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Why aren't more auto engines being used

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nerobro

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You're inserting hard returns, it's best to let the forum handle word wrap. inserting returns makes your writing very, very, hard to read,

ekirkimbo said:
Turd, your reply is a perfect example of what this thread was an example of, well meaning persons who turn people away from the automotive engines by spreading misinformation. First, let me clarify the fact that many conversions can prove to be time consuming. They can also be simple and they can also prove to be more efficient, more economical over time, smoother, more powerful, and even more fun. Anyone with a conversion will probably attest to the satisfaction of having done it themselves. One thing you must accept is that only certain homebuilt airplanes have established common solutions to the problems all home builts present. Most certainly, Vans has such a large following that there is virtually no component you can't purchase rather than build, and no problem that a solution hasn't been found. When you step away from Vans though, its pretty much getting back to having problems and finding solutions on most other homebuilts...especially scratch builds.

Turd Fergusson said:
I'm not biased but I am cognizant of reality. It is "easier" to install a certificated engine because the basic process is "purchase a used engine, mount it in an airplane and bolt a prop to it.
While that may be oversimplifying, the actual process is still "easier" than installing a converted auto powerplant (and a minor nit, just because one installs a certified [sic] engine into a homebuilt, does not make it 'formerly' certified [sic] engine)

Eki said:
Yes, thats a real over simplification, and thats where it becomes misleading. What you left out is that
First a builder has to be able to find a prospective engine thats the size and type he wants. Often there are not many available in the builders local area...so he is forced to search the internet, tradeaplane,Ebay, Barnstormers, etc.

Then he must either decide on whether the log book is believeable...if there is a logbook. He must either accept on faith that the seller is honest, or travel to where the engine is located. Most often he will not get to hear the engine run.

"IF" an available engine is well documented and reasonably low time, he should expect to pay a premium price to get it.

If the engine is missing documentation he should still expect to pay dearly for it. Once he has that engine in his posession, if it does run properly and have no problems (the exception), he should realize that he should check all the ADs for the engine and insure they were complied with. Often, they haven't been. He may not be legally required to comply with them in an experimental, but since its his butt is on the line it would be wise to do so. ($$$$). He should then hire ($$$$) an AP to physically inspect the engine. Lets say all went perfectly to this point. Now the new builder should expect to have the engine inspected ($$$$) yearly if he wants to maintain its reliability. He should also expect to pay a lot more for aviation oil that has to be added regularly, and aviation fuel. In the likely event that he flies the engine for several years he should also expect to replace at least one cylinder ($$$$) before it reaches TBO. "IF" he does reach TBO he should then expect to lay out somewhere in the neighborhood of the original used engine cost to rebuild it.($$$$$$$$)

The builder is usually not looking at the big picture, because its so easy to just "plug n play"......or is it.

Lets think about that. Any engine you install is going to have to have similar controls and systems to operate properly. Depending on the type of systems you employ, they can often be simple or complex....builders choice.

All engines are going to require an exhaust system. Will it be any more difficult to make an exhaust for an auto engine than an aero engine. Nope. TOSS UP

What about the fuel system ? well if you use a carburetor it should be about the same level of difficulty. If he decides to use fuel injection it will be more complex but will result in greater efficiency and smoothness and no carb icing.

TOSS UP with Carb HARDER With Injection (but better result when finished)

Motormount...here again, the difference in building one or the other is a moot point. The aero engine can actualy be more difficult because of the special mounting. In all but the most popular kits a builder should expect to build his own.

TOSS UP (Maybe a slight edge to auto engine because of no complex dynafocal alignment)

Cooling System Here again, the builder will be faced with cobbling up something and making it work. It is not a given that all aircooled engines will automatically cool well. The inference is that water cooling can be more difficult. Air cooling often does not work and builders spend equal amounts of time trying to cool their engines...sometimes damaging their engines before successful airflow is achieved.

TOSS UP (Maybe an edge to the aero engines because some do cool without problems but you will have to experiment with many air cooled installations to get sufficient cooling. The water cooling will work better if done properly....no shock cooling probs or cht probs to ferret out later)

Weight Generally the auto will weigh more but it depends on the airplane and engine of choice. The alum V8 really starts to shine when compared to the larger and exceedingly expensive aero engines. As you move to smaller airplanes the reduction drives might be eliminated and direct drive used to keep weight down. LS engines are cheap, Rover engines even cheaper and then there are some nice V6s available too.

