Relation between Low and High Octane Timing Tables
Thread Starter
On The Tree
Joined: Dec 2001
Posts: 154
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From: Burlington, ON
Relation between Low and High Octane Timing Tables What is the relationship between the LOW and HIGH Octane Timing tables? When and how does the PCM determine its time to drop to the LOW OCTANE table? Does a certain amount of KR at different RPMs cause it? How does the PCM determine its time to jump back up to the HIGH OCTANE table?
I know the once my car was on the Low Octane table and I reset the PCM and it still remained on the Low Octane Table.. I have heard that when you fill the car with gas, that it will jump back up to the High Octane table until it is knocked back down. Is this true? If so, does the PCM monitor the fuel level and wait for it to raise, and then jump back up Octane Tables?
Thanks,
I know the once my car was on the Low Octane table and I reset the PCM and it still remained on the Low Octane Table.. I have heard that when you fill the car with gas, that it will jump back up to the High Octane table until it is knocked back down. Is this true? If so, does the PCM monitor the fuel level and wait for it to raise, and then jump back up Octane Tables?
Thanks,
TECH Fanatic
Joined: Nov 2001
Posts: 1,986
Likes: 1
From: Centrifugal City
Re: Relation between Low and High Octane Timing Tables I'm not sure what the threshold is re: how much KR. I thought refilling 5+ gallons did it and the 2nd table is considered a 'bad gas' table.
Often PCM programmers will set the tables to the same thing, so it won't matter and you don't get stuck on the low table.
Often PCM programmers will set the tables to the same thing, so it won't matter and you don't get stuck on the low table.
Re: Relation between Low and High Octane Timing Tables i tune like that.....tune for bad gas...93 octane <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" /> and make both tables the same. Then i tune for race gas...and eventually have both a bad/good gas table just like GM intended <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
