New diesel unveiled

[airguy]

I investigated the Wilksh diesel engine for my RV-9A a few years ago. At the time the WAM 160 was about to be introduced and this was the one I was most interested in. Wilksh designed a modular engine with a three cylinder, the WAM 120 (120hp) and a four cylinder WAM 160 (160hp). These are excellent designs, but since the WAM 160 has still not been offered, I have decided to use a Lycoming IO-320. I admire Mark Wilksh's company and the WAM 120, but I think it just underscores the difficulty in bringing any new aero engine, no matter what technology it uses, to market.

Same here - I think the WAM 160 would make a great engine for our planes, and I looked at it for my 9A initially. The lack of progress and lack of flying models just makes it a non-reality at this point. I'm planning an IO-360 and building (have built) the fuel system to be able to switch over to a diesel engine at some point in the future if they become a viable option. Turbocharging and direct drive with the diesels inherent high torque would be an excellent match for a good constant-speed prop.

 

[Rotary10-RV]

I believe their engine is a spin-off (or rip-off) of these two companies:

http://www.dair.co.uk/
http://www.dieseltech.cc/ (using dair's design under license, if at all)

dair's site dates back to at least 1999.

Like Zoche, lots of promise and no deliver.

Brester,
The little DAIR engine is one that showed a lot of promise but hasn't gone anywhere. The Gemini is the same. I don't think that the Gemini is under DAIR license because the DAIR engine is just a lightweight replica of the Fairbanks Morse twin crankshaft two-cycle diesel. The large versions were used in ships and locomotives! The design is very efficient too. The Fairbanks Morse engine had the record for lowest BSFC for a while IIRC. The system uses two opposed pistons per cylinder, with one crank timed slightly ahead, the other crank takes as much as 85% of the power. These designs were also known as "blow-down" diesels. There was even a triangular version used mostly in fire trucks in the UK. The delta version wasn't as popular but was also supposed to be very efficient. The idea is a good one as the engine can be oriented horizontally and fits the current aircraft profile. It would also be possible to place it main crankshaft up and it would be like the WAM engine. That way it would have to be a "blow-up" diesel, although I dislike the term almost as much as "dead reckoning"!
Bill Jepson

 

[Sig600]

Same here - I think the WAM 160 would make a great engine for our planes, and I looked at it for my 9A initially. The lack of progress and lack of flying models just makes it a non-reality at this point. I'm planning an IO-360 and building (have built) the fuel system to be able to switch over to a diesel engine at some point in the future if they become a viable option. Turbocharging and direct drive with the diesels inherent high torque would be an excellent match for a good constant-speed prop.

Whats different in the basic plumbing that you would need to modify for Jet-A in the future?

 

[kgood]

Basic Plumbing

Sig600,
the only thing I had to do for the WAM 120 diesel is to add a 1/4" return line. I routed it through an Andair fuel selector valve so that fuel returned to the same tank as it was being drawn from.

There also has been talk of using capacitance fuel senders instead of the resistance type (the ones that come with the kit), in order to avoid the possibility of an explosion like TWA 800. But I did not, because I didn't know about it until after I was flying. So I have the stock SW sending units, with no problems. I have trouble buying into the TWA 800 theory, since I drive my pickup around in 120F temps all summer, along with all other diesel pickup owners, same type sender, no problems. Anyone else have any ideas on this?

Kurt

 

[airguy]

Whats different in the basic plumbing that you would need to modify for Jet-A in the future?

Almost certainly the need for a fuel return from the injector pump, and flow-through venting to eliminate vapor in the tank. With gasoline fuel tanks the vapor/air mixture becomes too rich to burn within seconds so an explosion is not an issue - but diesel is much less volatile and you can have an explosive mixture in the tanks with a much longer dwell time, so "flow-through" venting is recommended. The airlines now use inerting gas (nitrogen-enriched atmosphere) as a purge gas on the Jet-A tanks, post TWA-800.

Aside from those two, you would need to install the larger Jet-A sized fill caps in the tank - though I left mine in the current 100LL size to avoid the possibility of accidental Jet-A fillup until that change is made later. I will have to open my tanks (through the inspection plate) to change the fill cap if I convert to diesel, but all the rest of the plumbing is in place. I have already made provisions for flow-through venting and have capped off the lines, waiting for that day. I also installed the capacitive fuel level senders in the tanks, they only need to be recalibrated to function with diesel or JetA.

To Kurt - the chain of events on TWA 800 (and in your pickup) would require an electrical short creating a spark in the tank, above the fuel level in the vapor space above the fuel, with an explosive mixture in residence at that point in time. A bit rare to be sure - which is why we've only seen it happen once, that we know of. Rare does not mean impossible. I had an in-tank electric fuel pump short out on me and melt the insulation off the wiring leading to it on my 1998 Chevrolet pickup (gasoline), resulting in an electrical short that finally blew a fuse - it can happen. I can only surmise that the vapor level in my fuel tank at the time was too rich to burn, because my only indication of a problem was when the engine died as the fuel pump wires shorted inside the tank and I lost fuel pressure.

 

[terrye]

One point, my pet peeve if you will, diesels might get better fuel economy than SI engines but they don't outperform them from a hp or torque standpoint per unit displacement or unit manifold pressure nor will they ever. That being said, they are well suited to powering all types of vehicles.

Hi Ross,
Sorry, I don't agree. To take an example from the automobile world (couldn't find an apples to apples airplane example), BMW offers its cars with both gasoline and diesel engines. From their website engine performance figures for the 335i (gasoline) and 335d (diesel) cars:

Gasoline Diesel (Sorry, formatting problem here, should be two columns for Gasoline and Diesel)
Displacement (cc) 2996 2993
Cylinders/Valves per cylinder 6/4 6/4
Stroke/Bore (mm) 88/85 90/84
Power/RPM (HP) 306/5800 286/4400
Torque (Nm/RPM)* 400/1300-5000 580/1750-2250
Compression Ratio 10.2:1 17:1
Turbocharged Yes Yes

*Torque is flat between the two quoted rpms
I suspect that the gasoline engine power at 4400 rpm would be lower than the diesel, but I don't have a power curve to verify this. So yes, the peak power of the gasoline engine is higher than the diesel, but at 31% higher rpm. But note the 45% greater torque of the diesel.

Diesels get better fuel economy as a result of their higher compression ratio (which is knock limited in gasoline engines) which makes them more thermally efficient therefore has better brake specific fuel consumption. Again the limiting manifold pressure depends on which fuel you are using. The trick in an diesel aero engine is getting them light enough to compare with a gasoline engine (lbs/bhp). Two stroke diesels have the advantage here.

 

[Sig600]

Almost certainly the need for a fuel return from the injector pump, and flow-through venting to eliminate vapor in the tank. With gasoline fuel tanks the vapor/air mixture becomes too rich to burn within seconds so an explosion is not an issue - but diesel is much less volatile and you can have an explosive mixture in the tanks with a much longer dwell time, so "flow-through" venting is recommended. The airlines now use inerting gas (nitrogen-enriched atmosphere) as a purge gas on the Jet-A tanks, post TWA-800.

