Lycoming Superiority

[cobra]

Ron,
I disagree with your comments that the Chevy small block has not changed in 50 years- imho, it is an excellent example of how modern technology has continually improved old technology. The current crop of rice burners is probably an even better example, as they are getting huge HP out of small displacement, efficient engines. Chevy is getting 2-3 times the power and far better economy than they did in the 50-60s.

George,
If anything, lawyers and govt regulations/costs involved with certification have impeded Lycoming's potential growth over the years. The Lyc is a good engine design built for a specific purpose- it has its good and bad points; superior- probably not, but it will always be the easiest and the best choice for most builders and will remain the industry's standard for a long time to come.

FWIW, bulletproof should be a measure of reliability- in engineering terms, a design that has eliminated potential failure points, but as you said, the fewer parts the better. Historically, the most problematic failure point has involved pilot error/fuel problems far more then mechanical things, like valves, drivetrain (pistons, rods, crankshafts), and electrical problems. Some are generally catostrophic, some less so.

Regarding your comment regarding rotaries, FOD will bring down any engine; the rotary is probably less suseptable than other designs, imho, simply because of its simplicity, part robustness, and lack of valves. The downside of the rotary involves overheating, particularly the involving high oil temps, which can damage seals and reduce compression; seldom is it catastrophic as long as the engine is not shut down (wont restart). Rotaries work fine with either carburation or fuel injection, some folks have also used magneto ignition- conventional electronic parts have proven safe and far cheaper, redundant electronics in critical systems are preferred obviously.

 

[Mike S]

Regarding your comment regarding rotaries, FOD will bring down any engine; the rotary is probably less suseptable than other designs, imho, simply because of its simplicity, part robustness, and lack of valves.

As in all things, this also depends on specifics. The lack of valves----poppet style----in a rotory is one of the main reasons for FOD issues.

In a conventional engine, the valve spring allows the valve to be held open by a foreign object, a rotary will try to sheer anything that gets in there. And unless the foreign object is really soft, there is going to be damage to the rotor, seal, or housing.

A major problem for early generation rotories was carbon chunks comming loose, and getting caught in a port. Even something as soft as carbon was often enough to cause damage requiring a rebuld.

Just FYI.

Mike

 

[cobra]

MikeS,
Fair enough, point taken and noted.

I just have a hard time imagining how something big enough to cause a problem can get thru an air filter, but it could be an issue through an unfilered ram-air scoop. The "carbon chunk" is more a non-aviation issue these days- most av guys remove the rotor injector pump/injectors and instead mix 2-cycle oil with fuel for lubrication of rotors- 2-cycle oil burns clean (unlike oil pumped from crankcase). BTW, that gunk build up is what causes most of the reported apex seal problems/ forced a rebuild- not wear or part failure.

I was thinking more of the problem resulting from valve failures, where the valve head is the part that destroys pistons/heads catastrophically in overheated air-cooled engines, for whatever reason (valve head separates from the valve stem, lube failure, timing gear/belt problem, etc). Not real common, but it happenes more often that it should. I still think ports are safer than valves when it comes to potential points-of-failure (broken parts, premature head wear, camshafts).

I believe George was referring to an engine stoppage reported a few years back, caused by a loose pin from a botched intake manifold modification- it seized the engine.

 

[N62XS]

Unobtanium?

Not to change the subject, but I can't find any Unobtanium on the Periodic Table. Roswell? Area 51? Is it mined in Outer Slongvolia?

CaptainRon proved that all leading edges should at least be made of an alloy containing unobtanium to minimize the damage with falling aliens(outer space, not illegal...I guess they would be illegal, too). I bet it would take a titanium bucking bar to buck a unobtanium rivet.

All jest aside, I'm with Ron and George. I don't like reinventing that wheel. Just make it run on water or air and everybody would be complaining about that, too.

BTW: Ever notice you don't see much roadkill on a drag strip. Wonder why?

 

[xl1200r]

BTW: Ever notice you don't see much roadkill on a drag strip. Wonder why?

Probably because there's so much fumes that anything that brethes faster than a human would pass out within a 1/2 mile from the strip

I kept myself quiet about the SBC in this thread, but now that someone else brought it up I feel I can add a few points.

The original SBC is no longer used in production auto engines - they have been completely moved to aftermarket applications (or OE replacements). The new Gen IV engines are quite a bit different being all aluminum and such, but the basic design is the same as it was in 1955.

Also, the new Malibu doesn't utilize any engine based off the old SBC that I'm aware of. The V6 that was based off the SBC was the 4.3 liter, which is still used in the trucks today as far as I'm aware. The Malibu would use V6's based off the 2.8 liter which was first introduced in the late 1970's. Some of the larger cars, however, still use the 3.8L V6, which was first developed by Buick in the 1950's, sold to Jeep shortly after, and then bought back and has proven to be one of the most reliable automotive engines to date (though it is showing it's age by now as far as performance goes - supercharging has helped a good deal).

The bottom line is the Lyc is not the only example of an old engine design living a long life - the reference to the early Rotaries was a good example. And as someone else stated before, the recip internal combustion engine really hasn't changed too much for nearly a century. Some changes stick (like electronics, water-cooling, and OHC), and some don't (like a rare bird that used shaft-driven OHC).

That all said, I also think that someone could really do better than the current Lyc - maybe not a whole new deisgn principle, but a fresh start. I hark back to the SBC: For a long time there were many who believed there was NOTHING better. But then the LS1, LS2 and LS7 (and the other varients) made it to market. Again, nothing really "new" in there, but they blew away the competition, including their predessesors.

And don't poke fun a "water-fueled" engine. Say what you'd like, but I'm working on such a thing as we speak.

But yes, people will still complain

 

[captainron]

Who's complaining

We've asked the engine builders to come up with something different, and if I remember a couple of the posts here, one company changed their crankshaft throw by 1/8 inch, and it caused some consternation because it was no longer an exact copy of what is already is out there! Who can win?

 

[captainron]

BTW: Ever notice you don't see much roadkill on a drag strip. Wonder why?

Because you can make methanol from the carcass? "Total Critter Method"?

