Subaru to destruction

As I see it, the biggest problem with auto conversions is the unknown unknowns (thank you Donald Rumsfeld). Lycoming installations are fairly standardized and the things that can go wrong are well known. The thousands of production airplanes, each with exactly the same systems and configurations have weeded out most of the unknown problems. In a small group of auto conversion installations, it is impossible to know all the potential failures. Those of us who choose to use auto engines have to continue to be vigilant on our engines and learn from the failures to eliminate as many possible problems as we can.

I like to tell myself that by running a known configuration and keeping a careful inspection regimen, I can have reliability close to a Lycoming. I think the engine itself, when kept to a conservative HP level is more reliable than a Lycoming. I worry more about the support systems, such as prop, gearbox, electrical system, fuel system.

In any case, flying single engine, Lycoming or otherwise, has caused me to be ready to deal with a power loss at anytime.

Randy, thanks for all your work on these engines. It was great getting to know you last summer.

-Andy

Randy,

I think that's an excellent post you made, thanks for taking the time to write out where you are at. Like Ross said it underscores the importance of details. I know how difficult it must have been to make that post here knowing you'd likely hear (or at least know people were thinking) "I told you so...". In the end, posts like yours will actually help people, whether Alternative or Conventional.

I have nothing much of value to add other than to say thanks for the post. As you know, most people won't actually come back and report their failures OR success just because of how emotionally charged this subject gets when discussed.

Cheers,
Stein

Ross,

Trying to summarize and just thinking about where the challenges are:

It seems that the gearbox problems are solved if an appropriate selection is made, is that correct?

There are weaknesses (meaning not to a 2000hr TBO yet), but valve train, piston/ring/liner, rods, and bottom end are pretty good.

So, is it proper to conclude that the engine management system is needed to:
1. provide proper A/F mapping and management
2. Timing mapping and management
3. detonation management and mitigation
4. internal engine monitoring with issue mitigation using timing, A/F , and maybe throttle?

Is this the real (not "answer") area for reliable development that would then provide a stable operating platform for further engine improvements with longer hours?

Note I did not address previous discussions about torsionals, as it is assumed to be either solved or solvable but it is not a critical need for reliable push to some reasonable overhaul life.

Also the rod bearing cavitation issue you found, is assumed to be solvable too.

So - If you had a bucket load of OPM (other peoples money) to further the development of this engine package where would you spend the first money?

Thanks

BillL said:

Ross,

Trying to summarize and just thinking about where the challenges are:

It seems that the gearbox problems are solved if an appropriate selection is made, is that correct?

There are weaknesses (meaning not to a 2000hr TBO yet), but valve train, piston/ring/liner, rods, and bottom end are pretty good.

So, is it proper to conclude that the engine management system is needed to:
1. provide proper A/F mapping and management
2. Timing mapping and management
3. detonation management and mitigation
4. internal engine monitoring with issue mitigation using timing, A/F , and maybe throttle?

Is this the real (not "answer") area for reliable development that would then provide a stable operating platform for further engine improvements with longer hours?

Note I did not address previous discussions about torsionals, as it is assumed to be either solved or solvable but it is not a critical need for reliable push to some reasonable overhaul life.

Also the rod bearing cavitation issue you found, is assumed to be solvable too.

So - If you had a bucket load of OPM (other peoples money) to further the development of this engine package where would you spend the first money?

Thanks

Click to expand...

I'm not so sure the gearbox problems are solved so that they will go 1000 hours with no maintenance or trouble in the majority of cases but that is certainly solvable.

The engine is very reliable and capable of powering aircraft in completely stock form. We have hundreds flying proving just that when de-rated to about 85-90% of the stock power level.

The engine management side is well understood, well proven and little different from what is required on a road racing engine. You can't have detonation or pre-ignition happening at these power levels or the engine life is measured in seconds rather than hours. I've seen the same mistakes repeated many times and the result is always predictable.

I don't fly with a knock sensor and I've driven turbocharged race and street cars my whole life without knock sensors. They work fine and are very reliable with proper engine mapping. Knock sensors will not protect against poor mapping as we have seen many times and particularly with the 2008-2009 STi debacle.

We have a number of engines over 1000 hours without being touched, a few over 2000 and one near 4000. That means when everything is right, they can last a long time and cost a fraction per flight hour of a certified type engine.