TOSS UP I say this because the auto engines will always be heavier in smaller airplanes but they are generally capable of more power .....thru increased rpms.... to help offset the weight. I give a slight edge to the aero engine strickly on weight.

Ignition System Both types of engines are going to have to have some type of ignition system. Many/most builders are going to have an electrical system of some kind. Even if you have magnetos on the aero engine the builder wiill also fabricate an electrical system. Is adding a modern multicoil ignition that comes with the auto engine going to be any more difficult than building the rest of the electrical system ? Many builders add electronic ignition to their aero engines anyway. TOSS UP

The Bugaboo This is where the aero engine has the advantage. Adapting a prop to the engine. With the aero engine you certainly can just bolt a prop on to it as long as you have enough money. Just remember that if you install one which is not the one the factory recommended , you have changed the resonanant frequency and no longer know where it exists, or to what magnitude it may be. That affects reliability. Yes you can test other props, but thats the same situation you have with the auto engine. So prop testing and mounting should ensue.

So Turd, this reply is a real world explanation of "just bolt it on and go flying" . There is a big difference between buying a new discounted Lycoming for a Vans kit and buying a questionable used engine to install in a plans only homebuilt.

The statement that its much more difficult to use an auto engine is sometimes true, but since building an airplane requires fabrication of mostly the same components, I think its often overstated. To me the only real difference and difficulty is how to adapt the propellor to the crankshaft. I feel the 5th bearing idea is reasonably easy for someone to do. It would be great if someone made a universal 5th bearing and only an adapter plate was needed to utilize it on various engines.


I still believe that technology is not the biggest impediment to auto conversion success, its the negativity continually espoused by air cooled engine purists and the oft mis-stated "plug n play" scenario.


Picture



I would also like to agree with your statement that " many people are not interested in developing a converted powerplant", but I hate to think that reason is because they have been misled about the difficulty of one vs the butter smooth ease of the other.


As for a certified engine maintaining its certification after its installed on an experimental airplane, my understanding is that it loses its certified status. Maybe there is an exception to the rule, but thats how I understand it.
 
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BJC

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Turd, your reply is a perfect example of what this thread was an example of, well meaning

persons who turn people away from the automotive engines by spreading misinformation. First, let me

clarify the fact that many conversions can prove to be time consuming. They can also be simple and they

can also prove to be more efficient, more economical over time, smoother, more powerful, and even more

fun. Anyone with a conversion will probably attest to the satisfaction of having done it themselves. One

thing you must accept is that only certain homebuilt airplanes have established common solutions to the

problems all home builts present
. Most certainly, Vans has such a large following that there is virtually no

component you can't purchase rather than build, and no problem that a solution hasn't been found. When you

step away from Vans though, its pretty much getting back to having problems and finding solutions on most

other homebuilts...especially scratch builds.

Turd quote : I'm not biased but I am cognizant of reality. It is "easier" to install a certificated engine because the basic process is "purchase a used engine, mount it in an airplane and bolt a prop to it."

While that may be oversimplifying, the actual process is still "easier" than installing a converted auto powerplant (and a minor nit, just because one installs a certified [sic] engine into a homebuilt, does not make it 'formerly' certified [sic] engine)

Eki response: Yes, thats a real over simplification, and thats where it becomes misleading. What you left out is that

First a builder has to be able to find a prospective engine thats the size and type he wants. Often there are not

many available in the builders local area...so he is forced to search the internet, tradeaplane,Ebay, Barnstormers, etc.

Then he must either decide on whether the log book is believeable...if there is a logbook. He must either accept on faith

that the seller is honest, or travel to where the engine is located. Most often he will not get to hear the engine run.

"IF" an available engine is well documented and reasonably low time, he should expect to pay a premium price to get it.

