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911st 911st is offline
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Join Date: Jan 2004
Location: Sacramento
Posts: 7,269
Some points of reference and thoughts:

US 930's stock on boost max seems to be around -16 or -17.

Euro 930's stock on boost max seems to be around -19 or -20 (better fuel).

The 91 Turbo spec on boost max (.75 bar) is -21 +/- 3 deg depending on intake temp.

These are all for .8 bar. I belive 1 bar requires one point or more total advance though most seem fine at 1 bar using the factory settngs.

These might or might not be conservative settings depending on boost, build and fuel run. Intercooler & turbo effecency and AFR's may be significant factors.

A twin plug may or may not require less timing on boost than a single plug but not sure how much if any difference. It may be that the high effective compression ratio that comes with boost makes single and twin plug burn rates close to the same on boost.

One thing for sure, a twin plug should not take more advance than a single plug on boost.

Pre-boost twin plug runs less timing than single plug.

Best to set it up on a dyno that can hold different levels of rpm at full load to test for ideals and pull it back some for safety depending on environmental conditions and changes in AFR's.

At low load under cruse a 930 can take around -40 or more but it has to be pulled back quickly with acceleration. Stock 930's run -26 on cruse for US and -29 or Euro but that is more a limitation of a mechanical system. More advance on cruse can translate to more MPG and cooler temps.

Last edited by 911st; 12-13-2009 at 12:34 PM..
Old 12-13-2009, 12:30 PM
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