dmhines

I have a 91 Performance tune currently installed. I've been putting 93 octane fuel in. Instead of spending the extra $$$ on a 93 tune I advanced all the timing values up +2 using my SCT tuner. Car definitely runs stronger. Now I'm wondering if it an handle +4 advance. Will 2 octane points let me advance timing 4 degrees since it does 2 degrees with no issues? I was curious whether there was a table or chart for this besides just using trial and error if I hear pinging ...

I did find this basic chart ...

Basic Ignition Timing
Vehicle / Retarded 5 degrees / Standard / Advanced 5 degrees
A 88 / 91 / 93
B 86 / 90.5 / 94.5
C 85.5 / 88 / 90
D 84 / 87.5 / 91
E 82.5 / 87 / 90


This would indicate a car tuned for 91 octane could be advanced 5 degrees if 93 octane is used.

Getaway

You're pretty close to the correct ratio with the +2 global advance. I'm not sure how much room for error (richness) SCT puts into their tunes, but I think +4 may be too much. If you advance it too far, the knock sensors may keep it safe by reducing the timing a little, but I would not rely on the knock sensors to be safe.

Getaway

Even if you had a chart, it would not help if you did not know the baseline, which SCT probably will not provide you.

dmhines

This is actually a B A M A tune ...

Getaway

If you want the max safe zone. Get a custom tune.
Sorry for the 3 posts when I could have put it into one. It was easier to post three rather than edit, and edit.[&:]

Getaway

In that case, it's probably pretty close to the correct ratio. You could maybe go +3 if you get good quality gas. I didn't check your profile, so I don't know where you live, but winter's coming and the cold dense air will lean outthe tune a little. Just something to keep in mind.

dmhines

Thanks for input .... unfortunately .... the SCT 3 tuner only lets me input advance in increments of 2 degrees ....

I supposed i could do:

RPM:

0 - 2000: + 2
2000 - 4000: +4
4000 - 8000: + 4

That is assuming it is programmed to be richer at the higher RPM's ...

dmhines

Well ... the decisions were made for me ... the SCT tuner only allowed a max of +3 at 2K-4K RPMS and a max of +2 at 4K-8K RPMS .... I also bumped up the fuel + 2% at WOT to be on the safe side ...