redundant FADEC system...I have seem the wiring diagram and install of one....holy smoke are there alot of extra wires.
The highest evolution of the modern, spin it fast approach seems to be trying to replace the 5L Lyc, with the 2.5L Sube, modern everything....in fact it seems that those installs would get alot better if they reduced technology, replacing the sube ECU with a more simple Haltech, or SDS system...map out all the points on a dyno and do some tuning in the air with perhaps a trim control. Find some reliable way to have a mechanical fuel pump, and PSRU/CS prop, and you would be in business.
Sort of like the old injection on the VW buses...bone simple, and robust, with no single sensor failures that can crash it. You may loose the small advantage of colsed loop runing, but the high CR engine has greater thermal efficiency, and it would be simple.
Or even build a balance manifold and go to TBI..two redundant injectors in one spot...clean sheet the thing from block up.
David-aviator
Well Known Member
Jconard said:
Are you referring to vibration or stress?
Actually, it does't matter as I know little about either from an engineering perspective. I do know vibration is apparent with Lycoming and stress, well, everyone has it now and then.
Yes, I know you are referring to gear stress. So far, the 1.82:1 PSRU has worked well. No one has reported a problem with it that I know of except it barfs a little oil out the breather now and then. The 2:1 PSRU is not that much different and I predict it will be OK. The 2:1 mesh will obviously allow more HP at 2700 prop rpm, and probably will require a different prop. I do know a big 4 blade prop was used with the 2.5:1 belted redrive, but that effort has been cancelled.
Ah yes, "the limited value of subjective smoothness". Did you know that the MT-7 electric prop weighs just 31 pounds? The prop is light and not as beefy as for a Lycoming. This is because of the inherent smoothness of the engine. The only vibration I feel is through the muffler attach points on the bottom of the fuselage and that is annoying - there is an internal muffler being flight tested at this time. I tried flying without a muffler and it was impossible - much louder than Lycoming for an unknown reason. I had to pull the power back to talk to the tower.
Evidently, the noise is outside the range of standard noise cancel headsets.Frankly, re the red knob, I wish we had one. But that's impossible with mother hen ECU running the show.
dd
Jconard
Well Known Member
Good to know...I just read that they tried for odd ratios to prevent gear stress.
As for the MT...well the WW151 is 28 lbs....and regardless of the MT's weight, the combination of WC and PSRU is heavy....
I have never been bothered by the vibration of a lyc, or continental for that matter. I do find the simplicity to be elegant, like a vontage formula car, nothing extra, nothing beyond the necessary mission...just me though.
As for the MT...well the WW151 is 28 lbs....and regardless of the MT's weight, the combination of WC and PSRU is heavy....
I have never been bothered by the vibration of a lyc, or continental for that matter. I do find the simplicity to be elegant, like a vontage formula car, nothing extra, nothing beyond the necessary mission...just me though.
Jconard said:
Smaller engine spinning faster weighs less. Revs don't weigh anything. Integrated redrive might weigh 20 lbs. if done right. You don't believe this, look at an Indy Car or F1 engine. About 3hp/ lb. Obviously we won't be spinning 19,000 rpm but the basic idea is the same.
Quite right. VW coil on plugs were very bad with integrated power transistor living in the valve cover. Denso and Diamond very good. Me like Japanese electronics.
Direct injection and liquid cooling allows high CR and a wide choice of fuels. Allows engine to run much leaner with no fear of detonation. Well worth it. The weight, size and power consumption of these new pumps is minimal.
The naturally aspirated EJ25 cannot match an IO-360 as we have seen. A properly done EZ30 should albeit at a weight penalty. A 2.5 Legacy turbo running low boost would be closer in weight and would certainly run away but nobody is running that combo at the moment. We'll have to wait for a flyoff with the new redrive and prop. Maybe Robert and Dan can have another go in the future?
We've done some twin ECU setups and you are right- a lot more switch gear to isolate the the two from faults, probably making it more likely to lose both. Our recommendation to customers is to use one and wire it properly. The ECUs never fail unless someone gets them wet. Programmed defaults on most of the sensor parameters get around most types of sensor failures and SDS provides a red ...er black knob too. No need for a dyno on aircraft installations as we have that prop. Install a wideband, give me 10 minutes and it will run sweet.
The belly rad on RV3-RV9 airframes presents many problems with coolant line routing and possibly cowling revisions so I don't think you'll see many of these around- hence the cowling mounted solutions used by most. There are a couple of RV10s being done with Wankels and new rad/ ducting ideas. Hopefully we'll see how these work in a couple years.
Interesting stuff.
Idea for a new redrive
If someone could make a constantly variable ratio redrive like on the new cars conversions could simply run at wide open throttle all the time and use one lever to control prop rpm. just think someone could take a honda s2000 engine naturaly asperated run it at 9000rpm's all the time and have 200HP on demand like a dual shaft turbine. or how about something like an 8-6-4 setup like GM or shut half the cylinders off like chrysler for economy cruse. Don't stop me im on a roll here, just kidding im going superior XP-360+ with p-mags
I would also like to point out cams only work for a certain rpm range low rpm mid, high but since car engines have to perform at a very broad rpm range they had to impliment variable cam timing also valves have mass and at high rpm they are just like a paddle ball you know the old wooden paddle's with a rubberband and ball. well anyway if you want to run an engine at higher rpm's at some rpm the valves will begin to float. this means that the valve keeps moving towards the piston even after the cam is past the high point on the lobe. to eliminate this problem engine designers went to multi valve engines to reduce mass. the variable cam timing is unnessary in a conversion because the engine still only needs to make power in a narrow rpm window.
If someone could make a constantly variable ratio redrive like on the new cars conversions could simply run at wide open throttle all the time and use one lever to control prop rpm. just think someone could take a honda s2000 engine naturaly asperated run it at 9000rpm's all the time and have 200HP on demand like a dual shaft turbine. or how about something like an 8-6-4 setup like GM or shut half the cylinders off like chrysler for economy cruse. Don't stop me im on a roll here, just kidding im going superior XP-360+ with p-mags
I would also like to point out cams only work for a certain rpm range low rpm mid, high but since car engines have to perform at a very broad rpm range they had to impliment variable cam timing also valves have mass and at high rpm they are just like a paddle ball you know the old wooden paddle's with a rubberband and ball. well anyway if you want to run an engine at higher rpm's at some rpm the valves will begin to float. this means that the valve keeps moving towards the piston even after the cam is past the high point on the lobe. to eliminate this problem engine designers went to multi valve engines to reduce mass. the variable cam timing is unnessary in a conversion because the engine still only needs to make power in a narrow rpm window.
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L.Adamson
Well Known Member
rv6ejguy said:
I live under an airport pattern, and those high rev "sewing machine" engines sound like "****"! Get too many, and I think I'll have to start complaining about noise pollution!
L.Adamson --- Lycoming 0360 Hartzell C/S
edit: the **** word was c-r-a-p, but since it was surprisingly blanked out, other substitutions will fit just as well!
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L.Adamson said:I live under an airport pattern, and those high rev "sewing machine" engines sound like "****"! Get too many, and I think I'll have to start complaining about noise pollution!
L.Adamson --- Lycoming 0360 Hartzell C/S
edit: the **** word was c-r-a-p, but since it was surprisingly blanked out, other substitutions will fit just as well!
I guess the sound is in the ear of the beholder. Even die hard Lyco guys comment on how nice my turbo Subie sounds. Some people like the sound of a Harley... go figure.
favorite sounds
I have to confess I prefer the sound of sailplanes and bicycles!
Funny how when I'm making the noise it doesn't bother me at all!rv6ejguy said:I guess the sound is in the ear of the beholder. Even die hard Lyco guys comment on how nice my turbo Subie sounds. Some people like the sound of a Harley... go figure.
I have to confess I prefer the sound of sailplanes and bicycles!
gmcjetpilot
Well Known Member
Neat idea, but how?