If the engine is missing documentation he should still expect to pay dearly for it. Once he has that engine in his posession,

if it does run properly and have no problems (the exception), he should realize that he should check all the ADs for the

engine and insure they were complied with. Often, they haven't been. He may not be legally required to comply with

them in an experimental, but since its his butt is on the line it would be wise to do so. ($$$$). He should then hire ($$$$)

an AP to physically inspect the engine. Lets say all went perfectly to this point. Now the new builder should

expect to have the engine inspected ($$$$) yearly if he wants to maintain its reliability. He should also expect to pay a lot

more for aviation oil that has to be added regularly, and aviation fuel. In the likely event that he flies the engine for

several years he should also expect to replace at least one cylinder ($$$$) before it reaches TBO. "IF" he does reach TBO

he should then expect to lay out somewhere in the neighborhood of the original used engine cost to rebuild it.($$$$$$$$)

The builder is usually not looking at the big picture, because its so easy to just "plug n play"......or is it.


Lets think about that. Any engine you install is going to have to have similar controls and systems that need to be

built.
Depending on the type of systems you employ, they can often be simple or complex....builders choice.

All engines are going to require an exhaust system. Will it be any more difficult to make an exhaust for an auto engine than an aero engine. Nope. TOSS UP


What about the fuel system ? well if you use a carburetor it should be about the same level of difficulty. If he decides to use fuel injection it will be more complex but will result in greater efficiency and smoothness and no carb icing.

TOSS UP with Carb HARDER With Injection (but better result when finished)



Motor mount...here again, the difference in building one or the other is a moot point. The aero engine can actually

be more difficult because of the special mounting. In all but the most popular kits a builder should expect to build his own.

TOSS UP (Maybe a slight edge to auto engine because of no complex dynafocal alignment)

Cooling System Here again, the builder will be faced with cobbling up something and making it work. It is not a

given that all aircooled engines will automatically cool well. The inference is that water cooling can be more difficult.

Air cooling often does not work and builders spend equal amounts of time trying to cool their engines
...sometimes

damaging their engines before successful airflow is achieved.

TOSS UP (Maybe an edge to the aero engines because some do cool without problems but you will have to
experiment with many air cooled installations to get sufficient cooling. The water cooling will work
better if done properly....no shock cooling probs or cht probs to ferret out later)


Weight Generally the auto will weigh more but it depends on the airplane and engine of choice. The alum V8

really starts to shine when compared to the larger and exceedingly expensive aero engines. As you move to smaller

airplanes the reduction drives might be eliminated and direct drive used to keep weight down. LS engines are cheap,

Rover engines even cheaper and then there are some nice V6s available too.

TOSS UP I say this because the auto engines will always be heavier in smaller airplanes but they are

generally capable of more power .....thru increased rpms.... to help offset the weight. I give a slight edge to

the aero engine strictly on weight.

Ignition System Both types of engines are going to have to have some type of ignition system. Many/most

builders are going to have an electrical system of some kind.
Even if you have magnetos on the aero engine the

builder will also fabricate an electrical system. Is adding a modern multicoil ignition that comes with the auto engine going

to be any more difficult than building the rest of the electrical system ? Many builders add electronic ignition to their aero

engines anyway. TOSS UP

The Bugaboo This is where the aero engine has the advantage. Adapting a prop to the engine. With the aero

engine you certainly can just bolt a prop on to it as long as you have enough money. Just remember that if you install

one which is not the one the factory recommended , you have changed the resonanant frequency and no longer

know where it exists, or to what magnitude it may be. That affects reliability. Yes you can test other props, but thats the

same situation you have with the auto engine. So prop testing and mounting should ensue.

So Turd, this reply is a real world explanation of "just bolt it on and go flying" . There is a big difference between buying

a new discounted Lycoming for a Vans kit and buying a questionable used engine to install in a plans only homebuilt.

The statement that its much more difficult to use an auto engine is sometimes true, but since building an airplane

requires fabrication of mostly the same components, I think its often overstated. To me the only real difference and

difficulty is how to adapt the propellor to the crankshaft. I feel the 5th bearing idea is reasonably easy for someone

to do. It would be great if someone made a universal 5th bearing and only an adapter plate was needed to utilize it

on various engines.


