High and Low Octane Spark Tables

[20Softtail00]

I am going back to recheck my MAF and VVE tuning and have a question regarding the high and low octane spark tables. I read a post some time ago that said you should make these tables the same while tuning because when failing MAF to tune VVE, the ECM will reference the low octane table. Last time I checked my tunes, I made these tables the same, adjusted for any knock and once finished reduced the low octane spark table by 5 degrees. I have a gen 4 E67 controller with a stock LS3 crate motor stuffed inside a 1959 corvette.

Thanks in advance for any advice you can share.

[edcmat-l1]

Was there supposed to be a question in there somewhere?

[20Softtail00]

Okay, I am beginning to scare myself a bit. Yes, the question is, do I still need to make the high and low octane tables the same when tuning MAF and VVE separately.?

[edcmat-l1]

Okay, I am beginning to scare myself a bit. Yes, the question is, do I still need to make the high and low octane tables the same when tuning MAF and VVE separately.?

When you fail the maf it runs off the low octane table.

[20Softtail00]

Thank You!

[04silverado6.0]

I have never paid attention to this on gen 4-5. Do all gm controllers resort to the low octane table with maf failed?

[edcmat-l1]

Yes.

[04silverado6.0]

That subject is very unclear on some forums from the past. Normally i set the low octane 20% lower so probably not enough difference to make a change in wideband reading for temporary maf fail.

[edcmat-l1]

That subject is very unclear on some forums from the past. Normally i set the low octane 20% lower so probably not enough difference to make a change in wideband reading for temporary maf fail.

I don't ever recommend lowering the entire table. Only the higher load part of it. Same as what GM does. Lowering the low load area does affect the burn and subsequently the AFR.

I also don't tune part throttle open loop with a wideband.

[04silverado6.0]

I forgot to mention i normally use the 1bar sd os on all gen 3 that support the modification. Vehicles that dont have the modification normally get minimal time spent on ve/vve(smooth and under 10% error), fine tuning done via maf and left in cl maf only, no ltft and no stft on ol. Fine tuning on either i shoot for 2% or less, normally rich error with wot being smooth and 1.5% rich or less on wideband.