Diesel efficiency
 

Here's a paper on diesel efficiency, especially see page 7:

http://mandieselturbo.com/files/news..._low_speed.pdf

It's neat that they preheat the fuel to 250C.
Best auto engine is 43% I think, a 5 cyl Audi.

regards
Mech

They run that icky bunker fuel right?

read the article.

they run pretty much anything which burns and is liquid or vapor.

Love to but this computer doesn't do pdfs.

Lets gear our diesels to a turn a little slower.

I wonder what makes them so efficient. They stopped producing 2-cycle diesels for trucks in the late 80s because they were so inefficient and wouldn't meet emissions.

...inefficient? No. Two-stroke engines don't "waste" separate 'intermediate' cycles for intake and exhaust, so they are roughly twice as powerful for their size as four-stroke engines...and weigh less too.

...emissions, yes, they're terrible.

As has been mentioned here a few times, new 2-stroke engines with fuel injection are much cleaner (hydrocarbons were the old 2-strokers' sin, iirc). You can find them in some snowmobiles, and Peugeot makes a scooter with a FI'ed 2-stroke (diesel?).

As for the large, slow-turning diesels' efficiency, my guess is that two things are a helping factor:

1. Low rpms -> lower friction losses,
2. Very large displacement -> less surface area (per volume) through which heat can escape.

Does anyone have any idea at how hot those engine run? I mean, what are the typical coolant and exhaust gas temperatures?

Inefficient in trucks, yes. The notoriously thirsty Detroit diesels of yore basically converted fuel into noise. Obviously their fuel injection systems were more crude than what is possible now. Maybe it was the duty cycle of the average truck (not a steady load at rated speed) that led to the demise of the screamin' demon.

I am well aware of the effects of modern technology coupled with the lowly two stroke. Piwoslaw: the Peugeot scooter you mention is a gasoline engine, not a diesel. With direct injection, it blows equivalent 4-stroke scooter engines away in power, economy and emissions.