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911st 911st is offline
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Join Date: Jan 2004
Location: Sacramento
Posts: 7,269
Interesting.

934 CIS Turbo: 41/41 ports (equal size), major-major overlap cams, TQ peak at 5400rpm, HP peak at 7000rpm. 530hp @ 1.35 bar w 6.5/1 compression.

If 41mm ports support a 7000rpm peak , a 5500rpm peak thus 'might' require 36/36mm ports.

Not a perfectly valid comparison but fun.
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Bruce Anderson's book notes on tuning a 930 recommends opening up the intake ports from 32mm to 36mm for what it is worth. That would give us 36 intake/34mm exhaust.

He also basically notes that if the exhaust remains restrictive with a change to SC cams it will lose low end.


So far:

I am thinking the stock cam for pre boost response and a 5500peak, SC for mid range depending on timing and 5500-6000peak, and C2 for upper mid range depending on timing for +/- 6100 rpm peak.

36mm intake also fits between the 34 & 39mm 3.0 CIS normally aspirated ports.

The question remains for most non stock builds is if a 32mm intake port is small enough to inhibit in any way the cylinder from seeing full boost and filling at any point.


Again, still learning and having fun.
Old 02-02-2010, 03:14 PM
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