E38 Octane tables low and high

[rich24v]

Hello,
I have a LS3 with supercharger running a 2 bar speed density tune (maf-less) operating system 12624402 -> 1250223

The HO spark table is accross the board 3deg more advanced than the LO spark table.

Question is, does the tune combo actually use both tables (bearing in mind tune is maffless)....or does the
PCM default to the LO spark table because there is no maf ?

Aside, my friends LS2 has a supercharger and does run a maf, operating system 12619078
I found both of his HO and LO spark tables were identical....is this normal ?

Thanks in advance.

[5FDP]

I believe it uses the high octane table until knock is present then switch to the low octane table with a mix of numbers inbetween. I'd still leave the low octane table a tad lower than the high octane table. If you have failed the MAF correctly in the tune it should run just like normal.


Someone has changed both your friends tables to be the same, they do no come that way from the factory.

[StopGap]

Hello,
I have a LS3 with supercharger running a 2 bar speed density tune (maf-less) operating system 12624402 -> 1250223

The HO spark table is accross the board 3deg more advanced than the LO spark table.

Question is, does the tune combo actually use both tables (bearing in mind tune is maffless)....or does the
PCM default to the LO spark table because there is no maf ?

Aside, my friends LS2 has a supercharger and does run a maf, operating system 12619078
I found both of his HO and LO spark tables were identical....is this normal ?

Thanks in advance.

The ECM works from the HO table to the LO table based on knock retard events and the knock learn factor. This can be set/changed. Whoever tuned your setup might have modified that.

If the HO and LO tables are the same, a tuner left them that way. Making them the same is usually a first step in tuning, but tuner could/should have returned the LO table after tuning, or he might have forgotten.

[rich24v]

Guys, thanks for replies.