 

[rv6ejguy]

The LS engines are like the old SBC only in one way- they are both V8 engines. Almost every other part is different. Out of the box, the LS engines are WAY better than the SBC in almost every way. This is one of the best engine designs to come out of any OE in the last 15 years.

Despite the fact that many here say there is no new technology on engines today- this is just wrong and if people bothered to be informed they would know that. Would this technology have a place in direct drive aircraft applications? Some parts and processes could be applied but many are suited more to high speed applications so it is likley you won't see them in a Lyco soon.

 

[xl1200r]

The LS engines are like the old SBC only in one way- they are both V8 engines. Almost every other part is different. Out of the box, the LS engines are WAY better than the SBC in almost every way. This is one of the best engine designs to come out of any OE in the last 15 years.

I was basing this off of the fact that the Gen IV engines are not only V8's, they are also 90 degree V8 with overhead valves, etc. It's no secret that they don't share any parts in common with the Gen I V8's, but if you take out a set of blueprints for each, you'll see that they share a lot in common design-wise. I think you's find that if you took certain materials out of the equation (i.e. composite intake manifolds, electronics etc.), there would be no real reason why a Gen IV V8 coudln't have been concieved in 50's.

 

[Mike S]

Dont confuse design with executation

The LS engines are like the old SBC only in one way- they are both V8 engines. Almost every other part is different.

First off, the LS series is a SBC--------small block chevy.

Second, the design is still a 90 degree v, pushrod, paired rod crank pin, offset cylinder, cross flow heads, bore/stroke ratio, rod/stroke ratio, ETC ETC is either totaly unchanged, or very little so. Lifters are still lifters, roler or not. ETC.

Your comment about different parts is accurate, but the overall design is quite similar. The executation of that design is where most of the changes have occured.

But arn't we supposed to be discussing the merrits of a Lyc??

Mike

 

[cobra]

The LS engines are very well designed- too bad you have to order a GM car along with them . I particularly like their design with the 4-bolt caps over the crankshaft bearings.

I'm also impressed with the Modular motor that Ford is making these days, particularly the DOHC Cobra version- I believe it is an improvement over the older 5.0L engine Im currently driving (95Cobra, intercooled Incon twin turbos @ 450hp/500 torque). Gotta love that low-end torque!!!

 

[captainron]

The original SBC is no longer used in production auto engines -... The new Gen IV engines are quite a bit different being all aluminum and such, but the basic design is the same as it was in 1955....
The bottom line is the Lyc is not the only example of an old engine design living a long life -...
That all said, I also think that someone could really do better than the current Lyc - maybe not a whole new deisgn principle, but a fresh start. I hark back to the SBC:... LS1, LS2 and LS7 (and the other varients) made it to market. Again, nothing really "new" in there, but they blew away the competition, including their predessesors.

And don't poke fun a "water-fueled" engine. Say what you'd like, but I'm working on such a thing as we speak.

But yes, people will still complain

Well.... Both the obsolete Chevy and the obsolete Lycoming have both gone to roller cam-followers, but as you say, nothing really "new" in there.

Hmmm... now I'm confused. Have I made my point or have I disputed it? Is it really hard to improve upon a great original design? Chevy has made some really great stuff- the stuff of legends, in fact. They've also made some real junk, as can be seen in any scrapyard, or broken-down along the side of the highway.
Lycoming has had their problems- the infamous "H" engine comes to mind. But Lycoming, who never has and never will, have the resources of a General Motors behind them has been turning out a great product that people have staked their lives on for decades.
If you really think that Subaru or Mazda worries about the filet radius in their engine shafts, hardfacing thicknesses left after running at high power settings for thousands of hours, or what the effects of having a propeller hung on the drive end of their engines will have on your lifespan, you are only kidding yourself.

I like the idea of a water-fueled engine, but unless I'm wrong about this too, there ain't no BTU's in water.

BTW, looking at your username, I would think you're a fan of some really antiquated engine designs.....too! (FXSTS)

 

[xl1200r]

I like the idea of a water-fueled engine, but unless I'm wrong about this too, there ain't no BTU's in water.

BTW, looking at your username, I would think you're a fan of some really antiquated engine designs.....too! (FXSTS)

Ahh, a fellow bretheren. Yes, antiquated for sure!

There may not be any BTU's in water, but there's BTU's in hydrogen - and please don't start harping on me about the dream of the hydrogen economy. The bottom line is water will split at 2500 degees Celcius, and will just as easily burn right away. Look at the dragster analysis - the exhaust was hot enough to seperate and burn the hydrogen in the moisture in the air. My engine works on this pricinple, though I will not let any other details out

And GM was putting roller-lifters in thier small blocks since 1984 - possibly earlier - , and roller rockers since 1986 - possibly earlier.

out of curiousity, when did Lyc start using them?

 

[captainron]

please don't start harping on me about the dream of the hydrogen economy.
And GM was putting roller-lifters in thier small blocks since 1984 - possibly earlier - , and roller rockers since 1986 - possibly earlier.

out of curiousity, when did Lyc start using them?

I won't and can't harp on anyone who wants to help find new energy alternatives,....unless you bring up the "Fish" carburetor!
But there is only so much you can do with an airplane with an empty weight of 1050 pounds, or so. As you know, car manufacturers went to roller cam followers to reach CAFE requirements, which meant low viscosity oils among other things. Sure wasn't done because they wanted to make a better product, in my opinion.
I don't know when Lycoming went with them, but I'm disappointed that they can't take advantage of lighter weight oils which would improve fuel economy.
I hope you are sucessful with the Hydrogen project and get rich!

 

[rv6ejguy]

Sorry, have to disagree with you both here on the LS engines. You might want to read the SAE release paper on this by GM powertrain. Every aspect of the old SBC Chev was evaluated to see if it could be improved on. Completely new ways of making some of the parts like sintered/ cracked rods not to mention different oiling system, improved valvetrain limits, cooling, block design, crank design, windage studies, chambers, ports, NVH, emissions target etc.

Yep. 90 degree V8 but an all new design.

Interestingly, when TAC asked a well known aircraft engine dyno operator if he saw any improvement in hp with roller cams fitted he said "nope". Not all new technology will have a place in Lycos.

