Aircraft Engines vs. Auto Engines

TripleZ said:
Automotive fuel injection..... for all the expensive sensors and computing power is basically only controlling fuel and spark. Sure, there are cam phasers, variable valve lift, multi-length intake systems, etc, but these systems are all designed around transient torque. Airplanes have a built in slipper clutch that allows the engine to rev up, closer to peak power, and removes the need for rapid RPM transitions.
Click to expand...

I'm not sure what you're talking about in a slipper clutch, unless you're referring to the constant-speed prop. Since aircraft engines are designed to work in such a narrow band of RPM (unlike auto engines), there isn't any benefit to the additions like cam phasers, variable valve lift, etc. It's easy to optimize for a particular range and just use that.

The big advantage of FI, is the ability to monitor the engine and run it right on the ragged edge of temperature / knock / combustion stability limits. Something a human controlling only load and AFR can't do. But.... that assumes an automotive type engine with a 10:1 CR or higher, and running at the edge of knock.
Click to expand...

That is an advantage, and it works well with the various automotive engines out there. However when you apply it to an aircraft engine as they currently are, it ends up providing no benefit unless you want to see your reliability suffer.

Yes, you could increase compression ratio in an airplane engine, add FI, and be more efficient during leaned cruise. Make more power at all altitudes. And probably protect the engine better.
Click to expand...

Depends. Your reliability would probably suffer vs. the current ones, because you probably wouldn't end up keeping your temperatures within the optimal range.

But that's also the problem.... and why I think you don't see automotive systems making the transition. The ECU doesn't know you want peak power for climb, or maximum leaning for fuel economy, it just understands RPM. The strategy programmed into automotive ECU is very complicated, and relies on the transients to give the computer an idea of what the operator wants.
Click to expand...

This can be programmed around. The big reason I think you don't see the systems is that they are expensive to design, expensive to certify, and don't offer much in the way of benefits beyond easier starting. You really need a clean-sheet engine that is designed to take advantage of these extra tools to see it.

kyleb said:
They do work, give more power, give more power for less fuel, etc. The problem most introduce is that they are more complicated than a magneto (now you are dependant on electricity, a small computer, a manifold pressure transducer, a hall effect sensor, plumbing for the MP lines, etc.
Click to expand...

It does depend on the unit, but overall I've found they don't do much besides add additional points of failure.

MSPAviator said:
Automotive engines can be efficient and powerful because the intricacies combustion is not only well understood, but completely engineered. Using supercomputers, we now do things like engineer a contra-rotating swirl pattern inside the cylinder and inject very precise amounts of fuel in a lean burning pattern at the right times in order to minimize heat being lost by absorption into the cylinder walls for greater thermodynamic efficiency.
Click to expand...

I agree fully, and this is the biggest thing that could and would help aircraft engines. However, one also needs the funding to take advantage of it. As I said, a clean-sheet design is really needed.

Sac Arrow said:
My point on electronic ignition is that it is simpler than a magneto system. A modern stick coil ignition system isn't mechanical, doesn't require high voltage distribution or wiring, isn't altitude sensitive, and timing doesn't drift. They are pretty bullet proof. More efficient? Probably not. Ever hear of these systems crapping out? I've never experienced it. Ever hear of magnetos crapping out? I've experienced that.
Click to expand...

I have had the modern electronic ignition and injection systems crap out on me. On an hour per hour basis, I have had more problems with magnetos without question. I think that there are a lot of potential benefits in reducing cost in the experimental world. I can buy injectors and ignition coils from Ford for a lot cheaper than I can buy a Bendix fuel servo or a Slick magneto. The problem is that once you remove the Ford dealer as your principle parts supplier, your costs will go way up and you'll suddenly have the same price as current stuff, if not higher (probably higher).

Similarly with EFI. The only real disadvantage is that these systems typically require a relatively high pressure boost pump compared to mechanical fuel injection. Otherwise fuel distribution is about perfect, and priming and hot starting issues go away. More efficient? Probably not except that a more even fuel distribution could allow LOP operation closer to the "box".
Click to expand...

