Sotiri

I've set both my main and extended spark advance tables as well as setting my coolant correction is at 0. Why is my scanner showing me different timing values than the ones i set? What is changing them? Is there different variables i don't know about?

white2001s10

iTrader: (4)

What system are you running?

Depending on the system you may have other things affecting the advance, like the IAT, knock retard, PE timing table, or maybe you didn't really zero out your ECT vs spark table like you thought. On older TPI systems the mask value is 20 instead of actually zero.

What exactly have you got and what is the difference you're seeing?

Sotiri

I am running OBD1. Knock retard is off. Air temperature and PE affect timing? I haven't seen any tables on that!!!

white2001s10

iTrader: (4)

Old TPI has another timing table for PE, and the LS1 has a table for the IAT, though it doesn't have much in it.

Are you talking timing only at idle, or everywhere? and how much is it off by?

Sotiri

about 5* everywhere

white2001s10

iTrader: (4)

What is your base timing constant set at?
and are your scans showing 5* more or less than the tables?

Sotiri

They are showing 38* instead of 33*. What is base timing constant?

white2001s10

iTrader: (4)

older cars with a real distributor used it to tell the ECM where initial timing was physically set at.