The tips of the fan on the GE90 with a 120" fan would go supersonic at sea level on a standard day at 2132 RPM. Tips on turbofans routinly exceed Mach 1 by a large margin. For example the tip speed on the 98 inch dia. fan at max N1 of 3665 (Max N1 is 117.5% N1) is 1124 MPH or about Mach 1.5. You can tell when the tips go supersonic at high power settings by the sound. To help reduce the loss of the supersonic FAN, controlling the air flow at the tips gives gains in thrust and efficiency. The FAN tips are so close to the cowl, they actually rub and touch intentionally. There are sacrificial rub strips in the cowl of many jet engines. Also interesting, when they intentionally blow a FAN blade off with a explosive charge, during FAN blade containment testing on a stand, it's spectacular and catastrophic. Don't worry the cowl is wrapped in multilayers or dry Kevlar cloth to keep the blades from leaving the cowl. If a blade did fly out at full speed, it would be a weapon of mass destruction.
So the FAN is going way faster than needed, so the idea of a gear reduction or muti speed fan gear box (aka transmission) has been dreamed of. Also variable pitch jet FANs' is another dream. When you consider the forces at the base of the fan that is even harder then a gear box. Designers want to go even bigger with the FAN diameters still. The GE90 is up to and just shy of 11 foot dia. Sadly the law of physics affects both RV's and jet aircraft.
You mean a transmission? I have thought of that, but what does a transmission weigh? May be you mean something else? However that is an interesting idea, and one that even Pratt & Whitney has thought of. The FAN, the big one on the front, has limited efficiency at max RPM, because of it large diameter. It is tied to smaller turbine wheels in the back of the engine that can and do run much faster. You hear it when a hi-bypass jet takes off. The sound you hear is the FAN tips going supersonic. Fancy cowls and sound absorption helps but the sound is distinctive and totally different than an old jet, with it's rocket sound. You actually hear new jets coming more than going.dserratt said:
The tips of the fan on the GE90 with a 120" fan would go supersonic at sea level on a standard day at 2132 RPM. Tips on turbofans routinly exceed Mach 1 by a large margin. For example the tip speed on the 98 inch dia. fan at max N1 of 3665 (Max N1 is 117.5% N1) is 1124 MPH or about Mach 1.5. You can tell when the tips go supersonic at high power settings by the sound. To help reduce the loss of the supersonic FAN, controlling the air flow at the tips gives gains in thrust and efficiency. The FAN tips are so close to the cowl, they actually rub and touch intentionally. There are sacrificial rub strips in the cowl of many jet engines. Also interesting, when they intentionally blow a FAN blade off with a explosive charge, during FAN blade containment testing on a stand, it's spectacular and catastrophic. Don't worry the cowl is wrapped in multilayers or dry Kevlar cloth to keep the blades from leaving the cowl. If a blade did fly out at full speed, it would be a weapon of mass destruction.
So the FAN is going way faster than needed, so the idea of a gear reduction or muti speed fan gear box (aka transmission) has been dreamed of. Also variable pitch jet FANs' is another dream. When you consider the forces at the base of the fan that is even harder then a gear box. Designers want to go even bigger with the FAN diameters still. The GE90 is up to and just shy of 11 foot dia. Sadly the law of physics affects both RV's and jet aircraft.
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gmcjetpilot said:
We still see premature failures for things like valve guides off center, heads out of round, that sort of thing. That is manufacturing 101 these days. It is probably economics of scale, you can only justify so much modernization for a niche market plant.
There has been a lot of progress in alloys for parts at the top (valves in particular come to mind). Again, this is economics of scale. If you don't have the volume you may not be able to justify the equipment, tooling, and training.
rv6ejguy said:
I'd have to concur, it is getting surprisingly close. But folks who think we are missing out on massive improvements are (I think) dreaming.
-jjf
gmcjetpilot
Well Known Member
Good point but its not the material
I hear you. I think that is just the nature of the beast. An aircooled plane with Horz cyl. is tough on valves.
The relationship of guide material and valve hardness is an ART. If you use beryllium copper, the guides will last FOREVER, but the valves stems will be whittled to a tooth pick. If you use soft guides for lower valve wear, the guides don't last. I think Lycoming has figured it out the best balance. You get balanced guide and valve wear. Actually I think it was figured out by the US government (NACA) and industry (P&W, Wright, Jacobs, Kinner, Warner, Packard, Ranger) during WWII engine development. They came up with the right balance we still use today.
If you follow Lycs recommendation for operation, maintenance and pay attention to your engine (say know what a sticking valve is and sounds like) you can go TBO with no problem.
I will freely admit the valve / guide is a "weak point", if you want to call it that. It is NOT a material thing. There is just no material on the planet that will cure all that environment can dish out. You can blame the design, but, there is not a lot you can do, at least do that is not heavy or prohibitively expensive. You can't help it. Deposits happen and wear happens. That is life. The pilot can be aware and pay attention to CHT, oil changes and operational technique (read Lycomings Key reprints on their web site).
In exchange you get a light low drag air cooled engine. Yes water cooling is superior, but it does not fit in (fast) planes real well, especially planes designed for air cooled engines.
What about consistency? Why do some engines go TBO and others do not do to valve issues? You can't always blame the pilot, right, and if it is not the material, what is it? Could it be manufacturing? I am into air cooled Porsche's. I am told by 911 experts, believe it or not, they don't always control the valve to guide tolerance very consistently. Each engine is like different, one from the other? I guess they are hand made. Well that is kind of like a Lyc top end. Some mechanics will lap the guide and seat by hand, which was common in manufacturing. It's still common in field overhauls. The little guy does not have the specialty CNC multi angle valve seat and guide cutter. These machines have been used for mass automotive engine assembly for some time, due to the volume. There is nothing wrong with cutting the seat and guide by hand, but it takes an experts touch, skill and experience. The CNC takes less skill and adds consistency, so you don't have the made on Monday engine syndrome. Just a theory, but some valve problems have been from poor manufacturing or overhaul. Read Sacramento Sky Ranch Engineering manual for more info.
Some Porsche's have valve guides that go +200,000 miles, others only last 30,000 miles. For some reason stock Porsche valve guide material is soft. May be they want to sacrifice the guide and not the valve stem. Porsche engine builders make guides using their own material when doing top overhauls. The new guides last much longer than the stock ones. You'd think an expensive sports car would have the best materials. To be fair we are talking about a +300 hp engines that is wound up pretty tight. May be Porsche figures they want to keep valve wear to a min and sacrifice the guide. That is if you accept you may need a top overhaul ever 60k. Guides are cheaper than valves.
This puts it into perspective. I think Lycoming has a pretty good valve/guide/seat design, uses good materials, consistent performance and reliability, but it must be installed and operated with care, no doubt.
In the Nexis of design and materials, I think all the engines we are using have achieved their optimal. The question is what is best suited for our application. We know where I stand. And you others know who you are. Again there is no perfect, just a series of choices and compromises. You just hope when the whole thing comes together it works to its optimal.
Fitz said:
I hear you. I think that is just the nature of the beast. An aircooled plane with Horz cyl. is tough on valves.
The relationship of guide material and valve hardness is an ART. If you use beryllium copper, the guides will last FOREVER, but the valves stems will be whittled to a tooth pick. If you use soft guides for lower valve wear, the guides don't last. I think Lycoming has figured it out the best balance. You get balanced guide and valve wear. Actually I think it was figured out by the US government (NACA) and industry (P&W, Wright, Jacobs, Kinner, Warner, Packard, Ranger) during WWII engine development. They came up with the right balance we still use today.
If you follow Lycs recommendation for operation, maintenance and pay attention to your engine (say know what a sticking valve is and sounds like) you can go TBO with no problem.
I will freely admit the valve / guide is a "weak point", if you want to call it that. It is NOT a material thing. There is just no material on the planet that will cure all that environment can dish out. You can blame the design, but, there is not a lot you can do, at least do that is not heavy or prohibitively expensive. You can't help it. Deposits happen and wear happens. That is life. The pilot can be aware and pay attention to CHT, oil changes and operational technique (read Lycomings Key reprints on their web site).
In exchange you get a light low drag air cooled engine. Yes water cooling is superior, but it does not fit in (fast) planes real well, especially planes designed for air cooled engines.
What about consistency? Why do some engines go TBO and others do not do to valve issues? You can't always blame the pilot, right, and if it is not the material, what is it? Could it be manufacturing? I am into air cooled Porsche's. I am told by 911 experts, believe it or not, they don't always control the valve to guide tolerance very consistently. Each engine is like different, one from the other? I guess they are hand made. Well that is kind of like a Lyc top end. Some mechanics will lap the guide and seat by hand, which was common in manufacturing. It's still common in field overhauls. The little guy does not have the specialty CNC multi angle valve seat and guide cutter. These machines have been used for mass automotive engine assembly for some time, due to the volume. There is nothing wrong with cutting the seat and guide by hand, but it takes an experts touch, skill and experience. The CNC takes less skill and adds consistency, so you don't have the made on Monday engine syndrome. Just a theory, but some valve problems have been from poor manufacturing or overhaul. Read Sacramento Sky Ranch Engineering manual for more info.
