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911st 911st is offline
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Join Date: Jan 2004
Location: Sacramento
Posts: 7,269
Skimmed this thread. Did this get resolved?

With a 930 dist that has two vacuum connections, timing at idle with vac retard connected retards timing about 9 -10 deg so it should be near TDC/Z1. It hould then be near 10 deg advance with vac retard hose disconnected.

I good simple test to see if your vac-retard is working is to pull the tube closest to the motor while the motor is warmed up and at idle. If it works right, the motor will speed up.

For a US car, timing should be set at about 25 deg advance at 4000rpm with both lines disconnected. If they are left connected timing would be about -16 as there wold be a vacuum present that would retard timing.

This is a smog setting with timing retarded by idle vacuum for emission purpose. If you then pull the vac retard line, idle will increase. You could plug the vac retard tube and run like this for a cooler exhaust. It is the connection closest to the dist. You might even find your car funs a little crisper off the line.

Some have found that they can advance timing some past stock specs and pick up some power and throttle response. From the little I know about 930 ignition, if you have dicent fuel and are not doing something like runing a 1 bar spring with a stock intercooler you might be able to set timing to euro settings of -29 at 4000rpm. This will give you 4 deg more advance at the other settings. This should give you a bit better low end, power on boost, and improve fuel economy some. However, you should have decent fuel and should know you are taking an educated risk.

Running anymore advance than this requires a method to pull timing back to a safe level on boost. Some use an MSD system that can retard on boost to make up for it. Another want is to modify the Retard Pot to increase boost retard.

I believe a stock US 930 runs at about -16 to -18 on boost. The later C2 Turbo are more aggressive than this but have some safe guards like being able to pull timing back a bit with heat to keep the motor safe.

Last edited by 911st; 03-07-2010 at 08:16 AM..
Old 03-07-2010, 08:13 AM
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