 

[Walter Atkinson]

**Well if the engine needs fuel to cool itself it ought to be factored into BSFC. Lycoming procedure calls for full rich up to 5000' or at more than 75% power. That sort of blows a BSFC (min) number out of the water. If the full rich BSFC were factored into the total flight efficiency of the engine, it would be close to .435 not .390. **

Nope. The BSFC(min) is how the efficiency of the engine is rated--period. That occurs at approximately 40dF LOP where it will run nice and cool.

**Fuel distribution is so uneven with these engines, I don't see how a LOP procedure can work. Two cylinders might be just fine while the other 2 are starved of fuel (or too rich). In theory it might work, but not in the real world. Is LOP even recommended by Lycoming? **

Well, there an awful lot of them running LOP with great success... as long as they have balance F:A ratios... which they don't come that way from the factory... so GAMIjectors were born to solve the problem.

A full rich BSFC, SHOULD be in the .68-.70 range an all of these engines. OPTIMAL cruise BSFC as designed by the engineers is as I have stated... about .39 on the NA enignes, and about .42-.43 on the TC'd models. Those numbers are atained at about 40dF LOP.

 

[captainron]

Yep. 90 degree V8 but an all new design.

Gosh, can it have anything in common with the "old" 90 degree V8 after 51 years?

Is it still a lightweight, cast design?
Does it still have staggered cylinder banks?
Does the block still end at the crankshaft centerline?
Is the camshaft still located in the block?
Is the cam still driven off the crankshaft?
Is the cam still driven at one half the crankshaft RPM?
Does it still have a pushrod operated valve system?
Is it still a four-stroke, Otto-cycle type engine?
Does it still consume gasoline as a fuel?
If so, does it still use a fuel-air ratio of about 15-1 by weight?
Is the fuel mixture still ignited by electrical spark from some kind of plug?
Is it still liquid cooled?
Do two connecting rods still share each crankpin?
Does the all new engine still have five main bearings?
Is it still a wet-sump oil system?
Are the main engine bearings still plain, sleeve type, pressure lubricated?
Does it still have two valves per cylinder?
Is the combustion chamber located completely in the heads?
Do the heads still bolt onto the block?
Does the intake manifold still cover and seal the top of the block?
Have we gotten past the old, friction causing piston-ring problem?
Is the oil pump still driven off the camshaft?
Would Zora Duntov recognize any part from this engine were he alive today?
Are its accessories still belt driven?
Is it still an upright "V" configuration with the crank on the bottom?
is the firing order still 1-8-4-3-6-5-7-2?
Is it still painted Chevrolet Orange?

 

[rv6ejguy]

New design means none of the parts are compatible.

GM set out to reduce weight, increase power, decrease emissions and reduce NVH. They did this with a clean sheet design and accomplished every goal. A design and testing synopsis was generously published by Jim Contes from the GM Powertrain Group in 2000 if you are really interested in what goes into a new automotive design these days.

The LS engines are possibly the best thing GM produces today. Crate engine sales may eventually exceed production engine sales in the Corvette as they are extremely popular today for off road use and engine swaps. LS2s and LS6s sell for $5200-$5500 (405hp).

I say there is a lesson to be learned from what the Japanese did to the domestic auto industry. Complacency in producing the same old thing because it was deemed good enough put the nail in the coffin. The Japanese produced better vehicles using newer technology, procedures and tools. Lyco and Conti are just responding now before there is a bigger threat which is smart business on their part. Thielert, ECI, Superior and Rotax are already taking some of their pie. If Honda or someone like that ever seriously comes into their market, they better hope they are partners. It is totally myopic to think that they can't do it better and cheaper.

Conti is back into the LSA market with their "new" O-200C to make sure Rotax has some competition. Actually lots of parts in this are new or at least new process.

 

[zav6a]

Progress

Maybe ECI and Superior pay attention to this thread. We ought to focus on what we could realistically hope for them to do if enough interest were expressed.

I'd say:

Better valve stem/guide cooling/lubrication so we can be relieved of the wobble test and reaming:

There ought to be something they could do to reduce cam corrosion/spalling -if in fact it is not really caused the above issue. If roller cams really accomplish this then great, I'll ask no more:

NO crank recalls. If this means a change in design to make it less critical, so be it. (not seeing any recalls from ECI and Superior)

It would be nice if they were to offer well designed baffles as as option that we could then just trim to height and length for our application:

All the improvements need to continue to be backward compatable and compatable across the various manufacturers so that we can continue to find and upgrade cheap old iron. Don't discount this point. If Lycoming were continually "updating" like Microsoft we would be outraged. Be careful what you ask for.

Cheaper - competition seems to be accomplishing that.

Once you get back down to reality, it is a pretty darned short list!

Duane Zavadil
IO-320, 6A

 

[Mike S]

Gentlemen, if you please.

There seems to be a major confusion about the word "Design".

Captain Ron is correct in listing the factors of design.

Rv 6 guy is talking about how that design is achieved.

Kind of like the difference between tactics, and strategy.

As I said before, design, and executation---------too different things.

If you want a different "Design", I submit the Crysler turbine car of the 60's, the Wankle from Mazda, the Stanley steamer, or any of the miserable failures in electric cars that have come and gone over the years.

Now, how about back to the thread topic---------Lyc.

Oh, by the way, the Design or a Lyc---------same as a Franklin, Continantal, Corvair, ETC. That is, they are All opposed, pushrod, aircooled gasoline fired internal combustion engines.

Mike

 

[rv6ejguy]

Well this thread is sure popular- top 5 of all time or something. Nothing ignites the passions more than engine discussions it seems. For the time being, I'll concede that the Lyco (it would be a clone for me though) offers a decent mix of the right stuff for the RV mission and will continue to be the choice of the majority for a while to come yet. It is the most proven in aviation applications and the airframe is designed for it. Two really good reasons to choose one. So in that context, it is superior.

Based on my 28 years as a professional engine builder, tuner, racer and R&D (porting, flow bench, dyno, component design) guy, I find little in the design that is superior to modern auto engines however and more people agree with me on that every day as they choose alternatives. For those on the fence waiting for more data on TBO, reliability, cost and performance- continue to sit. In a couple more years there will be a much bigger database to evaluate and make an engine choice based on your wants and mission profile.