Some Porsche's have valve guides that go +200,000 miles, others only last 30,000 miles. For some reason stock Porsche valve guide material is soft. May be they want to sacrifice the guide and not the valve stem. Porsche engine builders make guides using their own material when doing top overhauls. The new guides last much longer than the stock ones. You'd think an expensive sports car would have the best materials. To be fair we are talking about a +300 hp engines that is wound up pretty tight. May be Porsche figures they want to keep valve wear to a min and sacrifice the guide. That is if you accept you may need a top overhaul ever 60k. Guides are cheaper than valves.
This puts it into perspective. I think Lycoming has a pretty good valve/guide/seat design, uses good materials, consistent performance and reliability, but it must be installed and operated with care, no doubt.
Yea who knows, it is good to dream. Hey what would piston aircraft engines be like if jets happened 10 or 15 years later and technology and capital was invested into better light aircraft engines? May be out engines just dove tail into fundamental laws of the universe. I have some back ground in engineering and design. I see all designs as a series of compromises.Fitz said:
In the Nexis of design and materials, I think all the engines we are using have achieved their optimal. The question is what is best suited for our application. We know where I stand.
And you others know who you are. Again there is no perfect, just a series of choices and compromises. You just hope when the whole thing comes together it works to its optimal.
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Kevin Horton
Well Known Member
We might have seen something like the Napier Nomad. It only ran as a prototype, but it burned Diesel fuel, weighed 0.88 lb/hp, and had a specific fuel consumption of 0.345 lb/hp/hr (all data from Wikipedia, so it could be good gen, or complete fiction - pick whichever suits your biases).gmcjetpilot said:
gmcjetpilot
Well Known Member
Thanks cool engine
I hope we may get a light, small, efficient diesel in the future for GA. I think because of the internal pressures, the crank, rods, heads and so on are pretty stout, therefore heavy. I remember GM, Buick or someone tried to make a car diesel from a gas bottom end. It ended badly. My friend's son is a professional diesel mechanic. They have pistons and cranks (some not even valves) but they are very different than gas engines.
Very interesting. I know, those diesel two-stroke, supercharged are very efficient, especially one tied to a turbine! They mention how complex it is. I suspect it may be better suited for a 3,000 hp engine than 160 hp, weight wise. The one they list is 3,580 lbs! The liquid cooling I guess is mandatory, which from my previous rants I'm against, for installation, weight and drag reasons. However just looking at it from a technical aspect, I admire it very much.Kevin Horton said:
I hope we may get a light, small, efficient diesel in the future for GA. I think because of the internal pressures, the crank, rods, heads and so on are pretty stout, therefore heavy. I remember GM, Buick or someone tried to make a car diesel from a gas bottom end. It ended badly. My friend's son is a professional diesel mechanic. They have pistons and cranks (some not even valves) but they are very different than gas engines.
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I read through this whole thread and feel I just need to interject my .02.
Before I start, please understand that I am in no way an aircraft engine expert. I don't even have an RV kit yet (gotta finish school first), and have only flown a handful of planes, mostly C 172s and Katanas.
That said, there are a number of subjects here that need to be addressed. Forgive me for not remembering names.
Anyone who feels like a high-rpm engine (jets aside) is "better" for any reason is just being unreasonable. High-rpm engines wear out fast. It's documented in so many cases it would make your spin about as fast the engine does. Someone made a comment comparing superbike engines. Are they reliable? To an extent, but you're going to see a 12,000rpm engine fail a lot sooner than a 6,000 rpm engine, not mention the maintence is mind-numbing. Valve adjustments every 5,000 miles is not uncommon. I'd put my "ancient" Harley-Davidson aircooled V-Twin up against a super-modern race-bike engine any day and not think twice about which would fail sooner. Not to mention you have to look at the power gain. I ride a 1200cc Harley-Davidson. Through some very simple modifications I'm putting roughly 76hp to the ground, and over 80ft-lbs of torque. By comparison, a 1000cc Yamaha R1 makes 180hp from the factory. The kicker is you have to rev it to the moon to get it to do anything, and forget about torque - it just doesn't exist in an engine like that. And someone else made a comment about F1 cars and how they make 3hp/CID. That's all well and good if you want to replace the motor every weekend at a cost of god knows how many $100,000s. Better yet, take a top fuel drag engine at ~600CID making 2000hp...then you get to rebuild it EVERY RACE (that's about 1/2 mile of total driving for those not into drag racing).
This is why the Rotary engine just doesn't fit in an airplane. Sure, you can get 300hp out of them, but it's at an RPM that's just too high to use. 200hp at 2700rpm from a Lyc is pretty ######## (snipped by moderator-that's TWO!) good. Not to mention the fuel usage - again, I can only comment in automotive terms, but a new RX-8 with a 1.3 liter rotary making something like 240hp only gets 22-23 mpg. Not acceptable. My 205hp supercharged 2.0 liter Ecotec in my Cobalt averaged 37mpg on a trip home form Michigan (love the economy of a blower running in vacuum!) and will make so much more torque than that rotary it's not even funny.
Like others have already said, the mostly single RPM useage range of an aircraft engine makes variable valve timing and anything along those lines unecessary.
KISS is absolutely key. I can't see engine longevity being more important than it is in an aircraft. Water-cooling adds radiator(s), hoses, thermostats, water pumps and other tid bits, all things that are more than prone to failure (6 years working in a garage taught me a thing or two), let alone the drag and weight that's added. EFI might be a good thing, but it's so easy to tune a carb for a single range of use, and I can do it with a 49 cent screw driver as oppsed to a $2000 laptop.
****, if someone made a 2-stroke flathead single-cylinder deisel that made 180hp, I'd be all over it.
Before I start, please understand that I am in no way an aircraft engine expert. I don't even have an RV kit yet (gotta finish school first), and have only flown a handful of planes, mostly C 172s and Katanas.
That said, there are a number of subjects here that need to be addressed. Forgive me for not remembering names.
Anyone who feels like a high-rpm engine (jets aside) is "better" for any reason is just being unreasonable. High-rpm engines wear out fast. It's documented in so many cases it would make your spin about as fast the engine does. Someone made a comment comparing superbike engines. Are they reliable? To an extent, but you're going to see a 12,000rpm engine fail a lot sooner than a 6,000 rpm engine, not mention the maintence is mind-numbing. Valve adjustments every 5,000 miles is not uncommon. I'd put my "ancient" Harley-Davidson aircooled V-Twin up against a super-modern race-bike engine any day and not think twice about which would fail sooner. Not to mention you have to look at the power gain. I ride a 1200cc Harley-Davidson. Through some very simple modifications I'm putting roughly 76hp to the ground, and over 80ft-lbs of torque. By comparison, a 1000cc Yamaha R1 makes 180hp from the factory. The kicker is you have to rev it to the moon to get it to do anything, and forget about torque - it just doesn't exist in an engine like that. And someone else made a comment about F1 cars and how they make 3hp/CID. That's all well and good if you want to replace the motor every weekend at a cost of god knows how many $100,000s. Better yet, take a top fuel drag engine at ~600CID making 2000hp...then you get to rebuild it EVERY RACE (that's about 1/2 mile of total driving for those not into drag racing).
This is why the Rotary engine just doesn't fit in an airplane. Sure, you can get 300hp out of them, but it's at an RPM that's just too high to use. 200hp at 2700rpm from a Lyc is pretty ######## (snipped by moderator-that's TWO!) good. Not to mention the fuel usage - again, I can only comment in automotive terms, but a new RX-8 with a 1.3 liter rotary making something like 240hp only gets 22-23 mpg. Not acceptable. My 205hp supercharged 2.0 liter Ecotec in my Cobalt averaged 37mpg on a trip home form Michigan (love the economy of a blower running in vacuum!) and will make so much more torque than that rotary it's not even funny.
Like others have already said, the mostly single RPM useage range of an aircraft engine makes variable valve timing and anything along those lines unecessary.
