The goal is to warm the incoming air so the fuel will vaporize and burn more efficiently. Cooling the air results in some fuel not vaporizing and it sails out the tail pipe without developing any power. Poor vaporization is why carbureted engines needed a choke. It causes more fuel to be drawn in which is needed because a lower percentage vaporizes.
Turbocharged diesel engines use air coolers because the air becomes real hot when compressed by the turbocharger. That expands the air so fewer molecules of air enter the engine. Diesels are wide open to take in as much air as possible. The fuel / air mixture isn't critical as it is with gasoline. Engine speed with diesels is controlled by how much fuel is injected. There only needs to be enough air to match the amount of fuel, or extra air. If the air isn't cooled after turbocharging, there could be insufficient air.
In gas engines, the theory is that cooling the air compacts it so more molecules get into the cylinder. The mixture must be correct so that means more fuel must be added too. The effect is to pack in the same amount of air / fuel that would enter a slightly larger engine. That is normally done by pushing the gas pedal a little further.
Thursday, February 10th, 2011 AT 11:35 PM