Lycoming Superiority

[Andy_RR]

Ross,

I think, like a lot of people, if you see a spectacular fuel consumption number or power figure, it's too hard to resist believing it. Unfortunately, there is so much heavily optimistic data out there you really have to be a little cynical about it.

I am, because having worked developing GDI engines in the past I have first hand experience that a) it takes some effort to accurately measure fuel consumption, b) it's really hard to achieve good FC figures, leave aside spectacular ones, and c) there is so much hype out there, that any optimistic figures that come off the dyno tend to get published in an attempt to steal the limelight.

Lets have a look at some of your examples:

Firstly, the R3350 is turbo-compounded, so having two working cycles, it has a significant cycle efficiency advantage - while it's undoubtedly a great way forward, it's complicated and potentially doesn't scale well so let's dismiss this as not apples-with-apples comparison.

Your quote on the Robinson LS-6 conversion doesn't square with either the reality of IC engines, or what I found quoted here (http://www.seabee.info/seabee_engine_conversions.htm) about the LS-6 - it's more like 0.45-0.50lb/hp.h

The Lexus numbers you quote are more like reality. Again, they're giving you the best possible FC, so it only gets worse from the 0.408 they quote

The GM 3.6L GDI V6, which I know reasonably well from things I've heard around the traps, is running lean-stratified with all the toys to achieve its 0.372. Again, this will probably be the best ever figure from this engine and anywhere else in the speed-load map will be worse and as soon as you go stoich, much worse than an equivalent MPI version. Honestly, the old 3.8L pushrod V6 is a much better engine for fuel consumption in the real world.

You've said a lot about BMW engines, but so far I'm guessing they've not published any BSFC data for you to see - you certainly haven't quoted me any. The 15% you claim is from which baseline? It's quite easy to move from 0.55 to 0.47 by minimising your throttling losses - that makes 15%, but doesn't give you the spectacular FC you are looking for

Now Jess Myers claim of 0.34 leads me to another point. I don't know what an EFI-equipped SBC is, but if it runs on gasoline, I just don't believe this data. 0.34 is superlative diesel territory!!!! Why is it, that people can see these dynos spit off an absolutely ridiculous number and no-one questions it? I see this all too often, especially in the tuning industry, where superflow-type dynos are popular. Not very far from standard NA engines suddenly are producing 16Bar BMEP and 140% volumetric efficiency without a turbocharger! Clearly these power figures are rubbish! If you can't measure your power accurately, then there is no way you will be able to measure realistic BSFC!

I really think your hope of significant gasoline fuel consumption gains in the future is a folorn one. It is possible to produce class-leading gasoline fuel consumption with an air-cooled, carburettored, push-rod, two-valve engine with manual mixture control, none of which is 'modern' technology. It's all in the way you use it and the compromises you need to make.

For aviation, the real leap forward in FC will come with diesel engines, if and when. Thermodynamically, they have so much going for them, it's not funny. It's just a shame that the current products either don't capitalize on diesel's strengths or are so embryonic and lacking realistic development funds.

We can live in hope though.

A

[gmcjetpilot]

Originally Posted by Andy_RR

For aviation, the real leap forward in FC will come with diesel engines, if and when. Thermodynamically, they have so much going for them, it's not funny. It's just a shame that the current products either don't capitalize on diesel's strengths or are so embryonic and lacking realistic development funds. We can live in hope though. A

It's that Darn weight which is so critical to light planes which is a bummer for the Diesel. Also radiator placement, ie drag, is an issue. It does not matter if you have an efficient engine with a draggy airframe.

[Andy_RR]

Who mandates that diesels must be liquid cooled?

I think an air-cooled diesel, far from being just possible, is actually the best way forward.

[frankh]

A german manufacturer (at least I think its German) Deutz and Yanmar both make aircooled diesels.

Of course they weigh a metaphoric ton as well!

Frank
7a...Phase 1 complete!

[Walter Atkinson]

Several things to ponder on this thread so far:

1) So far, no one has yet produced a GASOLINE auto engine with a BSFC(min) as good as the .385 of the TCM and Lycoming NA engines. This includes the turbo-normalized TCM engines.

