# What engine would YOU build

Discussion in 'General Auto Conversion Discussion' started by Winginitt, May 15, 2019.

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1. May 18, 2019

### Vigilant1

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Rotax 912 (UL?) HP, Air cooled, direct drive, simple construction, cheap, reliable, electronic ignition and injection: Sounds like you want a 2180cc or 2400cc VW derivative with SDS EFI and ignition. About 75-80 HP, about 160 lbs, Cost: about $8000 (engine about$5500--with starter and alternator, no carb or magneto + EFI + fuel pump, injectors, etc--maybe $2500?) That ain't free, but$100 per HP is dang reasonable for a ready-to-run engine with a strong prop hub (zero failures) and the trimming/tuning capabilities that the SDS electromagic adds to the package.
"Something old, something new . . ."

The flat-4 VW can't earn those extra credit points.

Last edited: May 18, 2019
2. May 19, 2019

### pictsidhe

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I hate to be a grammar nazi vigilant, but it's electrickery, not electromagic. It's all very real and verifiable, even the imaginary parts.

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3. May 19, 2019

### Pops

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Electrickerysmoke.

4. May 19, 2019

### pilot103

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For me there is no need to reinvent the wheel. air cooling direct drive and opposed cylinders have worked very well for a long time. I'll take the basic bones of an O-300 and add todays EFI and ignition.

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5. May 19, 2019

### Pops

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With C-85 pistons. I like the 0-300 and have owned 3 straight tail C-172's.

6. May 19, 2019

### sotaro

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Inverted industrial V twin with a reduction drive. Cause the cylinders should be down low.

Another couple million dollars: Radial two stroke 3 or 4 cylinder plain bearings high pressure oil system, direct drive, direct injection a la BRP, supercharged or turbo charged.Prefer liquid cooled, but air cooled might be ok. 55 hp/75 hp, 3000 rpm

7. May 19, 2019

### Pops

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A modern P&W 985. Saving as much weight as possible.

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8. May 19, 2019

### poormansairforce

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Care to elaborate on the C-85 pistons? Thx

9. May 19, 2019

### Pops

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Same as using C-85 pistons in a 0-200, higher CR. Gain a couple HP per cylinder.

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10. May 19, 2019

### Toobuilder

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The 200hp market is flooded with good aircraft engines, and plenty of "bargains" abound if you are willing to put in some time scrounging. By the time you invest in the research and development of an auto conversion, you could have scrounged up a cheap aviation engine.

That said, 300 HP is my personal next minimum for a fast 2 seater. There are also plenty of well engineered aero engines in this class and the 540 Lyc WAS about half the price of a 360 before the RV-10 came along, but bargains can still be had. But for the sake of experiment, I still like the 500 inch LS V8, direct drive. I have a lightweight bolt on drive assembly sketched out which takes ALL prop loads, has hydraulic provisions for a C/S prop, and has an easily replaceable quill shaft for resonance tuning.

With the exception of the inverted oiling system for tractor applications, the engine components are off the shelf and available today. The cost would probably exceed that of a scrounged 540 Lyc though.

Originally, I planned on doing this with Bendix FI and the simple plug and play ignition available from several sources, but today I'd just do SDS EFI and be done with it.

So, there would have to be a trade study to see if it makes more sense to buy an inexpensive crate engine from GM and add turbos to make up for the smaller displacement or go aftermarket (big inches, big dollars) and go NA.

In the end, I'll bet you are looking at 25 -30k for this dream auto conversion. Still cheaper than a new Ly/Cont, but that kind of money will buy TWO used aero engines with a little digging.

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11. May 19, 2019

### TarDevil

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Love this.
Fly in the ointment is lack of standardization. If someone took your approach with the LS as Mark Kettering, it would have broader appeal in the EAB community. Eventually a used engine market would emerge.
All the while, cost of replacement parts may counter the high initial cost.
An OEM customer would help distribution, but at the expense of certification.

12. May 19, 2019

### mcrae0104

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Are you thinking inverted?

13. May 19, 2019

### Toobuilder

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Tractor - yes
Pusher - maybe

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14. May 20, 2019

### pictsidhe

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Hard part? Lotus tried to do an integral reduction with cam drive. It nearly sank the company. There is a reason that successful redrives never use an integer ratio...

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15. May 20, 2019

### PMD

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One of the most difficult questions in aviation!

For the "out of a car" solution, one thing should be kept in mind: four cylinders or less of four stroke or two and under for two stroke means torque reversals - thus very heavy propeller and exceedingly difficult re-drive (take a look at a Thielert or Austro engine to see what I mean). You need 5 or more cylinders to make rotating elements light and extremely long stroke to eliminate re-drive. Gasoline as a power source is IMHO about the worst thing you could ever inflict on an airframe, but if you insist, there is really only one good answer: Rotary. But, yanking a Renesis our your RX8 and plopping it into you RV8 isn't going to go well. As has already been mentioned, swapping out the cast iron side and end plates for aluminum is a good step, but aviation is essentially a constant speed condition, so there really isn't any need for side ports. You can build peripheral port rotaries from off the shelf components that are far lighter and shorter, thus 3 and 4 rotor configurations easy. Still, the thermal efficiency sucks due to large combustion chamber area, and you NEED a re-drive (but can be light due to smooth angular velocity. BUT: since we are talking compromise at its greatest, it is probably the least compromising auto conversion (short of, of course, the fully certified Ford V8-60 aero engine that old Henry sold).

As has already been mentioned, the absolute best choice of design to hang on the nose of an airplane is the opposed piston diesel. Packaging, inherent prop speed reduction, fantastic thermal efficiency (can be over 50%), extremely simple (as few as 1/3 parts count) but most of all, when built as a uniflow diesel, far, far simpler and more suitable for aviation use than anything that burns an aspirated charge containing gasoline. The Junkers Jumo 205 engine still holds unrefueled distance records set in normal operation in the '30s.

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16. May 20, 2019

### pictsidhe

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I believe that Mazda redrives have been among the most challenging to perfect...

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17. May 21, 2019

### ap_aero

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There's this guy, Gary Spencer, he put a ford V8, direct drive, normally aspirated.
His current engine is an aluminum block but before he used a regular cast iron block as a proof of concept,
http://forum.canardaviation.com/showthread.php?t=5027

The fact that you can get a ford v8 for less than $2k on ebay, and then spend about$1k to overhaul it and that it can be used in direct drive within reasonable rmps makes me feel it's a winner.

18. May 21, 2019

### pictsidhe

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337lbs!

19. May 21, 2019

### proppastie

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Not far off from Lycoming 0-360 which fuel burn of 15 gph would be close. Not unreasonable at the price.

20. May 22, 2019

### mm4440

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There are no low cost Al blocks available for the 5 l. Ford pushrod engine, that I know of so figure \$4000 more. More current engines are worth considering.