TV issues are obviously not an issue on the engines mentioned above so this is entirely solvable too.

The cavitation damage I saw is so rare, I've never seen a case in real life before- with over 30 years in the business and it's not something common in these engines at all. I have no certain answer what caused it in my engine.

I don't think it would take a bucket load of money to offer reliable and proven FF Subaru packages. You just copy the successful conversions that have proven reliable over many years. We pretty much know what works and what doesn't now for the most part. Most serious, quick failures are due to overlooking some of the basic fundamentals or stepping over the known limits.

I'd spend the money on an instrumented test stand which could run the engine over the full spectrum of load and rpm ranges with PSRU and prop installed for many hours. Most of the money would be for fuel and TV instrumentation. Once it passes those tests for 500+ hours, I'd continue to flog it in flight on a test aircraft.

Randy said:

VAF folks,

There was not a lot of runway left and I was up a ways, so I needed to gain enough altitude to make the big turn to get back, or put it in the cactus in very steep terrain. I had automatically pulled the throttle back when I felt that shudder and it came back again when I pushed the throttle back in to gain the altitude. I think I went through a few more cycles of throttle up, feel the shudder and pull it back. Without actually thinking about it I turned out to the the right a ways before bringing it all the way around to the left to line back up with the runway and I got it down about two thirds of the way down with out any issues. It was nice to have the AOA during that turn

Click to expand...

Randy, congratulation on successfully making "the impossible turn" and getting back to the runway. At least you now have an unbent aircraft in which to instal a Lycoming.

Ross,

The appeal of the engine is certainly strong for me. Like many I was hopeful with the eggie solution, but really happy I wasn't far enough along to get caught up spending dollars on it.

Today, if someone were going to consider the subbie, where would you start for say something around 100-150 hp?

What about the PSRU? Is there one on the market that one could purchase? How much of a tinker'er/engineer would I need to be?

Thanks,

Bob

bhassel said:

Ross,

The appeal of the engine is certainly strong for me. Like many I was hopeful with the eggie solution, but really happy I wasn't far enough along to get caught up spending dollars on it.

Today, if someone were going to consider the subbie, where would you start for say something around 100-150 hp?

What about the PSRU? Is there one on the market that one could purchase? How much of a tinker'er/engineer would I need to be?

Thanks,

Bob

Click to expand...

If you were looking for around 150hp and to be weight competitive with an O-320, you could probably just use a 2003-2005 non-VVL sohc EJ253 and don't touch anything internally.

For gearbox, I'd probably go with the Autoflight Heavy unit and run a flywheel of at least 12 pounds.

ECU- I am biased towards the SDS but you could go MoTec as a number of people in Australia and NZ have done.

Radiator- with the success of ventral rad setups, this appears to be the way to go to get good cooling with minimal drag.

Prop- Always the hard choice. IVO in flight adjustable 3 blade Magnum if cost is a concern. MT electric (watch the price tag) if you want the best performance.

You'd probably need some fab/ welding skills or a close friend who has them and you'll need some spare time of course. Lots of hours to do this project. I don't think you need to tinker too much if you follow the advice of the successful people flying these engines.

I'll take a stab at your question.

If you were to take an Egg 4 cylinder engine set-up and use the best known parts, you would have a reliable 150HP set-up that weighs about what a Lycoming O-360 weighs.

It would include a Gen 3 gearbox with a dual mass flywheel set-up. This gives a spring "damper" between the engine and gearbox. I believe that this is the secret to making the gearbox last.

As far as fuel and ignition, Ross could set you up with a great system. My engine uses the original Subaru ECU and injectors plus a knock sensor. This works well but has very little adjustability and you would have to use a 1999 or 2000 model. The newer ECU's are too complex and have too many inputs to get to work in an aircraft.

I would stay away from the 6 cylinder engines and anything newer that has variable valve timing. The EJ-25 with single overhead cams seems to be the best.

As far as tinkering goes, you would need to be able to tweek the installation to make sure you get enough cooling and that you have a reliable electrical system. The fuel system needs to run MOGAS primarily. The lead in 100ll causes stuck rings in Subby's.

One of the Egg firewall forward packages with a 4 cylinder will get you close.