I still believe that technology is not the biggest impediment to auto conversion success, its the negativity

continually espoused by air cooled engine purists and the oft mis-stated "plug n play" scenario.


Picture



I would also like to agree with your statement that " many people are not interested in developing a

converted powerplant", but I hate to think that reason is because they have been misled about the

difficulty of one vs the butter smooth ease of the other.


As for a certified engine maintaining its certification after its installed on an experimental airplane, my understanding is

that it loses its certified status. Maybe there is an exception to the rule, but thats how I understand it.


View attachment 52547 VS View attachment 52548


Which will be the most troublefree starting point for a new builder ?
eki:

I have installed several Lycomings and a Continential, so I have a reasonable understanding of what is involved with typical HBA aircraft engines, but I never have done an auto conversion.

Clearly you have lots more experience than I do, so please tell us which engines you have installed, which were more difficult in your experience, and which needed follow up attention to deal with issues after you installed them.

Also tell us how many trouble free hours each engine flew after you installed them.

Or just ignore these questions, as you have in the past when asked about your actual experience.


BJC
 

RJW

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Hey eki. Instead of asking this question over and over again, why not grab a motor and make a direct drive or redrive (belt, gears, chain, or whatever), bolt a prop or test club to it, and see what happens? I know you have the skills and the facility to do it. Design the setup for some make believe but realistic airplane and go at it knowing the project will never leave the ground. If you assume the project will never fly the whole business will become very inexpensive. It will also become fun. And it will give you the experience that anyone would need to understand how difficult/easy/costly/cheap the undertaking is. Think of it as taking Redrive 101.

A friend of mine and I are doing this very thing right now. We are designing and building a redrive for a Suzuki G10 made almost entirely from cheap, off-the-shelf industrial and automotive stuff (about $100 invested in parts so far—the motor cost an additional $130 and runs well). The exercise has been very enlightening and a boatload of fun. Right now we have no real idea if it will work out. We will have some idea in about a week when we run the thing. I don’t really care if it works or not. The experience of actually building this is providing new insight into the reality of making an inexpensive and flyable drive.

What ever happened to your direct-drive LS project? If you still have it why not bolt it to a stand and make it run?

Rob
 

ekimneirbo

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Would assembling an aircraft be considered to require "aptitude for assembling mechanical assemblies?" If you can follow the steps to assemble an RV (or what have you) you have the aptitude to assemble a VW or Corvair. So this reason is off the table.

Eki reply: Whoa, we are on the same side here. I was trying to point out that many people do not feel comfortable or capable of building their own engine.
My opinion is that if they try to do it, they probably can....just by researching and asking questions just like for the airplane build. I will say that building your own engine entails more precise measurement and assembly and the use of some special tools. The thing is, using an auto engine doesn't have to entail actually assembling the engine yourself. Complete engines are available reasonably, and partially assembled short blocks and long blocks are also available. Its really just a matter of the potential builders not getting scared off by naysayers before he gives it a try.



A proven conversion need not cost the same as a certified engine. You are ceding too much ground. Again, VWs and Corvairs are proven (and probably others but these are the ones I'm familiar with).

Eki reply: With the Corvairs, it depends on the depth the builder wants to go. Some of the Corvair cranks have been identified as having an incorrect
fillet radius which can lead to breakage of the crank. If a builder elects to go with a new forged stroker crank, the price will increase $3k, but a more powerful and safer package will be had. There are many flying with stock cranks that have been checked and nitride. The range to build a basic Corvair
will probably run between $5k and $10K. Never priced the VWs. I'm just saying that being honest about the cost of a conversion engine and taking
Murphys Law into account, one should expect to invest a reasonable amount of money.....but will have virtually a new engine as a result. I do agree that
prudent builders can assemble a decent engine for less money.

Look, the same could be said for Lyc/Cont. Virtually anything you slap a redrive on will give you more power at RPMs useful to airplanes. There are viable direct drive auto conversions.

Eki reply: Agree 100%



Not if you follow a proven pattern. Make a clone of something that works and you can expect to have the same results.
Eki reply: Again we are in agreement, but not every conversion will have a successful example that one can follow. Often though, something similar is close enough to be an example that will yield good results without complete re-engineering.
 

ekimneirbo

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eki:

I have installed several Lycomings and a Continential, so I have a reasonable understanding of what is involved with typical HBA aircraft engines, but I never have done an auto conversion.

