Technology Today vs the 1960 Mooney Design

[cliffy]

1 minute ago, MikeOH said:

And, for the wet-rag point-of-view, here I am!

Automobile engines are engineered for use in, wait for it (credit to Dave Barry), automobiles, NOT aircraft.  As such, they are NOT designed to operate at even mid (50%) power levels for very long before overheating problems occur, not to mention compromised longevity.  They are water cooled with all those attendant 'advantages'  Their rpm vs torque and power curves are way off from what is optimal for propeller driven aircraft; hence the need for an expensive reduction gearbox which just adds another expensive point of failure.  Then you need to gen up a way to drive the prop governor.  Are you ok with a single plugs/ignition per cylinder?  What are GM's altitude specifications? What happens above, say, 15K feet?

Thanks, but I'll stick with powerplants designed and built for aircraft.

You posted at the same time I did :-)

It all comes down to MTBF Even 1 plug per cylinder. You now have 1 coil per cylinder there by having less chance of a single point failure, 8 cylinders suffer an output loss one half as severe as a 4 cylinder  engine and a 6 cylinder suffers a 17% loss opposed to a 12.5% loss on an 8 cylinder engine. 

When was the last time you had a spark plug fail in your car (2000 or newer) if it had proper maintenance? Never? 

Ford had 100,000 mile plugs in my 2006 truck and I started to have a plug misfire at 97,000 miles. That's about 1500 hrs of use with no maintenance. Sure beat plugs at every 100 hrs don't it? 

A back up computer at the flick of a switch would take care of the ignition dual back up. I'm not worried about plugs and when was the last time your engine computer failed? 

As I said it all comes down to MTBF AND as I noted after you- equal HP output continuously.  And I mentioned - cooling would have to be surmounted. Merlin did it. Allison did it. Just to name a couple from history. Its only a physics problem. 

[FlyingDude]

I get very excited about any idea that could cut costs in Aviation. That said, automotive engines are designed and calibrated for different mission profiles than aviation engines. They more accelerations, idling and not so often constant power settings. I would imagine that a diesel would be more aviation-like. I think this idea was implemented in some planes. Also, will automotive engines, with their extreme precision machining, handle the abrupt atmospheric changes in a climb or descend? I was told that aviation engines leak oil due to their coarse tolerances that are in place for these extreme variations in ambient conditions. Am I onto something or am I wrong?

[cliffy]

7 minutes ago, MikeOH said:

I'd be VERY interested to see MTBF data for an LS3 at, say, 200 HP continuous (around 50%) at 10,000 DA....my gut says it won't make 2000 hours.

I would think that the DA would affect the Heat Rejection (cooling) more than any mechanical issue at altitude. 200 HP is 200 HP to the crankshaft.  

Also I looked at the torque/HP curves on the engine. They're pretty good. 

kodiak-power-curve-62LS3.pdf

[cliffy]

FlyingDude-

I think the large tolerances are more attributable to being air cooled as opposed to water cooled. Especially in the cylinders.  

[carusoam]

GM likes to test some of their vehicles around Nurburgring...

Corvette and Cadillac...  full speed, and 24 hours...

That was record setting and good enough for their sales brochures...

 

As for spark plug failures... I have one.  I posted pics of it a year or so ago...

The ceramic insulator broke free and was moving around... up an down the center terminal...

It was held in place by a hoop shaped outer terminal...

The spark was strong enough, it came out the bottom of the center terminal...

Only the computer knew there was something wrong with it... until my mechanic pulled it out... 

It was a brand new plug, manufacturing defect...

 

 

As for modern car engines in experimental planes...

Find the Raptor project... Audi Diesel engine... the plane is currently flying...

Plenty of heat challenges... coolant, oil, and every seal the engine and ‘re-drive’ have in them...

The re-drive has a pair of belts delivering power...

Plane T/O speed is around 85kias...

That is kinda fast for an off-field experience...

Best regards,

-a-

 

[MikeOH]

Ah, the old "it's only physics"...well, yeah, but the devil is most definitely in the details!

You hit the nail on the head with "surmounted"...there are MANY obstacles to be surmounted in the forced adaptation of an engine which was NEVER designed to be used in an aircraft.  You mention the issue Merlin and Allison had with getting high continuous power (for a very SHORT life span) with water cooling....and THOSE engines were designed for AIRPLANES!

I've read the supposed "wonders" of adapted auto engines since the 1970s...odd, with all that 'potential' for success you'd think they'd be prolific by now...gee, I wonder why?

[cliffy]

Granted the operating regime for car engines is different but they do use them in long distance racing running hrs on end with throttle changes every turn. Think how much less abuse an LS3 might have running at a constant RPM. What about industrial engines running for months driving pumps etc?