-Andy

-Andy

Subaru Factory Tuning Values

I have finally purchased a Subaru 2009 Forester with the SOHC engine and run it on a dyno to see what advance and fuel values the factory ECU runs at high power settings.
The runs were quite an eye-opener with timing going from 40.5 degrees advance at 3,500 RPM and 50% MAP down to 20 degrees at 6,000 RPM and 100% MAP. Needless to say my use of 30 degrees would have been sufficient to destroy engines to date.
Interestingly the factory runs close to stoimetric at 80% MAP, 4,000 RPM and below. However the fuel figure climbs to an AFR of 10.9 at maximum power and may even be a bit richer although this may have been a response to increasing engine temperature.
I have not yet dismantled the last engine but will probably do so soon.
The good news is that because the insurance industry operates with a Written Off Vehicles Registry in Australia you can buy a whole car for less than $2,000 with engines down to 21k miles on the clock and perfectly capable of being run to maximum power on a dynamometer with no issues flagged by the OBD data output.
Naturally I will also be looking at oil analysis, leak down tests and timing belt replacement before proceeding but rebuilding engines like this is probably not justified.
Regards to all.
Rupert Clarke

clarkefarm said:

I have finally purchased a Subaru 2009 Forester with the SOHC engine and run it on a dyno to see what advance and fuel values the factory ECU runs at high power settings.
The runs were quite an eye-opener with timing going from 40.5 degrees advance at 3,500 RPM and 50% MAP down to 20 degrees at 6,000 RPM and 100% MAP. Needless to say my use of 30 degrees would have been sufficient to destroy engines to date.
Interestingly the factory runs close to stoimetric at 80% MAP, 4,000 RPM and below. However the fuel figure climbs to an AFR of 10.9 at maximum power and may even be a bit richer although this may have been a response to increasing engine temperature.
I have not yet dismantled the last engine but will probably do so soon.
The good news is that because the insurance industry operates with a Written Off Vehicles Registry in Australia you can buy a whole car for less than $2,000 with engines down to 21k miles on the clock and perfectly capable of being run to maximum power on a dynamometer with no issues flagged by the OBD data output.
Naturally I will also be looking at oil analysis, leak down tests and timing belt replacement before proceeding but rebuilding engines like this is probably not justified.
Regards to all.
Rupert Clarke

Click to expand...

I find all the values you observed are legit... Subaru's main goal is to provide a durable engine that produces decent power with minimum warranty claims... The reduced timing and extra fuel flow will prevent the motor from melting down. Also keep in mind a vehicle operates in all kinds or dynamic conditions, and aircraft engine spends most of it's life in a very narrow powerband... With a tunable ignition and fuel delivery system, any engine can be dialed in to any application. Ross can explain it better then me but taking a bulletproof auto engine as a start and implement common sense running parameters, the end result will be a safe and reliable powerplant.. IMHO.

clarkefarm said:

I have finally purchased a Subaru 2009 Forester with the SOHC engine and run it on a dyno to see what advance and fuel values the factory ECU runs at high power settings.
The runs were quite an eye-opener with timing going from 40.5 degrees advance at 3,500 RPM and 50% MAP down to 20 degrees at 6,000 RPM and 100% MAP. Needless to say my use of 30 degrees would have been sufficient to destroy engines to date.
Interestingly the factory runs close to stoimetric at 80% MAP, 4,000 RPM and below. However the fuel figure climbs to an AFR of 10.9 at maximum power and may even be a bit richer although this may have been a response to increasing engine temperature.
I have not yet dismantled the last engine but will probably do so soon.
The good news is that because the insurance industry operates with a Written Off Vehicles Registry in Australia you can buy a whole car for less than $2,000 with engines down to 21k miles on the clock and perfectly capable of being run to maximum power on a dynamometer with no issues flagged by the OBD data output.
Naturally I will also be looking at oil analysis, leak down tests and timing belt replacement before proceeding but rebuilding engines like this is probably not justified.
Regards to all.
Rupert Clarke

Click to expand...

These figures are pretty typical as we tested a stock EJ22 years ago with similar results- up to 45 degrees timing at light load (that's just for emissions), 36 degrees at medium throttle and 3500 to 4750 rpm. Closed loop operation would vary depending on MAP and rpm- as low at 22 inches and 2900 rpm would kick it into open loop where AFRs would go to 10.5 to 11.4 at high rpms at WOT (data a bit suspect with the OEM narrow band O2 sensor). This on 87 octane fuel.

