Luke, air will only expand to measurable volumes when it is trapped in a chamber. When flowing it will not have the same effect. It will warm but not expand by a noticable volume. As we all know, air is made up of gasses. Nitrogen, oxygen, argon, neon, helium, krypton, hydrogen, xenon, etc. Gases will increase in volume by roughly 1 percent for every 6 degrees farenheit. So if it is 70 degrees outside and these engines (nitro) reach about 95 degrees then the increase in volume is 4.166. That is trapped air. Moving air expands less by constantly being replenished. Joe

BTW, there is a big engine in the bus and if air expands like you said it will, he better pull over because the hood must be ready to blow off.