Opposed piston 2 stroke diesel.

[Tesla]

I was looking around at engine types and thought this one was interesting.

http://www.youtube.com/watch?v=JMAEin5iU4Y

One Crank Opposed Piston Engine
Hybrid Opposite Piston Engine - HOPE & Portable Range Extender / State of the art

Having a single cylinder with two opposed cylinders eliminates cylinder head and valve train, this reduces area for heat rejection and offers opportunity for high efficiency, reduced emissions as well as reliability and wear reduction because of reduction of components.
On the downside it does require presurised air intake to improve scavanging and clearance of exhaust.

[freebeard]

On the downside it does require presurised air intake to improve scavanging and clearance of exhaust.

...that, and two crankshafts. Or massive rocker arms.

[some_other_dave]

Junkers Jumo 205 did it back in WWII. One of very few diesel aircraft engines.

http://www.youtube.com/watch?v=h2QxEXYlc2w

The Napier Deltic was more or less three of those joined together in a triangle.

Napier Deltic - Wikipedia, the free encyclopedia

-soD

[Mustang Dave]

Fairbanks-Morse has been building this type of Diesel engine for many decades.

[cRiPpLe_rOoStEr]

There were some British trucks with a similar engine concept.

[Allch Chcar]

I'm rather opposed to that configuration. My concern is having two crankshafts and the super wide design would make packaging difficult in anything mobile. This one seems more favorable to me. Though the oilpan looks oversized.

http://www.youtube.com/watch?v=pGaISFg_ZIw

But my predisposition is to SI engines that would function more efficiently on Alcohols for use in compact/midsize cars.

[serialk11r]

The other packaging issue I see is that to get the same degree of balance especially in reciprocating forces, you need way too many pistons and connecting rods.

[cRiPpLe_rOoStEr]

2-stroke Diesels are actually still an interesting design, still providing a good power-to-weight ratio for ships, altough nowadays for other uses I'd rather get a 4-stroke Diesel.

Originally Posted by Allch Chcar

But my predisposition is to SI engines that would function more efficiently on Alcohols for use in compact/midsize cars.

I'm still favorable to spark-ignited 2-stroke engines.