The Navajo runs about 40 psi - same as on EFI engines. You won't see any efficiency benefits vs. a properly-tuned mechanical system. In fact, you'd be surprised how accurate those mechanical systems are when properly tuned, and that once properly tuned they're able to keep in good order.

I don't view operation being any different. I don't see using fancy oxygen sensor loop control or fixed fuel mapping. Fuel flow would be proportionate to throttle setting and mixture lever position.
Click to expand...

I have proposed a system like this before, based on the principle that it has easier starting characteristics and still leaves a great deal of control in the hands of the pilot, where I want it to be for my purposes. Plus then I could buy my parts at the Ford dealer. Again, in the experimental world, it would work. It requires a good plan for electrical backups, but that is relatively simple to perform - especially on a twin. The reality is I want my electrical system to be as rock solid as my engines, especially for IFR flight, so I think that can be dealt with fine.

It would work, and it would work well.

But if I were building my own plane, I'd be doing much like Ben Haas did.
 
Jim Logajan said:
I think that makes about 8 posts of you repeating your opinion.
Click to expand...


I am not repeating my opinion when new subjects come up on the same thread.

The thread started out talking about auto conversions, then a specific destroyed RV10 that I have knowledge of, then two different auto conversion packages that I am intimately familiar with as an EAA Tech Counselor having built an RV 12 with a Rotax912.

Maybe you should stop counting my posts and listen to what I am saying based on my personal and professinal experience and dealing with selling airplanes with these POS bolted on the firewall claiming to be aircraft engines. ;)

How many aircraft have you built again? How many have you bought and sold? How many have you repaired and sold? How many hours do you have in experimentals? How many auto conversions have you flown? Worked on? :dunno:
 
Last edited:
Geico266 said:
I am not repeating my opinion when new subjects come up on the same thread.

The thread started out talking about auto conversions, then a specific destroyed RV10 that I have knowledge of, then two different auto conversion packages that I am intimately familiar with as an EAA Tech Counselor having built an RV 12 with a Rotax912.

Maybe you should stop counting my posts and listen to what I am saying based on my personal and professinal experience and dealing with selling airplanes with these POS bolted on the firewall claiming to be aircraft engines. ;)

How many aircraft have you built again? How many have you bought and sold? How many have you repaired and sold? How many hours do you have in experimentals? How many auto conversions have you flown? Worked on? :dunno:
Click to expand...

The issue was your immediate linking of Todd's automotive engine to his fire. Do you feel that was a fair way to portray it?
 
MSPAviator said:
I keep hearing stuff like this being parroted as of all auto engines were designed and built equally. They are not.

Making 200hp continuous power out of a 360 cubic inch engine out of a purpose-built, clean sheet aero piston engine design using the latest auto engine technology would be trivial in anything but unit price.

If there is one thing I dislike about aviation, it's all the glorified 1930s technology that is no different than what you'd see in a Mercedes from the 1950s. It is the certification standards and perhaps the culture at Lycoming/Continental that stand in the way of evolution.
Click to expand...

The most important question is what would be gained by incorporating new technology into aircraft engines. It's not likely to improve efficiency beyond what's currently obtainable with our 1930's designs when operated LOP and I doubt you'd see a HP/weight improvement (might actually be worse). Reliability might get better (reduced number of wearing parts in the ignition) but it might get worse and IMO there's no doubt that any electronic control is going to be more susceptible to RFI and lightning damage. That pretty much leaves convenience and simplicity of operation. I'd sure like to see an aircraft engine that only has one or two controls and it sure would be nice if my airplane's engines could start instantly when cold or hot without requiring three hands and not a little patience. But I don't think I'd be willing to pay an extra $10-25k per engine for that convenience.
 
EppyGA said:
The issue was your immediate linking of Todd's automotive engine to his fire. Do you feel that was a fair way to portray it?
Click to expand...

No, the issue was with Jim that I posted 8 times in the same thread, all different items within the same subject. I didn't realize there are thread police to warn us of how many posts we have made in a thread. :rolleyes:

The issue (with Todd's plane) was a link to video showing it as an example of a succesful auto conversion. Unfortunately, it was not.

