Supercharger/Timing question

[GreenBeast]

How much does the timing need to be adjusted per pound of boost?

[caffeine]

I'm running around 10-12* of spark advance at 9 psi. I have it gradually reduce from about 20* at 0 psi.

[TurboGTU]

Idealy 2*-3* retarted per lb from total spark advance to a point on pump gas. Racing fuel and alky is another story. Just watch knock on the scanner and EGT.

[timg]

I've always used 1 degree of timing per pound of boost as a starting point.

Tim

[TGP37]

Turbocharged 3100 5-speed at 8 psi. Used 97 Lumina stock figures for spark tuning.

This table shows where I reduced spark from stock tables.


Edit: Beyond 6000 RPM is reduced for safe over run.

[GreenBeast]

Okay thanks. Whats the limit for pump gas? Just curious

[dskopek]

So far on a 3400 with 8.6 CR the most timing in the motor under boost has been 24 deg without knock at higher rpms (8 lbs) but that is pushing it on pump gas. I would agree with Timg to start with at least 1 deg per pound retard and tune from there.

[caffeine]

I dunno with only 12* and stock 9.8:1 compression the car pulls really hard at 9 psi. I'm running 94 octane which is only available at chevron here. Haven't really played too much with timing under boost though.

[TGP37]

I dunno with only 12* and stock 9.8:1 compression the car pulls really hard at 9 psi. I'm running 94 octane which is only available at chevron here. Haven't really played too much with timing under boost though.

Same here, I found 12-13 degrees at 8psi to work well.....pulls hard. Using 93 Octane.

low 20's pre-boost but spooled.

Scaled in between.


Of course this is turbo. I would imagine turbo likes a lower spark for the turbine compared to a S/C. But can't be too much different.