Clearly you have lots more experience than I do, so please tell us which engines you have installed, which were more difficult in your experience, and which needed follow up attention to deal with issues after you installed them.

Also tell us how many trouble free hours each engine flew after you installed them.

Or just ignore these questions, as you have in the past when asked about your actual experience.


BJC
BJC, you never cease to amaze me with your continued attempts to pry into my background and experience with feined interest in it. It has reached the point where I actually enjoy the speculation because I know it bugs you and several others on here. :roll:

Now, with all the wisdom and experience you have just professed about aero engines, would you like to take a shot at any of the factual information I presented and tell me where it is in error ? Even with no real automotive experience, surely you have some opinions about why the aero engine is better. Usually when someone declines to address the subject matter its because they know they have a weak argument. So then they turn to trying to discredit the OP.

Even thoughyou have no real experience with building an engine mount for an automotive conversion, I would be interested in why you THINK it would be more difficult for a builder. Next I would like to hear why you THINK the building of an exhaust system is more demanding and difficult ? Perhaps you could share with me the complexities that make the fuel system such a monumentally excruciating task for a carbureted auto engine . I realize you admit to not having any experience, but surely you can share with me some vision of why you think its so problematic just based on your experience with aero engines. After all, this thread was supposed to be about auto engines....surely you can contribute some helpful tidbit of knowledge on the actual subject at hand......


Those are all examples of the cumulative difficulties encountered when using an auto engine, and the kind of things the aero engine purists like to use to make their argument sound more substantive.....so enlighten me. Why is building many
of these components and systems more difficult when they employ virtually the same components?

And , one more time, tell me where anything I have stated is incorrect.....that's really what this should be about, isn't it?
 
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Dan Thomas

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History has some hard lessons. And those who ignore history tend to repeat the worst parts of it.

There have been thousands of attempts to fly auto engines, and many of them end up with Lycs or Conts in the airplane because the builder got fed up and frustrated with the innumerable issues that can crop up and consume so much time and money. It's not because people aren't trying that we don't see many conversions out there; it's because it's not as simple as it looks. I speak as one who installed an already converted (RAF) Subaru EJ22 in that Glastar, and still had a huge pile of engineering and fabricating to do.

One can ignore the naysayers, some of whom have no experience, many of whom do, either directly or though watching a friend struggle with a conversion. And then he either becomes a successful converter/flyer, or he becomes another naysayer. The problem with so many eager guys is that they are optimistic to the point of foolishness and won't listen to, or read of, the difficulties others have had so they can avoid them. There is no lack of information on what has worked and what hasn't, though it would be nice if the guys who have been trying conversions would publish the details of their failures. It's hard to do that, of course, but it would educate us all.

I don't mean to be a naysayer. I did that Glastar and flew it, and had some troubles. Others have been more successful, many less.
 

ekimneirbo

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History has some hard lessons. And those who ignore history tend to repeat the worst parts of it.

There have been thousands of attempts to fly auto engines, and many of them end up with Lycs or Conts in the airplane because the builder got fed up and frustrated with the innumerable issues that can crop up and consume so much time and money. It's not because people aren't trying that we don't see many conversions out there; it's because it's not as simple as it looks. I speak as one who installed an already converted (RAF) Subaru EJ22 in that Glastar, and still had a huge pile of engineering and fabricating to do.

One can ignore the naysayers, some of whom have no experience, many of whom do, either directly or though watching a friend struggle with a conversion. And then he either becomes a successful converter/flyer, or he becomes another naysayer. The problem with so many eager guys is that they are optimistic to the point of foolishness and won't listen to, or read of, the difficulties others have had so they can avoid them. There is no lack of information on what has worked and what hasn't, though it would be nice if the guys who have been trying conversions would publish the details of their failures. It's hard to do that, of course, but it would educate us all.