Re-read my post about Todd's plane, my position is clear.
 
Last edited:
MSPAviator said:
I'm talking about using auto technology as an input in a clean sheet aero engine design.
Click to expand...

The cost of the engine would be way past what people would be willing to pay. The production numbers just are not high enough to recoup a new engine design and make a profit in a reasonable amount of time to satisfy stockholders or CFO's.;)
 
Last edited:
Geico266 said:
I am not repeating my opinion when new subjects come up on the same thread.
Click to expand...

Every one of your posts contained the anecdotes of a few others, along with your views, never any description of your own experience (that I could see.)

Maybe you should stop counting my posts and listen to what I am saying based on my personal and professinal experience and dealing with selling airplanes with these POS bolted on the firewall claiming to be aircraft engines. ;)
Click to expand...
This is the first post I see in which you finally make the claim that you have the experience and professional background to judge auto engines in aircraft. I can see how selling aircraft with auto engines might give you insight into their low resale value, but beyond that I missed your other qualifications.

How many aircraft have you built again? How many have you bought and sold? How many have you repaired and sold? How many hours do you have in experimentals? How many auto conversions have you flown? Worked on? :dunno:
Click to expand...
I suppose if it was I, rather than you, that had been making a string of strong assertions about auto engines in aircraft, those questions might have some relevance.
 
Geico266 said:
The issue (with Todd's plane) was a link to video showing it as an example of a succesful auto conversion. Unfortunately, it was not.

Re-read my post about Todd's plane, my position is clear.
Click to expand...

It is your opinion that Todd's conversion was not successful and apparently that was responsible for the fire. Having not seen the report, does the FAA back up your opinion?
 
Who said that the best 'conversion engine' for a RV is the one where you convert $21,000 into a good used IO360 ?
 
Geico266 said:
No, the issue was with Jim that I posted 8 times in the same thread, all different items within the same subject. I didn't realize there are thread police to warn us of how many posts we have made in a thread. :rolleyes:
Click to expand...

Too late - I have a warrant for your arrest.
 
MSPAviator said:
If there is one thing I dislike about aviation, it's all the glorified 1930s technology that is no different than what you'd see in a Mercedes from the 1950s. It is the certification standards and perhaps the culture at Lycoming/Continental that stand in the way of evolution.
Click to expand...

The cost of certification, yes. Lycoming and Continental's attitude, absolutely not. Their market is extremely tiny compared to any automaker's, a few hundred engines a year, and carries huge liabilities. To their credit, both have in the past created new engines that the aviation community demanded and then refused to buy (like Continental's liquid-cooled Voyager, among other engines) and they also created geared engines in response to demand that turned out to have endless difficulties with the gearing, or with operators who were uncomfortable running them at 3500 RPM all day where they were designed to run but sounded like they were going to explode. Both manufacturers have built such geared engines. Now Continental has bought the SMA diesel technology and is developing it, again in response to perceived demand by the aviation community. Lycoming is building the IE2, with EFI and FADEC and electronic ignition and everything.

If we demand better technology we should be prepared to pony up when it's available. Otherwise we're just a bunch of cheapskate complainers.

Dan
 
Last edited:
Engines are engines are engines; this is all silliness. As for reduction sets come on, there is no impossible Voodoo involved, reduction drive was used on the Write Flyer and tens of thousands or more aircraft engines since. Personally I'd try a Lenco to 2 speed it.
 
Henning said:
As for reduction sets come on, there is no impossible Voodoo involved, reduction drive was used on the Write Flyer...
Click to expand...

Not impossible. Just very expensive to develop something that won't self-destruct. As a member of the homebuilding community I have read endless articles about guys who have tried just about everything--gears, V-belts, timing belts, chains. Almost all of them have issues and some have failed catastophically. I have experience with a Subaru EJ-22 with an RAF redrive that was much less than perfect and at certain RPMs would make ugly and noisy vibrations. Not the most reassuring thing to encounter in flight and a bit disconcerting in the runup before a flight.

