[gpskinzhut]

Originally Posted by Martinjlm

In a sense it’s both. Thermal efficiency is a measure of how much of the energy produced from burning fuel actually goes towards moving the wheels. In typical gasoline engines from the mid 1950’s until the late 2000’s it remained within a fairly steady 25 - 30ish %. Diesels with common rail technology came in around high 30s to mid 40s. Now gasoline engines are getting into the high 30s low 40s. Part of the improvement in TE comes from significant improvement in air fuel ratio and drives the need to get more air into the combustion chamber efficiently. That’s why the “flow-tie” is more than a gimmick. I’ll look for a diagram that I used to use that breaks down where the energy from a unit of gasoline goes after combustion. Some goes to heat transfer and can be channeled into the passenger compartment, some is lost to friction and pumping losses, some actually turns the crankshaft (obviously). That is the 30 - 40% I am referring to.

This is very close to the graphic that I used to use. https://goo.gl/images/gTXQJk

My graphic was on my GM laptop. I didn’t keep the graphic when I turned that in.

Gotcha!