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(personal) Fantasy Land auto engine candidate

Freemasm

Well Known Member
No reason to reply and tell me all of the things not considered here. I'm aware. However, if I were to fantasize about myself adapting an auto engine to an aircraft I probably start here (thanks to Shadrach of MS for the numbers):


BMW N57 TDI

Aluminum block 365lb dry weight

Turbo 3L in-line 6 cylinder

compression ratio 16.5:1

BSFC 36

Power in road going configuration (max torque is a flat 413lbft between 1500-3000rpm) so no reduction gear needed.

196hp @ 2500rpm burning 8.4 gph using a BSFC of .368

212hp @ 2700rpm burning 9.4 gph using a BSFC of .368

These would be great numbers to fly behind and be Avgas independent. Shoot holes in this if you wish but there's no need. I'm sure there's other candidates others would prefer. I stated it's my fantasy basis. Man I'd love a flat torque curve over 400 lbft with low engine rpm and no PRSU, ignition system, etc. If I can make it to retirement, this would be awfully fun to play with, frustrate myself with, and prove to myself just how hard such an adaptation would be; thrust load being the first expected big obstacle.

Maybe we'll have other viable options by then.
 
The TDI approach just sings to me - keeping good power up in the flight levels.

But...

Not for me on this current airframe - I'm already cruising 20 below Vne, I don't have room for much improvement. I've already got a build planned for the next one, but my wife informed me that the next thing I build is going to be a house, for her! :D

We are currently on round three of the drawings with the architect, so I'm going to have permission at some point soon!:cool:
 
This looks like a good candidate if you can find a reliable ECU to run it and duplicate what the factory ECU does. Second, you'd want to develop a bearing housing to take the prop loads and possibly feed oil to a C/S prop- or just use an electric MT, minding any TV issues which might surface.

The weight and hp put it in between 4 and 6 cylinder Lycomings so not the best fit for most RVs but could be workable for other designs. Might be ok to replace a 390 but a bit heavy still.

Would be an interesting project for sure!
 
No reason to reply and tell me all of the things not considered here. I'm aware. However, if I were to fantasize about myself adapting an auto engine to an aircraft I probably start here (thanks to Shadrach of MS for the numbers):


BMW N57 TDI

Aluminum block 365lb dry weight

Turbo 3L in-line 6 cylinder

compression ratio 16.5:1

BSFC 36

Power in road going configuration (max torque is a flat 413lbft between 1500-3000rpm) so no reduction gear needed.

196hp @ 2500rpm burning 8.4 gph using a BSFC of .368

212hp @ 2700rpm burning 9.4 gph using a BSFC of .368

These would be great numbers to fly behind and be Avgas independent. Shoot holes in this if you wish but there's no need. I'm sure there's other candidates others would prefer. I stated it's my fantasy basis. Man I'd love a flat torque curve over 400 lbft with low engine rpm and no PRSU, ignition system, etc. If I can make it to retirement, this would be awfully fun to play with, frustrate myself with, and prove to myself just how hard such an adaptation would be; thrust load being the first expected big obstacle.

Maybe we'll have other viable options by then.
Probably retarded timing for PCP and NOx emissions that yield a poor BSFC. A fun thing to spend all your retirement and investment money on. Gotta do something!:D
 
Probably retarded timing for PCP and NOx emissions that yield a poor BSFC. A fun thing to spend all your retirement and investment money on. Gotta do something!:D

Per the car guys, which I'm not:

The subject engine is detuned and efficiency is hampered by emissions equipment. Many of these engines on the road running pushing well north of 500ftlbs between 2000-3000rpm with slightly better BSFCs.

I can't validate this quote but if true, Holy Sh!t.
 
I've been similarly day-dreaming about a Mercedes Benz M-275 6 liter V-12. It would be perfect for a 75% scale Spitfire. As usual, the biggest challenge is a good PSRU and integration of a supercharger.
 
Probably retarded timing

This is a diesel engine.

The torque comes in at a low enough RPM that a direct drive may be usable-----but the power pulses could become an issue. Torsional vibration may bite you in the butt.
 
BMW makes some whizzy stuff these days- near 700hp actual (claimed 617hp) on the new M5 in stock form on pump fuel.

I always fancied converting an M54 straight 6 as I own 3 of these currently. They are light, uber smooth and reliable, 225-235hp depending on spec. Maybe if the Sube ever dies and I need a retirement project...
 
BMW makes some whizzy stuff these days- near 700hp actual (claimed 617hp) on the new M5 in stock form on pump fuel.

I always fancied converting an M54 straight 6 as I own 3 of these currently. They are light, uber smooth and reliable, 225-235hp depending on spec. Maybe if the Sube ever dies and I need a retirement project...

Retire? Please Nooooooooooo!
 
if you can find a reliable ECU to run it and duplicate what the factory ECU does. Second, you'd want to develop a bearing housing to take the prop loads and possibly feed oil to a C/S prop- or just use an electric MT, minding any TV issues which might surface.

Just a couple of minor issues that can be solved on the back of a napkin I guess.
I am not one to be dissuaded by challenges and as you can see in my tagline, the tried and true did not appeal to me either.
If you enjoy engineering and testing this is definitely for you.
 
While not a diesel and a little small for the RV (maybe EZ?) I like the engine out of my Honda Aquatrax.
*Straight 4cyl
*Aluminum case/heads (weighs about 195 dry, but with all accessories - or so I have read)
*DrySump
*Fuel Injected
*coil over plug
turbocharged w/electronic waste gate control
Minimal electronic controls (ie not a ton of emissions stuff, could be converted to MegaSquirt or similar)

factory rated to 165HP, but regularly aftermarket bumped to as much as 300, so 165 is probably ok for T/O power and still be reliable.
The output shaft is already intended for a coupler with damper.

Would need a PSRU though and is liquid-cooled of course. The intercooler is also air/water so that would have to be replaced as well.
 
One of the thoughts I've had concerning the power pulses of a diesel engine would be to incorporate a viscous coupling. There might be some slippage under high torque loads, but that's what would smooth out the ignition power pulse impacts to the prop.
 

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PSRU PSRU PSRU

Critical and often weak point of all engine conversions. I won't bother too tell you all the issues since you say you know, but you need to design a gear box. Will it be able to drive a hydraulic CS prop?

I ask what do you expect or goals for the use of a car engine on an airplane?

Cheaper?
Faster Built time?
Faster airplane than a Lycoming?
Lighter airplane than a Lycoming?
Higher plane value than one with a Lycoming?

Good luck. You should look at some of the more successful automotive engine conversions (successful being number flown) Subaru and Mazda.

There is a 2.0 TDI VW/Audio Diesel in a C172 in Europe, with Youtube Videos. No performance numbers but it flew.
 
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RSRU with sprague clutch ?

I think that this idea may have been discredited already but NSI marketed a Subaru package some time ago that incorporated a sprague clutch in the gearbox to deal with torsional vibration.
I am not sure how this was meant to work as the clutch would apparently lock above 2,000 engine RPM which is more or less idle speed for the 2.12 to 1 gearing.
I have been using this product for a while now and like one of the side effects of the free-wheeling prop. Electric pitch control can access 22° of beta which would be good in itself but the propellor will accelerate without reference to the engine as it moves through fine pitch. The result is a substantial air brake whether the engine is operational or not.
I attach a link to a video of a steep high speed glide approach and subsequent landing in a 9A, which may be of interest.
https://youtu.be/2AeCXW2vRSU
 
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