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911st 911st is offline
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Join Date: Jan 2004
Location: Sacramento
Posts: 7,269
There are relative values.

As to cylinders, they are probably best if forged and need special plating unless you want to sleeve them. Then matching the piston and the cylinder thermal expansion rates so that the piston dose not bind or slap takes some work and that they do not expand and pull the head studs out.

I suspect one of the best value ways to build a tubo motor would be to sell your motor and buy a solid 3.2 Carrera motor for about $5k. Get a 84-86 or an 89. They come with the good cylinders. It already has the EFI plumbing and manifold all in place. They have a great turbo cam and the heads are already ported and matched to the manifold. Just an easy way to begin. The AFM can be sold off. The heat exchangers are good and a factory 930 J pipe can but purchased used for $100 so most of you plumbing is done.

Then just go through it with new up grade rod bolts, rings and valve guides. May not even need to split the case though it is better to do so. Can have the tops cut off the pistons for 8/1 or get J&E's for $1000.

Aftermarket inter-cooler cores can be purchased on the cheap if you have the skills to make and weld your tanks or a complete off the shelf IC can be used and elbowed into the throttle body.

Some have run more through the 915 but I trust people that know more than me that 300-325 is about the limit. Do a search on 915 transmission titles in the 930 section there is lots of info I believe. I know I asked this in one thread myself. Things can be done. Rear tire size, car weight, open v LSD are probably a few of the variables. The side plate is another. The main shaft, size of the gears are others. Porsche also heat treated there first couple of gears in the 944 Turbo S and the 996TT with the optionally larger motors. Limiting boost with some type of active boost management in first and or second might help.
Old 10-27-2009, 09:56 AM
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