What is the ideal max advance timing....

[pjv911]

I would like an experienced opinion on where I should set my total advance timing at on a 2.7 cis motor that runs on 93 octane . Im seeking maximum power while staying a few degrees short of detenation . Please no guessing I can do that myself. Im afraid I wont hear detonation over the fan and exhaust so I dont want to take any chances.

Kurt Williams

[Early_S_Man]

38° BTDC, per the '74 spec book ...

[Wayne 962]

'Nuff said...

-Wayne

[911pcars]

Let me add:

The 38º rule probably applies, but it may not be the optimum. I don't know the particulars of your engine, but variations in compression ratio, fuel octane, altitude, piston dome shape, combustion chamber shape, carbon buildup, inlet air temperature, etc. could change this maximum figure. The best way to maximize the advance is to put it on a chassis dynomometer and check for the max. power at various rpm's under load while somehow monitoring threshold detonation. After testing through the rpm range, you can plot a custom distributor advance curve that stays safely below the detonation threshold. As you might imagine, this will take time (& money).

Sherwood Lee
http://members.rennlist.org/911pcars