I think Im stuck on the low octane spark table

[BrianC98Z28]

Ok so last night I flash a tune and unplug the maf and drive it for a little while. I then want to flash my original tune back in so I plug the maf back in and flash my original tune back in. Everythin goes ok. I make some log files last night and notice that my timing is only going to like 19-21 degrees WOT when it should be 26-28. Thats a pretty big difference. I reset the pcm via fuse pulls, and cleared any DTCs which there werent any anyways since I plugged the maf back and ive feflashed it a couple of times to see if it would go back right. Its like its stuck on the low octane table. Does anyone have any ideas or any help would be appreciated. Thanks

Brian

[Blacky]

Log the {GM.ASPARK} PID. It shows the percentage of high and low octane tables.

0% = fully in the low octane table
50% = halfway between the two tables.
100% = fully in the high octane table.

You should also try logging most of the {GM.ESC_xxx_DMA} PIDs. Together all those PIDs go to make up the final spark advance. It should be fairly easy to see which one is the culprirt for pulling timing.

In the [PIDs (F8)] table page, right click on any of the PIDs to see which Tuning Tool table controls them. That will give you a place to start looking in the Tuning Tool.

Regards
Paul

[Black02SS]

Are you seeing any KR on the runs?

[BrianC98Z28]

I wasnt getting any KR, it was sprinkling earlier so I didnt want to make any log files on drag radials with it bein a lil wet, ill make some in the morning with what paul said.

[GMPX]

You don't even need to run the engine to read the Adaptive Spark value.

Cheers,
Ross

[Bruce Melton]

Not to butt in but> What causes timing to revert to low octane just knock?

[Blacky]

Yes.

But it's not a case of reverting to the low octane table.
The spark "adapts" based on knock history. When knock occurs the the adaptive spark scaler to move towards 0%, the absence of knock (and the presence of throttle activity) causes the adpative spark scaler to move towards 100%.

At 0% the low octane table has full control.
At 100% the high octane spark table has full control
And anywhere in between has the weighted high/low octane value.

i.e. if the High octane table has 28 degrees and the low has 10 degrees and the adaptive spark is 75%, then the calculated spark will be 10+((28-10)*0.75)=23.5 degrees

Regards
Paul

[Bruce Melton]

Thanks!