Dual Spark Maps - Difference ?

[Happy Jim]

Hi all,

I've gone over to COS3 now, however I can't seem to make sense of the difference between High and Low spark maps by looking at other stock GM tunes.

In simplistic terms would I be safe in sorting out my high octane table and then copying that to the low octane table and applying a minus % figure across the board?? if so, would 15% sound a sensible margin?

Any thoughts?

Thanks

Jim

[Tordne]

Do you understand the way the High and Low octane tables work?

If not THIS POST (http://forum.efilive.com/showpost.php?p=23279&postcount=5) explains it a bit :)

[johnv]

Just use the factory low octane table,
as long as you tune the High octane table so your not seeing any knock retard the table will not be used, but will give a safety net if you ever need it - (have to run lower octane fuel or get a bad batch of gas etc)

[Happy Jim]

I'm happy with what it's there for, and how the COS makes it work (and allows us to force the issue if we want).

What I don't get is where the lower table should be, as the stock tunes are...er...varied to say the least.

To make it simple, imagine your high octane table was a flat 38 deg across the board, what should the low octane table be set at? (cell minus Xdeg, or cell minus Y%).

I quite like the idea of having a safety net in case I pick up a tank full of duff fuel, and I don't feel like leaving it where it is given that my high octane table will be tweaked all over the place (once I get going).

Cheers

Jim