So, I found these 2 tables in S_AUJP, which are mulitpliers. One based on MAP, and the other based on RPM. I have entries in both tables, integers of 1.00 or less. In the description, it mentions that all these values (S_AUJP) are =0, so this feature is disabled. Is there some kind of low octane sensor, in my ride, that would trigger to use these tables?

I am looking at this for tuning SA in my '90 C4 L98 ride.

 

The knock detection and reporting system is used. Which is basically the knock sensor and ESC filter (on the MEMCAL).

IIRC, it has been awhile, this feature (!?) is used to retard the SA for the duration of key-on, engine-running. Thereby preventing knock from occurring. Or something like that.

RBob.

 

Interesting. So, can we just forget about the phrase "low octane", WRT this parameter? Obviously a multiplier in these tables, gets used in the code to calculate a value for knock retard. Thus, a multiplier of 0 x anything=0. So, can we say that these tables can eliminate knock retard, totally, in the bin?

The only 0's I have in my tables, are at MAP of 20,25,30.

I'm just wondering how does the ECM know you have low octane fuel in the tank?

 

ECM knows its knocking via knock sensor output.

These settings are more a failsafe for a tank of bad gas.

 

So is there some sort of time component? If the ECM has to invoke knock retard for some period of time, it assumes theres a bad tank of gas?

 

MikeT: an oldy but a goody, I knew a former mod dissected this feature (?), and did a decent write up on it:

https://www.thirdgen.org/forums/diy-...d-routine.html

Hopefully it answers some questions.

RBob.

 

Aaaaaa, the old famous Grim Reaper poster.....sure I remember him. Good post, read it a few times, and bookmarked it. Gonna have to spend some more time on it!! I found most of them scalars he was referring to, but I originally asked about the 2 tables. Obviously scalars are enablers, and would likely invoke table settings at the specific conditions. Or vice-versa! It generally appears, that disabling it altogether is the best option.
And, by the way, I did perform a search on this subject, before posting, but certainly did not go back to 4/16/2001 to read the answer!