I don't mean to be a naysayer. I did that Glastar and flew it, and had some troubles. Others have been more successful, many less.
Dan I actually take what you said as being a good response. I know you are mechanically very wise and proficient, and you always address the subject
pretty objectively. If anyone on HBA could successfully build an auto conversion, I would think you could do it. The fact that you struggled with it
cannot just be dismissed by someone like me, because it truly happened. But, on the other hand the Subaru conversions are pretty well documented
and in widespread use. Many people with much less knowledge and experience than yourself have successfully built and flown them with few problems.
Those that have done so successfully have some economical airplanes to fly. The aero purist all tend to choke up when then they see honest to goodness success stories. I have also read some of your objective posts about the perils of used aero engines. The thing is that though we often disagree on certain subjects...vehemently at times, I respect the fact that you try to be objective which ever side you present....

My question now becomes, with so many completed flying examples of Subarus out there (thousands), should a builder look only at Dans experience, or should they consider that this particular engine conversion has had most problems resolved and presents an excellent example of a proven path? Is installing a Subaru going to be that technically difficult, or should it now be considered comparable in difficulty to installing a Lycoming?
 

Dan Thomas

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It will never be a simple as installing a Lycoming. The aircraft engine has well-defined and integral engine mount pads, in places where they make the most sense. The Subaru needs that sort of thing engineered and built. I had to make a mount that had 17 pieces of tubing in it to reach from the firewall's five mounting points all the way to the top front of the engine and lower bottom about halfway forward. And I had to make pads to fit those points on the engine. The top mounts were to the redrive plate and the bottoms picked up the original mounting lugs but I can't remember what they looked like, since this was nearly 20 years ago. The problem with such engines is that we're using the business end of the engine to drive the prop, and that's where the hard points are for mounting. Way out front instead of at the rear or beneath as with aircraft engines.

For many homebuilts, especially kits, ready-made mounts are available to fit Lycs or Continentals, and they cost a lot less than having one special deal designed and cut and fit and welded up. If I had added up my time to figure out that mount, make the jig, cut and fit all the tubing and tack it together for the professional Tig guy to weld, it would have cost the aircraft owner $10K for that mount, in 1996 dollars.
 

Turd Ferguson

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There have been thousands of attempts to fly auto engines, and many of them end up with Lycs or Conts in the airplane because the builder got fed up and frustrated with the innumerable issues that can crop up and consume so much time and money.

On the other hand, how many people have you come across that installed an aircraft powerplant and regretted that choice, wishing instead they had went with a converted auto engine?
 

Dan Thomas

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I once had a dream: Take an old Navion, remove the engine, take all the landing gear off it, throw away the nosewheel, convert the mains to taildragger configuration by mounting them ahead of the spar, make a tailwheel for it, and convert an SBC to fit the nose, with a redrive. Cowl it up tight to resemble the P-51, which was the daddy of the Navion, designed by the same guys that did the P-51. Take a look at the side and top views of those two airplanes sometime. The Navion would make a dandy poor man's P-51.

But I'd have to live to 90 and be rich to do it.
 

Turd Ferguson

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Eki, I think you may be guilty of oversimplifying the differences between aircraft engines and converted auto engines. You include a number of generalizations that don't make for a convincing argument.


I don't really see a lot of people on the fence being swayed or discouraged by negativity.

I do see a lot of people on the fence waiting for someone else to either go first and/or waiting to see if those or other attempts are successful or not.

Nobody wants to be first to fail and there is no glamour in repeating an already failed experiment. That is where I'm at. I follow every conversion I come across to see how well they do so that if I ever reach that point I'll have enough info to follow the example(s) that offer the best chance for success.
 

Wanttaja

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My question now becomes, with so many completed flying examples of Subarus out there (thousands), should a builder look only at Dans experience, or should they consider that this particular engine conversion has had most problems resolved and presents an excellent example of a proven path? Is installing a Subaru going to be that technically difficult, or should it now be considered comparable in difficulty to installing a Lycoming?
There are 581 Subaru-powered aircraft listed in the January 2016 FAA registry. Over a third are gyros. There are also about 7600 aircraft registered with "unknown" engine types. Years ago, I used the NTSB accident database to estimate what percentage of those "unknown" engines were specific types. Roughly 9% were Subarus, so we can project that there are probably around 1300 Subaru-powered aircraft in the US.