Running on our 91 octane premium fuel over here, we find the engines live if you keep AFRs in the low to mid 11s and timing no more than 26 degrees. HP falls off considerably with timing values of less than 22 degrees and EGTs skyrocket as well. While power is diminished with such rich AFRs and reduced timing, it is required to keep the pistons alive. On 100LL you can run the full 32 degrees of timing and 12.5 AFRs to make best power with no fear of detonation but the valves don't enjoy the leaded fuel over time.

And just for the benefit of Mr Clarke and any other Aussies reading, the fuel octane ratings Ross has mentioned for mogas is (R+M)/2. Our fuel numbers at the pump are straight RON numbers. So stick to the 98.

Detination issues

I've been building muscle cars for some time now; I'm also a Pilot with UVU. The first thing I would like to point out is that most auto's run between 8-9:1 compression stock. The Subaru water boxer engines, such as my EG33 runs at 10.1:1; considerably higher. The higher the compression ratio the higher the octane required. In your case I would not go less then 100 Octane simply because you're already at a high compression ratio, but you're also running at altitudes which would require a slower burn rate to prevent detonation. Such as when we run Top-Fuel Drag at high elevation we mix our fuel to be a little more potent. If I were you; I would mix a Lt of stilled alcohol per 20 gal.

You're also running a water cooled engine so it's likely masking any issues which would be more evident if running an air cooled engine. What you might want to arrange is a vacuum advance on your ignition, rather then a computer controlled advance; if possible depending on your distributor arrangement. Otherwise I would probably convert to an AEM programmable ECU for your application. The issue with stock ECU's is that in many cases you'll get an error code when the RPM are up for more then 2 minutes but the speedometer does not match what the computer predicts. This can lead to all kinds of false computer issue with the ignition and fuel mixture. In some cases such as Ford you can go to the sport and racing department which will sell you a kit to override the OEM programming for about 200 USD.

The final alternative is that you may consider converting to a more trust worthy set up of carburetor, and electronic ignition from MSD or Mallory.

Coughtry said:

I've been building muscle cars for some time now; I'm also a Pilot with UVU. The first thing I would like to point out is that most auto's run between 8-9:1 compression stock. The Subaru water boxer engines, such as my EG33 runs at 10.1:1; considerably higher. The higher the compression ratio the higher the octane required. In your case I would not go less then 100 Octane simply because you're already at a high compression ratio, but you're also running at altitudes which would require a slower burn rate to prevent detonation. Such as when we run Top-Fuel Drag at high elevation we mix our fuel to be a little more potent. If I were you; I would mix a Lt of stilled alcohol per 20 gal.

You're also running a water cooled engine so it's likely masking any issues which would be more evident if running an air cooled engine. What you might want to arrange is a vacuum advance on your ignition, rather then a computer controlled advance; if possible depending on your distributor arrangement. Otherwise I would probably convert to an AEM programmable ECU for your application. The issue with stock ECU's is that in many cases you'll get an error code when the RPM are up for more then 2 minutes but the speedometer does not match what the computer predicts. This can lead to all kinds of false computer issue with the ignition and fuel mixture. In some cases such as Ford you can go to the sport and racing department which will sell you a kit to override the OEM programming for about 200 USD.

The final alternative is that you may consider converting to a more trust worthy set up of carburetor, and electronic ignition from MSD or Mallory.

Click to expand...

Welcome to the forum.

Actually, octane rating requirement drops with altitude on an atmo engine because peak cylinder pressure is lower. Alcohol is very detrimental to aircraft fuel systems and simply not needed.

There are many hundreds of Subarus flying successfully all around the world just fine on premium mogas, including turbocharged ones and EG33s, virtually all with ECU controlled fuel and spark. The stock, SDS and Motec ones are the most popular. AEM could work too but have almost no pedigree by comparison in aviation. In this case, the Motec used is probably more capable than AEM, being one of the most sophisticated ECUs on the market. The issues with the stock ECUs are well known and there are some easy work arounds to use them.

http://www.motec.com/home

http://www.sdsefi.com/aircraft.html

Motec and SDS both have data logging capability so it's easy to look at all parameters after a test run and reprogram accordingly.

