I have been trying to tune my 94Z with tunercat. I created a spark advance curve based off a generic carb curve, the problem is I set max spark advance to 40* but according to datamaster it maxes out at 44-45* and does so from approx. 2200 to redline. I have set spark correction table vs. cool @ .1 , knock retard set for 220*, max spark advance is set to 40*, actual max timing (in table) is 38*.

where is the extra advance coming from??
Is there something I'm missing?

I just want to actually use spark tables I create

 

ok so no one has any ideas?

 

iat sensor

 

So just tune around it... take out 6 degrees in the high KPA ranges of 90-100. I also have experienced this and its only during WOT but I just took out timing till I see on my scanner what I want despite what the tables are set to.

 

so could I just use the spark correction table and adjust to compesate for the extra timing??

 

Well, you could but thats gonna pull timing in all KPA/MAP ranges and all you want is 90-100 KPA. The better solution is to just take it out of the main and extended spark advance tables.

 

Just wondering, is your spark reference angle set to something other than zero within the ECM Constants Table? Might cause this condition I think.

 

This is a problem that's been around for a long time on the LT1's. I'm not sure where it comes from, but most tuners generally just accept that it's going to have 2-3 more degrees timing than the table says.