Aside from those two, you would need to install the larger Jet-A sized fill caps in the tank - though I left mine in the current 100LL size to avoid the possibility of accidental Jet-A fillup until that change is made later. I will have to open my tanks (through the inspection plate) to change the fill cap if I convert to diesel, but all the rest of the plumbing is in place. I have already made provisions for flow-through venting and have capped off the lines, waiting for that day. I also installed the capacitive fuel level senders in the tanks, they only need to be recalibrated to function with diesel or JetA.

To Kurt - the chain of events on TWA 800 (and in your pickup) would require an electrical short creating a spark in the tank, above the fuel level in the vapor space above the fuel, with an explosive mixture in residence at that point in time. A bit rare to be sure - which is why we've only seen it happen once, that we know of. Rare does not mean impossible. I had an in-tank electric fuel pump short out on me and melt the insulation off the wiring leading to it on my 1998 Chevrolet pickup (gasoline), resulting in an electrical short that finally blew a fuse - it can happen. I can only surmise that the vapor level in my fuel tank at the time was too rich to burn, because my only indication of a problem was when the engine died as the fuel pump wires shorted inside the tank and I lost fuel pressure.

So is it correct to assume the regular gasoline setup just provides positive pressure to the distribution system with fuel dead ending there... and diesel/jet-a setups the fuel basically passes through in a continuous loop, with the engine taking in it's demand as the fuel goes by?

 

[Dave_Boxall]

Many gasoline engine installations include a fuel return line. Its very common on Fuel Injected systems, and is fitted on some carburetted systems (especially ones designed for Mogas) to reduce the possibility of a vapour lock.

Without the return line the Wilksch injector pump would be very reluctant to self-prime, which would be a bad thing if you ever ran one tank dry...

Dave

 

[rv6ejguy]

Not Again

Hi Ross,
Sorry, I don't agree. To take an example from the automobile world (couldn't find an apples to apples airplane example), BMW offers its cars with both gasoline and diesel engines. From their website engine performance figures for the 335i (gasoline) and 335d (diesel) cars:

Gasoline Diesel (Sorry, formatting problem here, should be two columns for Gasoline and Diesel)
Displacement (cc) 2996 2993
Cylinders/Valves per cylinder 6/4 6/4
Stroke/Bore (mm) 88/85 90/84
Power/RPM (HP) 306/5800 286/4400
Torque (Nm/RPM)* 400/1300-5000 580/1750-2250
Compression Ratio 10.2:1 17:1
Turbocharged Yes Yes

*Torque is flat between the two quoted rpms
I suspect that the gasoline engine power at 4400 rpm would be lower than the diesel, but I don't have a power curve to verify this. So yes, the peak power of the gasoline engine is higher than the diesel, but at 31% higher rpm. But note the 45% greater torque of the diesel.

Read my post in this thread- performance is what I said.

We thrashed this many months ago and should you wish to research what I wrote then, you are welcome to: http://www.vansairforce.com/community/showthread.php?t=46472 Read posts #22 and #35.

I used the same example as you. The diesel 335 runs 3 times the manifold pressure of the SI engine to develop this torque. The SI BMW is still faster 0-60 and in the 1/4 mile on one third of the boost pressure. Area under the hp curve determines acceleration, not peak torque.

If you can find ANY diesel engine of the SAME displacement running the SAME manifold pressure as an SI engine that develops the same hp and torque, let me know and I'll retract my statement.

Sorry, I'm a stickler for correct information and I'm tired of seeing the "diesel torque myth" being perpetuated yet again. If you want to say that a diesel has a very high torque output because it runs very high boost pressure, I'll buy that statement- same applies to any SI engine. Ever wonder why there are no more atmo diesels being made today for cars, trucks and aircraft?

 

[airguy]

Ever wonder why there are no more atmo diesels being made today for cars, trucks and aircraft?

Basically, because they NEED to be boosted for good performance! And diesels just naturally lend themselves well to boosting, much more so than SI engines, without adverse effects.

 

[terrye]

Hi Ross,
Thanks for directing me to the previous discussion. So much to read...so little time.

 

[kgood]

Basically, because they NEED to be boosted for good performance! And diesels just naturally lend themselves well to boosting, much more so than SI engines, without adverse effects.

You're right. As Ross says, he's been making his point about SI engines being better, inch per inch, boost per boost, than a diesel (leaving efficiency out of the equation), and he's probably right, but I'm still waiting for a factory-stock SI engine that can come close to handling the boost that a diesel can. We run 90 PSI boost in our GM Duramax Bonneville streamliner. Stock block, crank, and heads.

Fact is, there's no reason to develop and market a super-strong, high boost gasoline engine, because you'd end up with same basic characteristics current diesels provide, minus the economy. Yeah, it would accelerate faster, but the current crop of diesels are certainly quick enough for most of us, and I'll give up a tiny bit of acceleration for a LOT more pulling power.

It's just not an apples-to-apples comparison, but I think Ross is slowly warmin' up to the diesel idea..
Kurt

 

[breister]

Brester,
The little DAIR engine is one that showed a lot of promise but hasn't gone anywhere. The Gemini is the same. I don't think that the Gemini is under DAIR license because the DAIR engine is just a lightweight replica of the Fairbanks Morse twin crankshaft two-cycle diesel. The large versions were used in ships and locomotives! The design is very efficient too. The Fairbanks Morse engine had the record for lowest BSFC for a while IIRC. The system uses two opposed pistons per cylinder, with one crank timed slightly ahead, the other crank takes as much as 85% of the power. These designs were also known as "blow-down" diesels. There was even a triangular version used mostly in fire trucks in the UK. The delta version wasn't as popular but was also supposed to be very efficient. The idea is a good one as the engine can be oriented horizontally and fits the current aircraft profile. It would also be possible to place it main crankshaft up and it would be like the WAM engine. That way it would have to be a "blow-up" diesel, although I dislike the term almost as much as "dead reckoning"!
Bill Jepson

Thanks for the history Bill - my guess about the relationship was based entirely on timing of the "we're here!" announcements and the fact that they both looked like the Jumo-Junkers design (opposed pistons/dual crankshafts).

I'm curious about the offset of the timing, though - what is the advantage? Is it meant to escape harmonics, or is there another reason? Seems like your gears & other parts could be more symmetrical if they were evenly loaded.

Another thought that springs to mind with this design is that since the prop shaft is gear driven there ought not be a particular limit to the number of cylinders in line - thus making the engine very "scalable." Just have the prop shaft run the length of the engine with drive gears every couple of cylinders. This would also allow lighter crankshafts and gears, as each gear need only support the power generated by a single pair of pistons. The main drive shaft could be hollow and thus fairly light while conveying incredible torsional strength.

Well, speculation is all fun and no real work. Someone will figure out a better mousetrap one of these days, and I'll undoubtedly opt to double the horsepower in my toy when that happens.

 

[rv6ejguy]

"Pulling Power"

You're right. As Ross says, he's been making his point about SI engines being better, inch per inch, boost per boost, than a diesel (leaving efficiency out of the equation), and he's probably right, but I'm still waiting for a factory-stock SI engine that can come close to handling the boost that a diesel can. We run 90 PSI boost in our GM Duramax Bonneville streamliner. Stock block, crank, and heads.

Fact is, there's no reason to develop and market a super-strong, high boost gasoline engine, because you'd end up with same basic characteristics current diesels provide, minus the economy. Yeah, it would accelerate faster, but the current crop of diesels are certainly quick enough for most of us, and I'll give up a tiny bit of acceleration for a LOT more pulling power.

