vw diesel engines

[rv6ejguy]

I agree with Andy's assessment in an earlier post. People assume that diesels can take unlimited boost and last for a very long time. There are subject to the same mechanical issues as a gasoline engine. Boosting power a street engine via more boost in unlikely to affect longevity since full power stresses only last for a few minutes out of each hour of operation. Torsional vibration/ fatigue levels in the crank would be my biggest concern on a highly boosted aircraft diesel.

I once turboed a naturally aspirated Toyota Landcruiser diesel with about 9 psi. It was way faster than stock. The owner commuted about 120 miles per day on the highway with it. Lasted about 2 years and the crank broke one day. This crank was absolutely massive compared to a TDI crank and heat treated alloy steel to boot.

Thielert has found out that successful auto diesels do not always work the same on aircraft. While I encourage experimentation, just don't forget the underlying physics here. Get one flying and let's see how it works!

The propeller longevity might be another issue with a direct drive diesel.

[gmcjetpilot]

It's out in Euro. May be next year for US market? want one. I can got free fast food joint french fry oil and make my own diesel fuel.

http://www.youtube.com/watch?v=-G5TcWg0TMc

[rv6ejguy]

The bad news for using this engine in aircraft is that you need the OEM ECU and it is heavily tied into the chassis with sensors, anti-theft interlock codes and other nasties. It will be a mess to decipher all this junk to make the computer run just the engine happily without the car attached. No option to install a mechanical pump and injectors easily on this engine unfortunately. Apparently Bosch is able to sell a programmable ECU for common rail diesels now- the bad news- you need $25K.

[pvansrv3]

Two serious considerations come to mind when evaluating an auto engine for airplane use.

1. How do you deal with the thrust load generated by the propeller pulling the airplane through the sky? Auto engines transmit torque to the transmission and have very little thrust loads. On air cooled VW auto engines converted to motorglider use, Limbach in Germany makes major modifications to the crank and case to incorporate thrust bearings.

2. Airplane propellers can only turn about 2700 rpm efficiently because the tips begin to go supersonic if you rev them higher, unless you have a very small diameter prop. So, how do you make the auto engine make the horsepower at low rpm? Or you need a gear reducer which only adds yet more weight and complexity.

What will it really cost when figuring the entire expense of all the parts, motor mount, cooling, cowling, etc as compared to a tried and true Lycoming? Looking at the Eggenfellner? Subaru conversions sold to the RV market, I see no cost savings anywhere, but I do see a decreased resale value.


Just because it can be done does not make it a good idea. Consider Iraq today. I rest my case.

[zzapp]

Unfortunately political may overshadow the practical. Shutdown the lead additive plant in England and many aero engines become expensive museum pieces. It might be easier to cobb up a bearing package for the subie diesel than train your high compression lycon to run on nolead. I am very happy with my lycon, even with paying a performance price for having low compression pistons.
Mogas will at least keep it flying, Jet-A might be the only future.

[John Courte]

Originally Posted by rv6ejguy

The bad news for using this engine in aircraft is that you need the OEM ECU and it is heavily tied into the chassis with sensors, anti-theft interlock codes and other nasties. It will be a mess to decipher all this junk to make the computer run just the engine happily without the car attached. No option to install a mechanical pump and injectors easily on this engine unfortunately. Apparently Bosch is able to sell a programmable ECU for common rail diesels now- the bad news- you need $25K.

Are the sensors encrypted or something? What's to stop you from using something like an AEM unit or a modified SDS unit to handle fuel injection? I'm sure you've thought this out already, but I just wonder, beyond the added car stuff, what's so special about the mechanicals of this engine? Could you not replace the turbo with a belt-driven supercharger? The mechanical fuel pump is a problem, but could that not be solved with redundant electrics? I tend to oversimplify complex problems, but unless there's some kind of realtime adjustment for injection timing, isn't it just a question of delivering fuel to the cylinder at the right time with the right amount of compression? I would also guess that the case would fit happily together with a Marcotte or Sub4 PSRU.

[rv6ejguy]

Most new diesels do up to five injections of varying pulse width per combustion event. Right there all the programmable ECUs for gas engines are out of their league. The anti-theft interlocks on the new Sube ECUs are very difficult to get around with digital wireless codes it looks like.

You'd never want to replace a turbo on a diesel with a supercharger. Might just need a different unit for aviation use at altitude but a lot of repackaging would be required anyway and lots of issues with the PSRU unit I'd think as well.

[SIIaCanuck]

I know of a suitable computer geek that would probably sort out the coding problem over lunch (he's a VW/Audi tuner that runs a DTM team in Germany and chipped my uncle's Skoda Octavia).

Having followed the Subaru scene for a while, I see this new Subie diesel as a good core. It's not yet out and running so the aftermarket tech support to do what you want with it will take some time. However, between the V-dub TDI tuners and the Subie rally crowd, I wouldn't be surprised before you saw these engines being used for all sorts of nefarious purposes (diesel rally car?)

Direct drive would worry me. A solid PSRU like the Marcotte would be a better bet. Trying to get an auto engine to take thrust/gyro loads would be an engineering mountain to climb, time that would be better spent getting a solid independant engine computer/wiring harness sorted out. Not to mention, a lot of new prop blades seem to be more efficient at much lower RPM when flying at RV speeds. This will be even more apparent to anyone who likes to climb to oxygen levels to cruise. Big slowish prop and fuel sipping diesel sounds brilliant to me.

I'm a way off an RV project as my Gyro is still not complete (can't be too greedy or my wife will kill me). However, I reckon that within a year of Subie's diesel being in full production, the prospect of it being a good aero-conversion core will look a lot more rosy!

If Thielert can do it, why can't we. Plenty of capable engineers building RVs!

[AllanC]

pvansrv3??

Just a short comment about your post:-

'What will it really cost when figuring the entire expense of all the parts, motor mount, cooling, cowling, etc as compared to a tried and true Lycoming? Looking at the Eggenfellner? Subaru conversions sold to the RV market, I see no cost savings anywhere, but I do see a decreased resale value'

You are correct, the cost of a new 6 cylinder Subaru conversion is probably no cheaper than the 4 cylinder Lyconing - after all, the engine mount, the cowl, and solving the cooling issues (which is apparently soved in the latest version of rad and cowl combination) are the same in both engine types.

'Looking at the Eggenfellner? Subaru conversions sold to the RV market, I see no cost savings anywhere, but I do see a decreased resale value'

Inital investment cost, no. But factor in reduced operating costs - fuel over 2000 hours say 14,000 gals at a reduced cost of $2/gal. That's significant. Reduced maintenance costs - look at plugs, oil, filters, and I'm sure the cost over 2000 hours is again significant.

2000 hour engine overhaul. Don't do it with a Subaru, just replace with a factory brand new short block at $5,000, and that's if you need it at 2000 hours. Probably don't need it until much later, if maintained and operated properly. How much is a Lyc overhaul up to and including 2000 hours service?

Add in smooth operations, possibly more efficient and less fluel flow, great winter operations with liquid heating through car type heater, quieter, less vibration, no shock cooling issues. Why would you want to resell it so no worrying about resale value?

OK, I'm an Egg H-6 owner and flyer, and, despite my issues and tribulations with oil cooling and an older type gearbox, I still prefer it to the daily problems I see at my home base with certified/clone air cooled engines. OK, I may be slower, but I'm quieter, smoother and reliable. No price on that for me, but it is your choice, after all. Just don't knock it until you've tried it - with an open and interested mind.

If this is the wrong thread, I apologize, just responding to the post.....

Allan