KISS is absolutely key. I can't see engine longevity being more important than it is in an aircraft. Water-cooling adds radiator(s), hoses, thermostats, water pumps and other tid bits, all things that are more than prone to failure (6 years working in a garage taught me a thing or two), let alone the drag and weight that's added. EFI might be a good thing, but it's so easy to tune a carb for a single range of use, and I can do it with a 49 cent screw driver as oppsed to a $2000 laptop.
****, if someone made a 2-stroke flathead single-cylinder deisel that made 180hp, I'd be all over it.
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If you can produce documented evidence that high rpm engines wear out sooner, please present it. I think you will find that this is simplistic reasoning without all facts considered. This goes hand in hand with the outdated notion that modern auto engines can't run at high rpm for sustained periods- utter nonsense. I've asked these people to back up their assertions countless times. None have to date.
Things like piston speed, bearing area, bearing journal surface speed, crank support and stiffness, block stiffness, temperature control, Valvetrain mass, cam ramp rates, fit tolerances, materials, hardness and lubrication have the greatest effects on wear rates. High speed liquid cooled engines are very intelligently designed and validated. To suggest otherwise implies that all the engineers that design these engines are fools. Unlikely.
I know lots of Japanese sport bike engines which have many 10s of thousands of miles on them and have never been opened up. Harley's have historically not had stellar reliability and is a silly design by any modern standard of engineering. It works, has tradition and that noise that some people like but it is crude. The massive engine mounts are a vain attempt to make the bike rideable for a couple of hours.
People out of the know put forth uninformed ideas about this topic regularly on here and other forums. One derided a popular 5 main bearing, 4 cylinder opposed, auto crank, forged, heat treated with rolled fillets and a demonstrated real world capability to handle nearly 1000hp to a 3 main bearing Lycoming crank which has shown to be prone to numerous failures at 1/5th of this hp level. Bigger is not always better. Small parts have lower mass and lower inertial. More main bearings means less deflection, less vibration, tighter possible clearances. More crank pin overlap makes for a stiffer, stronger, lighter crankshaft and this is proven in the ability to reliably deliver extreme power levels.
EFI and rad hoses failing, hmm. those big auto companies must be dummies. I've owned 5 early-mid '80s Toyotas all with over 250,000 km (one with 450,000km) all but one had the original rad, hoses, injectors, pumps, ECU etc. There is over 1 million km. Pretty darn reliable.
No one in their right mind today would design a clean sheet engine with uneven firing intervals nor with 2 throws between main bearings (shared throw V8s an exception perhaps) as these designs are inferior in almost every way from a longevity, strength and vibration point of view.
The growing number of people fitting auto engines to experimental aircraft, not to mention Thielert auto based diesels for certified aircraft show that many value the smoothness, low maintenance and refinement of more modern designs.
The Ecotec looks like a great design and several people are planning to fit these to aircraft. With some producing over 1200hp with stock block and crank, these have the basic makings of a reliable 200-250hp powerplant for aircraft.
Not all programmable EFI systems need laptops. With SDS, I can adjust any parameter in less time than it takes to unscrew a float or jets to make adjustments to a carb without getting fuel on my hands. We can easily do 25-35 dyno pulls per hour with changes between each run with EFI. Can't do that with any carb, even Webers with external jet access.
Things like piston speed, bearing area, bearing journal surface speed, crank support and stiffness, block stiffness, temperature control, Valvetrain mass, cam ramp rates, fit tolerances, materials, hardness and lubrication have the greatest effects on wear rates. High speed liquid cooled engines are very intelligently designed and validated. To suggest otherwise implies that all the engineers that design these engines are fools. Unlikely.
I know lots of Japanese sport bike engines which have many 10s of thousands of miles on them and have never been opened up. Harley's have historically not had stellar reliability and is a silly design by any modern standard of engineering. It works, has tradition and that noise that some people like but it is crude. The massive engine mounts are a vain attempt to make the bike rideable for a couple of hours.
People out of the know put forth uninformed ideas about this topic regularly on here and other forums. One derided a popular 5 main bearing, 4 cylinder opposed, auto crank, forged, heat treated with rolled fillets and a demonstrated real world capability to handle nearly 1000hp to a 3 main bearing Lycoming crank which has shown to be prone to numerous failures at 1/5th of this hp level. Bigger is not always better. Small parts have lower mass and lower inertial. More main bearings means less deflection, less vibration, tighter possible clearances. More crank pin overlap makes for a stiffer, stronger, lighter crankshaft and this is proven in the ability to reliably deliver extreme power levels.
EFI and rad hoses failing, hmm. those big auto companies must be dummies. I've owned 5 early-mid '80s Toyotas all with over 250,000 km (one with 450,000km) all but one had the original rad, hoses, injectors, pumps, ECU etc. There is over 1 million km. Pretty darn reliable.
No one in their right mind today would design a clean sheet engine with uneven firing intervals nor with 2 throws between main bearings (shared throw V8s an exception perhaps) as these designs are inferior in almost every way from a longevity, strength and vibration point of view.
The growing number of people fitting auto engines to experimental aircraft, not to mention Thielert auto based diesels for certified aircraft show that many value the smoothness, low maintenance and refinement of more modern designs.
The Ecotec looks like a great design and several people are planning to fit these to aircraft. With some producing over 1200hp with stock block and crank, these have the basic makings of a reliable 200-250hp powerplant for aircraft.
Not all programmable EFI systems need laptops. With SDS, I can adjust any parameter in less time than it takes to unscrew a float or jets to make adjustments to a carb without getting fuel on my hands. We can easily do 25-35 dyno pulls per hour with changes between each run with EFI. Can't do that with any carb, even Webers with external jet access.
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XL,
Some good points, but mostly mistaken about Rotary use in aircraft. In daily driver automotive apps, rotary tuning has to be tweaked to produce low end torque which hurts high end operation- not so in aircraft, or in auto racing for that matter. If your contention regarding rpm were true, turbines and jet engines would not be preferred over large piston engines in aircraft as has been the case since WWII.
The internal forces in a rotary mostly cancel out at 6000 rpm (near peak torque, btw), and show very little measured wear. Also a factor, the 2 rotors rotate at 1/3 the crankshaft speed; so they do not turn as fast as many assume. Rotaries are notorious for their longetivity and durability in long races- fewer parts to break, and they are made very strong. Piston engines often are broken down for overhaul after each race, rotaries often last through an entire racing season. Reciprocating piston engines have internal stresses that continually try to tear the engine apart, made much worse when the design uses large bore pistons AND long strokes, not to mention loose air-cooled tolerences.
Most reciprocating automotive apps do not run well or safely with lean mixtures- rotaries do well up to 25:1 air/fuel ratios (21:1 is a safer target, btw). Id guess the best the Lycs, and most other reciprocating engines, can safely run for any length of time, without overheating under power, is closer to 12 or 13:1. The cast iron rotors do not melt like aluminum pistons tend to do when run lean. Naturally aspirated rotaries are also relatively unaffected by detonation, which helps when running lean mixtures.
The BSFE of rotaries is slightly higher (several hundredths, ~0.45 vs 0.46) than reciprocating engines, but not by much, when tuned correctly. Cost wise, the differences are more than made up in the differences in fuel costs between avgas and mogas.
FWIW, an interesting project is underway with a compounded rotary that could prove to be a quantum step forward in gasoline-powered efficiency. Basically, the lack of (overheating) exhaust valves in a rotary enable an exhaust driven turbine to be coupled, through a friction drive, to the driveline; it converts waste exhaust heat into crankshaft power over and above the normal efficiency numbers. The idea is similiar to turbocharging, except the power goes directly to the crankshaft instead of driving an air compressor. Efficiency improvements of about 35-40% are expected; time will tell.
Some good points, but mostly mistaken about Rotary use in aircraft. In daily driver automotive apps, rotary tuning has to be tweaked to produce low end torque which hurts high end operation- not so in aircraft, or in auto racing for that matter. If your contention regarding rpm were true, turbines and jet engines would not be preferred over large piston engines in aircraft as has been the case since WWII.
The internal forces in a rotary mostly cancel out at 6000 rpm (near peak torque, btw), and show very little measured wear. Also a factor, the 2 rotors rotate at 1/3 the crankshaft speed; so they do not turn as fast as many assume. Rotaries are notorious for their longetivity and durability in long races- fewer parts to break, and they are made very strong. Piston engines often are broken down for overhaul after each race, rotaries often last through an entire racing season. Reciprocating piston engines have internal stresses that continually try to tear the engine apart, made much worse when the design uses large bore pistons AND long strokes, not to mention loose air-cooled tolerences.