2) Valve temperature is not related to EGT. It is very closely related to CHT and that's why auto engines have less trouble with exhaust valves than aviation engines.

3) The slight roughness felt LOP in a well-balanced F:A engine is the cycle to cycle variability. As noted, this can be improved upon with better head design and better fuel vaporization. It can never be completely addressed since there is also an efective ignition-drift factor involved and you do eventually get to Idle Cutoff!

4) As a Navy Admiral once said, "Water cooling an aircraft engine makes about as much sence as air cooling a submarine engine." <VBG>

5) There is compelling evidence that the next, significant improvement in BSFC for aviation engines is going to be the ability to alter timing according to the direct measurement of thetaPP (no "mapping"). That is under developement. The engines so equipped are showing BSFC(min) values in the .37 range on 100LL and, so far, have proven impossible to make detonate at any mixture setting! We've been miserable failures at inducing detonation in these engines for the last five years--and we have tried--even on 95UL aviation fuel.

6) The TC-18 varient of the R-3350 had a TBO of 600 hours when operated ROP. It had a 3600 hr TBO when operated at approximately 50dF LOP AT THE SAME POWER. That was based on about 400 MILLION hours of flight data collected, compiled, and evaluated by American Airlines.

7) We must be careful in trying to make direct comparisons in auto and aviation applications. While the combustion process it, no doubt, the same, the application of % power is quite different. If all we required of our aircraft engines was 30% power, they might have 10,000 hour TBOs also.

8) If auto engines were better than aircraft engines for aircraft applications there would have been some successful attempts, but so far there is no wide-spread success using auto engines in aircraft. (see #4 above!) A leading test facilty in Detroit has told me that they cannot get ANY auto engine to last more than 200 hours at full power on mulit-weight oil, while they have been able to get them to almost 300 hours on single-weight oils. If we were getting 2-300 hour TBOs on Lyc and Cont. engines we would be screaming. Just ask the guys who run at the 24 Hours of Lemans how easy it is to get an auto engine to last 24 hours at the powers we ask of our aviation engines on every flight for 1500-2000 hours!

Walter

[rv6ejguy]

I'll make a few observations here. One, I follow all the latest developments in auto engines very closely through a number of sources. Two, as pointed out by Andy, how can we trust the numbers published? Truth is, we can't. However, I do believe the stuff that SAE publishes and I believe what friends in Europe driving the latest offerings tell me about fuel consumption.

The Valvetronic when applied to GDI would seem to be a huge advantage in keeping BSFC figures low at so called part throttle settings-typically not an efficient range for gasoline engines. This has helped to narrow the gap on diesels.

I only am the messenger here. Depending on the vintage of Superflow dyno, airflow measurement on some models was known to be inaccurate however this does not affect BSFC figures. I too find the figure of .34 for a SBC hard to believe unless they had 15.5 to 1 CR, but I wasn't there.

Diesels, well the the Deltahawk is only marginally better than the best Contis and 4 stroke diesels as pointed out are too heavy in their present form.

The SAE World Congress report this year forecasted a resurgence in GDI and a slight softening of diesel sales trends over the next few years due to the efficiency gains on new gasoline engines. This is the overall opinion from engineers from all car companies. I think you have to respect that.

BMW is pursuing both low pressure variable geometry turbocharging and turbocompounding. The former is to be released in the 2008 model years according to what I've read. I don't see a problem scaling TC technology. Cummins has been using it for several years on their DTC11-01 engine.

The Lexus combined MPFI and GDI technologies in the new 3.5. This engine demonstrates only slightly higher BSFC values even up in the 4000-4500 rpm range where it might operate in an aircraft.

Walter's comment about submarines made me laugh. Good one. I think Honda's forray into piston aircraft engines needs to be looked at closely. In their 3 year study with Continental they concluded that liquid cooling was the way to go. I don't think Honda who is one of the leading producers of engines of all types (except aircraft) and vastly experienced would have done this if it wasn't deemed better after all this study. Honda stated publicly that their design gave better BSFCs, lower noise, lighter weight and lower emission than comparable aircraft engines, probably true given their expertise.

Point one- It seems that GM has produced an engine now with lower BSFC figures and probably so has BMW who rarely releases figures like this.

