Heat and performance. Myth or fact?

PV = nrT is the general form and just describes the relationship between pressure, volume, the number of molecules, and temperature(degrees Kelvin). For an NA engine P and V are fixed so if the temperature goes up fewer molecules will fill the cylinder at that pressure. If the temperature goes down more molecules will fit. This still applies even with boosted engines even though the pressure can be enhanced hence the intercooler. Boosting the pressure raises the temperature but the intercooler lowers it back down. The gas law can be applied just about anywhere humans can survive and isn’t limited to “special case” scenarios. It’s what makes the AC work and your refridgerator keep the beer cold.

 

Of course, in any closed system , P and T are interchangeable.

i.e. one molecule at sufficient T will display the same P as 10^12 colder molecules.

Put another way, In the absence of T, there is no P.

Ain't it a wonder how science works ;-)

 

It can’t be taken to quite such extremes but like I said it works well anyplace we can survive. At our present level of knowledge the best we can do is approximate what happens with formulas that work over a range of parameters but go outside that range and they don’t work. Not surprising given how old that particular equation is but most day to day engineering problems don’t have to deal with the heat/pressure inside a sun or the lack of both in space. Likewise Newtonian mechanics are insufficient for describing relativistic motion.