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911st 911st is offline
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Join Date: Jan 2004
Location: Sacramento
Posts: 7,269
Another point of referance.

In Bruce Anderson's book he gives a formula for sizing the throat of carburetors. We might accept that this was to be the smalles restriction in a normaly asperated performance motors intake tract. From looking at Porsches EFI turbos the ports seem to be the same as there N/A motors.

The formula is: 20 times the square root of (one cylinder volume/1000 + RPM at HP peak/1000)

The results being for a 3.3:

At 5500rpm = 34.8mm
At 6000rpm = 36.3mm
at 6500rpm = 37.8mm

For a 3.5 at 5500rpm, 35.8

Most of us with SC and stock cams are making peak hp at 5500. If the C2's were timed to factory stock setting they could make HP at 6000rpm.

This is just a point of referance.

It might be this is the smallest we want to consider. Do not want pressure to build in front of the intake port as boost pressure builds should it become a restriction. We want it to build in the cylinder.
Old 02-07-2010, 08:00 AM
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