what does an intercooler do?

 

your intercooler cools the temperature of the air entering the combustion process... the cooler the air, the more efficient the process...

 

because the cooler the air is the more it can be compressed. The more it can be compressed, the more of it the turbo can ram into the cylinders. The more air in the cylinders, the more efficient and stronger the combustion.

 

An excerpt pulled from an article on turbocharging found on the <a href="http://www.turboclub.com/aturbo.htm">TurboClub</a> website:
<i>So, previously we left off with high pressure air leaving the compressor outlet. Unfortunately, physics has worked against us this time, and the act of doing work to our inlet air to compress it has raised its temperature.
This is bad.
Not only are we reducing density, we're increasing the possibility of the great bugaboo - detonation. Remember, the onset of detonation is usually the limiting factor on the amount of power a given engine can produce, and that increased intake temperature (as measured at the intake valve) increases the chance of detonation.
So we have to cool the air back down again, without losing any pressure.
That's the job of the intercooler, basically a "air radiator" placed in the flow stream between the turbo compressor outlet and the intake manifold. There's really not much else to say about them, except:
1) The more you can cool the air flow, the better. This _normally_ means the bigger the intercooler, the better. (There are some smaller coolers that are better designed than the lower-end "big" coolers though, so size does not necessesarily indicate effectiveness.
2) The cooler must be placed in a location where ambient air can flow through it. This means that your cooler must have an intake path and an _exhaust_ path. Mounting a cooler flush against a plate does no good!
3) There's always a pressure drop across a cooler. How much depends on the cooler design.</i>

 

What does that big thing under the hood that makes all of that noise do?

 

Ram, huh huh huh he said Ram

 

Cooler air is denser. Denser air has more oxygen molecules per cubic inch. More air=more fuel=more power. It also has the secondary effect of reducing preignition/detonation (they are NOT the same!).

Fuel burns, not detonates, most efficiently in any engine. A gasoline Otto cycle relies on a smooth, fast combustion to produce power most efficiently. Detonation transfers heat to the cylinder walls in lieu of pushing a piston down. In the turbo engine, high heat coulpled with hot intake can cause the charge to ignite prior to the spark plug firing. This is preignition. Detonation is defined as a transonic (faster than the speed of sound) flamefront propagation. It is usually accompanied by the charge autoigniting in multiple locations due to shock wave effects. Both are bad news for any engine.

Keith J
Mechanical Engineer