My ecm has a couple of tables for manipulating Pump Shot. It is similar to the pump shot you find in a carb. One table is for differential TPS% and the other is differential MAP. Both tables have data fields where you manipulate the uSeconds added to the pulse width.

Anyway, I modified these two tables so that I thought I added more fuel, but looking at my DataMaster scan I had spark knock out the ying yang. I mean it was like counting up to 255 then it rolled back to 1 and counted up to 255, rinse and repeat. I don't go lean when this happens nor do I seam to go too rich. I do see that my ecm is retarding spark because of the knock. Can anyone shed some light on why I would get that much knock?



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1991 Chevy C2500HD 5.7L HD. 16147060 ECM
Mods: Crane PowerMax 2030 cam 204I 214E @ .050 and 423I 446E lift, Jacobs Pro Street Ignition System. Using DataMaster and TunerCat with $85 ECM files.

 

IMO, if all you did was increase the ms data in those tables (nothing else at all on the PROM) then you couldn't have knock as a result. Did you save the PROM wrong or modify anything else in the PROM to cause this???

I assume you did NOT have the knock problem before and just didn't see/scan it??

[This message has been edited by fast_broker (edited October 25, 2001).]

 

Those two tables were the only things I changed. Didn't have a knock problem before. It seems strange, but I'm pretty confident that I saved the file and tranferred it to the prom correctly.