Most reciprocating automotive apps do not run well or safely with lean mixtures- rotaries do well up to 25:1 air/fuel ratios (21:1 is a safer target, btw). Id guess the best the Lycs, and most other reciprocating engines, can safely run for any length of time, without overheating under power, is closer to 12 or 13:1. The cast iron rotors do not melt like aluminum pistons tend to do when run lean. Naturally aspirated rotaries are also relatively unaffected by detonation, which helps when running lean mixtures.
The BSFE of rotaries is slightly higher (several hundredths, ~0.45 vs 0.46) than reciprocating engines, but not by much, when tuned correctly. Cost wise, the differences are more than made up in the differences in fuel costs between avgas and mogas.
FWIW, an interesting project is underway with a compounded rotary that could prove to be a quantum step forward in gasoline-powered efficiency. Basically, the lack of (overheating) exhaust valves in a rotary enable an exhaust driven turbine to be coupled, through a friction drive, to the driveline; it converts waste exhaust heat into crankshaft power over and above the normal efficiency numbers. The idea is similiar to turbocharging, except the power goes directly to the crankshaft instead of driving an air compressor. Efficiency improvements of about 35-40% are expected; time will tell.
Since we are back on this topic again let me examine a few more design points between the Subaru and Lycoming engines:
The Sube uses a low pressure diecast crank case. Pressure die castings have higher strenth, lower porosity and better heat dissipation than sand castings.
As per modern race engine design, the head bolt fasteners are threaded into the crankcase near the base of the main bearings webs. The cylinders are integrated into the block. This is far stronger and stiffer than base bolted cylinder/ head assemblies in the Lycoming which are basically cantilevered out in space, leading to large ringing assemblies and high vibration. The cylinders are under compression due to the fastener placement rather than tension as on the air cooled design.
The 4 valve OHC heads outflow the Lyco heads because they have more valve area per unit displacement, resulting in higher fill ratios and higher VE. The OHC valvetrain has lower mass and can therefore use lower rate springs for less friction. The cam design, metallurgy and oiling with modern lightweight synthetic oils (Mobil 1 0W20 and 5W50 now) ensures that cam corrosion and wear is never an issue.
The liquid cooled design with stiff, lightweight, small diameter parts permits very close fits of shafts and pistons, resulting in lower wear during warmup cycles, lower deflections and lower stresses during operation than the wide fits required with air cooled engines. Thinner rings with lower static tension fitted to low friction piston designs reduce ring mass, land wear and ring flutter. Tight piston and ring fits reduce gas leakage and crankcase contamination. Far lower oil consumption and longer oil change intervals are the result especially with full synthetic oils. Moly or cermamic faced rings, low expansion rate alloy piston materials, sintered rod materials, nodular iron crankshafts, modern bearing materials, CFD head development and CAVA- these are all advances commonly employed in modern auto engines. The QC and tolerances on the Japanese engines are also impressive. Less than 5 grams on reciprocating parts and bearing/ piston fits with A,B, C, D selections down to .0002 typically, OE.
Being liquid cooled, the Subaru can keep all aluminum parts below temperatures which diminish strength and cause fatigue failures like often happen on air cooled heads. (aluminum loses half its strength at 400F) Since the majority of wear on all engines occurs during cold start and warmup, the liquid cooled engine with tight tolerances and thin multigrade synthetic oils has a huge advantage in wear rates.
This is not to say that the Lyco does not have advantages over liquid cooled engines. There is no perfect engine. The EJ25 Subaru at 175 hp is competitive in weight with an O-360. With the MT prop, it is a few pounds heavier, with the Sensenich carbon prop a few pounds lighter. Analysis includes redrive (M-200), rads, coolant, extra mount weight, backup battery, hoses. The lyco was fitted with typical Hartzell C/S prop and baffling. It was a wash on starters, alternators and exhaust systems for both engines as lightweight versions are readily available for the Lyco. The Lyco is lighter in both cases when fitted with the MT prop. The simplicity of the air cooled engine cannot be disputed for aircraft use but is is hardly state of the art design. The Lyco might be superior in some ways but not in every department.
The Sube uses a low pressure diecast crank case. Pressure die castings have higher strenth, lower porosity and better heat dissipation than sand castings.
As per modern race engine design, the head bolt fasteners are threaded into the crankcase near the base of the main bearings webs. The cylinders are integrated into the block. This is far stronger and stiffer than base bolted cylinder/ head assemblies in the Lycoming which are basically cantilevered out in space, leading to large ringing assemblies and high vibration. The cylinders are under compression due to the fastener placement rather than tension as on the air cooled design.
The 4 valve OHC heads outflow the Lyco heads because they have more valve area per unit displacement, resulting in higher fill ratios and higher VE. The OHC valvetrain has lower mass and can therefore use lower rate springs for less friction. The cam design, metallurgy and oiling with modern lightweight synthetic oils (Mobil 1 0W20 and 5W50 now) ensures that cam corrosion and wear is never an issue.
The liquid cooled design with stiff, lightweight, small diameter parts permits very close fits of shafts and pistons, resulting in lower wear during warmup cycles, lower deflections and lower stresses during operation than the wide fits required with air cooled engines. Thinner rings with lower static tension fitted to low friction piston designs reduce ring mass, land wear and ring flutter. Tight piston and ring fits reduce gas leakage and crankcase contamination. Far lower oil consumption and longer oil change intervals are the result especially with full synthetic oils. Moly or cermamic faced rings, low expansion rate alloy piston materials, sintered rod materials, nodular iron crankshafts, modern bearing materials, CFD head development and CAVA- these are all advances commonly employed in modern auto engines. The QC and tolerances on the Japanese engines are also impressive. Less than 5 grams on reciprocating parts and bearing/ piston fits with A,B, C, D selections down to .0002 typically, OE.
Being liquid cooled, the Subaru can keep all aluminum parts below temperatures which diminish strength and cause fatigue failures like often happen on air cooled heads. (aluminum loses half its strength at 400F) Since the majority of wear on all engines occurs during cold start and warmup, the liquid cooled engine with tight tolerances and thin multigrade synthetic oils has a huge advantage in wear rates.
This is not to say that the Lyco does not have advantages over liquid cooled engines. There is no perfect engine. The EJ25 Subaru at 175 hp is competitive in weight with an O-360. With the MT prop, it is a few pounds heavier, with the Sensenich carbon prop a few pounds lighter. Analysis includes redrive (M-200), rads, coolant, extra mount weight, backup battery, hoses. The lyco was fitted with typical Hartzell C/S prop and baffling. It was a wash on starters, alternators and exhaust systems for both engines as lightweight versions are readily available for the Lyco. The Lyco is lighter in both cases when fitted with the MT prop. The simplicity of the air cooled engine cannot be disputed for aircraft use but is is hardly state of the art design. The Lyco might be superior in some ways but not in every department.
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Now we're in areas that I don't know. I know this is possible with aftermarket systems.rv6ejguy said:If you can produce documented evidence that high rpm engines wear out sooner, please present it. I think you will find that this is simplistic reasoning without all facts considered. This goes hand in hand with the outdated notion that modern auto engines can't run at high rpm for sustained periods- utter nonsense. I've asked these people to back up their assertions countless times. None have to date.
Simplistic reasoning is all that's needed here. I'm not saying engines can't run a high rpms for a sustained amount of time, all I'm saying is that an engine running fast will wear out faster than an engine running slow (lugging aside wich I would believe to be an non issue in this application anyways).
Things like piston speed, bearing area, bearing journal surface speed, crank support and stiffness, block stiffness, temperature control, Valvetrain mass, cam ramp rates, fit tolerances, materials, hardness and lubrication have the greatest effects on wear rates. High speed liquid cooled engines are very intelligently designed and validated. To suggest otherwise implies that all the engineers that design these engines are fools. Unlikely.
The engineers that design them are not fools, and I never implied such. Engines are engineered for very specific applications. A 180hp, 12,000rpm engine does very well in a 380 lbs sport bike, but will do nothing in a 3,000 lbs car. At the same time, a 500hp V8 is not the optimal engine for a motorcycle (though I admit it can be fun at times
I know lots of Japanese sport bike engines which have many 10s of thousands of miles on them and have never been opened up. Harley's have historically not had stellar reliability and is a silly design by any modern standard of engineering. It works, has tradition and that noise that some people like but it is crude. The massive engine mounts are a vain attempt to make the bike rideable for a couple of hours.
