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Old 11-09-2008, 03:20 PM   #25 (permalink)
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Originally Posted by instarx View Post
Ahhh, but that pressure drop you are measuring across the intercooler isn't from a restriction in the IC, it results from the cooling of the air and it is desirable. Pressure drops caused by flow restrictions are bad, but pressure drops caused by cooling are good.

When the very hot compressed air from the turbo is cooled by the IC its pressure (and volume) drops proportionally and so it contains more air molecules per volume than did the hot air (Boyle's Law). This allows even more O2 to be stuffed into your cylinders than if you didn't have the IC.

All things being equal, the IC allows you to use less boost to get the same number of air molecules into the cylinders - and that improves fuel economy (or power, whichever way you want to look at it).
Actually it isn't from cooling. You can have hot air on one side of a room and cold air on the other side and they will be at the same pressure. If it indeed there is a 3 psi drop across the intercooler he should really consider looking at an after market intercooler to reduce this loss as it a serious loss in useful energy. I also don't know where he measured the the pressure drop from. If it was right before and right after the intercooler then the drop is all too the intercooler. If it was between the outlet of the turbo and the manifold the plumbing route could be a big contributing factor. Yet another factor is the velocity of the air at the two points of measurement as this will have different static and dynamic pressure if they are different.
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