Quote:
Originally Posted by stownsen914
The conventional wisdom is that highly stressed 911 race engines can benefit from additional cylinder and cylinder head cooling. A flat fan is a great option, but out of reach for some. There are some options to speed up a 245mm fan, like using the smaller fan pulley on a later fan (84mm?), and using one of the larger crank pulleys, also off a later 911. I've heard of a couple reports of this working well.
So, would it help to speed up the fan even more? For a turbo engine running high boost, for example. A larger crank pulley could be adapted/made to do this. Is there a limit to how fast the 245mm fans can spin and deliver air efficiently?
Scott
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No!!
At the RPMs we are running our race engines at, if anything, we want to slow them down. That's exactly what Porsche did! Why? Because all you are doing is burning up horsepower spinning fans as fast as our race engines do.Why? The fans loses efficiency at provides virtually no more cooling benefit beyond a certain speed. Porsche designed the fans to be most efficient at the fan speeds they would see in a street car.
That's why 3.6 liters engines have smaller crank pulleys available. Too slow the fans down, not speed them up.