Continental-powered Fly Babies use stock production-aircraft components forward of the firewall. To put a Subaru on a Fly Baby (and yes, I've considered it) meant TOTALLY re-engineering things up front. New engine mount, new cooling system, new thrustline, new cowling, possibly new propeller, etc. It is a whole separate project, one likely to take just as many hours to realize as the airframe takes to build.

For the Fly Baby, there's a step-by-step set of instructions for building the aircraft. Similar manuals exist for the VW and the Corvair, but I'm not aware of any for the Subaru. This handicaps the typical non-engine-specialist homebuilder.

There are companies that sell firewall-forward packages...great approach! Two problems with that approach, though. First, the price is likely to be nearly what one would pay for a certified engine. Many people who want auto-engines are doing it to save money, and thus reject the firewall-forward approach. The second is...well, the companies don't tend to stay in business long. Support may dry up, which cripples people who aren't engine experts.

The last factor is the safety record. I took my homebuilt aircraft accident database and split out the Subaru (including NSI, Stratus, etc.) vs. the Lycoming/Continental accidents. About 22% of the accidents affecting the Lycoming and Continental-powered involved problems with the engine (Undetermined power failures, engine mechanical failures, Carb Ice, and failures of the ignition system). The results for Subaru-powered aircraft were 38%...almost twice as high. The Subaru occurrence of mechanical failure alone (24.6% of accidents) was higher than the total Lycoming/Continental result.

It's certainly possible to build a reliable auto-engine conversion. What we haven't seen is good transference of HOW to do this to the average builder. And, of course in some cases, there are those new builders unwilling to spend the time/money to do the things right.

Ron Wanttaja
 

ToddK

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The airboat guys are great source of information on auto engines, props, psru and vendors.
If you don't check out their forums and blogs you are missing out on a wealth of information.

If you are thinking about putting it in an airplane, there is probably some guy who has already put one in an airboat. Seriously those guys have figured out how to put propellers on way more engines then home built aviators ever have. They can afford to experiment since there is little risk in dying, so they generally know what works and what does not.

The only real difficulty is they are not nearly so concerned about weight as we are. I think, if we want to be using auto engines in our aircraft, we really ought to design them with that in mind, vs. trying to cram a heavier engine in a plane designed for a lighter one.
 

fredoyster

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Joined
Mar 20, 2012
Messages
333
Location
Monterey Bay, CA
I'm an engineer, but not an aero or propulsion engineer. But a lot of things are completely common across all of engineering. Number one, every design is a compromise. If you constrain one variable, the others wander. If you have more time or money, the engine can perform better and can be lighter. Answering eki's perennial question, more auto engines aren't being used because the handful of people actually building planes have more money than time and don't mind spending the money they have on an engine. Like most kids in my town, I rebuilt my mom's car engine when I was 15, who does that now?

A brand new 80 hp Rotax for under $15K, 134 pounds with redrive, electrics, coolers and exhaust is a pretty good deal when you look at all the alternatives, and people who are building $50-80K airplanes have no problem with that price.

A practical $20K airplane would be a really interesting exercise, and probably doable if you were building 1000 of them. If someone does it as a turnkey project, it would happen only if enough were made to spread the cost around enough that people could get paid for their work. Otherwise you're still talking about hundreds of hours researching how to make your Corzukibaruwagen happy on an airplane.

I think the problem is principally marketing. You can build a Pietenpol with a 2700 cc Corvair, or any number of lighter 1970s EAA champs with a VW, for $20K and a couple thousand hours, just like you could in the 70s for $5K. But people want faster, and to carry more weight. How to do that, especially if they also want the additional constraint of the light-sport definition? Yes, it can be done, if enough people are doing it. I think that's the major hurdle.
 

gtae07

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Joined
Dec 13, 2012
Messages
2,013
Location
Savannah, Georgia
I'm an engineer, but not an aero or propulsion engineer. But a lot of things are completely common across all of engineering. Number one, every design is a compromise. If you constrain one variable, the others wander. If you have more time or money, the engine can perform better and can be lighter. Answering eki's perennial question, more auto engines aren't being used because the handful of people actually building planes have more money than time and don't mind spending the money they have on an engine. Like most kids in my town, I rebuilt my mom's car engine when I was 15, who does that now?
I don't think anyone rebuilds the engines in their daily drivers now. There's no need--in most cases the engine will last longer than the economic lifetime of the vehicle.