10's of thousands of miles is nothing for a modern engine, and to brag that an engine has such is useless. Keep in mind that a bike might average 40mph over it's lifetime. At 50,000 miles, that's only 1250 hours. And please don't forget the countless times the valves have been adjusted in that time. And to correct you, Harleys have historically had stellar reliability outside of the AMF days of the lates 60's to early 80's. It is not uncommon for an HD v-twin to go over 100,000 miles and not be opened up, even for valve adjustments. Also, the 45 degree, common crankpin V-twin offers many advantages over other twin designs, despite it's oddfire design. And BTW, you obviously haven't ridden a modern V-Twin, as I've done numerous 8+ hours on mine and engine vibration was not a factor to my discomfort.
People out of the know put forth uninformed ideas about this topic regularly on here and other forums. One derided a popular 5 main bearing, 4 cylinder opposed, auto crank, forged, heat treated with rolled fillets and a demonstrated real world capability to handle nearly 1000hp to a 3 main bearing Lycoming crank which has shown to be prone to numerous failures at 1/5th of this hp level. Bigger is not always better. Small parts have lower mass and lower inertial. More main bearings means less deflection, less vibration, tighter possible clearances. More crank pin overlap makes for a stiffer, stronger, lighter crankshaft and this is proven in the ability to reliably deliver extreme power levels.
No arguments here. Small and light is better in my book to a certain degree.
EFI and rad hoses failing, hmm. those big auto companies must be dummies. I've owned 5 early-mid '80s Toyotas all with over 250,000 km (one with 450,000km) all but one had the original rad, hoses, injectors, pumps, ECU etc. There is over 1 million km. Pretty darn reliable.
Again, the engines are built for specific tasks. And I think you can agree with me that a popped radiator at 45mph on the ground is a lot different that it is at 15,000 ft going 180mph. Also, it sounds like you are claiming to have owned all 5 Toyotas from new - how else would you know that all of those parts are original? That aside, radiator hoses and radiators and all those other things fail all the time, regarldess of car. If you truely had all those cars for that long with all those original parts, then you've been blessed with a collection of freak vehicles.
No one in their right mind today would design a clean sheet engine with uneven firing intervals nor with 2 throws between main bearings (shared throw V8s an exception perhaps) as these designs are inferior in almost every way from a longevity, strength and vibration point of view.
I can't disagree with this statement, though it is still being done. I believe a number of inline 6 engines out there run more than 1 throw between mains, and I know that unshared V8's do as well. And that oddfire V10 that dodge builds seems to do pretty well...
The growing number of people fitting auto engines to experimental aircraft, not to mention Thielert auto based diesels for certified aircraft show that many value the smoothness, low maintenance and refinement of more modern designs.
The Ecotec looks like a great design and several people are planning to fit these to aircraft. With some producing over 1200hp with stock block and crank, these have the basic makings of a reliable 200-250hp powerplant for aircraft.
I love my Ectoec, and can't think of a better small car engine, but would have to see it proven in a aircraft application.
Not all programmable EFI systems need laptops. With SDS, I can adjust any parameter in less time than it takes to unscrew a float or jets to make adjustments to a carb without getting fuel on my hands. We can easily do 25-35 dyno pulls per hour with changes between each run with EFI. Can't do that with any carb, even Webers with external jet access.
The Toyotas were all bought from friends or had the complete service history available. One GTS Corolla, two Supras and two Celicas, all EFI cars. I could add another friend's Cressida with 425,000 km and my dad's Nissan truck 325,000 km and another Celica owned first by one brother then another and then finally bought by a Toyota dealer in Ottawa as a showpiece with over 600,000km on it. All have original injectors, pumps and ECUs in them.
As someone who's worked in the service and race industries for 28 years now on all types of cars- American, German, French, British, Italian, Japanese, Russian, my view is that the Japanese engineering is second to none. Their designs are generally reliable, easy to work on (a few exceptions come to mind) and logical. EFI is far more reliable than carbs as I've worked on all types and cooling systems are very reliable if any sort of maintenance is done on them like replacing hoses every decade or so. I think if you look at what Honda, Toyota, Nissan and Fuji have done in the last 30 years, it is very impressive. Forward thinking has taken them from nowhere to the top of the heap.
I guess the Harley vs. Japanese bike thing is like the Lycoming vs. auto engine thing. There are two distinct camps there neither side is likely to sway the other. My brother and friends have owned and raced many Japanese bikes and they have all been pillars of reliability. I have never seen them do any valve adjustments with bucket type valvetrains. No sideloads on the stems so almost no valve guide wear. I've ridden a Ninja 900 many years ago and sat on running Harley's. As an engine guy, there is no comparison in refinement between the two and you must be a tough lad to ride a V twin for 8 hours!
I support whatever turns your prop. Fly what you like and enjoy the experience. People fly and ride Harley's and love them. I don't see anything wrong with that. Hog Aero powered RV12, I can see err... hear it now!
As someone who's worked in the service and race industries for 28 years now on all types of cars- American, German, French, British, Italian, Japanese, Russian, my view is that the Japanese engineering is second to none. Their designs are generally reliable, easy to work on (a few exceptions come to mind) and logical. EFI is far more reliable than carbs as I've worked on all types and cooling systems are very reliable if any sort of maintenance is done on them like replacing hoses every decade or so. I think if you look at what Honda, Toyota, Nissan and Fuji have done in the last 30 years, it is very impressive. Forward thinking has taken them from nowhere to the top of the heap.
I guess the Harley vs. Japanese bike thing is like the Lycoming vs. auto engine thing. There are two distinct camps there neither side is likely to sway the other. My brother and friends have owned and raced many Japanese bikes and they have all been pillars of reliability. I have never seen them do any valve adjustments with bucket type valvetrains. No sideloads on the stems so almost no valve guide wear. I've ridden a Ninja 900 many years ago and sat on running Harley's. As an engine guy, there is no comparison in refinement between the two and you must be a tough lad to ride a V twin for 8 hours!
I support whatever turns your prop. Fly what you like and enjoy the experience. People fly and ride Harley's and love them. I don't see anything wrong with that. Hog Aero powered RV12, I can see err... hear it now!
I don't have nearly the experince you have in the service industry - I worked in a full-service garage for 6 years and only built a handful of engines in my life, mostly SBC with no more than 400hp or so. But being there, I have seen those water cooling and EFT parts failing on one vehicle or another pretty much daily. I would, however, in no way say that modern EFI water-cooled engines are unreliable, there's just more stuff to break. I am a fan of EFI in every way, but water-cooling I only like when needed.
And yes, the HD vs. Jap bike thing is one side or the other. I've grown to love a certain powerband that a short stroke I4 just can't deliver. The best motor I've ridden was one of the new 122hp BMW Boxers in the new R1200S - that was a trip! 1st gear wheelies with no fancy clutch work right off idle - almost as good as my buddies Buell.
Of course now you just gave me a huge bump in my pants about an HD powered airplane. I'll either have to seriously hop-up a big-inch Twin Cam or buy a lighter kit
And yes, the HD vs. Jap bike thing is one side or the other. I've grown to love a certain powerband that a short stroke I4 just can't deliver. The best motor I've ridden was one of the new 122hp BMW Boxers in the new R1200S - that was a trip! 1st gear wheelies with no fancy clutch work right off idle - almost as good as my buddies Buell.
Of course now you just gave me a huge bump in my pants about an HD powered airplane. I'll either have to seriously hop-up a big-inch Twin Cam or buy a lighter kit
xl1200r said:Of course now you just gave me a huge bump in my pants about an HD powered airplane. I'll either have to seriously hop-up a big-inch Twin Cam or buy a lighter kit
Alright, here is the alternative engine for RV12s: http://www.hog-air.com/hogindex.htm
pierre smith
Well Known Member
Yeah, right!
Of course now you just gave me a huge bump in my pants about an HD powered airplane. I'll either have to seriously hop-up a big-inch Twin Cam or buy a lighter kit[/QUOTE]
Two things come to mind here. XL, you might just want to read more posts before you start bashing high revving auto engines since this forum has an incredible number of very talented, intelligent engine men and Mechanical Engineers and this subject has been beaten to death....search the archives.