In the meantime enjoy (or force) your way through the construction process as the case may be. The flying experience in the aircraft that you built will be worth all the toil no matter what powers it.

 

[Stephen Lindberg]

This is a great thread and I have learned much. Many people on this list have in-depth knowledge acquired over a prolonged period of time and I'm glad you take the time to discuss these questions and help educate the rest of us. My question is this: Is the Lycoming/Continental design (large displacement, slow turning, direct drive, air cooled, opposed removable cylinders, etc.) still the model to use if one were to begin a clean sheet design, assuming an adequate budget? If not, which design parameters are best, and why? Considering power to weight, cost, ability to retrofit to existing airframe designs, adaptability to modern manufacturing techniques...where today should an engine designer begin? And, as an aside, who has the resources to actually do this? Would it be a prudent business decision even to begin? Not a bomb thrower, just wondering. Also wondering if a scaled up Rotax 4 stroke that puts out 150-200 hp is feasible. Just wondering...

 

[rv6ejguy]

Stephen,

I think if you ask all those questions, this thread will reproduce into Typhon (the mythical monster with 100 heads) and you'll get 100 more opinions.

I'm willing as long as people continue to find this interesting (seems like it from the views and responses) and Doug figures it fits into "The Rules". These threads do stray off topic sometimes.

Before we take this too far, maybe we should start a new thread- New Engine Ideas or Clean Sheet Superiority or something similar. I would like to see someone develop something new which would run on non-leaded fuel and cost no more than $15,000 in the 200hp class. Would the oil companies consider introducing an unleaded aviation fuel to replace 100LL? Most engines now are being fitted with hardened or Stellite valve seats anyway.

 

[G-force]

The problem with the idea of a "clean sheet" motor is it would be financial suicide to not make it backwards compatable, ie fit in all the airframes designed around a Lyco during the last 50 years. That right there pretty much throws a whole lot of limitations on a designer. Imagine if every Ford engine from 1920's to 1970's had to fit under the hood and between the frame rails of a Model T! Talk about a handicap to progress and design freedom. So if we are stuck with improving the opposing 4 or 6 cylinder...modern materials and techniques are where imporvement could be made. Case casting: are they sand cast? (I don't know) but I suspect they were when they were designed. With modern casting techniques, stricter quality control of the casting process and alloys, cases could be made stronger, faster, and cheaper, and require less final machining. Cranks: alloys, heat treating, and forging techniques have improved by leaps and bounds in 50 years. Using a crank of the same dimentions could be made twice as durable for similar cost. And if we are working off a clean sheet, put main bearings between all throws or pair up the rods. This would probaly allow case mods to stiffen up the bottom end as well. Throw in a gear driven counterbalancer too. Cylinders: Water cool them along with the heads. Nothing improves longevity,efficency, and emissions than being able to run tighter tolerances possable with a stable opperating temp. They could be cast as one piece per side or as part of the cases as is typical with all modern aluminum engines. Cylinders could either be lined with a process such as Nikasil or steel sleeves. Both are rebuildable, its under $175 per cylinder to be stripped, re-nikasil plated and diamond honed to final size. Steel cylinders can be bored and honed oversize as is typical with all auto and motorycle cylinders. The argument of "watepumps and radiators are too complicated" doesnt seem to hold water (pun intended!), its no different than the oil pump and externaly mounted cooler that has worked fine for cooling oil in Lycos for 50 years. Pistons: Same as cases, the materials and forging techniques have improved so much in 50 years, and with water cooled cylinders, tolerances are tighter from the get go. Heads: Same improvements in casting materials and techniques. 3D modeling, flow testing, and CNC chamber and port maching can make big improvements. Not to mention the sever duty one piece stainless and inconel valves available today and better valve seat and spring materials.
I guess my point is there are alot of ways to improve the Lyco design. Modern materials would give better service life and durability. Modern casting, forging, and machining techniques can produce higher quality parts that faster, that require less machining, and all held to a tighter size and weight tolerance. All this resulet in cheaper manufacturing costs, longer TBO, and more HP per cubic inch. I havent even touched on fuel injection, computer controlled ignition, etc. Lets face it, as much as Lyco purists like to fly the "simple is better" flag, not many aircraft seem to be leaving the assembly lines (or garages) with mags, carbs, steam gauges, and FP props. Everything else usualy adds possable modes of failure, more complicated wiring and plumbing, etc. But it is accepted for the added benifit. I predict water cooling, better balancing, better materials, more modern designs, etc will eventualy become as common and accepted as fuel injection, FADEC, and glass screens hooked to 40 sensors are today. Or I could be wrong

This is a great thread and I have learned much. Many people on this list have in-depth knowledge acquired over a prolonged period of time and I'm glad you take the time to discuss these questions and help educate the rest of us. My question is this: Is the Lycoming/Continental design (large displacement, slow turning, direct drive, air cooled, opposed removable cylinders, etc.) still the model to use if one were to begin a clean sheet design, assuming an adequate budget? If not, which design parameters are best, and why? Considering power to weight, cost, ability to retrofit to existing airframe designs, adaptability to modern manufacturing techniques...where today should an engine designer begin? And, as an aside, who has the resources to actually do this? Would it be a prudent business decision even to begin? Not a bomb thrower, just wondering. Also wondering if a scaled up Rotax 4 stroke that puts out 150-200 hp is feasible. Just wondering...

 

[gmcjetpilot]

BRP and Honda

Also wondering if a scaled up Rotax 4 stroke that puts out 150-200 hp is feasible. Just wondering...

To answer you question two BLANK sheet engines have been rumored to have come out in the last hand full of years, one was from Bombardier. The other was from a little company that you may have heard from, Honda.

Rotax is part of BRP which is a Bombardier company, or something like that. They have their fingers in Aerospace, Transportation and recreational vehicles. The engines are called V220 and a V300. There was lots of smoke about them in 2003 but nothing much since. The BIG water cooled jobs I recall where only going to be sold to OEM plane makers. I say big because they where 220 HP/418 lbs and 300 hp/495 lbs DRY! Think about the added wt from hoses, radiator and fluids. Too heavy and too much for RV's. Cost is going to be more than current engines by a large factor (recall $60,000-$100,000), that's if they ever sell them or sell them to individuals. Both are unlikely in my opinion.

