How does a intercooler work? Can it be used without the turbo?

 

It's basically an air-to-air radiator, that cools air instead of coolant. There are water-to-air (or is that air-to-water?) ones also. They reduce the temperature of the charged air, thus allowing you to run more boost without as big of a threat of detonation. Not sure why you would want to run one without a blower...you can use them for both turbos and superchargers though.

 

It would be air-to-water, heat transfers from hot to cold.

the reason for running the intercooler is, when the turbo or supercharger compresses the air, it heats up to a higher than ambient temp. we all know that a engine makes more power with cold air. so the intercooler is a way of bringing that hot compressed air back down to a reasonable temp. allowing us to run more boost with a less of a chance for detenation.