It's just not an apples-to-apples comparison, but I think Ross is slowly warmin' up to the diesel idea..
Kurt

I am coming around. I think you and WAM can be proud of what you have proven in the real world. The WAM 120 is the first alternative engine to match an equivalent Lycoming (O-235) on all counts (hopefully TBO too). We Subaru guys certainly can't make that claim. I hope to soon see what the 140 can do in an RV.

90 psi is impressive all right. The best Merlins run 70 psi with 2 stage superchargers and at that point they say the ignition systems are doing nothing much useful as the engines are in CI mode at that point. Top fuel engines ditto. I guess the point is, the SI engine makes so much cylinder pressure and hp at these boost levels, it is not possible to make it live very long from a structural standpoint. I guess the other point which has already been made by airguy it that diesels need very high boost to develop high hp which is what I've been saying for a long time too. SI engines don't need high boost to make a lot of hp. So there is really no need to make an SI engine design that will withstand 90 psi.

At some point fuel octane becomes the major limitation in boosted SI engines but at this level the HP is just silly anyway. Diesel engines do not have this limitation. 25 years ago, the BMW F1 engines were developing specific outputs of 1000 hp/L and this was at only around 10,000 rpm. With current technology applied and running the same 60 psi boost, no doubt nearly 2000hp/L could be obtained at 20,000 rpm.

I'd generally agree with the first part of your second paragraph too. Diesels fill that role very well with the best fuel economy to boot. The last sentence there confuses me though- maybe I'm still not getting the "pulling power" concept through all that thick black smoke you diesel guys have been breathing.

Torque is essentially meaningless, it is not work, it is force. HP is the "pulling power" that accelerates and keeps all types of vehicles in motion. SI engines develop more hp in any given situation, apples to apples, therefore they have more "pulling power" than CI engines. I think it is the truck world that has created this misconception and misinformation because there are no turbocharged SI truck engines out there really to compare with.

With modern turbo setups and especially variable geometry turbos, we see many popular SI turbo engines with torque peak rpm down in the 1750-1900 rpm range BMW, AUDI, VW etc. yet 70%+ of the peak torque is still available at 6000+ rpm. This creates a very large area under the hp curve as SI engines don't run out of breath at high rpm like CI engines do. The low torque peak rpm FEELS nice and impressive in both SI and CI engines and we often equate that with "pulling power". Fact is the SI engine does more work and can remain in a lower gear longer due to its higher revving nature so accelerating a given mass in a given time is something it can do better than a CI engine.

Both engine types have their advantages and disadvantages like most things mechanical. I'm glad to see CI engines making their way into aircraft again. I was actually very intrigued when the Thielert was adopted by Diamond a few years back and read everything I could on it because it was new and interesting. That one did not work out but perhaps the SMA, Austro and WAM will prove long term they have the goods to replace the venerable SI Lycoming and Continental.

 

[kgood]

Torque is meaningless?

I am coming around. I think you and WAM can be proud of what you have proven in the real world. The WAM 120 is the first alternative engine to match an equivalent Lycoming (O-235) on all counts (hopefully TBO too). We Subaru guys certainly can't make that claim. I hope to soon see what the 140 can do in an RV.

90 psi is impressive all right. The best Merlins run 70 psi with 2 stage superchargers and at that point they say the ignition systems are doing nothing much useful as the engines are in CI mode at that point. Top fuel engines ditto. I guess the point is, the SI engine makes so much cylinder pressure and hp at these boost levels, it is not possible to make it live very long from a structural standpoint. I guess the other point which has already been made by airguy it that diesels need very high boost to develop high hp which is what I've been saying for a long time too. SI engines don't need high boost to make a lot of hp. So there is really no need to make an SI engine design that will withstand 90 psi.

At some point fuel octane becomes the major limitation in boosted SI engines but at this level the HP is just silly anyway. Diesel engines do not have this limitation. 25 years ago, the BMW F1 engines were developing specific outputs of 1000 hp/L and this was at only around 10,000 rpm. With current technology applied and running the same 60 psi boost, no doubt nearly 2000hp/L could be obtained at 20,000 rpm.

I'd generally agree with the first part of your second paragraph too. Diesels fill that role very well with the best fuel economy to boot. The last sentence there confuses me though- maybe I'm still not getting the "pulling power" concept through all that thick black smoke you diesel guys have been breathing.

Torque is essentially meaningless, it is not work, it is force. HP is the "pulling power" that accelerates and keeps all types of vehicles in motion. SI engines develop more hp in any given situation, apples to apples, therefore they have more "pulling power" than CI engines. I think it is the truck world that has created this misconception and misinformation because there are no turbocharged SI truck engines out there really to compare with.

With modern turbo setups and especially variable geometry turbos, we see many popular SI turbo engines with torque peak rpm down in the 1750-1900 rpm range BMW, AUDI, VW etc. yet 70%+ of the peak torque is still available at 6000+ rpm. This creates a very large area under the hp curve as SI engines don't run out of breath at high rpm like CI engines do. The low torque peak rpm FEELS nice and impressive in both SI and CI engines and we often equate that with "pulling power". Fact is the SI engine does more work and can remain in a lower gear longer due to its higher revving nature so accelerating a given mass in a given time is something it can do better than a CI engine.

Both engine types have their advantages and disadvantages like most things mechanical. I'm glad to see CI engines making their way into aircraft again. I was actually very intrigued when the Thielert was adopted by Diamond a few years back and read everything I could on it because it was new and interesting. That one did not work out but perhaps the SMA, Austro and WAM will prove long term they have the goods to replace the venerable SI Lycoming and Continental.

Ross,
I don't get it. If "torque is meaningless" and HP is everything, then I need you to explain to me and every other modern diesel truck owner why: My suburban, which is gasoline powered, lighter than my diesel truck, with the exact same HP rating, will pull my boat up a certain grade at 55 mph max. My truck, weighing at least 2000 lb more (with even more load in the bed), will pull my boat up the same grade at 80mph, still accelerating at the top.

I've got a friend with 502 chevy in his truck, rated at around 100 hp more than my truck, and it works the same way; I have no problem leaving him in the dust. So what gives? If it isn't torque, what is it?

I'm sure you'll talk about boost here, but you're saying it's about HP. And the HP between the two is the same.

BTW, I used to have a pickup (an International crew cab, if you remember that far back) that had a Detroit Diesel 2 stroke 6V53 Normally Asperated engine conversion. 318 cubic inches of 2 stroke smokin' fury. It would eat the big-block chevys too, but you had to wear ear plugs! So it can be done even without the boost.

Kurt

 

[rv6ejguy]

Average not Peak

The key is hp under the curve not peak values. A turbo diesel will have far more area under the curve than an atmo engine SI of the same displacement because it produces pretty impressive hp at such low rpm. The atmo engine doesn't produce much power in comparison until well up in the rpm range. By the time the atmo SI engine has dragged the load up into its useful power band rpm in first gear, the turbo diesel is well down the road.

The comparison falls right back into the old "turbo diesel vs. atmo SI engine mode" again. If you remove the turbo from your diesel and repeat the test, I think you know which one will win the contest. Likewise add a turbo and run even 10 psi boost to the SI V8 and you'll be looking at tail lights from your diesel. Comparing atmo and turbo engines is apples and oranges.

