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copbait73 copbait73 is offline
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Join Date: Nov 2003
Location: Chesterfield IN
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Dave, you are correct, but more to the point. High compressor efficiency, high CAC efficiency equate to lower intake manifold temperature. All things being equal lower intake manifold temperature gives you denser charge at a fixed firing pressure therefore more knock margin. Firing pressure and knock margin for available octane makes these critical considerations. This is a point I donít hear discussed often enough.

One engine can have a modern Garrett and another KKK with large compressor wheel. Each can deliver the same boost pressure at equal temperatures. Both engines make the same power, right? Wrong. The Garrett will do so with a turbine of higher stage efficiency that also has a correct power balance match with the compressor wheel. This turbo will require less backpressure to drive the turbine. Net, the engine makes more power.

In the world of ultimate HP, the best turbocharger match has the highest positive differential of intake pressure to exhaust backpressure - at a fixed boost level. In this situation my money would be on a Garrett.

On the street, a good turbo match is more appropriately described as the best compromise to fit the expectations and needs of the owner; performance, installation and cost. Here Garrett, KKK production or KKK hybrid show strengths and weaknesses. I listen to everyone on this site and see no two are exactly alike in their assessment - and that is very natural.
Old 01-04-2010, 07:12 PM
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