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911st 911st is offline
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Join Date: Jan 2004
Location: Sacramento
Posts: 7,269
I believe cams did not change with the 3.6 CIS Turbo.

However, SC's cams were in the hand full of special build 'S' optioned 3.6 cars.

I also believe the stock ports were also the same 32mm intake on the 3.6T. The exhaust ports however were larger (34v38mm)

No reason to cam or port it unless you want to make more HP mid to up top. I think Porsche may have stayed with the small ports to help overcome the poor fuel atomization particular to CIS at low duty by keeping port velocity as high as possible. Just a guess.

CIS SC's were the same. Once Porsche went to EFI they opened up the intake ports a bunch. For example, the 3.6T was 32mm and the 3.6TT was 43mm. The 83SC 3.0 was 34mm and the 3.2 Carrera was 40mm. Thus, there is something about CIS going to small ports.

In spite of that I am interested in the idea of stock cams with larger intake ports. The stock CIS turbos are very 'port limited and should respond better to reducing the port restriction more quickly than increasing duration. I think by about 45% of valve lift the intake valve is at 100% of the stock port volume.

Reducing the port restriction should increase breathing more effectively and keep the TQ aspects of the stock RV style cam. SC cams lower the effective compression ratio about a half a point over stock 930 cams. Can not prove this is true but it seems to make sense after you compare the volume of the curtain area under the intake valve seat to the cross section of the ports.
Old 07-30-2010, 04:14 PM
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