One of the biggest (cheap) HP boosts in automotive performance is ducting cool outside air into the induction system.
Under hood or inside the cowl air temperatures are markedly higher than outside air. After all, aren't we pulling heat from an air cooled engine in our case. That makes the air inside the cowl much hotter than the outside air. Cooler inlet temperatures allow more aggressive spark advance & on glow engines can help prevent detonation.
On a radial or other engine with a rear facing carburetor, the air could even be pulled through the firewall from inside the fuselage.
Last edited by SrTelemaster150; 07-08-2014 at 04:09 PM.