ECUs can control the spark and fuel much more precisely over the whole range compared to any mechanical setup with MAP, rpm, IAT, CLT, AFR and knock sensor inputs. Putting carbs and a distributor on an engine designed for EFI would be a big step backwards as a number of people have found out with EJ and EG engines. EFI is very well proven on these engines by comparison.

In this case, the cause and solution and known now. Most failures occur on these engines due to too much spark timing and/or too lean AFRs- easily corrected with a bit of reprogramming.

The title of this thread is somewhat humorous.

....Subaru to Destruction, hang it on an RV and fly it for a while....

Just kidding you-all Subby lovers. It is a tough little engine and if properly installed will satisfy most anyone so inclined to be adventurous with an alternate engine. The PSRU is half the challenge and has nothing to do with engine reliability.

I was once totally intoxicated with Subby cool aid....it was fun...for a while...now I am content and somewhat bored with Lycoming (Superior) reliability. But at my age it is just fine.

I wanted to make one last comment to this oil issue you had. Install the breather above the engine with a hose. If you already did so; then use a larger diameter hose to prevent bubbles.

If I remember Right I originally wrote about detonation on this form in response to an other post. If your Subaru is experiencing detonation (pre ignition) then you need to checkout the Knock sensors (two on top, each side of the crank case). These sensors will retard the timing to prevent preignition.

Coughtry said:

I've been building muscle cars for some time now; I'm also a Pilot with UVU. The first thing I would like to point out is that most auto's run between 8-9:1 compression stock. The Subaru water boxer engines, such as my EG33 runs at 10.1:1; considerably higher. The higher the compression ratio the higher the octane required. In your case I would not go less then 100 Octane simply because you're already at a high compression ratio, but you're also running at altitudes which would require a slower burn rate to prevent detonation. Such as when we run Top-Fuel Drag at high elevation we mix our fuel to be a little more potent. If I were you; I would mix a Lt of stilled alcohol per 20 gal.

You're also running a water cooled engine so it's likely masking any issues which would be more evident if running an air cooled engine. What you might want to arrange is a vacuum advance on your ignition, rather then a computer controlled advance; if possible depending on your distributor arrangement. Otherwise I would probably convert to an AEM programmable ECU for your application. The issue with stock ECU's is that in many cases you'll get an error code when the RPM are up for more then 2 minutes but the speedometer does not match what the computer predicts. This can lead to all kinds of false computer issue with the ignition and fuel mixture. In some cases such as Ford you can go to the sport and racing department which will sell you a kit to override the OEM programming for about 200 USD.

The final alternative is that you may consider converting to a more trust worthy set up of carburetor, and electronic ignition from MSD or Mallory.

Click to expand...

Coughtry said:

I wanted to make one last comment to this oil issue you had. Install the breather above the engine with a hose. If you already did so; then use a larger diameter hose to prevent bubbles.

If I remember Right I originally wrote about detonation on this form in response to an other post. If your Subaru is experiencing detonation (pre ignition) then you need to checkout the Knock sensors (two on top, each side of the crank case). These sensors will retard the timing to prevent preignition.

Click to expand...

Detonation and pre-ignition are two very different things and the failure modes are also different. Knock sensors cannot sense pre-ignition. Turbo EJs use a single knock sensor. For aviation, we generally don't use the knock sensors due to safety and setup concerns however with care and understanding they could be used. Instead, we rely on conservative base mapping of the ignition timing along with running rich mixtures which also keeps the piston crowns alive. The OEM also runs very rich mixtures at WOT.

David-aviator said:

I was once totally intoxicated with Subby cool aid....it was fun...for a while...now I am content and somewhat bored with Lycoming (Superior) reliability. But at my age it is just fine.

Click to expand...

Good for you David! You were good enough in years past to pass along your trials and tribulations of trying to make your Eggie work like it was billed originally as (ready to go FWF, etc) to this list; and it's now good that you don't have to work quite so hard to just go flying. I hope to get back at my Mazda 13B powered "9A" this winter when pools and grass cutting, etc. are no longer issues! Fly safe Doug Lomheim RV-3A (restored and flying) RV-9A moving to the top of my "TO DO" list again.