If I increase the compression ratio of an engine, should it run cooler or hotter? I suppose it would run cooler due to higher efficiency (i.e. the extra hp all the rest being equal are taken at the expense of heat), but i have read the opposite on another site or two (referring to air cooled engines to be honest, does it make a difference?). When I increased comression in my 308 many other things changed as well so it is difficult to judge.. Federico
The engine should make more heat when is is being run at wide open throttle. In normal cruising mode, it should be the same.
From my horrible recollections of high school chemistry, I recal Boyles law, that states that pressure, volume and temperature are all directly related, V=PT, (or something like that). With volume held constant, if you double the pressure, you will double the temperature, (in degrees calvine cline or something). So, if you increase the CR you will automatically increase the temperature of the compressed mixture, everywhere from closed throttle to WFO. Come on you guys that did chemistry without the aid of a tutor, help an old auto x major figure it out. Eschewing Obfuscation, I remain, chris
With the same volumn being compressed you would be correct but you are not taking into account that with the increased CR, power for any given intake quantity would be increased. At any given POWER OUTPUT the temps should be similar, and at any given THROTTLE POSITION temps and power will be higher. There are many variables but in a general way Horsepower = Heat