For the Fly Baby, there's a step-by-step set of instructions for building the aircraft. Similar manuals exist for the VW and the Corvair, but I'm not aware of any for the Subaru. This handicaps the typical non-engine-specialist homebuilder.
YES! The average homebuilder knows little about engines and lacks most of the skill to do conversion work beyond assembling and simple hose/bracket/sheetmetal work. Most don't own lathes or mills, don't know how to weld, and don't know (without instructions or a guide) what they need to hook up. At the very least, you'll need to give prospective customers a complete parts list of stuff to buy and detailed instructions to hook it up, otherwise they won't know what they need or how to install it.

Examples of successful conversions prove it can be done, but simply showing something can be done is a lot different than showing how it's done.
 

plncraze

Well-Known Member
HBA Supporter
Joined
May 11, 2006
Messages
1,907
Mr. Wanttaja, thank you for supplying some numbers. Doing research on homebuilts requires some skill as you have shown with the "unknown" engines. My bet about the popularity of Subaru's in gyros is thanks to RFI which sold plans and kits. Also the owner of RFI was a writer for a gyro newsletter.

There have been various manuals for converting engines but as was stated for the Fly Baby one then has to install the conversion. If the conversion is fuel injected that might get complicated.
 

Dan Thomas

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Joined
Sep 17, 2008
Messages
5,473
There are 581 Subaru-powered aircraft listed in the January 2016 FAA registry. Over a third are gyros. There are also about 7600 aircraft registered with "unknown" engine types. Years ago, I used the NTSB accident database to estimate what percentage of those "unknown" engines were specific types. Roughly 9% were Subarus, so we can project that there are probably around 1300 Subaru-powered aircraft in the US.
And of those 1300, how many are actually flying versus sitting in a shop or hangar somewhere having bugs worked out, or just sitting because the owner got fed up with the bugs or can't afford to spend any more money on it?

We know well how many airplanes, either certified or homebuilt, are sitting and rotting away for no other reason than the owner has lost interest or a medical or wants too much for the airplane or can't afford to fly it anymore. Most of them have Lycs or Continentals or Franklins in them. Yet we see numbers registered in the database and get the impression that they're all active, when many actually aren't. I'd be surprised if more than two-thirds of those 1300 Subes are flying.
 

ekimneirbo

Banned
Joined
Oct 31, 2014
Messages
1,009
Location
Deep South
There are 581 Subaru-powered aircraft listed in the January 2016 FAA registry. Over a third are gyros. There are also about 7600 aircraft registered with "unknown" engine types. Years ago, I used the NTSB accident database to estimate what percentage of those "unknown" engines were specific types. Roughly 9% were Subarus, so we can project that there are probably around 1300 Subaru-powered aircraft in the US.


Ron Wanttaja
. Good post Ron. I wanted to clarify one thing I said. My understanding is that Australia has a large number of Subaru powered gyros too. I believe Ross put that out on another thread if memory serves me correctly.
 

Wanttaja

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Joined
Sep 15, 2013
Messages
1,566
Location
Seattle, WA
And of those 1300, how many are actually flying versus sitting in a shop or hangar somewhere having bugs worked out, or just sitting because the owner got fed up with the bugs or can't afford to spend any more money on it?

We know well how many airplanes, either certified or homebuilt, are sitting and rotting away for no other reason than the owner has lost interest or a medical or wants too much for the airplane or can't afford to fly it anymore. Most of them have Lycs or Continentals or Franklins in them. Yet we see numbers registered in the database and get the impression that they're all active, when many actually aren't. I'd be surprised if more than two-thirds of those 1300 Subes are flying.
The FAA assumes that 40% of homebuilts are not active. That's based on their annual survey, which, in my opinion, has some bad methodology. Almost 7,000 homebuilts were removed from the rolls during the re-registration effort, and the FAA's statistics method assumed that 4900 of them were active, flying aircraft.

So don't get me started. :)

Ron Wanttaja
 
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