[David-aviator]

To quote Rod Schneider regarding the tear down of the Subaru H6 (3.0) engine core I gave him for that purpose,

"Hi, Dave,

Well, I finally got the engine taken apart this afternoon. I was waiting
for some tools I'd ordered to come in, and they arrived yesterday. There is
good news and bad news.
The good news is: I couldn't really find anything wrong inside at all.
The bad news is: I couldn't really find anything wrong inside at all........
The cylinders look fantastic and measure well within specs for taper and out
of round. There was just the slightest bit of a carbon ridge at the top of
the bores. The pistons and rings look equally good with no signs of any
deposits in the ring grooves or any hint of detonation damage to the ring
lands or piston surface. Piston ring end gaps are per spec in all six
cylinders. I discovered that the tan deposits in the combustion chambers
and on the tops of the pistons will scrap off very easily with a fingernail...."


The bad news here is we really do not know why the performance of the engine had dropped off earlier this year. Two items could be the cause since the 245-250 degree temperature excursion last summer appears to not have damaged the engine or be the cause.

1. The little bit of 100LL fuel used did leave some oxidized lead deposits which may have caused the low compression readings. Three cylinders were running below the 185 bottom limit on the last compression check in July.

2. The $1315 internal muffler I bought from Jan in March 08 could have caused a loss of power due to excessive back pressure. Jan had asked me to remove the muffler to see if it was the cause of the performance loss but I couldn't because the headers had been changed to accommodate the muffler. I simply ran out of patience with the matter and felt the muffler should have been flight tested to where it worked without loss of performance.

To summarize, this is good news for guys with this engine. Early on I had a conviction that it was a good tough little motor and so far the evidence would seem to support that early feeling. If anything we have reduced the list of causes for the drop in power.

Do I regret bailing out of Subaru? Considering the economic situation since the decision was made and these findings, I probably could have hung in there a little longer. But I am not one to look backward with regrets. There still are cooling and performance issues I remain weary of dealing with. Unlike Ironman Paul who turned the big 50 this week, I will turn the big 70 next February and feel a need to back down a bit if I am to continue flying.

The really good news here is the engine is not all that fragile and guys with it certainly can work on the cooling and performance issues with some confidence in the engine itself. The overall development has evolved with larger radiators and a dedicated cowl to make them work much better than the early versions.

One final note, the guy doing this tear down and inspection is a maintenance inspector with a major airline and knows his stuff. Rod says the engine is remarkably clean inside and so far all tolerance measurements are OK.

 

[rv6ejguy]

Thanks for the update David. I was not too keen on the very small exit pipe on the new muffler- almost certainly restrictive on a 3 liter engine running WOT and high rpm.

 

[TSwezey]

Some of those parts look brand new. Thanks for sharing.

 

[rodrv6]

Here are a couple more pictures of the engine. This thing was extremely clean inside and I'm very impressed by the engineering in this engine. This was the first Subaru engine I've been into. I've done a number of Honda, Porsche, VW, and Chevy Small Blocks in my lifetime, and this is an absolute jewel. It really makes me feel good about the one on my RV-6!




Edited to add: I did not clean these parts before photographing them, but I did wipe the oil out!

 

[rodrv6]

And here is a picture of cylinders 2, 4, 6.

 

[rv6ejguy]

Looks pretty mint inside. Pretty typical what I see on other Subes I've taken apart. Nothing really wears.

 

[gmcjetpilot]

Amazing

Looks pretty mint inside. Pretty typical what I see on other Subes I've taken apart. Nothing really wears.

Nothing wears really? Really.........so than why take it apart.

Can't wait for the TDI Subaru to come to North America (turbo diesel). I want to drive one not fly it, but the diesel in a subie boxer config should be fantastic.

 

[rv6ejguy]

Nothing wears really? Really.........so than why take it apart.

Can't wait for the TDI Subaru to come to North America (turbo diesel). I want to drive one not fly it, but the diesel in a subie boxer config should be fantastic.

I re-used all the bearings in my EJ22T because they were perfect after 46,000 miles and the valves still had all the Parkerizing on the stems. Every part was right in the middle of new spec so it was pretty much just rings and seals plus the new forged pistons to zero time it. There was no measurable or visible wear on any part in mine but I magged the crank and rods to be extra sure.

We want to establish life on these things and find any high wear or problem areas to build a database for others. We have to take 'em apart to confirm that nothing is wearing.