Secondly, if you ever install that shake-'n-bake WW1 Harley engine in any airplane, double the size of the called-for rivets and definitely add a BRS parachute! I have many, many miles on Harleys and Gold wings.....no comparison and still you see guys shelling out over $20,000 for a shaker Harley? No wonder they don't have an airplane!
'Nuff......
Of course now you just gave me a huge bump in my pants about an HD powered airplane. I'll either have to seriously hop-up a big-inch Twin Cam or buy a lighter kit
[/QUOTE]Two things come to mind here. XL, you might just want to read more posts before you start bashing high revving auto engines since this forum has an incredible number of very talented, intelligent engine men and Mechanical Engineers and this subject has been beaten to death....search the archives.
Secondly, if you ever install that shake-'n-bake WW1 Harley engine in any airplane, double the size of the called-for rivets and definitely add a BRS parachute!
I have many, many miles on Harleys and Gold wings.....no comparison and still you see guys shelling out over $20,000 for a shaker Harley? No wonder they don't have an airplane! 'Nuff......
Walter Atkinson
Well Known Member
To Mike Parker:
In your post you referenced high temps from running too lean. Lean mixtures do not run hotter, they run cooler--meaning Lean of Peak mixtures. I think you were refering to rich of peak mixtures that are not rich enough, right?
The mixture that results in the highest CHT is about 40dF ROP. The mixture that results in the hottest-running exhaust valve tempertaure is 25dF ROP. Both are RICH mixtures. In those contexts, if you mean "too lean" as in "not rich enough," then we agree.
In general, auto engines aren't set up to run LOP--although that is changing. In general, they are set up to run at peak, not because they can't run LOP, but because the driving operational issue is emissions, not efficiency or temperature since they are liquid cooled.
Walter
In your post you referenced high temps from running too lean. Lean mixtures do not run hotter, they run cooler--meaning Lean of Peak mixtures. I think you were refering to rich of peak mixtures that are not rich enough, right?
The mixture that results in the highest CHT is about 40dF ROP. The mixture that results in the hottest-running exhaust valve tempertaure is 25dF ROP. Both are RICH mixtures. In those contexts, if you mean "too lean" as in "not rich enough," then we agree.
In general, auto engines aren't set up to run LOP--although that is changing. In general, they are set up to run at peak, not because they can't run LOP, but because the driving operational issue is emissions, not efficiency or temperature since they are liquid cooled.
Walter
pierre smith said:Two things come to mind here. XL, you might just want to read more posts before you start bashing high revving auto engines since this forum has an incredible number of very talented, intelligent engine men and Mechanical Engineers and this subject has been beaten to death....search the archives.
Secondly, if you ever install that shake-'n-bake WW1 Harley engine in any airplane, double the size of the called-for rivets and definitely add a BRS parachute!
'Nuff......
I'm not really bashing anybody. I know it's been done and worked with good results, and I'm perfectly aware of the talent that exists in the EA world. That aside, I'm allowed to have my opinion, regardless of how far off anyone might see it as being. Even driving the car or bike, I like to keep the revs low - the engine just seems happier there (not saying I don't wring them out here and there
). Personally, I've read a bit about these auto-conversions (not just for RVs mind you, and not as much as I guess should have read), but I'm still not 100% convinced that they're the way to go.Second, a new HD engine is hardly WWI technology, and calling it such is being ignorant. I can see the vibration being an issue, but they do smooth out once you hit a sweet spot in the rev range. And isn't vibration one of the many concerns with the Lycs anyways? Are people using rivets that are half the size of spec when using a Rotary or Subaru?
I'd check yourself on the price of HD touring bike. Yes, you can spend over $20,000 for an EG Ultra Classic, but you don't have to get the Ultra. And a new Goldwing actually costs a hair more than a comparable HD.
I'll let you guys battle this out now and I'll try to absorb as much as I can.
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xl1200r said:
We don't worry about lock wiring very much with the Subaru. They are certainly much smoother than a Lyco.
Walter's comment about EGTs and mixture are correct. LOP results in lower EGTs of course and we really don't worry about overheating exhaust valves with todays materials or sodium filled valves. Very durable indeed.
Since about 2004, most cars are now fitted with wideband O2 sensors and cruise at targeted AFRs much leaner than stoichiometric. This possible with computer modelling of the airflow within the port, chamber and the combustion process itself plus the advent of more effective catalysts to keep emissions at the mandated levels. Combined with high CRs and fully optimized timing of the spark and valves, the results are impressive SFCs (.35-.38) under cruise.
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Walter,
Very good point. You are using exhaust temps to define rich vs lean- probably for setting manual mixture adjustments. Im looking at the actual air fuel ratios for tuning fuel injection parameters.
Finding the ideal mixture for conditions is a compromise, is it not- looking for the best economy and power setting w/o overheating valves? Head temps rise as the mixture ratio goes higher (gets leaner w/ more air), up to the point where further leaning causes the engine to run roughly, and lose HP due to fuel starvation, until it eventually stops. Richer mixtures run cooler in the combustion chamber, and waste some fuel in the process.
Head temps and Exhaust temps are not the same. I believe the reason exhaust temps are higher with richer mixtures is because some combustion is occurring in your exhaust manifold and pipes (converting then into a secondary combuston chamber of sorts), while it cools your cylinder heads and intake manifolds. IMHO, Head temps (actually exhaust valve temps) is the item you should monitor and control if possible. IMHO, EGT's involve approximations of what is occuring, and slower to react to changes- possibly notifying you that detonation damage has already occurred in extreme situations.
My reference point (actual F/A mixture) is a little harder to nail down because the ideal ratio varies with power output, full power operation requires a bit more fuel to avoid overheating than light loading does. We need a wide-band oxygen sensor to measure the A/F ratio accurately; lead in avgas tends to contaminate oxygen sensor coatings.
The ideal mixture is probably one that supports best power without overheating. The ideal stochiometric mixture of gas and oxygen, where the hydrocarbons burn completely, is generally close to 14.5:1 at sea level. That ideal mixture is considered lean, because it is too lean to safely support full power levels, but it is a reasonable target for economy operations under low-load conditions. In most reciprocating engines, 13:1 is a safe all-purpose mixture, ~12:1 is a good full-power target mix, particularly under boost, to limit detonation.
The reason the Wankel can run lean under higher power levels is believed to involve stratification of the intake charge- the mixture becomes richer near the spark plugs, which ignites easily, and fires the harder-to-ignite lean mixtures in the rest of the chamber. The stratification likely occurs becuse of increasing centrifugal forces as the rotor (and combustion chamber) spin faster. It is not something that one could take advantage of during automobile operations, because of the lower engine speeds involved, but it is likely a favorable factor to economical aircraft operations.
Very good point. You are using exhaust temps to define rich vs lean- probably for setting manual mixture adjustments. Im looking at the actual air fuel ratios for tuning fuel injection parameters.
Finding the ideal mixture for conditions is a compromise, is it not- looking for the best economy and power setting w/o overheating valves? Head temps rise as the mixture ratio goes higher (gets leaner w/ more air), up to the point where further leaning causes the engine to run roughly, and lose HP due to fuel starvation, until it eventually stops. Richer mixtures run cooler in the combustion chamber, and waste some fuel in the process.
Head temps and Exhaust temps are not the same. I believe the reason exhaust temps are higher with richer mixtures is because some combustion is occurring in your exhaust manifold and pipes (converting then into a secondary combuston chamber of sorts), while it cools your cylinder heads and intake manifolds. IMHO, Head temps (actually exhaust valve temps) is the item you should monitor and control if possible. IMHO, EGT's involve approximations of what is occuring, and slower to react to changes- possibly notifying you that detonation damage has already occurred in extreme situations.
My reference point (actual F/A mixture) is a little harder to nail down because the ideal ratio varies with power output, full power operation requires a bit more fuel to avoid overheating than light loading does. We need a wide-band oxygen sensor to measure the A/F ratio accurately; lead in avgas tends to contaminate oxygen sensor coatings.
The ideal mixture is probably one that supports best power without overheating. The ideal stochiometric mixture of gas and oxygen, where the hydrocarbons burn completely, is generally close to 14.5:1 at sea level. That ideal mixture is considered lean, because it is too lean to safely support full power levels, but it is a reasonable target for economy operations under low-load conditions. In most reciprocating engines, 13:1 is a safe all-purpose mixture, ~12:1 is a good full-power target mix, particularly under boost, to limit detonation.
