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AFM744 AFM744 is offline
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Join Date: Dec 2001
Location: Campbell, CA
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Larger turbo (compressor) can compress the same volume of air without heating it as much as a smaller turbo. The larger turbo however takes more time to achieve boost ("spool up") as the larger diameter wheel has more inertia. A smaller turbo can reach requested boost/flow sooner, but will also create more heat, especially at higher flow rates (higher RPMS) as the turbo is spinning so fast it's whipping the air into a froth and creating a lot of aero friction, as well as having to compress the air "faster" due to it's smaller size.
As we know, intake charge heat reduces intake charge density, thus the intercooler. Though the IC can only reduce intake charge somewhat, and comes with it's own compromise as an intake restriction (pressure drop).

I spat this out on a lot of coffee, but I'd be glad to further explain.
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Old 07-15-2008, 10:06 AM
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