The Honda engine is also MIA? It was also a water cooled engine and looked slick like a Honda engine you see in a car, just a cover with a few wires sticking out. It looked like they had a prototype or mock-up but no word in years. No idea of cost and likely never to be seen. Seems like they are focused on the Honda Jet, and making little jet engines for the VLJ (very light jet).

May be they (BRP/Honda) are testing the market. May be the market made them run?

I can say both the BRP and Honda went with water cooling, and here inlays the rub as they say. Engine development and airframe development go hand in hand, right. It is often said engine technology drives new air frames. Jets pushed swept wing high flying pressurized airframes. Jets on a DC-3 is silly. Since water cooling was chosen or proposed by both BRP and Honda, I assume they expected someone to come to the plate with a new type of airframe, one made for water cooling. As I said BRP was not going for home-builders but production planes. Honda no doubt the same. However it's such a little market, even if it doubled tomorrow, I doubt either will come to pass. Honda probably makes more Civics in an hour than all their perspective future airplane engine production.

Continental has a water cooled engine they can sell you. I think it cost $100,000. Lyc could make a water cooled engine, and has not only thought about it but tried it. People don't relize Lycoming in the 1920's made water cooled V-12's for cars! There is a company in California that is making a new generation of water cooled cylinders (Cool Jugs) as after market parts for Lycomings. They might have the Gen -II jugs out in a year or so (experimental only). I have talked to them and who knows, they might have something nice in the future. However still the airframe gets into the way of any water cooled airplane engine.

We have so much knowlege gleaned since the 1930's, WWII and through today on how to make low drag airframes with AIR-cooled engines. The P-51 famously water cooled was not perfect. It was in fact hot running on the ground. The reason the plane was great was the 2000 hp engine and first laminar flow wing, but the plane was made around the water cooled engine, not the other way around, as an afterthought, as many water cooled engine installations are sometimes (no offense). The P-51 was nice but the "SCALE" and speed are not directly translatable to small water cooled planes, at least not a direct copy. If anyone can do a P-51 deal on a RV, my money is on rv6ejguys RV-10 project. GO get'em dude.

In conclusion water cooling has lots of advantages, NO DOUBT. However in an airframe not made for it, it can be a burden. The word "airplane" has the word air in it. Airplanes have LOTS of air to cool the engine, therefore air-cooling is very efficient and apparently Porsche and VW did a good job of it for many decades. It was only noise and emissions that killed air-cooled car engines, neither of which are a factor for plane engines (sorry Mr. Al Gore), but even water cooled engines alone without catalytic converters and smog stuff would NOT meet EPA limits. Water cooled engine have to shed heat to the air at some point, you just have the water, pump, hoses and radiator as middle man. Why not get rid of the heat direct, from the engine to air. Great idea!

No doubt Honda and BRP went with what they know, water cooled. Besides TCM and Lycoming have the air-cooled market pretty tied up, much to the chagrin of many. Thank goodness we have what we have. What else is there, some Eastern European engine maker? No thanks, made in the USA will do fine for me.

 

[cobra]

Why not get rid of the heat direct, from the engine to air?

Excellent question- here are at least some parts of that argument (and Im sure there are excellent arguments either way with the engines sizes we use in RV's):

1. As engines get more powerful, they need to shed a lot more heat, since they are designed to burn more fuel. There is a finite area available for cooling fins- as the engine heads grow in size (to increase surface area), they must become bigger and heavier, which complicates space issues and ducting requirements to get cooling air where it needs to go.

Bigger and heavier reduces the advantages of air cooling up to some point- Id personally guess the crossover point is somewhere around 300 cu inches, based on durability history/part recalls. That tradeoff point is probably the reason water cooled engines become a viable alternative in the later RV's as the allowable engines increase in size and output. The Lycoming 320 (<~ 150 hp) and smaller engines have excellent service reputations from what Ive seen reported.

Unless the engine happens to be a radial design, the rear cylinders tend to run hotter than front ones. Also, air cooling requires a lot of mass to absorb, conduct, and radiate all that extra heat away. What Im saying here, is air cooling is probably a better choice with smaller, lighter engines; as size/power increases, their advantages decrease.

Water cooling works better as engines get bigger, the designs are easy to scale up to remove excess heat better. The radiator can be placed in an optimal position to maximize air flow/cooling efficiency, not that it always is when shoehorned into air-cooled engine designed cowls. The downside, water cooling will always be less efficient- because water and the extra needed parts are heavier up to some point, but mostly because water cooled heads run cooler (lower delta T).

2. Air-cooled engines heads run hotter. Excessive heat results in three bad things- a.) metal expands when hot, which requires loose tolerences between moving parts. Loose tolerances create vibration and excessive wear rates. b) Heat breaks down oil's lubrication capabilities, which decreases engine life and increases the chance of part breakage. c) Heat causes detonation- detonation causes exponentially higher internal stresses that destroys valves, pistons, heads, and bearings.

3. Air cooled engines tend to be more noisy and vibrate more. Vibration creates problems with air frame durability, propeller choices, and wear on the pilot and passengers.

4. In air-cooled engines particularly, heat seems to be the factor that regulates high-power usage. It also brings along the need to closely monitor air:fuel mixtures.

5. Water cooled heads STAY regulated at lower temperatures (less expansion) than air cooled heads, which means tighter tolerences and lighter parts can be used, which SHOULD result in smoother operation, longer life, and lower mechanical stresses.

 

[David-aviator]

$$ Rule

In conclusion water cooling has lots of advantages, NO DOUBT. However in an airframe not made for it, it can be a burden.... Water cooled engine have to shed heat to the air at some point, you just have the water, pump, hoses and radiator as middle man. Why not get rid of the heat direct, from the engine to air. Great idea!

Good post, George.

That's why Lycoming works so well in an RV and the liquid cooled engine is struggling to catch up. (I say liquid because we do not use water, but NPG+)

Like the 51 and Spit, cooling is adequate but not perfect. But then neither is oil cooling in the Lycoming as there are lots of guys bumping the red line on hot days. (I made many a partial throttle climb to cool air with the 0360 in the Cozy due to oil temperature.)