Point 6- TBO is a misnomer as applied to aircraft engines. This term seems to include any parts replacements not involving crankshaft removal. Today in the auto world, we'd consider opening up the engine in any way and replacing internal parts unacceptable. I can assure you that NO R3350 EVER went 3600 hours without LOTS of parts replaced along the way. As I said, my father flew these things and a good friend here was a flight engineer on them. Popped jugs and dropped exhaust valves were routine on these things. Please share that AA data with me and what parts were replaced on the way to that 3600 hour overhaul!

Point 7 and 8- This is the oldest argument about auto engines and it holds no water today. GM and Lexus who share some of their data more readily do various 250, 400, 1200 and 1600 hour tests under WOT high rpm and other conditions which would make an aircraft engine guy faint on ALL their new engine designs. You might want to follow some of the stuff published by GM Powertrain and SAE. I don't know who your source was in Detroit but this does not align with what has been widely published. This simplistic reasoning does not transfer into the European market where cars are routinely driven at power settings between 60-100% for their entire lives and demonstrate the same sort of life we seen in North America. By the way, Rotary Airforce has used Subaru engines in their gyrocopters for over a decade and has accumulated well over 100,000 flight hours with zero mechanical engine failures to my knowledge to date. Eggenfellners conversions seem to be doing pretty well too from an engine perspective.

From personal experience building showroom stock endurance racing and all out road racing for 20 years professionally, I can tell you the thing about limited life on multigrade oils is completely incorrect. We run Mobil 1 15W50 and now 5W50 in all our engines and have NEVER had a lubrication related failure. One fellow put 25,000 miles on his Toyota 4AG SS engine over 6 years, shifting at between 7500-7700 rpm for its entire track life. The engine was pretty mint when opened up after this long term abuse.

I've run turbocharged engines producing over 200hp/L for almost a decade at up to 8000 rpm on Mobil 1 and reused the bearings for 4 seasons regularly. This was not the case using conventional single weight oils. Mobil 1 is light years ahead of traditional oils. To put this abuse and power level into an aircraft perspective, this would be about 1800hp on a IO-540. How long do you think a Lycoming or Conti would last at this equivalent power level? Aircraft engines have such low specific outputs that nothing is taxed very hard. It would be comparable to running a Viper V10 at 3000 rpm and 1/2 throttle. I have little doubt it would last 3-5000 hours to generate the nominal 200hp cruise of an IO-540. This equates to 67 hp on my Subaru conversion, hmm. I think it will last pretty much forever at 67hp, this is about 2500 rpm and 30 inches.

The notion that auto engines can't last running at something like the 4600 rpm I run my turbo Subaru at in cruise is patently wrong and outdated. Millions of auto engines world wide do it day in and day out without fragging. So for about the 6th time on this forum, I'd ask you to show me proof of this statement from a reputable source.

The point of all this is that a modern six from Toyota, Honda, GM or Subaru can do the same job as an IO-540 once fitted with a well developed redrive at a fraction of the 40K new Lycoming price. I'm putting my money where my mouth is and attempting to prove it. I could be wrong but I don't think so.

[gmcjetpilot]

Originally Posted by xl1200r

gmcjetpilot,

those HD race wins weren't with any run of the mill air-cooled engine. Those bikes are running liquid cooled V-ROD engines (based on the sort-of successful VR1000 of the 90's), which aren't exactly known for thier low-end grunt And like any proper race engine, they get torn down plenty over the course of a weekend.

I have to say, my 1200cc v-twin is sure scream-in and asking for more at 6000rpm

I have no delusions that the NHRA Pro Stock bikes have very special engines. My comments just to illustrate, the high rev many little pistons, verses, the two big piston approach. The V-rod is 1200cc v-twin, was introduced 2001 and still is in production. Yes it is water cooled, OHC and fuel injected. Yes I agree any PUSH ROD engine is limited practically to 6,000 rpm. However in a 2,700 rpm airplane engine that's not much of an issue.

If I was street racing motor cycles I would not have a H-D I would have a Suzuki GSX1300R, Hayabusa or something like that. Clearly the Japanese crotch rockets are faster off the shelf.

