Engine Combustion Temps

[BofKGB]

I was wondering if anyone would know if the combustion chamber temperatures of a small engine, like a motorcycle engine, could reach as high as heat treating temps. Thanks.

 

[yates]

Yes, combustion chamber temperatures are much higher than heat treating temperatures. However, the high temp. zone is in the gas flow, not on the metal surface, due to cooling water (or air) being just the other side of the combustion chamber wall. Also, high temperatures are only produced instantaneously since after the combustion explosion the resulting expansion (what pushes the piston) produces rapid thermodynamic cooling.

 

[JStephen]

"Heat treating" is a broad term and the temperatures that this could refer to vary considerably. Hardening vs. tempering vs stress relieving of steel covers a wide range, and that of aluminum a different range.

The temperature of metal parts in an engine would vary depending on the shape and position in the chamber. I assume something that protrudes into the chamber, like a spark plug, would run the hottest.

In addition to heat-treating issues, you can get distortion due to heat at much lower temperatures. And, all metals will weaken somewhat as the temperature goes up, even if you haven't reached heat-treating temperatures.

 

[119]

Temperatures of exhaust gas with in an engine can very greatly with RPM. Usually the temperature of the exhaust gas lieving the cylinder is 1400 to 1500 degrees F. This is more than enough heat to create heat treating characteristics, but as mentioned before the heat is quickly absorbed by the cooling system and external air flow.

 

[aviat]

There is a boundary layer that protects the metal normally, but when you have improper combustion such as detonation, it will breach the layer and can do much damage. See sites below:

http://www.motorcycle.com/mo/mcrob/rt-fuel2.html

http://www.streetrodstuff.com/Articles/Engine/Detonation/Page_3.php