The greatest challenge we have with liquid cooling is reducing drag. I believe the 3rd radiator inlet hole below the prop is culpable and would like to try a James type cowl to proof it. (So is the 120% exit area - but a moveable door here is doing some good. At one point a tried a scupper to increase air flow with some small success.) The EGG FWF kit is ingenuous in that it is easy to install in a RV but we have drag issues yet unresolved.

The only reason the James cowl has not happened with me to date is money. To spend more money on a project that is working OK but may or may not be better with a new cowl is as much a challenge as the drag issue itself.

dd

 

[rv6ejguy]

G Forces response mirrors my thinking and experience. Now we have two great minds thinking alike here. I'm scared now.

 

[xl1200r]

2. Air-cooled engines heads run hotter. Excessive heat results in three bad things- a.) metal expands when hot, which requires loose tolerences between moving parts. Loose tolerances create vibration and excessive wear rates. b) Heat breaks down oil's lubrication capabilities, which decreases engine life and increases the chance of part breakage. c) Heat causes detonation- detonation causes exponentially higher internal stresses that destroys valves, pistons, heads, and bearings.

The only thing I would like to speak on about this in terms of oils and detonation, since I really don't know the tolerance differences from an air-cooled motor compared to a similar water-cooled one.

Air-cooled engines run hotter, no doubt, but modern oils, especially synthetic ones, have reached very high breakdown temperatures, so much so that I almost can't see this as a hold back. This only becomes an issue when an air-cooled engine starts to run outside of its (or rather its oil's) temperatures boundries (which I agree may be more often than a water-cooled engine would), but the same argument can be made for a water-cooled engine as well. If a hose splits open, or a water pump breaks, those temps don't stay so low and regulated anymore, so oil breakdown can happen here as well.

- On a side note: A water-cooled engine with a inoperable cooling system is going to overheat faster than an air-cooled one (given the aircooled one was in a situation to overheat in the first place). On this same note, if an aircooled engine gets too hot, you can always climb to find cooler air, or reduce power. Most cases (not all), reducing power and finding cooler air will do little for a water-cooled engine that has a broken cooling system (in my automotive experience anyways).

As far as detonation goes, it's all factored into the design. If you know you're going to have an engine with a certain head temperature and a certain combustion chamber design and compression ratio, and will be burning a certain fuel, you always adjust (or design) cam and spark timing to work with those perameters to eliminate detonation.

Also, I don't know how "air-cooled engines vibrate more" argument holds up. When I think of air-cooled engines, two pop into my mind - Lycomings and Harleys - neither of which are known for thier smoothness. However, engines like the BMW boxer are as smooth as any liquid cooled engine out there, and from the little I can remember, my buddy's 1973 VW Beetle was reasonably smooth even when it was running on 3 cylinders. I would think vibration would be more a product of proper balancing as opposed to cooling techniques (though there is some argument that the greater mass would lead to greater dampening). If you have more data on this I'd be very interested to read it (not bashing, pure curiousity).

I will, however, concede that more horsepower generally makes the argument for liquid cooling MUCH stronger, especially in a covered up (or slow moving) engine like an airplane or a car...or a boat for that matter (though water cooling just seems so natural in a boat's case ). I coudln't imagine my dirttrack car running an air-cooled engine and surviving more than a few laps

 

[N62XS]

Elaborate!

Water coolded cylinders sound great. G can you elaborate?

BTW what we really need is a lyco that sounds like a radial! Then I could fly like CaptainRon and fly high and fast.

BTW II When a Canadian and a Californian agree what do you get? I don't know, but its sure gonna raise taxes! Just joking!!!!!!

 

[rv6ejguy]

Also, I don't know how "air-cooled engines vibrate more" argument holds up. When I think of air-cooled engines, two pop into my mind - Lycomings and Harleys - neither of which are known for thier smoothness. However, engines like the BMW boxer are as smooth as any liquid cooled engine out there, and from the little I can remember, my buddy's 1973 VW Beetle was reasonably smooth even when it was running on 3 cylinders. I would think vibration would be more a product of proper balancing as opposed to cooling techniques (though there is some argument that the greater mass would lead to greater dampening). If you have more data on this I'd be very interested to read it (not bashing, pure curiousity).

The design of the engine accounts for most of the vibration levels, liquid or air cooling have less to do with this aspect. Big cylinders (big power pulses) , 3 main bearing crank (large deflections), balancing tolerances of the rotating and reciprocating parts and the layout of the free standing cylinder/head assemblies on the Lycoming account for the higher vibration levels. The Lyco setup is not a stiff structure relatively speaking.

A monoblock design with 5 mains and typical Japanese balancing tolerances with a fully counterweighted crank would cut vibration levels to- well Subaru levels.

 

[TSwezey]

RV6ejguy,
When do you think you will have your 10 flying?

 

[Jconard]

Cobra Wrote:

Excellent question- here are at least some parts of that argument (and Im sure there are excellent arguments either way with the engines sizes we use in RV's):

1. As engines get more powerful, they need to shed a lot more heat, since they are designed to burn more fuel. There is a finite area available for cooling fins- as the engine heads grow in size (to increase surface area), they must become bigger and heavier, which complicates space issues and ducting requirements to get cooling air where it needs to go.

Answer: except that a smaller volume of air is needed as aircooling requires only one transfer action which occurs at high delta T...which gives the greatest efficiency of heat transfer, as opposed to transfering heat from metal...to liquid...to metal...to air. Each transfer is less than 100% efficient and occur at progressively lower delta T.

Bigger and heavier reduces the advantages of air cooling up to some point- Id personally guess the crossover point is somewhere around 300 cu inches, based on durability history/part recalls. That tradeoff point is probably the reason water cooled engines become a viable alternative in the later RV's as the allowable engines increase in size and output. The Lycoming 320 (<~ 150 hp) and smaller engines have excellent service reputations from what Ive seen reported.