Perhaps my example of the SSC Ultimate Aero best illustrates what low boost SI engines can do related to CI turbo engines in the truck displacement range- 6.3L, 1287hp, 1112 lb.ft. All done with a new billet block and about 13 psi boost.

It is just so hard to find a large SI turbo V8 truck to run a comparison in the real world with a turbo diesel but you don't need to use trucks to test the theory. Take two cars like a VW TDI and a 1.8T Jetta or a BMW 335D and 335is. Since the weight differences are minimal, it is apples to apples. In both cases the SI turbos win the 1/4 mile race. The SI turbo has accelerated the same mass over the same distance in less time and at a higher mph. It has therefore performed more work and has more "pulling power". BTW the new 335is has torque peak at 1200 rpm and a recent test, an auto put up 0-60 in 4.8 seconds without loading it up on the converter.

 

[L.Adamson]

The comparison falls right back into the old "turbo diesel vs. atmo SI engine mode" again. If you remove the turbo from your diesel and repeat the test, I think you know which one will win the contest. Likewise add a turbo and run even 10 psi boost to the SI V8 and you'll be looking at tail lights from your diesel. Comparing atmo and turbo engines is apples and oranges.

We'll have to go over this later, must head off to work. In the meantime, I don't think so!

L.Adamson --- Chevy Silverado & Allison trans..

 

[rv6ejguy]

We'll have to go over this later, must head off to work. In the meantime, I don't think so!

L.Adamson --- Chevy Silverado & Allison trans..

Diesel advocates simply won't let this go. If you truly believe that a diesel has more torque and more "pulling power" than an SI engine simply because it is a diesel, remove the turbo, recalibrate the fuel delivery and see how lame your engine is without the turbo. Most 6L class diesels would be lucky to make 225 hp and 300 lb./ft. without boost. If you really think this will outperform a modern 6L SI V8, do the test and publish the results.

Again, you might want to think why all modern diesel engines are turbocharged. Why would the factory engineers bother if the diesel was so superior without it?

People seem to want to deny the fact that with a given engine design, hp varies with mass flow. 2 ways to increase that- rpm and manifold pressure. If this sinks in, you can see there is no way a low rpm diesel can win this contest against a high rpm SI engine running the same MAP. The sports car and racing world would be totally dominated by CI engines if this was true. Accelerating a mass over distance and time is the same in a 2000 lb. race car as with a 8000 lb. truck if we are talking about performing work.

If you think 800 lb./ft. is impressive from a modded 6.5L class diesel just remember that the BMW F1 engine produced about the same torque from only 1.5L and if we scaled it up in displacement to 6.5L, it would produce 3467 lb./ft. and 6500hp.

If you can remember back to the first atmo VW diesel Rabbits. They were pitiful, in fact, the slowest car ever tested by R&T in the 1/4 mile in modern times. Both the torque and hp were way below comparable displacement atmo SI engines of that era. Turbos transformed these engines into something practical and fun just as they transformed all other diesels today. Take away that boost and you revert back to the diesel's old well deserved reputation for being very slow mobile chicanes.

This whole discussion has strayed far from the original post about the SMA diesel. I simply don't like to see statements that comparable CI engines "outperform" SI engines. It is patently untrue and contravenes science and the laws of physics as well as common sense.

Marine and road going diesels have better BSFC and demonstrated longevity than SI engines. These two factors alone make them highly suitable for these applications. When it comes to straight performance, they are not in the same league at all.

 

[kgood]

Ross, you're right - the thread has deviated, and it's partly my fault, so I apologize. Much of this was beat to death in the other thread - and made clear that you're not buying that diesels pull better.

So I'll bring it back to aviation. You completely disregarded my last paragraph regarding the fact that my NORMALLY ASPIRATED 318 cubic inch (5.2L) diesel routinely out accelerated and out-pulled many 454 cu in Chevys of the day, burning 1/3 less fuel. Why? because it's a two stroke. Granted, it was heavy, and a little bulky, but it did fit under the hood of a regular pickup.

My point is this: As the two-stroke aviation diesel evolves - I'm talking WAM, DH, and CMD, that I know of, but others may come - I'm convinced that we'll see a 5-ish liter non-turbo 180 hp, air cooled, light weight, two stroke aerodiesel, a platform that can be turbocharged to produce 250-300 hp. We're practically there now, if the CMD ever makes it to market. That platform, minus the turbos and the common rail, would very close.

Here's the reasoning: 1. The actual two-stroke diesel technology has been around for ages, both uniflow and loop scavenged, with the above parameters, minus the weight, being met. (my 318 cu in V6 mentioned above made 230 hp/470 ft/lb continuous with no turbo, bone stock, 2800 rpm). This engine, and millions like it routinely ran 500,000 miles between overhauls, pulling hard most of their lives.
2. The real technology needed to do this comes with computer modeling, new alloys and manufacturing techniques, giving the ability to make these engines light enough. This seems to be coming. My WAM weighs 220 lb with coolers. The CMD (310 hp) weighs about double that, with six cyl. so it's essentially two WAM's in a flat six configuration.
3. These engines do not need to be electronically controlled or have variable turbos, or have any other complicated systems to work well. This is proven, because myself and several others are flying them now (not to mention BILLIONS of road miles with the exact same technology - even the bore and stroke don't need to change).
4. Some new fancy technologies, like electronic common rail injection, airflow optimizing, etc. can be applied to make these engines even more efficient and green.

Yeah, I might be dreaming, but I think the writing is on the wall. In my eyes it's not if, but when. And I won't give up the idea that diesels pull better!
Kurt

 

[rv6ejguy]

I am sorry, I missed the 2 stroke part. My bad. But comparing 2 and 4 strokes is like comparing atmo to turbo.

Yes, it seems as though the 2 stroke diesel is the way to go in aircraft to get the power to weight ratios comparable to SI engines. The more I read, the more impressed I am. Now if WAM does a 6 cylinder, 300 hp version and can sell it for under $30K to go in my -10, I might even become a diesel guy.

I'm following the Austro AE300 engine with interest too since it is automotive based. I hope it does better than the Thielert. In 2-3 years we should know I guess. They seem to have performed more engineering and testing than Thielert did and it has enough power for the Twin Star where the Thielert was very marginal.

Getting back on topic, we shall see what Continental really does with the SMA. Let's hope they stop blowing smoke and get on with it.

 

[kgood]

I am sorry, I missed the 2 stroke part. My bad. But comparing 2 and 4 strokes is like comparing atmo to turbo.

I don't understand why. They're both atmo. But at lease we agree that 2-stroke diesels seem better suited for aircraft use.

I'm a bit disappointed that Continental went with the 4-stroke design. When I read last fall that they were going to purchase diesel technology rather than develop it themselves, I supposed that it would be something 2 stroke like CMD, since TCM's GAP engine was 2-stroke. But they must know what they're doing.

It just seems to me that the SMA is pretty maxed out right where it is, HP-wise, and weight-wise. The article mentioned that they could use the 4 cyl platform to create a 6 cyl 300 plus hp engine. IMO, that would add way too much weight.