The reason the Wankel can run lean under higher power levels is believed to involve stratification of the intake charge- the mixture becomes richer near the spark plugs, which ignites easily, and fires the harder-to-ignite lean mixtures in the rest of the chamber. The stratification likely occurs becuse of increasing centrifugal forces as the rotor (and combustion chamber) spin faster. It is not something that one could take advantage of during automobile operations, because of the lower engine speeds involved, but it is likely a favorable factor to economical aircraft operations.
Stoichiometry occurs at peak EGT and about 14.7 to 1 AFR with typical gasolines. One either side of stoich, the EGT cools.
Exhaust valve temperatures are not a concern these days as the typical stainless or Nimonic type alloys(or sodium filled types) can easily operate at 1800F continuously. High EGTs are a concern in air cooled engines as most waste heat is lost in the exhaust port area and the rate of heat transfer to the fins is relatively low compared to liquid cooled engines. The heat flux and material distortion in this area is the achilles of air cooled powerplants.
With any sort of reasonable spark timing, combustion is complete well before the exhaust valve opens.
Best power in dyno testing is in the low 13 to 1 AFR range and we find little difference between turbo and atmo engines in this respect. Best economy occurs at different AFRs in different engine types and to a large degree is determined by the combustion chamber design and the homogeny of the mixture and distribution between cylinders plus spark plug location. The AFR range for best economy is between about 15.5 to as much as 22 to 1 depending on the design.
With equal airflow and mixture distribution, shake is reduced and generally leaner AFRs can be run than with engines having poor mixture distribution.
With turbo compounding, studies on piston engines shows something like 12% TE gains are possible theoretically with complex designs. In practical use, this has been limited to under 10%. With Wankels and their lower thermal efficiency and high EGTs, more potential energy is available at the turbine so gains could likely be higher. I doubt if this could ever exceed 15% however practically. I think CAT is actively pursuing this technology for diesels where the gains would be lower due the diesels higher TE and lower EGTs. Assuming the PRTs (power recovery turbines) can be made reliable and lightweight, it is an intriguing idea with useful fuel savings. On the Wright 3350s the engineers and mechanics called them parts recovery traps however.
Exhaust valve temperatures are not a concern these days as the typical stainless or Nimonic type alloys(or sodium filled types) can easily operate at 1800F continuously. High EGTs are a concern in air cooled engines as most waste heat is lost in the exhaust port area and the rate of heat transfer to the fins is relatively low compared to liquid cooled engines. The heat flux and material distortion in this area is the achilles of air cooled powerplants.
With any sort of reasonable spark timing, combustion is complete well before the exhaust valve opens.
Best power in dyno testing is in the low 13 to 1 AFR range and we find little difference between turbo and atmo engines in this respect. Best economy occurs at different AFRs in different engine types and to a large degree is determined by the combustion chamber design and the homogeny of the mixture and distribution between cylinders plus spark plug location. The AFR range for best economy is between about 15.5 to as much as 22 to 1 depending on the design.
With equal airflow and mixture distribution, shake is reduced and generally leaner AFRs can be run than with engines having poor mixture distribution.
With turbo compounding, studies on piston engines shows something like 12% TE gains are possible theoretically with complex designs. In practical use, this has been limited to under 10%. With Wankels and their lower thermal efficiency and high EGTs, more potential energy is available at the turbine so gains could likely be higher. I doubt if this could ever exceed 15% however practically. I think CAT is actively pursuing this technology for diesels where the gains would be lower due the diesels higher TE and lower EGTs. Assuming the PRTs (power recovery turbines) can be made reliable and lightweight, it is an intriguing idea with useful fuel savings. On the Wright 3350s the engineers and mechanics called them parts recovery traps however.
BSFCs?
Ross,
I don't know where you're getting your BSFC data, but there is no way a automotive gasoline engine would ever do 0.35lb/hph (212g/kWh) at full load, leave alone part load cruise.
Running at stoich or at best power, a gasoline engine will be lucky to be better than 0.43/261 at any point on the WOT curve. It will only get worse than this as load is reduced.
You will need a diesel engine to achieve anything less than 0.35/212 and some will do nearer 0.325/197 at optimal speeds.
I would be surprised if a homogeneous lean-burn engine would achieve better than 0.41/250 at any point and a stratified charge GDI engine will likely be no better.
FWIW, this data is from my decade and a half of developing and calibrating gasoline engines, so whilst it's from memory, it's not too far from reality.
Andrew
Ross,
I don't know where you're getting your BSFC data, but there is no way a automotive gasoline engine would ever do 0.35lb/hph (212g/kWh) at full load, leave alone part load cruise.
Running at stoich or at best power, a gasoline engine will be lucky to be better than 0.43/261 at any point on the WOT curve. It will only get worse than this as load is reduced.
You will need a diesel engine to achieve anything less than 0.35/212 and some will do nearer 0.325/197 at optimal speeds.
I would be surprised if a homogeneous lean-burn engine would achieve better than 0.41/250 at any point and a stratified charge GDI engine will likely be no better.
FWIW, this data is from my decade and a half of developing and calibrating gasoline engines, so whilst it's from memory, it's not too far from reality.
Andrew
As just one data point with conventional port injection and nearly decade old technology now, the GM LS-6 engines used in the Robinson conversions is achieving .375 in cruise at 3300 rpm/ 24 inches in closed loop according the the numbers published in the Recreational Flyer magazine (May-June 2004).
The Continental IO-550s with crude Bendix type injection and modest CRs achieves similar SFCs as did the turbo compound R3350 50 years ago.
2007 BMWs fitted with widebands, 11.25 CRs, Valvetronic (no throttle plate) and SGDI are reporting 10-15% decreases in fuel consumption over their 2005 models which was already top of the pile. Users in Europe have reported similar mileage to 5-10 year old diesel models.
There has been a lot of progress on this front in the last 3 years.
The Continental IO-550s with crude Bendix type injection and modest CRs achieves similar SFCs as did the turbo compound R3350 50 years ago.
2007 BMWs fitted with widebands, 11.25 CRs, Valvetronic (no throttle plate) and SGDI are reporting 10-15% decreases in fuel consumption over their 2005 models which was already top of the pile. Users in Europe have reported similar mileage to 5-10 year old diesel models.
There has been a lot of progress on this front in the last 3 years.
rv6ejguy,
Sodium filled valves tend to be bulky and very expensive- seen occasionally, but "commonly found" might be a bit optimistic outside of racing circles. Are they even available for Lycs, Subaru's, etc., we are discussing here?
From your F/A notes targeting 13:1 ratios in boosted operations, I'm curious if you run only 100LL in your turbocharged engine? The turbo guys I know prefer a little wider margin-of-safety running turbos on mogas, particularly given subtile differences in pump gas quality. 100 octane would provide an excellent safety buffer.
Regarding turbocompounding, the process was hard on exhaust valves in the reciprocating engine trials (source of parts bin comments?) - My understanding is that the achievements reported were based on downgraded (limited) output levels and not optimised. Removing exhaust valves from the equsion eliminates a major limiting obstacle.
The 35% efficiency estimate I referenced came from Paul Lemar who has recently completed a prototype system for his rotary engine and has posted data on his website at http://www.rotaryeng.net/turbo.html ; the next step involves obtaining dyno data to provide credible comparions.
Sodium filled valves tend to be bulky and very expensive- seen occasionally, but "commonly found" might be a bit optimistic outside of racing circles. Are they even available for Lycs, Subaru's, etc., we are discussing here?
From your F/A notes targeting 13:1 ratios in boosted operations, I'm curious if you run only 100LL in your turbocharged engine? The turbo guys I know prefer a little wider margin-of-safety running turbos on mogas, particularly given subtile differences in pump gas quality. 100 octane would provide an excellent safety buffer.
Regarding turbocompounding, the process was hard on exhaust valves in the reciprocating engine trials (source of parts bin comments?) - My understanding is that the achievements reported were based on downgraded (limited) output levels and not optimised. Removing exhaust valves from the equsion eliminates a major limiting obstacle.
The 35% efficiency estimate I referenced came from Paul Lemar who has recently completed a prototype system for his rotary engine and has posted data on his website at http://www.rotaryeng.net/turbo.html ; the next step involves obtaining dyno data to provide credible comparions.
