Best figure I can remember is 270 g /kWh, for a Toyota Prius, that is 0.44 lb/bhph. That is 36% efficiency. Best I've seen for a diesel is 160 g / kWh.

Cheers

Greg Locock

Here is an aircraft site that discusses lean engine operation. Becareful, this guy has a financial intrest in GAMI. And, he is engineeringly incorrect in many of his statements. You will also notice, he doesn't think much of engineers. Especially aircraft engine engineers.

http://www.avweb.com/news/columns/182544-1.html

Michael996:  That's a great site.  Thank you for posting
it.  I'm a pilot, too and I think the guy has a lot of
common sense. (although I did see a few things I don't
agree with, any 35,000 hr. pilot automatically gets my
respect)

If you'll read what he writes, many times he states that
he has no financial interest in GAMI.  Unless he is lying?
He does state that the best and the brightest piston engine
engineers were a dying breed as of about 1942 as a result
of aircraft turbine engine and rocket engine technology.

Anybody who has interest in water injection, turbo
charging, fuel consumption, fuel octane, fuel flame
speeds and other aspects of high performance of piston
engine operation might want to spend several thousand
hours reading the previously well accepted and
established reasearch available for free here:

http://naca.larc.nasa.gov/

I love this guy.  John Deakin(the author of the articles
at the previously referenced link  

http://www.avweb.com/news/columns/182544-1.html
 
writes and I quote

"Use Your Head

The techniques in this column are not for unthinking pilots who prefer the easiest way of doing everything, and who can't be bothered with advanced techniques. If you're not willing to study and learn WHY these procedures do what they do, then don't use them! If you cannot use them regularly, in a careful, considering manner, then don't use them!

On the other hand, if you are prepared to study and understand how that incredible piece of machinery under your cowling really works, to use judgement about when these procedures might be appropriate, and if you're willing to put up with the abuse of those who prefer dogma over logic, this column is for you.

Be careful up there!"

Exactly the kind of guy I want flying the plane I ride in.

Chumley