 

[Rhouse9044]

exhaust back pressure

2. The $1315 internal muffler I bought from Jan in March 08 could have caused a loss of power due to excessive back pressure. Jan had asked me to remove the muffler to see if it was the cause of the performance loss but I couldn't because the headers had been changed to accommodate the muffler. I simply ran out of patience with the matter and felt the muffler should have been flight tested to where it worked without loss of performance

David-
On that note, I have an Egg 2.5 SOHC NA in my RV9A with the Supertrap muffler. I installed an open end plate from Summit Racing after welding a short tailpipe with a 20 deg. downward bend on it. I reduced the number of plates to 6 to save weight, and the airplane is still fairly quiet inside and out.
I am getting performance comparable to what the 320 Lycomings are reporting. At 4500 eng. RPM I get 152 KTAS cruise @ 6,500', dropping to 145KTAS @ 12,500' with a fuel burn of 8.4 GPH dropping to 6.9 at the higher altitude. I can maintain 1,000 FPM climb to 10,000' DA at full gross weight.
The catch, though, is that I did several other hot-rod mods to the engine before I flew it, so I don't know how much the free flowing exhaust is contributing to the power output. I did note that when I port matched the stock exhaust manifolds to the cylinder heads that the manifold openings were smaller than the ports and that can cause a substantial flow reduction.That is something others might want to check on their engines. These engines seem to respond very well to basic hot rod modifications. I am very happy with mine.
Bob House
RV9A N462BD 200 hours flying

 

[rodrv6]

I re-used all the bearings in my EJ22T because they were perfect after 46,000 miles and the valves still had all the Parkerizing on the stems. Every part was right in the middle of new spec so it was pretty much just rings and seals plus the new forged pistons to zero time it. There was no measurable or visible wear on any part in mine but I magged the crank and rods to be extra sure.

We want to establish life on these things and find any high wear or problem areas to build a database for others. We have to take 'em apart to confirm that nothing is wearing.

The main reason this engine was taken apart was because it got overheated due to a prop issue, and seemed to suffer a loss of power after that event, although it is possible that an exhaust system change may have contributed to that. David was kind enough to give me the opportunity to take it apart and check it out.
I still haven't taken all the valves out of the heads (I did remove 1 intake and 2 exhaust valves by hand--no fun) since my valve spring compressor will not fit these heads. I've got one on order that should work, and I'll report back on what I find with the valve seats. The three valves I've removed do not show any damage to the seats or the valves.
I believe the engine has around 250 hours on it, so it should be far from worn out and what I've seen seems to bear this out.

George, as a data point concerning modern automotive engines, I recently tore down my Nissan Maxima SOHC V6 that had 290,000 miles on it, mainly because of several seals leaking and the desire to check on things inside (it has to last me for a few more years). What I found was an engine that had no measurable wear on the bearing surfaces or the cylinder walls. The valves and seats were also "like new". In fact, the only wear I found was one lobe on the rear camshaft was trying to go round on me and was worn beyond limits, so it got a new cam and lifters. Not bad for an old car that spends most of its time at 70 or so going back and forth to work.

 

[RichB]

External components

Thanks for posting all that. Given the strength of the internals, I'm curious about a couple of the external components...

Did the injectors still flow the correct rate (wondering about the effect of 100LL on them)?
Was the ignition system still producing full power spark (wondering about effect of vibration and temperature)?

 

[David-aviator]

Thanks for posting all that. Given the strength of the internals, I'm curious about a couple of the external components...

Did the injectors still flow the correct rate (wondering about the effect of 100LL on them)?
Was the ignition system still producing full power spark (wondering about effect of vibration and temperature)?

Don't know how to answer the question except to say the fuel flow indication system never changed in terms of fuel being consumed. In other words, once I got it calibrated it was remarkably accurate and remained so. The system had no impellers but measured flow based on injector open time.

I would add 10 or 15 gallons when needed (usually mogas), reset the fuel remaining and go fly. At one point I drained all fuel to re-weigh the airplane and found the amount of fuel remaining was within a gallon of what the fuel totalizer indicator. I don't remember the exact amount of fuel burned but it was well over 100 gallons when I did this. The fuel flow indication was accurate to within 1% or better.

Conclusion, the injectors were metering the same amount of fuel through out the life of the engine. It did not change or the totalizer would have been off.

