Light wieght diesel engine

What sort of power/weight ratio are you looking for? There are loads of very high performance Diesel engines around these days. Small truck? Big truck? What sort of power are you after? What sort of racing?

 

From what I gather, diesel engines are heavy for their power output (ignoring the fact that they don't rev very hard) is due to their high compression ratio. The latest diesel engines in cars are dropping their compression ratios and becoming more like petrol engines so a mechanic friend was telling me. So I'd say look for the engines with lower compression ratios.

Additionally, the Abrahams tanks that can do something like 50km/h run on a turbine engine that uses diesel as a fuel. Turbine engines generally have a better power to weight ratio as far as I know.

Otherwise check out the details of the Audi R10 Prototype GT car and the Peugeot equivalent. Both ought to have high power to weight ratios as they are being raced (and doing well) in the LeMans 24hr and GT races. They run on diesel that has been made from gas though (gas -> diesel as they do in South Africa), so I'm not sure how much that has an influence on their performance.

 

Why do you need higher compression ratio for heavy turbocharging? A lower compression ratio will allow higher BMEPs with high pressure ratio turbocharging better than a higher compression ratio, since you'll be limited on peak cylinder pressures (or possibly exhaust temperatures).

I ask again, what sort of power are you looking for? What is your intended application (or duty cycle, are you entering drag racing events, or 24 hour rallies?). What's a "normal truck"? Are you concerned about anything else, like fuel consumption, reliability, durability, smoke, cost, heat rejection?

If we can understand what you're trying to do, you'll get some great advice here (I develop turbocharged Diesel engines for a living, and there are plenty of others here with engine and racing experience).

 

This isn't true. Compression ratios in modern diesel engines are just as high as ever since there is a minimum CR required for compression ignition. Modern diesel engines are lighter in some cases because the engine block is made out of higher strength materials, and turbocharging is more prevalent allowing smaller displacements for a given power output.

Turbine engines definitely have significantly higher power to weight ratios than piston engines, but it's obviously not realistic to tell this guy to put a diesel turbine in his truck.

The Audi Racing TDI engine is a very impressive engine, but where is the OP going to get one? One engine he might look into is the V6 TDI or V10 TDI out of a wrecked VW Touareg, although it might be difficult to find a transmission to mount up to it. The V-10 TDI puts out 309 HP and 553-627 ft-lb of torque depending on production year, pretty healthy for 4.9l of displacement. That's probably the best power to weight ratio from a diesel engine you will be able to find in a production car.

 

For durability, for something like that I'd probably be looking at something like a 11-13 litre truck engine, and very carefully revisit the turbocharging. But I don't know whether your definition of 'truck' is the same as mine.

 

The amount of horsepower you're looking for is a lot... what size engine are you hoping to get that out of? What size truck? How heavy? Do you really have a driveline that will put up with 2000 ft-lbs of torque?