[Gandalf_The_Gray]

Insulation?

Nice try, won't do a thing. The problem is too much area exposed to a relatively cool surface "quenches" the flame and prevents complete combustion. It is not a problem of temperature or heat transfer so much as the dynamic nature of the combustion process. I expect that if you could increase the head temperature by whatever means it might do some good but how do you do that when there is no "head" as such. Insulation may not be practical but air cooling rather then liquid would help, keeping in mind that as operating temperature goes up, lubrication becomes more problematical.

The overall efficiency of an engine is defined by the ratio of absolute temperatures of sink and source. Raising the operating temperature moves you in the right direction but not very far. Ultimately you have to face hot spots leading to pre-ignition and structural problems as materials reach there limits. That still leaves the issue of emissions from incomplete combustion.

Regards,
GtG

[edsheppa]

It seems to me that if you prevent heat flow from the hot gases through the combustion chamber surface, then all of it goes into expanding the gas. So it seems that if you can insulate the combustion chamber that virtually all of the waste heat will be in the exhaust.

Now I can see a problem with that - you don't want to melt the cumbustion chamber, but that sounds like a materials problem.