The CMD's at 310 hp, and about the same weight as the SMA. I personally think the CMD GF56 would be the hot ticket for your '10. If it were available, I would order one right away and build a '10 around it. In fact, I have considered building '10 with an SMA in it, just because I'd like to see how well it works. I have emailed SMA about it, but they haven't responded. You'll laugh at this, but what's holding me back more than anything is that Van's doesn't offer the '10 as a tail dragger

I bet you couldn't tell I'm a 2-stroke diesel fan. I could go on and on. But I'm happy to see the diesel movement gaining some traction, which ever way it goes.
Kurt

 

[L.Adamson]

I am coming around. I'd generally agree with the first part of your second paragraph too. Diesels fill that role very well with the best fuel economy to boot. The last sentence there confuses me though- maybe I'm still not getting the "pulling power" concept through all that thick black smoke you diesel guys have been breathing.

Torque is essentially meaningless, it is not work, it is force. HP is the "pulling power" that accelerates and keeps all types of vehicles in motion. SI engines develop more hp in any given situation, apples to apples, therefore they have more "pulling power" than CI engines. I think it is the truck world that has created this misconception and misinformation because there are no turbocharged SI truck engines out there really to compare with.

With modern turbo setups and especially variable geometry turbos, we see many popular SI turbo engines with torque peak rpm down in the 1750-1900 rpm range BMW, AUDI, VW etc. yet 70%+ of the peak torque is still available at 6000+ rpm. This creates a very large area under the hp curve as SI engines don't run out of breath at high rpm like CI engines do. The low torque peak rpm FEELS nice and impressive in both SI and CI engines and we often equate that with "pulling power". Fact is the SI engine does more work and can remain in a lower gear longer due to its higher revving nature so accelerating a given mass in a given time is something it can do better than a CI engine.

Sorry Ross, but you need more sleep or reading on the subject....

Torque is everything when it comes to comparing the heavy duty pulling power of my diesel truck engine to it's SI counterpart. While my diesel develops less overall horsepower , it's torque rating is far higher at much less rpm. Most of this is due to a much higher compression, in which that turbo charger is greatly responsible for supplying enough air, which is over twice as much during each compression stroke. And at the same time, diesel fuel has a greater btu content than gasoline, which is an added advantage in the mileage game.

So yes, we'd be silly to remove a turbo from a diesel, since it contributes so much to the higher air requirement. But the power to the turbo is essentially free, as compared to a super charger. And overall, the diesel in my truck will have more brute pulling power and use less fuel at the same time. Happily, diesel fuel is now at the same price as regular low lead, or even lower.

There is just no misconception in my mind. I've been driving pickups for four decades, and I'm very aware of the diesel advantage. And for 2011, GM/Chev has upped the anti again, with brute torque that almost doubles what's available with their SI counterpart. So yes, torque is far more than meaningless.

As for airplanes, I'll still take the Lyc..

L.Adamson --- RV6A

 

[Ted Johns]

You completely disregarded my last paragraph regarding the fact that my NORMALLY ASPIRATED 318 cubic inch (5.2L) diesel routinely out accelerated and out-pulled many 454 cu in Chevys of the day...

Kurt,
Specifically which engine are you talking about here?

Torque is everything when it comes to comparing the heavy duty pulling power...

It's as if there was no need to invent the term horsepower, ehh?

Torque is not work. Horsepower is work. The physics was settled a long time ago.

Now, if a manufacturer has not geared a vehicle to use said horsepower, they are incompetent, or (more likely) had a different mission in mind.

 

[kgood]

Kurt,
Specifically which engine are you talking about here?

A Detroit Diesel 6V53N. I have owned several of them over the years.


It's as if there was no need to event the term horsepower, ehh?

Torque is not work. Horsepower is work. The physics was settled a long time ago.

Now, if a manufacturer has not geared a vehicle to use said horsepower, they are incompetent, or (more likely) had a different mission in mind.

I won't even touch this one.
Kurt

 

[Ted Johns]

A Detroit Diesel 6V53N. I have owned several of them over the years.

Detroit Diesel 6V53N - 183hp to about 220hp - 1485lbs

454 Chevy - 230hp to over 450hp - 650lbs


So, did your 6V53N out accelerate the 454 Chevy due to some magic beans? Or is there perhaps more to the story?

 

[kgood]

Magic Beans

Well, you'd have to understand torque, and how it relates to work. Then you would have to understand how quickly 2-stroke diesels accelerated compared to 4-strokes. Then you would have to remember how poorly 454 Chevs performed in the '70's. Most of the answer lies in the fact that the 6V53 made 460-470 ft/lb torque and the Chevy was where, around 250?

Do yourself a favor. Go find someone with a modern diesel pickup, hook it up to a 6,000 lb load. Then find a modern gasoline truck of the same or more horsepower, hook it up to the same load. Then go pull a long grade with both of them. Then you'll understand.

I wish I could explain it better, but I assure you, pulling power is about torque, not horsepower. High hp's great for acceleration, but torque provides the "grunt" to do the hard work.

Kurt

 

[Ted Johns]

Well, you'd have to understand torque, and how it relates to work.

You mean ((torque * rpm) / 5252) = work (aka horsepower)? Yup, got it cold.

I wish I could explain it better...

Yup, me too.

Interesting that you assume I've never been in a diesel pickup. I assure you I have, and it was unremarkable, except for the rattle of the powerstroke 7.3L engine. I'm sure it pulled a load quite well. I'm also sure that a SI engine of the same HP would pull the same if run at a gear ratio that put the SI engine at the same HP on this "long grade". Nothing mystical about it.

Of course, many SI pickups are not geared that way, as they serve a more dual purpose mission, or they are less expensive, or both. Point being, a truck or an automobile (or an airplane, to try to stay on topic) is a large collection of compromises. Designers have chosen to focus diesel engine pickups toward the "pulling and towing" market, because of efficiency, tractability, and lack of smooth quick acceleration that would characterize a more dual purpose vehicle. The cooling system, gear train, and many other variables are optimized for towing.

Regardless, James Watt and Sir Isaac Newton (to mention but a few) were convinced that HP = work, and so am I.

 

[L.Adamson]

Interesting that you assume I've never been in a diesel pickup. I assure you I have, and it was unremarkable, except for the rattle of the powerstroke 7.3L engine. I'm sure it pulled a load quite well. I'm also sure that a SI engine of the same HP would pull the same if run at a gear ratio that put the SI engine at the same HP on this "long grade". Nothing mystical about it.

From the looks of your remarks, I can easily and justifiably assume that you've been in very "few" diesel pickups, as of late. I can assure you that the difference is quite remarkable! If I hadn't been pulling heavy loads up long & steep mountain highways all these years, then I might have a different opinion. Geeze, I'm quite sorry to say this (but not really), but I've been in too many diesels versus gas SI...................not to notice that remarkable difference. It IS not just gearing. It's TORQUE and there is much to be said for it. I refuse to sit here and read this "physics" BS, when I, as well as too many others have been around the results for far too long.

Rattle & smoke? That's the days of yesteryear....

edit: There are just far too many discussions on the Internet regarding torque & horsepower, to blatantly claim that horsepower is what makes all the difference. And many have to do with Mr. Watt and physics.