Answer: You realize that the "320" means 320 cubic inches, right? Regardless of the size of the engine, heat transfer, and other constants of physics will stay...well...constant. Packaging issues were main drivers in WWII water cooling, and those occured at very high speeds, and the cooling issues were remedied by advanced airframe design approaches. I know of only one similarly advanced attempt so far...on an RV-10...with a sube 6..waiting to see how it flies. At any size an air oil cooled engine will be simpler by the elimination of a cooling system.

Unless the engine happens to be a radial design, the rear cylinders tend to run hotter than front ones. Also, air cooling requires a lot of mass to absorb, conduct, and radiate all that extra heat away. What Im saying here, is air cooling is probably a better choice with smaller, lighter engines; as size/power increases, their advantages decrease.

ANSWER: For the reasons above, related to heat transfer, the rate of transfer is actually much greater, requiring less volume of air to accomplish the same level of heat dissipation. Since the engines loose approximately the same amount of heat energy, in proportion to power, this mathematical certainty means that less volume of air is necessary.

Water cooling works better as engines get bigger, the designs are easy to scale up to remove excess heat better. The radiator can be placed in an optimal position to maximize air flow/cooling efficiency, not that it always is when shoehorned into air-cooled engine designed cowls. The downside, water cooling will always be less efficient- because water and the extra needed parts are heavier up to some point, but mostly because water cooled heads run cooler (lower delta T).

ANSWER: Water cooling is necessitated by packaging, which is even the case in motorcycles and cars...the fastest bikes for many years were air cooled...up into this millenium, and went to the side for packaging needs. In an airplane, the radiator is very difficult to place in any optimal location, without a redesign of an aircraft. As you know, because you have seen all the work folks are doing to try and find an optimum location.

2. Air-cooled engines heads run hotter. Excessive heat results in three bad things- a.) metal expands when hot, which requires loose tolerences between moving parts. Loose tolerances create vibration and excessive wear rates. b) Heat breaks down oil's lubrication capabilities, which decreases engine life and increases the chance of part breakage. c) Heat causes detonation- detonation causes exponentially higher internal stresses that destroys valves, pistons, heads, and bearings.

Answer: Sorry, but this tolerance thing is a misnomer...I just saw the teardown of a lyc which was unfortunately extremely overheated, for many hours, by a bad installation. There was some discoloration, but no wear. In fact, I would bet my plane on those parts specing out. The tolerances are appropriate for the materials used, and if not allowed to corrode, these engines will go to TBO, in the case of the 320, a majority which are regularly flow approach 3000 hours.

3. Air cooled engines tend to be more noisy and vibrate more. Vibration creates problems with air frame durability, propeller choices, and wear on the pilot and passengers.

ANSWER: EJGUY already addressed this, but it has nothing to do with air cooling, for example one of the smoothest engines ever, the 911, was air cooled. What leads to the "vibration" (thump) of a lyc is the philosophy of low rpm, large bore, simplicity. But all engines create vibration. For example, it is often repeated that rotaries run whole seasons in racing without overhaul...true, in the "Formula Mazda" series where everyone must run a selaed engine. I have driven them, they feel very smooth. BUT when those cars fisrt hit the track, the engines would literally powderize the 4130 frames at the welds. They have a high pitched buzz, and I personally found them to be fatiguing to drive. No engine is free of vibration.

4. In air-cooled engines particularly, heat seems to be the factor that regulates high-power usage. It also brings along the need to closely monitor air:fuel mixtures.

ANSWER: If you optimize the amount of available air for the cruise regime, then at high power, high angle of attack, low forward speed (climb), temperatures will go up. If you optimize the available cooling air to a radiator for the same cruise range, it will behave the same. The only way a themostat can control engine temp is if the system has more capacity than it needs in any regime, as the thermostat can only restrict capacity...it cannot create any. Which means that if you want to avoid the climb heat trade off, you need more air...you will go slower, but many planes are designed with a bias in this direction (Cessna), many are not (Mooney, RV). It has nothing to do with coolant, except that the tradeoff may be more severe, if the overall heat transfer is less efficient, as with liquid cooling.

5. Water cooled heads STAY regulated at lower temperatures (less expansion) than air cooled heads, which means tighter tolerences and lighter parts can be used, which SHOULD result in smoother operation, longer life, and lower mechanical stresses.

ANSWER: Yes it should, I hope it does, but it hasn't yet. At this point the durability of the air cooled engines make tham a "lifetime" engine for the average pilot....I suppose if Subaru were to run a car at 150 mph for 5 hours, park the car for 2 weeks, and repeat over the next four years, it would simulate pilot usage, but I am unaware of a single 2000 hour water cooled installation in any RV.


Summary:

I really have been trying to stay out of this, as I have said before, I just do not think the current crop of alternatives offers much more than a challenge for the builder, and the ever present value of unique-ness.

I had to address some of this.

I really hope that the advances come to make this stuff make sense from a performance perspective, without complexity/installation tradeoffs (not asking much am I)

If it happens it will be with approaches like EJGUY's scoop/integrated airframe approach. I will be happy to hear how that one flies!

 

[rv6ejguy]

Well I've been smokin' my brain for the last 2 days on placement of the turbos, intercoolers and plumbing to feed the beast. I finally have a solution worked out in my now damaged brain (I think I thought that about 3 months ago too). I've had serious thoughts about 5 times to leave the turbos off but then I think how boring that would be. I'm addicted to that turbo whoosh on takeoff- must have boost, must have- . I even thought about putting EFI on a 540 for a few split seconds until my senses returned! I digress, hopefully the RV10 will be ready for paint late 2007.

This is not a project for the faint of heart- very time consuming from a systems design and fabrication point of view. It will be one of a kind when done though. See my slow progress here: http://www.sdsefi.com/air46.htm


In the meantime the chips are flying off the lathe, my TIG torch is warm, the bandsaw is chewing up 4130 and 321 and I'm hoping to have the twin Garretts hanging soon. Juicy pix to follow. You'll marvel at the complexity of it all. All in the name of science- I must be crazy! Onwards and hopefully upwards!