Many guys spend lots of money and time trying to save money by adapting an auto engine, and many of them finally have to abandon the project because they're broke and out of ideas, or they go out and buy the Lycoming just to get the stupid airplane flying.

Dan
 
Dan Thomas said:
Many guys spend lots of money and time trying to save money by adapting an auto engine, and many of them finally have to abandon the project because they're broke and out of ideas, or they go out and buy the Lycoming just to get the stupid airplane flying.

Dan
Click to expand...

Exactly. Hobbyists (and even small businesses) don't have the resorces (time, engineering skill, and money) to design, test, break, and redesign reduction systems. Other than a few geared engines in the GA fleet, which were developed by major players in the industry, the vast majority of geared engines were developed for the military with the benefit of generous resources and relatively deep pockets.
 
kyleb said:
Exactly. Hobbyists (and even small businesses) don't have the resorces (time, engineering skill, and money) to design, test, break, and redesign reduction systems. Other than a few geared engines in the GA fleet, which were developed by major players in the industry, the vast majority of geared engines were developed for the military with the benefit of generous resources and relatively deep pockets.
Click to expand...


Personally I'd start with a lightweight unit that is part of the only transmission I know of that routinely sees greater than 5000hp which happens to also be 2 speed.
 
kyleb said:
Exactly. Hobbyists (and even small businesses) don't have the resorces (time, engineering skill, and money) to design, test, break, and redesign reduction systems. Other than a few geared engines in the GA fleet, which were developed by major players in the industry, the vast majority of geared engines were developed for the military with the benefit of generous resources and relatively deep pockets.
Click to expand...

There are various certified engines with a reduction system.. it is not black magic... Garrett TPE-331 is but one of many that has pulled off the impossible.....
 
N801BH said:
There are various certified engines with a reduction system.. it is not black magic... Garrett TPE-331 is but one of many that has pulled off the impossible.....
Click to expand...


You're using a blower drive belt aren't you? those are good for about 800hp IIRC.
 
N801BH said:
There are various certified engines with a reduction system.. it is not black magic... Garrett TPE-331 is but one of many that has pulled off the impossible.....
Click to expand...

Every turboprop has a gearbox.

Of course, gearboxes have presented additional challenges for piston engines because of the torque pulses that exist. Belt drives really make more sense, and are very common in helicopters, and probably the most reliable part on the whole airframe in those cases. For some reason, you don't see them on certified fixed-wing aircraft, and I'm not entirely sure why.
 
N801BH said:
There are various certified engines with a reduction system.. it is not black magic... Garrett TPE-331 is but one of many that has pulled off the impossible.....
Click to expand...

I think we're talking in the context of reciprocating engines here. At least that's the context of the other posts. Turbines don't have the cyclic loading issues that recips do. That cyclic loading is one of several major issues which cause problems for redrive designers, builders, and operators.
 
Ted DuPuis said:
Belt drives really make more sense, and are very common in helicopters, and probably the most reliable part on the whole airframe in those cases.
Click to expand...

Which helicopters use belts? I've never paid enough attention to them to notice.

Also, claiming that a belt is the most reliable part on a helicopter may be damning with faint praise. ;-)
 
kyleb said:
Which helicopters use belts? I've never paid enough attention to them to notice.
Click to expand...

Pretty much every piston helicopter that I'm aware of (although I think a few old ones with vertical engines may not have). The Hughes 269A is one of the obvious ones, as the belt drive sticks right out. The Robinsons cover it up a bit better, as I recall.

Turbine helicopters are a bit different, and all of the ones I'm aware of feed directly into the gearbox. But I am far from a helicopter expert.

Also, claiming that a belt is the most reliable part on a helicopter may be damning with faint praise. ;-)
Click to expand...

That was somewhat the point. ;)

However, the belt drives on them are quite reliable. The ones on helicopters are also typically pretty big for minimal power, which would make them be unattractive for fixed wing. That can be addressed, as Ben has proven with his plane.
 
Henning said:
You're using a blower drive belt aren't you? those are good for about 800hp IIRC.
Click to expand...
..