L.Adamson

 

[rv6ejguy]

Since 2 strokes develop about the twice the hp of a 4 stroke, I was suggesting that is not really a fair comparison. Apples to apples:

1. Same displacement
2. Same # of power strokes
3. Same manifold pressure

Kurt, just curious, you mention a 2 stroke atmo diesel. I was always under the impression that these need a supercharger and/ or turbo to function? Am I wrong and how did your's work without this? Was it just used for starting or scavenging or did it also boost manifold pressure? The WAM has both, correct?

 

[rv6ejguy]

Physics BS?

Geeze, I'm quite sorry to say this (but not really), but I've been in too many diesels versus gas SI...................not to notice that remarkable difference. It IS not just gearing. It's TORQUE and there is much to be said for it. I refuse to sit here and read this "physics" BS, when I, as well as too many others have been around the results for far too long.

edit: There are just far too many discussions on the Internet regarding torque & horsepower, to blatantly claim that horsepower is what makes all the difference. And many have to do with Mr. Watt and physics.

L.Adamson

Well the reason there are so many discussions about torque and hp on the internet is because lay people continue to post nonsense and ignore the science and physics. It has been established long ago in all engine designer's minds what motivates vehicles and I can assure you it is not torque. Unfortunately the torque idea is well entrenched even in some people who should know better. Last month I was on a somewhat famous engine builder's website which had a ridiculous discussion about hp and torque, lambasting the "idiots" who thought hp was more important than torque. Ahhhh... I quietly left the site.

All knowledgeable engine builders and dyno operators look at average hp within the tested rpm band to compare results from run to run. More torque at a given rpm = more hp and power under the curve is what's important. Less informed people (and there are many dyno operators in this category) look at peak torque and hp figures which are pretty meaningless except for bragging rights.

"Physics BS", well what can I say about that? On this planet at least, the laws of physics are pretty well established, repeatable and apply to all of us and all things last time I checked.

 

[Mike S]

Not sure if it is really a diesel, or spark ignition, but take a look at this info.

Burns kerosene (diesel fuel)

 

[rv6ejguy]

Good luck to them if they can come back from the problems of the past. If they have not changed some of the parts of the old design like the gearbox/ clutch system, I'd be worried about the same old problems.

I'm mystified that Diamond is listed here as a possible client. To say that Thielert and Diamond did not part company in the best way is an understatement. I think Cessna also nixed any future dealings with Thielert after what transpired almost right after they inked the first deal with them.

Thielert has a lot to prove IMO.

 

[kgood]

Torque is meaningless?

Since 2 strokes develop about the twice the hp of a 4 stroke, I was suggesting that is not really a fair comparison. Apples to apples:

1. Same displacement
2. Same # of power strokes
3. Same manifold pressure

Kurt, just curious, you mention a 2 stroke atmo diesel. I was always under the impression that these need a supercharger and/ or turbo to function? Am I wrong and how did your's work without this? Was it just used for starting or scavenging or did it also boost manifold pressure? The WAM has both, correct?

First, the debate was atmo diesel vs atmo gas, because you were saying that without the turbo, the diesel would fall on its face. I disagreed. You can keep coming up with all kinds of things to make it "fair", but is still atmo diesel vs atmo gas. But I see where you're coming from - just no way to be on the same playing field.

Second, you are right. As far as I know, all 2-stroke diesels require a blower to run. I believe the term "supercharger" is used when a blower is used on a gasoline engine to create boost. But in the case of the 2-stroke diesel, the blower acts only as an air pump to provide air to scavenge the cylinders, not to create boost. My WAM does have a blower. Its function is to provide air for starting and idle. The turbo provides the boost. As you know, there are some companies developing a turbocharger with an electric motor to act as an air pump for startup and idle, then work as an alternator once boost is being produced. The Detroit Diesel 2-stroke engines are considered "normally aspirated" if they do not have a turbo or other device to produce boost.

Well the reason there are so many discussions about torque and hp on the internet is because lay people continue to post nonsense and ignore the science and physics. It has been established long ago in all engine designer's minds what motivates vehicles and I can assure you it is not torque. Unfortunately the torque idea is well entrenched even in some people who should know better. Last month I was on a somewhat famous engine builder's website which had a ridiculous discussion about hp and torque, lambasting the "idiots" who thought hp was more important than torque. Ahhhh... I quietly left the site.

All knowledgeable engine builders and dyno operators look at average hp within the tested rpm band to compare results from run to run. More torque at a given rpm = more hp and power under the curve is what's important. Less informed people (and there are many dyno operators in this category) look at peak torque and hp figures which are pretty meaningless except for bragging rights.

"Physics BS", well what can I say about that? On this planet at least, the laws of physics are pretty well established, repeatable and apply to all of us and all things last time I checked.

Here's a "ridiculous" scenario from a "less informed person", who really wants to understand: I have an over-the-road heavy haul rig with a CAT C15, 550 hp diesel in it. On a daily basis, it pulls 250,000 lb loads up steep grades at 45-60 mph. Now, lets replace the CAT with a 550 hp 502 Chevy, with whatever gearing you choose. You and I both know that it MIGHT, with very low gearing, pull the same load up the same grade at 5-10 mph. Now before you start bringing up cubic inches, power curves, rpm, - whatever -, remember, work is all about horsepower; it has nothing to do with torque. Somehow the fact that the CAT produces over 1800 ft/lb torque compared to the Chevy's 450-500 ft/lb has nothing to do with it (according to you and Ted).

I'm not trying to be a jerk here; it just seems absurd to me that you could leave torque out of the equation. In my scenario, torque is what makes ALL the difference, HP being equal. I must be missing something. I'm no physics major, just a diesel guy, so help me out.

And L Adamson's right; the difference between today's gas and diesel pickups is remarkable - and I'm sure a lot of "physics and science" went into them, just obviously not the kind you're talking about. As I said, before you say any more, do the homework. Go out and actually test a '10 or '11 diesel truck against its gasoline counterpart, under load. Work the stew out of 'em. then come back and tell us that torque is meaningless.
Kurt

 

[rv6ejguy]

Kurt, thanks for clearing up the blower part and 2 stroke diesels.

I'll stop debating here but provide the following link for more food or ammunition for thought: http://www.vansairforce.com/community/showthread.php?t=46423:) Enjoy!

As long as we are all having fun flying our RVs, I think it's all ok.

 

[Mike S]

As long as we are all having fun flying our RVs, I think it's all ok.

That is what it is really all about.

Soon...........

 

[kgood]

Kurt, thanks for clearing up the blower part and 2 stroke diesels.

I'll stop debating here but provide the following link for more food or ammunition for thought: http://www.vansairforce.com/community/showthread.php?t=46423:) Enjoy!

As long as we are all having fun flying our RVs, I think it's all ok.

Thanks Ross. I looked, I enjoyed, and I'm still confused! Amazing all the different opinions. At least I don't feel alone in my confusion. I am convinced, however, that HP and torque somehow work together to keep my RV 9 in the air. And that's a beautiful thing....

Kurt

 

[Ted Johns]

I'm not trying to be a jerk here; it just seems absurd to me that you could leave torque out of the equation.

No one is leaving torque out of the equation:
HP = ((torque * rpm) / 5252)

Somehow the fact that the CAT produces over 1800 ft/lb torque compared to the Chevy's 450-500 ft/lb has nothing to do with it (according to you and Ted).