[carusoam]

So...

Single data point...

My 95 LT1 has 180kmi on it...

If it was run continuously at 60mph...

that would be 1,300 hours...

It spent a few days doing 1/4 mil runs...

But, with a 6sp... it was loping around 1600rpm...

Full torque is provided about 4500 rpm...

Its biggest challenge was the optispark distributor... a wear item with a MBTF of about 50kmi...  probably a touch more, but not much more...

I ran it to failure each time... it had a back-up system, and a secondary ignition program to go with it...  run it that way too long, that cat gets filled...

It is currently on holiday... the last mechanic to work on it broke some exhaust bolts... and went out of business the next day...   

So...

If you have a spare LS3... I have a great test bed for it...   

L98, LT1, LT4, LT5, LS1, LS2, LS3...   (there are a few engines between mine and the LS3)

-a-

[MikeOH]

1 hour ago, cliffy said:

Granted the operating regime for car engines is different but they do use them in long distance racing running hrs on end with throttle changes every turn. Think how much less abuse an LS3 might have running at a constant RPM. What about industrial engines running for months driving pumps etc?

Yes, and how long do race engines last?  At one extreme are top fuel dragsters...I believe they get about 3 runs before the engine needs rebuilding...so, less than 10 seconds total life!  Look at the 24 hours of Le Mans, most of the field is gone due to mechanical failures... and those cars and engines were the best money can buy...and many won't make 24 hours!

Absolutely, industrial engines run continuously for a very long time at high power...that is EXACTLY what they are designed to do.  Every check out the WEIGHT on those puppies??

Good engineering is a delicate balance of many variables for the SPECIFIC requirements for a PARTICULAR application.  You truly can't have everything...technological advances incrementally improve the trade-offs, but that balance remains.  Trying to adapt a design to other than it's intended application is very difficult and commonly an exercise in futility.

[Blue on Top]

Engine (or electric motor for that matter) torque curves are not relevant in an airplane.  Torque required is defined by the propeller, and the engine/motor must match it.

LS3 engines run as pump motors at full power for 2.5-3 years at a time (stopping only for oil changes and routine maintenance). 

Yes, I would rather have 8 coils than 16 spark plugs.  The LS3 will continue to run on 3 coils.  I like that for a huge safety factor.

[MikeOH]

Just now, Blue on Top said:

Engine (or electric motor for that matter) torque curves are not relevant in an airplane.  Torque required is defined by the propeller, and the engine/motor must match it.

LS3 engines run as pump motors at full power for 2.5-3 years at a time (stopping only for oil changes and routine maintenance). 

Yes, I would rather have 8 coils than 16 spark plugs.  The LS3 will continue to run on 3 coils.  I like that for a huge safety factor.

Sure the torque curve is relevant, otherwise you would not need a gear reduction drive.

Please cite the data which shows an LS3 will run for 25,000 hours at 430 horse power.

Also, what is the weight and extent of the cooling system used in those applications?

Finally, educate me: Doesn't the LS3 use coil over plugs?  How do you lose 5 coils and the remaining 3 fire all the plugs?

[EricJ]

1 hour ago, MikeOH said:

And, for the wet-rag point-of-view, here I am!

Automobile engines are engineered for use in, wait for it (credit to Dave Barry), automobiles, NOT aircraft.  As such, they are NOT designed to operate at even mid (50%) power levels for very long before overheating problems occur, not to mention compromised longevity.  They are water cooled with all those attendant 'advantages'  Their rpm vs torque and power curves are way off from what is optimal for propeller driven aircraft; hence the need for an expensive reduction gearbox which just adds another expensive point of failure.  Then you need to gen up a way to drive the prop governor.  Are you ok with a single plugs/ignition per cylinder?  What are GM's altitude specifications? What happens above, say, 15K feet?

Thanks, but I'll stick with powerplants designed and built for aircraft.

FWIW, the only thing that keeps most automotive engines from being able to produce 100% power constantly for long periods of time is heat management.   If the coolant and oil temps are kept within limits they're probably way more reliable than aircraft engines.   We see this in endurance racing all the times, and there's an entire series that's been very popular for over a decade called the 24 Hours of LeMons where essentially junkyard cars are endurance raced for 24 hours (I did one of these, it was fun).    It ain't that hard once you get the temps under control.

That said, putting automotive engines in airplanes has been done over and over again forever and never catches on because, as you say, it's not a great idea in a fundamental sense.   A ton of money got dumped into the Orenda program and it still didn't work.   I ain't holding my breath on LSx motors, which I absolutely love in cars and have owned and driven many miles, having any success in airplanes.