Actually.. They transfer alot more then 800HP... The California racing shop that broached the teeth on my current bottom sprocket is the supplier for all the top ranked funny car and top fuel teams... They have set up a one of a kind blower dyno to measure the true HP requirments of a state of the art teflon lined, close clearence supercharger used in todays pro drag cars.....

Just to drive the blower is taking around 1200 -1275HP as of last years testing.... I run the exact same Gates GT belt as they do, only it is substantially shorter so my set up should be good for around 1400HP... Of course there is NO way I would even want to be in the same county when that was tested to the failure point.:no::no::idea:
 
N801BH said:
..

Actually.. They transfer alot more then 800HP... The California racing shop that broached the teeth on my current bottom sprocket is the supplier for all the top ranked funny car and top fuel teams... They have set up a one of a kind blower dyno to measure the true HP requirments of a state of the art teflon lined, close clearence supercharger used in todays pro drag cars.....

Just to drive the blower is taking around 1200 -1275HP as of last years testing.... I run the exact same Gates GT belt as they do, only it is substantially shorter so my set up should be good for around 1400HP... Of course there is NO way I would even want to be in the same county when that was tested to the failure point.:no::no::idea:
Click to expand...

Damn they're putting some pressure on them now... 1/5th of their HP just to run the blower. I could only afford to play with Fuel Altered since it was an iron block exhibition class where you got paid to show up. I only cranked up 1500-1700hp but even at that the costs got pretty freakin extraordinary.:eek: Fuel was only $25 a gallon back then so it only was around $200 a round in fuel; that's why it required appearance money.

A guy who was running C/E for years asked me what the scariest part of stepping up to driving fuel was was, I told him, "the bills".:hairraise::nonod:
 
RotorAndWing said:
Hughes/Schwiezer 269 series, Enstrom, Robinson R22 and R44
Click to expand...

How often do those belts have to be replaced ? I believe that they are used as a clutch to engage the main rotor as well.
 
weilke said:
How often do those belts have to be replaced ? I believe that they are used as a clutch to engage the main rotor as well.
Click to expand...

I'm not certain they are life limited beyond condition. The system I'm familiar with is the Robinson set up and yes, it is also the clutching mechanism.
 
weilke said:
How often do those belts have to be replaced ? I believe that they are used as a clutch to engage the main rotor as well.
Click to expand...

On condition. The belts are usually the most reliable part on the helicopter.

The 269's use 8 V belts. If one breaks then they are all replaced as a matching set.

Enstrom and Robinson use a single wide belt.

Even the turbine Enstrom (480) uses the belt drive.
 
On a hunch, I was interested to know a little about the use of motorcycle engines in experimental airplanes. I thought that the modern I-4 engine would work well. It's lightweight and produces 110SHP (600cc) and can run ~14,000 easily and designed for abuse.

About 1/3 down the article it discusses a project Honda had with Teledyne and how they couldn't get their engine to viability. Honda has a lot of engineering and financial resouces.

(article here)
http://thekneeslider.com/archives/2007/03/05/motorcycle-engine-powered-airplanes/

Far be it from me to discourage anyone from innovation, much to dismay of some of the haters in this thread, but unless you have a bright idea.....
 
Jaybird180 said:
On a hunch, I was interested to know a little about the use of motorcycle engines in experimental airplanes. I thought that the modern I-4 engine would work well. It's lightweight and produces 110SHP (600cc) and can run ~14,000 easily and designed for abuse.

About 1/3 down the article it discusses a project Honda had with Teledyne and how they couldn't get their engine to viability. Honda has a lot of engineering and financial resouces.

(article here)
http://thekneeslider.com/archives/2007/03/05/motorcycle-engine-powered-airplanes/

Far be it from me to discourage anyone from innovation, much to dismay of some of the haters in this thread, but unless you have a bright idea.....
Click to expand...

Actually, I think an air cooled twin like a Harley or a BMW boxer engine would be a the way to go if you had to put a motorcycle engine in. Either would still have to be geared.
 
Jaybird180 said:
On a hunch, I was interested to know a little about the use of motorcycle engines in experimental airplanes. I thought that the modern I-4 engine would work well. It's lightweight and produces 110SHP (600cc) and can run ~14,000 easily and designed for abuse.