What is patently obvious to the person who apprehends the equation above, is that the chevy can put out 1800 ft/lbs of torque at the same shaft rpm (1200) the Cat C15 does. It simply needs a gearbox.

You and I both know that it MIGHT, with very low gearing, pull the same load up the same grade at 5-10 mph.

Nope, I don't know that. It would pull the load at the same speed.

Now, it might have trouble getting to the same speed without more gears to choose from, due to a HP curve that is less flat. And it would be running much closer to it's design limits than the Cat C15, so it couldn't be expected to last nearly as long.

The Cat C15 is 928 cubic inches. If someone wanted to make a 928ci SI engine, it could be designed for a very flat torque curve at 550hp. It wouldn't be as fuel efficient as the diesel.

The issue you are likely struggling with is the shape of the HP curve. The flatter it is, the fewer gear changes are required to accelerate a given load at a given rate. Engine designers call this tractability. This is an important consideration for a heavy truck or towing vehicle.

Less so in an airplane.

 

[WAM120RV]

Torque

Hi

Horse power is the product of torque and RPM. It does not matter how fast you spin an engine if it is not prucing torque (turning monent), you won't get any horse power out of it.

Torque is the measurement of how much turning force the engine produces, diesels produce more than petrol engines.( thats what we call gas in the Uk).

The problem with diesels is that the moving parts have to be heavier to cope with the higher compression needed by the engine to cause ignition of the fuel. The heavier wieght of pistons and rods causes more interia which means the need for heavier gudeon pins etc. So, it is difficult to get them to turn over at high RPM. Thats why most diesels in cars dont go above about 5000 RPM.

Petrol engines though often turn at up to well over 7000. My Yamaha will hit 11000, and F1 cars can reach 20000 RPM. The torque from these engines compared to the same capaicty diesel engine will be lower, but the higher RPM allows the to produce more horse power.

What has allowed the diesel to catch up with the petrol engine in terms of horse power is the turbo, inter cooler and common rail systems.

Now here is something interesting, the Wilksch engine is 1.8 litres a lycoming 0.235 is 3.85, so has more than twice the capacity. The Wilksch produces 120 hp at 2750, the lyc 115 at 2800 rpm. oF course the Wilksch is a two stroke so has twice the power strokes of the lycoming, but uses less fuel.

So what is effectively a smaller capcity engine is producing more horse power at a lower RPM, which demonstrates the effect of torque. When you consider that two stokes never get as clean a burn as a 4 stroke so that the two powere stroke never quite produce twice the power, its shows again the effect of torque helping produce more Horse power at the lower RPM.

Now when the larger capacity cylinders are fitted which will make the Wilksch almost exactly half the capacity of the O.235, it produces 140 horse power at 2750. So for 50 rpm less you are getting an extra 25 HP, and still probably less fuel burn. Torque!!!

The extra bonus is that it doesnt loose power at altitude like the lycoming because of the turbo. If Kurt is one of the first with these The comparison should be re run against the 0.320 powered 9, I suspect at altitudes above 8000 that the Wilksch will run equal to the lycoming.

Don't get me wrong I think Lycomings are great engines, I have an 0.320 in my RV4, but diesels are improving and I love flying my 9 behind the Wilksch it is so simple to operate. No mags, no carb heat, no plugs to fowl, no mixture to lean.

Hey Kurt keep up the good work and let me know what mods you propose I may put them in my new cowl.

Steve

 

[Rotary10-RV]

power take off

Thanks for the history Bill - my guess about the relationship was based entirely on timing of the "we're here!" announcements and the fact that they both looked like the Jumo-Junkers design (opposed pistons/dual crankshafts).

I'm curious about the offset of the timing, though - what is the advantage? Is it meant to escape harmonics, or is there another reason? Seems like your gears & other parts could be more symmetrical if they were evenly loaded.

Another thought that springs to mind with this design is that since the prop shaft is gear driven there ought not be a particular limit to the number of cylinders in line - thus making the engine very "scalable." Just have the prop shaft run the length of the engine with drive gears every couple of cylinders. This would also allow lighter crankshafts and gears, as each gear need only support the power generated by a single pair of pistons. The main drive shaft could be hollow and thus fairly light while conveying incredible torsional strength.

Well, speculation is all fun and no real work. Someone will figure out a better mousetrap one of these days, and I'll undoubtedly opt to double the horsepower in my toy when that happens.

There are two reasons for the crank offset, it is supposed to make the port timing and therefore efficiency, better. Second, it makes the power takeoff easier, and the needed gearing between cranks lighter. In the dair engine I believe they use two equal cranks and take the prop drive off the gear between them, since it makes the layout more conventional.
Bill

 

[L.Adamson]

"Physics BS", well what can I say about that? On this planet at least, the laws of physics are pretty well established, repeatable and apply to all of us and all things last time I checked.

Fine....................then explain in exact scientic terms... as to what causes lift (in an airplane), and why modern 200 HP H6's can't seem to outdo those 70 year old 180HP designs. Should be easy, physics wise...

L.Adamson ---- RV6A & a lay person's diesel Silverado

 

[L.Adamson]

The issue you are likely struggling with is the shape of the HP curve. The flatter it is, the fewer gear changes are required to accelerate a given load at a given rate. Engine designers call this tractability. This is an important consideration for a heavy truck or towing vehicle.

Then there is no argument. A diesel truck simply wins in the pulling a heavy load contest; considering we're not going to the trouble of outfitting the vehicle with a much greater set of gear ranges. And of course, the diesel will last longer, use less fuel, but won't win any fastest speed trials at the Bonneville Salt Flats.

Personally, I think I'll improve on the "steam" powered plane. Then I can have full torque before the prop even makes a revolution. Could go electric, but it's too modern..

L.Adamson ---RV6A

 

[kgood]

, but won't win any fastest speed trials at the Bonneville Salt Flats.



L.Adamson ---RV6A

Actually, we have. Dad and I built a new Bonneville streamliner in '08, the Mormon Missile, powered by a 6.6L Duramax diesel. It currently holds both the FIA and SCTA records in its class. Our FIA record is 341 mph (two-run average). Top speed so far is 353 mph.

Interestingly, our record is faster than the Blown Gas Streamliner of the same engine class (although there are smaller engines with faster records, but not much faster). We are even pretty close to the Blown Fuel Streamliners in speed.

To put our records into perspective, the current overall wheel-driven, piston-powered record stands at 415 mph, A record set in '08, by a car with two blown fuel Chrysler hemis with 4-wheel drive. An amazing car, working on that record since 1985.

We're continuing to make adjustments and improvements to ours; we're sure we can get much closer to the 400 mph mark.

One more thing about diesel efficiency: the blown fuel streamliners burn 20-30 gals of fuel per run. Ours burns under 2 gals of pump diesel fuel. But we sure go through a lot of ice for the intercoolers!
Kurt

 

[L.Adamson]

Actually, we have. Dad and I built a new Bonneville streamliner in '08, the Mormon Missile, powered by a 6.6L Duramax diesel. It currently holds both the FIA and SCTA records in its class. Our FIA record is 341 mph (two-run average). Top speed so far is 353 mph.

Interestingly, our record is faster than the Blown Gas Streamliner of the same engine class (although there are smaller engines with faster records, but not much faster). We are even pretty close to the Blown Fuel Streamliners in speed.