[Blue on Top]

32 minutes ago, MikeOH said:

1) Sure the torque curve is relevant, otherwise you would not need a gear reduction drive.

2) Please cite the data which shows an LS3 will run for 25,000 hours at 430 horse power.

3) Also, what is the weight and extent of the cooling system used in those applications?

4) Finally, educate me: Doesn't the LS3 use coil over plugs?  How do you lose 5 coils and the remaining 3 fire all the plugs?

1) Optimum propeller efficiency determines propeller RPM and torque required.  Number of blades can be changed to optimize horsepower consumed.  The gear box is there for one reason: to put the propeller at the right RPM.  Single point design ... off point design is not relevant.

2) Sorry, proprietary.  When will an IO-550G (Ovation) or TSIO-550G (Acclaim) output 430 horsepower?  and for how long?  LS3s can be made to output over 750 horsepower ... but they don't last long.

3) Again, proprietary.  Cooling on the ground and cooling airborne is apples and oranges.  Rarely does it get to -25C with the wind blowing at 180 knots on the ground.

4) Yes.  You assumed all plugs were still being fired.  My 2007 car (old, but I love her) uses 3 of the six cylinders at highway speeds.

Hope this helps. -Ron

PS.  I agree that most auto conversions are poor.

[201Steve]

https://www.vice.com/en/article/4adpv9/us-navy-has-patents-on-tech-it-says-will-engineer-the-fabric-of-reality?utm_campaign=later-linkinbio-vice&utm_content=later-14163825&utm_medium=social&utm_source=instagram

[MikeOH]

19 hours ago, EricJ said:

FWIW, the only thing that keeps most automotive engines from being able to produce 100% power constantly for long periods of time is heat management.   If the coolant and oil temps are kept within limits they're probably way more reliable than aircraft engines.   We see this in endurance racing all the times, and there's an entire series that's been very popular for over a decade called the 24 Hours of LeMons where essentially junkyard cars are endurance raced for 24 hours (I did one of these, it was fun).    It ain't that hard once you get the temps under control.

That said, putting automotive engines in airplanes has been done over and over again forever and never catches on because, as you say, it's not a great idea in a fundamental sense.   A ton of money got dumped into the Orenda program and it still didn't work.   I ain't holding my breath on LSx motors, which I absolutely love in cars and have owned and driven many miles, having any success in airplanes.

Probably not that hard to get the temps under control long enough to run 24 hours Let me guess oversize radiator, bigger fans, high-flow water pump (maybe electric)...wonder how much weight that system would hurt in an airplane? And, for 24 hours??? Nah, I'll pass, thanks!

100% agree with your second paragraph!  Here's two of us 'not holding our breath' for the LSx 'miracle cure' for aviation

[MikeOH]

19 hours ago, Blue on Top said:

1) Optimum propeller efficiency determines propeller RPM and torque required.  Number of blades can be changed to optimize horsepower consumed.  The gear box is there for one reason: to put the propeller at the right RPM.  Single point design ... off point design is not relevant.

2) Sorry, proprietary.  When will an IO-550G (Ovation) or TSIO-550G (Acclaim) output 430 horsepower?  and for how long?  LS3s can be made to output over 750 horsepower ... but they don't last long.

3) Again, proprietary.  Cooling on the ground and cooling airborne is apples and oranges.  Rarely does it get to -25C with the wind blowing at 180 knots on the ground.

4) Yes.  You assumed all plugs were still being fired.  My 2007 car (old, but I love her) uses 3 of the six cylinders at highway speeds.

Hope this helps. -Ron

PS.  I agree that most auto conversions are poor.

1) EXACTLY my point!  The auto engine was NOT designed with max power at the proper RPM to match a prop!

2) Oh, puuhhleease!  That's a cop-out...you boast 25,000 life at 430 HP and come back with that??  Sorry, a convincing argument that is not

3) See 2 above. Additionally, my point was NOT that the environment is the same, but that cooling aircraft engines has always been difficult and throwing in a water cooled auto engine into an aircraft doesn't have the advantage of unlimited weight for cooling systems sufficient for the heat load.  Funny, I've spent more time managing to keep CHTs under 400 on warm days (high DA)...not too much experience with -25 OATs in my normally aspirated Mooney.

4) No, I did NOT assume anything.  I asked a question.  Your answer is actually what I assumed: the engine continues to turn over with only three cylinders firing.  That sounds just swell for an aircraft.