About 1/3 down the article it discusses a project Honda had with Teledyne and how they couldn't get their engine to viability. Honda has a lot of engineering and financial resouces.

(article here)
http://thekneeslider.com/archives/2007/03/05/motorcycle-engine-powered-airplanes/

Far be it from me to discourage anyone from innovation, much to dismay of some of the haters in this thread, but unless you have a bright idea.....
Click to expand...

Toyota spent a couple of years and millions and couldn't come up with a viable engine either. Big bores and long rods are what airplanes need.
 
I was partner on a project to put a Mazda rotary on a Velocity. I was previously a very strong believer in car engines in cars and plane engines in planes.

I overlooked the hype. Did my homework and went in with eyes open. The engine itself is a sound concept for non-auto use. The devil is in the details/peripherals

I read everything I could get my hands on. I networked with many other builders AND FLYERS on a dedicated listserv. I even listened to the looks to glean a tidbit here and there.

I bought three junk cores off eBay and made a single working rebuilt engine out of the remains. We bought a re-redrive and engine controller.

I built a crude intake but before it came time to start we had a stroke of luck and bought a cast intake designed by Mistral for their "Mazda based" rotary aircraft engine. They only offered it for a few months and we got one. We may have gotten the only one in the US. It's a beauty and saved countless hours and dollars making one ourselves.

I safety wired everything I could. Built the fuel and exhaust systems. Rigged it all up. Plumbed the ECU. It ran well but around this time the handshake partnership fell apart and it was time to walk. That engine got burned up as did the next, attributed to running it excessively/tuning without being instrumented properly and overheating. He ended up buying a third (brand new in box) engine and listening for a change Lots of electrical gremlins in that bird. Significant effort on rewiring/ reterminating connections by the owner.

They finally got sorted out and the plane got its special a/w certificate a few weeks ago at the 10 year mark. But hasn't flown due to cooling issues that haven't been resolved. Many of the hiccups were items I predicted, tried to address or build for, and in the end i felt i was disregarded.

Even now, with the current cooling probs I'm bring ignored on my suggestions even when they jive with the rest of the tribe. Needless to say, I know I made the right decision walking away from that project.

All that said, I believe in the rotsry engine. Done right, with good workmanship and cautious attention to detail I believe the auto engine can be adapted to aircraft use. You can't do it on the cheap. And you HAVE to read a lot and understand all the issues involved.

Your first one will likely cost as much as a timed out lycosaurus before you get it right. But once it's done your costs going forward will be much lower. The average home builder is not up for the task. You have to be part engineer, part mechanic, Part scientist and part trailblazer.
 
Last edited:
Ted DuPuis said:
Every turboprop has a gearbox.
Click to expand...

I was under the impression that this is not true for "backward blowing" free-turbine designs where the air exiting the turbine engine is turning another set of blades connected directly to the prop.

But I'm no expert on such things.
 
denverpilot said:
I was under the impression that this is not true for "backward blowing" free-turbine designs where the air exiting the turbine engine is turning another set of blades connected directly to the prop.

But I'm no expert on such things.
Click to expand...

I'm pretty sure the still use a gear reduction on the prop shaft, the gear that isn't there is the initial PTO gear.
 
denverpilot said:
I was under the impression that this is not true for "backward blowing" free-turbine designs where the air exiting the turbine engine is turning another set of blades connected directly to the prop.

But I'm no expert on such things.
Click to expand...

No expert either, but the ones I've studied all have gearboxes.
 
Ted DuPuis said:
No expert either, but the ones I've studied all have gearboxes.
Click to expand...

They all do, even the "backward-blowing" free turbines. For a turbine wheel to be connected direct drive to a prop, it would have to be massive.

Even many of the big turbofans have gearing for the fan.

The typical free turbine turboprop engine, the Pratt & Whitney PT-6:

pt6a.gif



pt6aengine2.jpeg



Typical turbofan with gearing:

pratt-whitney.jpg



Dan
 
You must log in or register to reply here.
Back
Top