Thread: 7.5 CR pistons?
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911st 911st is offline
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Join Date: Jan 2004
Location: Sacramento
Posts: 7,269
Yes, ignition is a solid way to add throttle response and increase efficiency on a 930.

A low compression 930 can take -40 and more at cruse (v -26 or less stock) for a bump in MPG. It can also take more advance off idle for improved throttle response. There is good opportunity hiding on the ignition side.

You can do a test by advancing your dist timing up to all the way) and test w/o going into boost to see for yourself if more advance off idle makes a difference. Again, do not go much into boost if you try this.

If you do go w an EFI ECU it can also drive an add on frequency valve(i.e. Andial Fueler Valve) so you can tune your Control Pressures for near perfect AFRs and motivate the metering plate with acceleration for a further improvement in throttle response (done it & it works well).

If a full conversion is not in the plans, a fully programmable MSD might be considered as a way to give near full control over spark and also add improvement w firing in low rpm's that can come with less than ideal AFR's that is often part of running CIS and such low compression pre boost.

The stock ignition can also be improved with a mod to the amount of retard and a dist recurve. Andial might still do this.

If the motor is coming apart anyway and the P&C's are in great shape, working the rods with 1mm in increased off set of the small ends to get to 7.5/1 is an option as noted above. I know only .5 increase in CR is not much but the next .5 is not much eather.

This would also allow you to correct for one of the weaknesses of the 3.3 which is to up grade the rod bolts. If you do not run much above 6600rpm or so it is not an issue. If you want to run at 7000rpm doing so or upgrading to stronger rods is almost a must. The case dose not have to be split to do the rods and this would also let you to do the rod bearings. I would not skip on an aftermarket rod bolt upgrade w a 3.2 or 3.3 but that is me.

Nothing wrong with a well tuned stock 930.

Just some thoughts.

Last edited by 911st; 12-09-2009 at 07:16 AM..
Old 12-09-2009, 07:13 AM
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