Great thread. I would just like to point out few things:
Quote:
Originally Posted by 911st
They shaved most the cooling fins off the cylinders to get the motor to run hotter
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No, they did it to try to equalize temperatures above and below the cylinder. It's only the top part of the cylinder that doesn't have fins and you might find that even 917/30 had shaven fins on the top of the cylinder.
Quote:
Originally Posted by 911st
they put small intake ports and funny tops on the pistons to get a better air/fuel mixing and who knows what else.
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Small ports are to boost air velocity and thus better cylinder filling at low revs. There are no "funny tops" on 930 pistons, they are completely flat. SC had crowned pistons.
Quote:
Originally Posted by 911st
They also seem to have made compromises with the ignition by adding a Vacuum-Retard function whose prime function is reported to increase heat in the motor for emissions. This appears to be at the expense of low rpm throttle response.
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This is only done on US (and Japan?) cars. ROW didn't have this.