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

So the small port creates momentum which keeps or pulls the mass with it.

And if we get this right, such effect is stronger than the losses with less effective compression that comes with the SC cam. I understand this with long runners can work well with a current EFI motor, MFI, webers, or even a SC that have a longer intake track (straw).


My gut feel was that with only about a 3" long runner and a restrictive metering system this effect might be minor or reduced.

That there would be more to be had from the mechanical pull of the piston during the intake stroke (930 or RV cam).

That reducing the already significant intake restriction via larger ports and keeping the longer intake cycle of a 930 cam might yield more improvement.

I wonder if there is anything in that Porsche's moving from 39mm intake ports to 34mm's with 1980-83 CIS 3.0 SC?

Again, I was thinking the small ports increased air flow right at the point where the CIS injectors had been spraying fuel in wait for the intake valve to open. This would help atomization and possible low end combustion.

In any case, better breathing results in more power (cam or port change). The more power we can create early, the faster the turbine is going to get us to boost.

Thank's for indulging me.

Lots to learn.

Last edited by 911st; 02-01-2010 at 09:12 PM..
Old 02-01-2010, 09:08 PM
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