I never had a problem with ignition. The engine started easily and never hesitated once it found its brain after initial start up. I did check timing with the OBDII now and then and it seemed quite normal, usually about 30+ advanced at low power and about 24 degrees at full power. If I got it into closed loop in flight it always ran very advanced which is what an auto does for good mileage numbers.

 

[RichB]

Don't know how to answer the question except to say the fuel flow indication system never changed in terms of fuel being consumed. In other words, once I got it calibrated it was remarkably accurate and remained so. The system had no impellers but measured flow based on injector open time.

I would add 10 or 15 gallons when needed (usually mogas), reset the fuel remaining and go fly. At one point I drained all fuel to re-weigh the airplane and found the amount of fuel remaining was within a gallon of what the fuel totalizer indicator. I don't remember the exact amount of fuel burned but it was well over 100 gallons when I did this. The fuel flow indication was accurate to within 1% or better.

Conclusion, the injectors were metering the same amount of fuel through out the life of the engine. It did not change or the totalizer would have been off.

I never had a problem with ignition. The engine started easily and never hesitated once it found its brain after initial start up. I did check timing with the OBDII now and then and it seemed quite normal, usually about 30+ advanced at low power and about 24 degrees at full power. If I got it into closed loop in flight it always ran very advanced which is what an auto does for good mileage numbers.

There were reports years ago of injected cars having issues running on leaded fuel (10% flow loss over 4400 km leaded vs 0% loss in 20000 km unleaded, here). The numbers I've seen recently suggest gum levels are similarly low in 100LL and mogas now, but the mentioned paper suggests the Pb might give the gum something to stick to? Sounds like you've done the math, but an injector flowtest could easily verify that the flow rates are okay.

Also sounds like the ignition packs survived the overheat. When you're talking about "closed loop" do you mean steady-state running, or O2-sensor feedback (and if so, how many hours on the sensor, do you have a pic to reference for Pb contamination), or some other feedback mechanism? Which computer was the engine running?

 

[rv6ejguy]

The OEM ECU reverts to open loop mapping at typical cruise power settings used in aircraft so if injector flow rates dropped, this would lean out those cylinders but it would take quite a flow loss to hurt the engine as Fuji defaults into the high 11s generally and we find it safe to run high 13s in cruise.

I run in open loop with 100LL exclusively. Mapping and AFRs are same as they were 285 hours ago so I see no evidence that lead in the fuel has any effect on injector flow rates.

We've tested the coil on plug units used on the EZ30 engines by substantially over driving them on the bench until they reached 284F. No damage. They appear to be very robust pieces.

 

[Rotary10-RV]

Prop related problems?

David,
You mentioned that a prop problem caused the original overheat. Is it possible you aren't getting correct prop function? MT? Or quinti? IF you have a prop controller that is malfuntioning SLIGHTLY by reading the wrong RPM for example, it could cause performance problems by holding too corse pitch. Since the controls on all the Subaru props are electric unless you have something special.
Bill Jepson

 

[dlomheim]

100 LL and Fuel Injector losses

There were reports years ago of injected cars having issues running on leaded fuel (10% flow loss over 4400 km leaded vs 0% loss in 20000 km unleaded...

I have chatted a few high time Mazda guys regarding the longevity of their 13B installations and I have never heard injectors being an issue when running on 100LL. The biggest 100LL issue most commonly mentioned is that spark plug life is reduced when compared to those using unleaded fuel.

Doug Lomheim
RV-9A/ 13B
OK City, OK

 

[rodrv6]

David,
You mentioned that a prop problem caused the original overheat. Is it possible you aren't getting correct prop function? MT? Or quinti? IF you have a prop controller that is malfuntioning SLIGHTLY by reading the wrong RPM for example, it could cause performance problems by holding too corse pitch. Since the controls on all the Subaru props are electric unless you have something special.
Bill Jepson

I believe David's prop issue had to do with the brush block coming loose or something, which didn't allow him to change the pitch. After he fixed the issue, the prop was working normally.

I finished taking the engine apart this week and was able to take a good look at the valve seats. Just like the rest of the engine, they all were in great shape and a coat of Prussian Blue showed nice, consistent contact patches. The lead deposits in the combustion chambers removed very easily--a fingernail was able to remove a good portion of it.
All in all, the engine is in great condition. I've put it back together and plan to keep it as a potential spare parts source. I sent David and Jan my findings, and Jan has posted them on his Yahoo group.
Thanks to David for giving me the opportunity to do this--it was a lot of fun