To improve a 930's ignition we need to come to what the ideal might look like. I contacted Steve Wong of 911Chips.com to see if he could give us any guidance.
I told him our target motor specs were stock 7/1 compression with SC cams, and a decent turbo & intercooler.
I noted that I thought our 930 timing looked as follows:
-15 to -19 on boost
-25 to -29 at cruse.
That idle started near 0, jumped to -10 w loss of vaccum.
He responded as follows:
Quote:
Keith,
I don't spend much time giving any thought to the ignition timing for a 930 turbo with 7:1 CR, but given the specs you've provided, it sounds around the ballpark, although I think with the low compression, a little more advance could be used, assuming pump gas. It's possible to achieve 18 to 20 degrees at WOT at full boost, but you need to carefully monitor for knock to determine the limits, and an intercooler, with optimum AFR is manditory. On a normally aspirated car, vacuum advance of 15 degrees over the WOT timing, (equal to 0 boost timing on a turbo) gives better part throttle efficiency and response. At 0 boost (neither vacuum or boost), the ignition timing should be able to go to 30-36 degrees BTDC, and using boost retard on the distributor to retard the timing down to the previously discussed target.
This means at cruise and light loads, the motor will make best efficiency and response anywhere from 45-50 degrees BTDC from 3000 rpm up. Hope this helps. Some of the Motec downloadable manual have a primer on setting base ignition tables. Anything else, let me know.
Steve
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