[David-aviator]

Originally Posted by Walter Atkinson

Several things to ponder on this thread so far:............
Walter

1) So far, no one has yet produced a GASOLINE auto engine with a BSFC(min) as good as the .385 of the TCM and Lycoming NA engines. This includes the turbo-normalized TCM engines.
Even Lycoming won't claim that figure. At least not with regard to the IO-360-C1C in the PA-28R-200. 75% power requires 10.15 gph which is a BSFC of .405. At 55% (8gph) it is .435 which is the number I've always used in trying to determine Lycoming HP.

4) As a Navy Admiral once said, "Water cooling an aircraft engine makes about as much sence as air cooling a submarine engine." <VBG>
The Admiral drinks sea water. The best of the best WWII fighters were liquid cooled. Unfortunately, the Navy had none of them, maybe that's why he said what he said.

6) The TC-18 varient of the R-3350 had a TBO of 600 hours when operated ROP. It had a 3600 hr TBO when operated at approximately 50dF LOP AT THE SAME POWER. That was based on about 400 MILLION hours of flight data collected, compiled, and evaluated by American Airlines.
Very interesting. My experience with the R-4360 (big brother of the 3350) was awful, I almost quit flying it was so bad having been assigned to a machine with it out of the F-86. At least one engine blew up or had to be shut down every 4th flight. ROP, LOP, hogwash, it would not have made a bit of difference - there simply were too many moving parts - something was bound to fail sooner than later and it always did.
7) We must be careful in trying to make direct comparisons in auto and aviation applications. While the combustion process it, no doubt, the same, the application of % power is quite different. If all we required of our aircraft engines was 30% power, they might have 10,000 hour TBOs also.
You have not read the report of a Subaru boxer engine auto running for some 19 days at an average speed of over 100 mph. It is a matter of record. The race was in Arizona.

8) If auto engines were better than aircraft engines for aircraft applications there would have been some successful attempts, but so far there is no wide-spread success using auto engines in aircraft.
More hogwash. You've been drinking sea water with the Admiral. The Subaru is making an ever wider ripple on the pond.

dd

[Kevin Horton]

Originally Posted by David-aviator

8) If auto engines were better than aircraft engines for aircraft applications there would have been some successful attempts, but so far there is no wide-spread success using auto engines in aircraft.
More hogwash. You've been drinking sea water with the Admiral. The Subaru is making an ever wider ripple on the pond.

The Subaru certainly is interesting. The core engine appears to be very durable. The ancilliary systems are probably the weak link (i.e. reduction drive, cooling system, fuel delivery system, etc.). The market isn't big enough to fund very much engineering or testing of those systems, so the early adopters are doing the developmental testing for the vendors. It is often said that you learn more from a failure or problem than from a successful test. The good news is that the Subaru guys are learning more each year.

It will probably be several years before anyone is selling a Subaru conversion that offers total system reliablity, weight and performance that match a Lycoming. To anyone who says we are already there, I ask: if this is true, why is the major vendor still making major design changes?

[rv6ejguy]

Originally Posted by Kevin Horton

The Subaru certainly is interesting. The core engine appears to be very durable. The ancilliary systems are probably the weak link (i.e. reduction drive, cooling system, fuel delivery system, etc.). The market isn't big enough to fund very much engineering or testing of those systems, so the early adopters are doing the developmental testing for the vendors. It is often said that you learn more from a failure or problem than from a successful test. The good news is that the Subaru guys are learning more each year.

It will probably be several years before anyone is selling a Subaru conversion that offers total system reliablity, weight and performance that match a Lycoming. To anyone who says we are already there, I ask: if this is true, why is the major vendor still making major design changes?

As you rightly point out, small companies, small budgets, slow progress in development. Still, after a relatively short time, Jan is making a $2M dent in Lycoming sales every year now. Lycoming is still making changes to crankshafts after 40 years! Textron has a somewhat larger R&D budget.

As David pointed out, the wave only gets bigger every day.

On the R3350, some sources were saying TWA had 10 in flight shutdowns per DAY in commercial operation. BATCAT sources did not have kind things to say about the reliability of R3350s either. I've contacted some friends who flew and worked on these things so Ill soon have the real answer here.