GT500 Race gas pulley on pump gas with tune to pull timing?

[walt6076]

For a GT500 stock long block and heads with a Whipple 2.9L blower I?ve got a good tune with WOT lambda = 0.78 and timing advance = 16 degrees with cold IAT2, pulled down to 10 degrees advance with warm IAT2 = 150 degrees. I use the same tune with a 16 PSI pulley on 92 octane and at the drag strip a 19 PSI pulley with 100 octane.

I race about once a month and it would be easier to swap tunes than pulleys. Would I be safe with a tune for 92 octane and the 19 PSI pulley that pulled more timing? I?m thinking I could have a tune just for this case that pulled 6 degrees out for load >= 1.4?

Any advice appreciated.

[Jn2]

So you are asking if you can make a tune for 92 octane and a smaller pulley for non track use right? If that is the case then yes, you should be able to make yourself a tune. You can make it safer by either running the car richer, say .75 lambda, or running less spark advance. Best way to know is to datalog it on 92 octane. Then when you go to the track flash your race tune on and you're good to go.

[tbrtuning]

You would be better off with a tune optimized for the higher octane also. Could likely add even more timing and see some gains.

[walt6076]

So here's a very serious tuning question. Without a knock sensor, how do you find with the max timing advance for your new situation? I really don't want to blow it up with to much timing. I can hear knock at moderate acceleration if I go too far and back off and retune. But at WOT and with headers I'm not sure I will hear the knock. And WOT at full boost is where I need to know what the detonation limit is.

Question two: should I trust and stick with the stock tables to pull timing for air charge temperature?

[yonson]

Old school way, install a new plug, make a pull, kill the engine, read the plug, adjust as needed.

Lambda, IAT, and ECT Base and Multiplier tables work beautifully if you populate them to do so...

[walt6076]

Thanks Chris, LOL. Yea, old school on the plugs 10-4.

[yonson]

Actually since I know you like to tinker with this stuff, you could alternately get a set of knock ears and either run the auxiliary input into the stereo of the car (I've done this with quite a few cars) or use the cans that come with it...