[911st]

How can we improve a 930's ignition?

I suspect there is a solid improvement to be made in off idle response, spool time, and fuel economy.

To see the potential of a more ideal timing, just pull the vacuum line off the inside connection to the vacuum-boost-retard-can on the distributor at idle. This will advance timing about 9 deg. Idle will increase about 300 RPM because the ignition will be closer at a more ideal setting. With this it will make more power with the same amount of air and fuel. Timing is ideal if combustion pressure reaches its max at about 12-14 After Top Dead Center on most motors.

I have reviewed many of the threads on timing and it looks like there seems to be some general misunderstanding on how our system works and a fair amount of miss-information. Further, most do not seem to know what a more ideal timing curve might look like. Together, lets fix this.

There also seems to be very few solid suggestions on how to make improvements in if there are they have gottin lost among all the clutter. Some even believe that some of the 930 tuners have figured out how to make improvements but are not talking.

When the 930 was built Porsche seems to have made many design accommodations in the name of emissions. They shaved most the cooling fins off the cylinders to get the motor to run hotter, they put a cat on it, they added an air pump, they put small intake ports and funny tops on the pistons to get a better air/fuel mixing and who knows what else.

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.

Of course the best way to achieve ideal timing would be to change to a fully programmable system and abandon the weights & springs with vac/boost-retard can. Porsche did this with the C2 turbo.

I am thinking one possibility for a best practices set up would be based on the newest fully programmable MSD with a locked distributor. However, I suspect significant improvement can be made with the stock set up by re-curving the distributor and shortening the mechanical advance to increase the advance off idle.