7 hours ago, 201Steve said:

https://www.vice.com/en/article/4adpv9/us-navy-has-patents-on-tech-it-says-will-engineer-the-fabric-of-reality?utm_campaign=later-linkinbio-vice&utm_content=later-14163825&utm_medium=social&utm_source=instagram

Now, we're talkin'

[EricJ]

15 minutes ago, MikeOH said:

Probably not that hard to get the temps under control long enough to run 24 hours Let me guess oversize radiator, bigger fans, high-flow water pump (maybe electric)...wonder how much weight that system would hurt in an airplane? And, for 24 hours??? Nah, I'll pass, thanks!

Once things are heat soaked after a few laps or however long, there's not much difference in cooling requirements between a half-hour and 24 hours other than environmental changes.   Most cars don't need a ton of changes to the basic cooling systems, usually more attention is required to oil cooling.

 

 

[N201MKTurbo]

Put one of these Pratt’s under each wing and put a radar up front.

The smallest jet engine Pratt a s Whitney makes. The TJ-150. I've seen them in real life, they are cute as a button. 

[MikeOH]

21 minutes ago, EricJ said:

Once things are heat soaked after a few laps or however long, there's not much difference in cooling requirements between a half-hour and 24 hours other than environmental changes.   Most cars don't need a ton of changes to the basic cooling systems, usually more attention is required to oil cooling.

 

 

Agree.  I just wonder about longevity at continuous high power levels even if the temps are controlled.  Mass produced auto engines were NEVER designed to output high levels of power for continuous time periods; that kind of specification would make NO sense for an automotive application.  It would amount to over engineering which would add cost... and I'm pretty sure Detroit would kill to save $0.10 an engine

This is the logic that further convinces me that auto engines will never be more than an experimental niche.  To think otherwise implies that an engine designed for short bursts of power will somehow maintain longevity at continuous high-power levels.  There is more to it than just temperature control.

 That is, longevity is NOT independent of time X power AOC (area under the curve).

[MikeOH]

33 minutes ago, N201MKTurbo said:

Put one of these Pratt’s under each wing and put a radar up front.

The smallest jet engine Pratt a s Whitney makes. The TJ-150. I've seen them in real life, they are cute as a button. 

So, how many pretty pennies for such a pretty face?

[N201MKTurbo]

8 minutes ago, MikeOH said:

So, how many pretty pennies for such a pretty face?

You don’t want to know...

[Hank]

1 hour ago, N201MKTurbo said:

Put one of these Pratt’s under each wing and put a radar up front.

The smallest jet engine Pratt a s Whitney makes. The TJ-150. I've seen them in real life, they are cute as a button. 

Sure would be nice in an RC model. I'm guessing it's in the 4-6" diameter size since it's on a flimsy plexiglass stand.

[carusoam]

2 hours ago, MikeOH said:

Agree.  I just wonder about longevity at continuous high power levels even if the temps are controlled.  Mass produced auto engines were NEVER designed to output high levels of power for continuous time periods; that kind of specification would make NO sense for an automotive application.  It would amount to over engineering which would add cost... and I'm pretty sure Detroit would kill to save $0.10 an engine

This is the logic that further convinces me that auto engines will never be more than an experimental niche.  To think otherwise implies that an engine designed for short bursts of power will somehow maintain longevity at continuous high-power levels.  There is more to it than just temperature control.

 That is, longevity is NOT independent of time X power AOC (area under the curve).

the logic used here... is admirable. But wait... there’s more...

Elon Musk has shown us a way to build a higher quality engine so we can re-use it, often... (the Raptor, not the Tesla) 

The way GM did things... was less than admirable... saving the cent, instead of taking care of business with the faulty ignition switch... 

Cost them a ton... select owners even more... and it didn’t work so well for the CEO at the time...

 

Products are changing...

Product development is changing...

What used to be impossible, is more possible today than ever before...

 

Somebody has to do it... with conviction...

How did the Porsche engine do so well in the M20L?

Best regards,

-a-

[tmo]

8 hours ago, N201MKTurbo said:

The smallest jet engine Pratt a s Whitney makes. The TJ-150. I've seen them in real life, they are cute as a button. 

There is a Cri-Cri Jet - just sayin'...

It is powered by one of the PBS Aerospace engines - the PBS-TJ20a (210 N thrust with the weight less than 2.1 kg). Didn't dare to look at what it costs.

Looking at the minijets.org site, it seems there are plenty of small jet engines around, so the issue must be cost and efficiency at typical GA altitudes.

[Hank]

1 hour ago, tmo said:

There is a Cri-Cri Jet - just sayin'...

It is powered by one of the PBS Aerospace engines - the PBS-TJ20a (210 N thrust with the weight less than 2.1 kg). Didn't dare to look at what it costs.

Looking at the minijets.org site, it seems there are plenty of small jet engines around, so the issue must be cost and efficiency at typical GA altitudes.

And certification expenses . . . . .