jrwilliams95z28

has anyone seen this mystery timing while datalogging?
I set my main spark tables for 30* advance @ WOT and it targets 34-36* in the areas I clearly set lower and it causes a bit of knock retard.

It was really bad before I tuned it, I've eliminated most of the knock retard though.

Anyone know why? should I just factor this extra timing into my tune and drop the main tables down a few degrees to compensate?

thanks!

96capricemgr

iTrader: (1)

pretty common knowledge that the pcm adds a few degrees to what you program. Mine is programmed to 29degrees in tunercat.
I see MSD opti in your sig though and maybe the timing adjustment thing on it is advancing the timing. Only way to know is keyed hub, timing pointer and timing mark of some sort be it timing tape, degreed damper or just a single mark and a dialback light.

jrwilliams95z28

Yah ok that's what I thought. If its common knowledge then it's odd how hard to find literature on it.
Yah I have an MSD opti but I set the timing to 0 advance/retard when I installed it. Good to know other people are running around the same timing as me though!

96capricemgr

iTrader: (1)

If you are getting retard with the setup in your sig at 30 programmed IMO there is something going on, be it lean or the MSD not truly "zero". The only way to know is the keyed hub and all.

I had mine at 30 degrees programmed for awhile an settled on 29 because it went faster not because it was knocking. I run a lot more compression than your sig would suggest you are.

jrwilliams95z28

yah fair enough i have stock heads and everything else. maybe it is the optispark, but I set the way the instruction said to do it, it was a long time ago though. the weird thing is wouldent that effect the timing at every RPM? when I am cruiseing/part throttle it seems to be right around the targeted advance. just in PE mode. oh well I'm going to play around with lowering it a little in the tune and taking the datalogged number as fact. I am going to buy a wideband soon, so Ill know if I'm lean.

Ed Wright

iTrader: (1)

Has nothing to do with where you set your Optispark. That is what the PCM is commanding. If you set your Opti differently, it won't show up on the scan tool.