VT2 EXEC LS1

I installed a 85mm truck MAF over the weekend and reprogrammed the MAF table with LS1 Edit. I manually entered the values of the 85mm MAF table from one links posted on the LS1edit.com mailing list.

Here's the problem I'm experiencing. At engine speeds higher than 4800 RPM @ WOT the timing starts to fluctuate wildly, then just pegs out at 14deg max. I'm using EFILive for my data logging. Below 4800 rpm the timing is as per programmed with LS1 Edit, and I've pretty much matched both the hi/low octane spark tables. I've scaled the IFR to 93% to overcome the 8 - 10% LTFT condition. LTFT's now sit at around -5 to -8 % at cruise and zero out at WOT.

Now the catch - if I adjust the Spark Retard Limit table and set the maximum spark from 4800 rpm and upwards to what I programmed in the hi octane spark table the ignition doesn't fluctuate anymore i.e. from 4800 rpm and higher @ .60 gms/cyl and higher I programmed in 22 degrees max timing. These values are also programmed into the Spark Retard Limit table.

I've tried many MAF table settings, all producing the same spark fluctuations albeit having different LTFT's.

Any suggestions?

Thanks.

VT2 EXEC LS1

Have logged MAF frequency and flow rate. No erratic changes to either value. Maximum MAF frequency the car is running is around 10500hz. Maximum flow rate is around 300 grams. I've reset the IFR back to stock and scaled the MAF table up 10% to see if that will zero the LTFT's, rather than relying on the IFR to do it.

Will post my results.

Doc99SSx

Just one suggestion: How about logging the MAF frequency and flow rate and see if the frequency signal from the MAF is flunctuating???? Maybe the MAF is bad.

AND: I think that you would be mainly interested in 8,000Hz and above.

<small>[ February 26, 2003, 12:08 PM: Message edited by: Doc99SSx ]</small>

Doc99SSx

I think that what you want to do is to get the mid-range fuel cell LTFT values to be 0% to -5%.
You want to scale only a portion of the MAF table at a time and blend each section together in a nice smooth curve. You might find that you need to scale the lower frequency cells in the MAF table by 110% (for example only) the middle frequencies by 105% and do nother to the upper frequency (say 8000Hz and above).

If you go too negative on the LTFTs, you will be reducing the timing called for by the PCM timing table. Why your timing is erratic, I dont know, maybe you have KR coming in and out.
When you log WOT runs, get the KR value also, as well as, the total timing as you reported.