I know this sounds like a newbie question but I have not been able to find this info by searching the archives. I have started scanning my car with craig moates software, and editing chips with winbin. I have an 89 iroc with maf system and a 350 engine, and has no mods other than a cat back exhaust.
I lucked out and the arap maf tables work well for me, the blm/int is very close to 128/128 everywhere but idle. I am getting some knock counts with the arap bin so I would like to correct my spark advance table. I have already lowered the power enrichment advance to 0 temporarily.
My question is about determining where in the table to lower the data.
I check the logged data to see what rpm and load the knock counts are picked, but I remember reading here that knock has to be prevented before it is detected. The easiest way to ask this is with an example.
At 3000rpm with an LV8 of 203 I get 1* of retard. The spark advance table has 24.96* for that load and rpm. It only got 1* of retard in 2 consecutive rows of data. Now should I lower the advance at that exact spot on the spark table? Or should I lower the advance at the spot right before the the retard showed up? If it should be corrected prior to the knock being detected, how far before should I look at to change?
Sorry for the length of this post, and I figure that in the end ill have to start right at the knock retard and work back slowly experimenting, but I thought id see what you guys have to say.
Thanks a lot if your still reading at this point, I really appreciate any info that I can get, especially since im still very new to this.
Thanks
Mike

 

ttt.

I have the exact same question. Can someone please answer this.

Thanks.

 

The ARAP was/is a good begining point for fuel since it deletes the 9th injector, and was the last of that series of calibrations, so it was the most refined.

Timing, is a whole nother matter.

Lean mixtures are slow burning, so lots of advance is needed.

Running alot of advance puts heat into the dome of the piston. And increases the loads on the rod and main bearings.

Adding EGR, from either the EGR valve or from using a larger cam, increases the need for more timing, since charges containing large amounts of EGR are slow burning.

The fooler in tuning the timing is that too much generally feels good. Since it artificially lets the motor think it has a higher compression ratio, and acts more responsive.

And then you need to closely look at your usage. Is this a real race car or just a mild fun car. If you want to treat it as a race car, then you'll want to run all the timing the motor can tolerate, with the down side being shorter life, or give the motor enough to be happy, and just have it last alot longer.

Also, the larger the combustion chambers the more timing you'll need.

24d ish for idle.
28-42 for light cruise
26-36 for WOT.
Are the ranges that seem to work for me. While they are vastly different, every engine is vastly different.