high octane main spark advance

**shady milkman** · 09-05-2010, 01:18 PM

i have a quick question..i was looking at my high octane main spark advance and i am confused why there is a valley with the bottom part being at 4800rpm. and starts at the high range of the cylinder airmass and tappers out in the lower range. why is it like that ? wouldnt it make more sense to have those values more equal with its surrounding values ? also what is with the random 0 value there for one cell ?

**pajeff02** · 09-05-2010, 06:30 PM

I pulled up my high octane spark table to compare. In the 4,800 rpm column it smoothly transitions from 41 at the top (low air mass) to 23 at the botton (high air mass). What does your 3D Chart look like?

**Cutlass** · 09-05-2010, 07:02 PM

ok I was curious so I looked at mine also. The dip is there but its actually at 4400 rpm on mine (Frost tune). The spark advance is a little more on either side (4000 rpm and 4800 rpm). Must just be what the motor likes. And there are no random zeros on my spark advance.
I looked at a stock M6 tune and the dip is also there but it stretches a little wider across the 4400 and 4800 rpm.

**shady milkman** · 09-05-2010, 10:23 PM

Originally Posted by pajeff02

I pulled up my high octane spark table to compare. In the 4,800 rpm column it smoothly transitions from 41 at the top (low air mass) to 23 at the botton (high air mass). What does your 3D Chart look like?

**shady milkman** · 09-05-2010, 10:30 PM

isnt the 4800ish rpm range where the ve tables stop being referenced and only get readings from the MAF ..i wonder if they cut timing because of that

**pajeff02** · 09-06-2010, 03:19 AM

Interesting. I see that the "0" in your table is actually part of the transition -- the numbers change evenly from top to bottom in that column. Here are my main spark table and chart:

Mods are listed in sig for comparison purposes.

**LSXZ28** · 09-06-2010, 06:28 AM

It is there because that is the peak torque band and the point at which detonation is most likely to occur... Once you change to a performace cam that gives the engine less dynamic compression (because of overlap), you will see that area start to come up some - closer to the peak timing numbers... but there will always be a lower value there, otherwise it would detonate.

**shady milkman** · 09-06-2010, 07:13 AM

Originally Posted by pajeff02

Interesting. I see that the "0" in your table is actually part of the transition -- the numbers change evenly from top to bottom in that column. Here are my main spark table and chart:

Mods are listed in sig for comparison purposes.

ahh did frost touch your spark tables ? or did you ?

**shady milkman** · 09-06-2010, 07:15 AM

Originally Posted by LSXZ28

It is there because that is the peak torque band and the point at which detonation is most likely to occur... Once you change to a performace cam that gives the engine less dynamic compression (because of overlap), you will see that area start to come up some - closer to the peak timing numbers... but there will always be a lower value there, otherwise it would detonate.

ahh thanks man! i saw it on my table and was really confused...what are your thoughts on the 0 value

**pajeff02** · 09-06-2010, 09:10 AM

Originally Posted by shady milkman

ahh did frost touch your spark tables ? or did you ?

That be Frost's magic. I go to school in 3 weeks to learn more about this stuff. Until then, HP Tuners is a glorified scanner in my garage.

**Frost** · 09-06-2010, 09:19 AM

You guys need to click the precision arrow to show at least one decimal place in those timing tables.. (it's almost right under the undo button, it's the arrow with 0.00's under it)

The other difference in the two posted here are the year differences. While everyone in the world is screaming an Ls1 is an Ls1 regardless of year, you can now see one of the reasons that they are wrong.

**Frost** · 09-06-2010, 09:21 AM

Also,

Shady, that's not how I last left your table; that looks stock.

**pajeff02** · 09-06-2010, 09:25 AM

Cool! Never played with that button before. Now I see that the table transitions from cell to cell by fractions of a degree. Thanks, Steve!

**shady milkman** · 09-06-2010, 10:27 AM

Originally Posted by Frost

You guys need to click the precision arrow to show at least one decimal place in those timing tables.. (it's almost right under the undo button, it's the arrow with 0.00's under it)

The other difference in the two posted here are the year differences. While everyone in the world is screaming an Ls1 is an Ls1 regardless of year, you can now see one of the reasons that they are wrong.

Originally Posted by Frost

Also,

Shady, that's not how I last left your table; that looks stock.

my bad. it was the stock tune i was looking at..the tune you gave me was much smoother.