To put our records into perspective, the current overall wheel-driven, piston-powered record stands at 415 mph, A record set in '08, by a car with two blown fuel Chrysler hemis with 4-wheel drive. An amazing car, working on that record since 1985.

We're continuing to make adjustments and improvements to ours; we're sure we can get much closer to the 400 mph mark.

One more thing about diesel efficiency: the blown fuel streamliners burn 20-30 gals of fuel per run. Ours burns under 2 gals of pump diesel fuel. But we sure go through a lot of ice for the intercoolers!
Kurt

Well, that's quite impressive! I just read a few additional links about the vehicle. The Bonneville Salt Flats was part of my RV6's phase one test area (Wendover airport). At least I had a lot of good landing spots as well as the freeway. Two hours after my initial revolutions around the pattern, I headed off to Wendover from U42, followed by a chase plane.

Back in 1970, the machine shop where I worked, did some modifications on a large disk (some kind of a catalytic converter) for the hydrogen peroxide & liquid natural gas powered ---- Blue Flame. It set a speed record that lasted for quite a long time.

In the meantime, here is two links for the "laymen" in regards to diesels, torque, and horsepower. Torque does have a direct relation, regardless of what a few, who haven't had much experience with diesels seem to imply. Anyone that's been driving Duramax's (as in your race car) has certainly noticed the difference between these and a SI powered vehicle. I've owned two Duramax's over the last seven years, drive in a mountainous area pulling loads; and I'm very aware of the difference, as so many others from around here are.

http://www.frontierpower.com/library/makingsense.htm
http://www.carkeys.co.uk/features/technical/636.asp

L.Adamson --- RV6A

 

[Ted Johns]

In the meantime, here is two links for the "laymen" in regards to diesels, torque, and horsepower. Torque does have a direct relation, regardless of what a few, who haven't had much experience with diesels seem to imply.

The two aforementioned links are an excellent primer. They indicate exactly what Ross and I have been saying. I encourage those confused by the relationship between HP and torque to read them.

 

[Mike S]

the relationship between HP and torque to read them.

Old saying; HP sells engines, torque wins races.

 

[kgood]

Ok Ross and Ted,
I've been thinking about this.... and I read part of one of the articles L Adamson provided, where it said that two engines producing the same HP at the same RPM, would produce the same torque.

Given my two comparisons: my 300 hp gas suburban vs my 300 hp Diesel pickup - and the Cat powered heavy haul rig vs the same rig with a 550 hp Chevy -

Are you saying that if I were to create some type of optimal gearbox for the gasoline engine - a torque multiplier -, then run the engine at the RPM required to achieve rated hp (300 or 550 in these examples), that the gas-powered rig would pull the same load up the same grade at the same speed as the diesel does? If that's what you're saying, then I think I get it. Not a very practical or reliable thing to do, but doable in theory I suppose, leaving efficiency and power loss from the gear train out of the discussion.

Let me know if I'm thinking straight. It would not make me a convert to the SI Gospel Fellowship, but I may be starting to understand what you're trying to tell me

Kurt

 

[JHines]

Ok Ross and Ted,
<SNIP>
Given my two comparisons: my 300 hp gas suburban vs my 300 hp Diesel pickup - and the Cat powered heavy haul rig vs the same rig with a 550 hp Chevy -

Are you saying that if I were to create some type of optimal gearbox for the gasoline engine - a torque multiplier -, then run the engine at the RPM required to achieve rated hp (300 or 550 in these examples), that the gas-powered rig would pull the same load up the same grade at the same speed as the diesel does? If that's what you're saying, then I think I get it. Not a very practical or reliable thing to do, but doable in theory I suppose, leaving efficiency and power loss from the gear train out of the discussion.

<SNIP>

Kurt

I'm not Ross or Ted, but that's exactly right. moving a load through a distance is WORK, and the rate (speed) at which it is done is POWER. No ifs, ands, or buts from a physics standpoint. Same power rating = same capacity to do work at a specific rate, or if you prefer the engine can input mechanical energy into a load at the same rate.

Now, keep in mind Ross' caveat about the shape of the power curve - horsepower ratings are commonly only given at their peak, which occurs at a specific, fairly high RPM. So in your example if you started the "optimal geared" gas rig and the Diesel rig up the same constant grade at the same speed, they would stay neck-and-neck. That does not necessarily mean the two engines would have the same ability to accelerate the load to a certain speed in a certain time from a standstill.

For example, the SI engine could be very "peaky" like a sport bike engine, In which case you'd need not only very low gears but a lot of gear ratios to allow the SI engine to quickly accelerate to peak HP RPM and stay there as the vehicle started at rest and accelerated to whatever speed.

 

[Ted Johns]

Are you saying that if I were to create some type of optimal gearbox for the gasoline engine - a torque multiplier -, then run the engine at the RPM required to achieve rated hp (300 or 550 in these examples), that the gas-powered rig would pull the same load up the same grade at the same speed as the diesel does?

Yes, precisely! (And there's no need for the gearbox to be any more "optimal" than the diesels).

There are no magic beans, despite our quite human tendency to anthropomorphise inanimate objects. The ability of a diesel truck to pull a load well has nothing to due with it being a diesel, or "extra torque-y" (whatever that means), or a CI type engine. It's ability comes from the engine designers carefully engineering a very flat torque curve. It's reliability comes from the same careful engineering. Take your 6V53 diesel, for example. It weighs well more than twice what a chevy 454 weighs. What do you think the purpose of all that "extra" steel and cast iron is? Well, to some extent extra strength is required by the diesels higher compression ratio (and this has implications for aircraft diesels) , but it is also an indication of design for reliability. If engine designers wanted to, they could take the same design approach to a gasoline truck engine. In fact, decades ago they did, and they worked just fine.

Where the "magic beans" come into play for a diesel is in the extra efficiency. And sadly, it isn't really magic, just thermodynamics. The high compression ratio gives the engine an advantage in thermal efficiency, relative to the typical gasoline engine. That diesel is a more energy dense fuel is a help as well. These are compelling advantages for commercial / industrial applications. Turbocharging, common on diesels now, is another efficiency improver. It captures some of the waste energy in the exhaust, just as it does in gasoline engines.

The wiki page on diesels is excellent, and covers the pros and cons vis-a-vis gasoline engines.
http://en.wikipedia.org/wiki/Diesel_engine

 

[David-aviator]

I believe the planet will run out of oil before there is a suitable diesel engine for light airplanes. We are living in the "golden age" of internal combustion engines. Enjoy what we have. It is all down hill from here with China coming on line with auto production and several billion people who too wish to drive down the road also, not to mention to fly a personal airplane.

The fact that we are now dealing with an oil leak 5000' below the Gulf surface is indicative of how things will be in the near future - crude oil, like fresh water, is a non-renewable commodity and its availability is about peaked world wide.

Things will be very, very different for our grandchildren 75 years from now. They will look back at our u-tube videos with wonder and amazement at the life style we enjoyed.

 

[ddurakovich]

Algebra is the answer!

If the formula:

Torque * RPM
-------------- = HP
5252

is rearranged, you get :


Torque = HP* 5252 / RPM


The higher the RPM for a given HP, the lower the torque.