[serialk11r]

drmiller I really don't mean to be blatantly offensive, but you touting your "theoretical schooling" is basically just as bad if not worse, especially given how you tend to frequently forget about some important factors at play.

t vago, not all theory heavy people are like him :P

kevman, when the temperature is high in the combustion chamber the pressure is also high, and if the heat escapes then the gas loses energy and pressure, and you get less work out of it. I think the reason we haven't seen the "6 stroke" engine in reality is because most of that heat energy is going out the gases in the tailpipe rather than being retained in the metal, and so you don't have much energy to work with. If you had an engine with no friction and perfect insulation you'd have something like 40-50% (depending on a bunch of parameters of course) of the heat energy of the fuel leaving in the exhaust gas itself. A cooling system can be thought of as sapping heat energy from the combustion itself, but it also cools the exhaust ports so it's not too clear how the heat energy is distributed there.

At any rate something like 30% of the heat energy is leaving the tailpipe at temperatures around 400-700 (or higher, which is kinda bad but it happens) C. The cooling system runs at 90-100C, and the engine internals are kept well below 200C, and the flame front shouldn't be hitting the piston early when temperatures are highest on a good combustion chamber design. The higher the temperature of the heat source the easier it is to get power out, so you can see why people are turning to the exhaust for waste heat recovery.