 

[xl1200r]

Well I've been smokin' my brain for the last 2 days on placement of the turbos, intercoolers and plumbing to feed the beast. I finally have a solution worked out in my now damaged brain (I think I thought that about 3 months ago too). I've had serious thoughts about 5 times to leave the turbos off but then I think how boring that would be. I'm addicted to that turbo whoosh on takeoff- must have boost, must have- . I even thought about putting EFI on a 540 for a few split seconds until my senses returned! I digress, hopefully the RV10 will be ready for paint late 2007.

This is not a project for the faint of heart- very time consuming from a systems design and fabrication point of view. It will be one of a kind when done though. See my slow progress here: http://www.sdsefi.com/air46.htm


In the meantime the chips are flying off the lathe, my TIG torch is warm, the bandsaw is chewing up 4130 and 321 and I'm hoping to have the twin Garretts hanging soon. Juicy pix to follow. You'll marvel at the complexity of it all. All in the name of science- I must be crazy! Onwards and hopefully upwards!

I know I'm not a huge Subaru fan, but that setup just looks too cool. I love how you modified a pro-stock hood scoop for the radiator inlet, and the plenum and runners on the engine look awsome. Being a car/motorcycle/boat nut, I really don't have a good argument when someone does totally different and cool like that - and hanging 2 turbos off thing doesn't hurt either

BTW - Maybe you need a break, sounds your brain is past it's TBO time If you ever consider a 540 again I think you better seek counseling

 

[captainron]

BTW - Maybe you need a break, sounds your brain is past it's TBO time If you ever consider a 540 again I think you better seek counseling

Oh, I don't know about that; I'm thinking about an IO-720!

 

[gmcjetpilot]

Great minds do think alike

G Forces response mirrors my thinking and experience. Now we have two great minds thinking alike here. I'm scared now.

David-aviator mirrors my thinking and experience. Now we have two great minds thinking alike here. I'm scared now.

I just want to remind you and Cobra that the points are correct but you skip over the draw backs of liquid cooling that can't be discounted, drag, weight and cost (yes cost).

Seriously rvejguy, I could not be happier when you get your RV-10 flying and can report (gloat) it out does every thing in the sky. I am counting on ya.

Airhead patrol, over and out.

 

[xl1200r]

Oh, I don't know about that; I'm thinking about an IO-720!

You seem to be a fabricator of types...maybe do up a custom cowl with a twin-tubo'd Falconer V-12. Now that I could appreciate

Better yet, run 2 of them side-by-side with a common prop drive between them. I can't see any advantage in doing that, but you'd definatley be the only one

 

[rv6ejguy]

Just so nobody gets too excited here- I've been doing this kind of stuff for a while but hold no illusions as to the performance of my creation. My background includes the science of performance gains (flow bench and dyno testing and lap times on the track) and the compromises of design.

My design goals were to equal the weight and performance of the IO-540 powered RV10 on the same fuel flow for less money than the $40K asking price from Vans for the Lycoming. I'll be happy if I achieve this. As with the 6A project, I'll report the facts from flight testing good or bad without too much bias if that is possible. We may be inferior in some aspects as before to the Lyco installation. I'm sure it will be an interesting journey. I have another friend close by who is just completing his -10 so we can do another side by side.

 

[David-aviator]

Oh, I don't know about that; I'm thinking about an IO-720!

Well, Ron, you are on the way with another guy who is thinking R3350.

dd

 

[cobra]

rv6ejguy,
You have a nice looking cooling system comming together. The belly scoop is a novel approach that I havn't seen yet in an RV. I'm interested to see how it looks and works out.

(Observation, not criticism ) Ive seen a few learned sources mention that ideally, the exit ducting should diverge into a smaller opening- to increase air flow velocity through the outlet, which helps DRAW air thorugh the radiator. Your pictures looks like the exit gets larger, like a nozzle; that I believe, increases drag and possibly might impede some air flow thru the rad???

I assume you plan to eventually shape the intake openings to a more rounded contour, to help divert cooling-air spill around the intake scoop at high speed (when exit door is closed, to reduce cooling drag). From the short straight intake duct and thick rad core, it looks like you are planning to keep duct turbulence/pressures on the high side, like Egg's Subaru and TCrook's rotary do, to FORCE air through the radiator.

FWIW, Im leaning towards the James cowl using Paul Lemar's thin horizontal radiator core w/wedge diffuser design, which slows the air velocity, at low pressure, through the radiator; it will be mounted under the rotary engine. I think it might have some advantages cooling at slower speeds and taxiing. I've noticed the two schools of thought seem to be somewhat at odds regarding radiator style and placement, which tends to be confusing. There have been several reports of overheating using thick radiator cores (i.e., several Eggs and from Crook's notes) when going taxiing/flying slow/climbing where the ram-air pressures are lower.

They say the P-51 actually obtained a small amount of positive thrust through its cooling system and exit design. If we can only be so lucky

 

[rv6ejguy]

We use a small inlet and diverge the air to increase pressure and lower velocity at the rad face then converge the air after the rad to gain back the velocity at the exit. Additionally we use a variable geometry exit flap like the WW2 fighters to have maximum mass flow at low speeds and reduced drag at high speeds.

Fixed duct designs are a major drag compromise on liquid cooled aircraft according to our testing and historical research. The laid down rad approach is also high drag according to my flow bench studies as the air has to turn 180 degrees total from inlet to exit which involves a large energy loss. Guide vanes can reduce this but it is still less efficient than a straight air path.

Most of the drag is internal on rads so throttling the exit is a very simple and effective way of reducing mass flow, through the core. The inlet in nicely contoured and has a smooth transition to the walls of the duct with low devergent angles to minimize separation. The inlet side of the duct is 19 inches so it is much longer than the cowl mounted rad setups used by Eggenfellner and Crook.

You are correct in saying that the thicker core design hurts ground cooling. Such are the compromises.

Modern analysis of the stock P51 setup suggests that it offset 300 of the 450hp required to overcome cooling drag at full power settings and speed compared to other designs like the Spitfire. There was still a drag penalty associated with cooling. Historical research suggest that the divergent angles on the inlet of the Spitfire's design caused flow separation and drag.

I plan to instument the RV10 duct to quantify exit velocities are shed some more light on the "Merideth Effect".

I'd be interested to see the flight results of your setup. It is a facinating area of research.