Spark Tables and knock sensors

[Lakegoat]

Here is a comment from a tuner that I read this morning. I always heard that the low table was to be lower in case of knock. As you can see, there is a different opinion. Which is correct??
"That is not true. As long as the knock tables are still active and aren't zero'd out, the PCM will retard timing when it detects knock. The high/low octane tables are for a scalar that will blend between the high and low octane tables when there is long term repeated knock. Instead of pulling timing whenever knock is seen, it will begin to default to lower timing cells. Plenty of people copy the high to low without issues because they keep their knock sensors active."


Thanks

[ericwilloughby]

Really, that's good to know. I've been trying to figure out how to reset back to the high octane table after having cleared up a high timing problem

[VFL77]

I always heard that the low table was to be lower in case of knock.

That's not a wrong statement, but it's incomplete.
As I've learned (here in HPT forums) the HI and LO spark tables are operated between depending on long term knock (Knock Learn Factor). If KLF=0 then your spark=HI table. If KLF=1.0 then you'll be fully on the LO table. If KLF <> 0 or 1 then it'll be that percentage into the LO table from the HI. eg, if KLF=0.13 then you'll be 13% of the way from the HI into the LO table settings.
Short term knock retard is still dealt with based on the Knock Retard settings.
That's how I've understood all the mumbo jumbo anyway.

[Lakegoat]

So if the Hi and Lo tables are the same, then if KLF=1.0, there is no way for the computer to deal with knock---correct?

[mowton]

That's not a wrong statement, but it's incomplete.
As I've learned (here in HPT forums) the HI and LO spark tables are operated between depending on long term knock (Knock Learn Factor). If KLF=0 then your spark=HI table. If KLF=1.0 then you'll be fully on the LO table. If KLF <> 0 or 1 then it'll be that percentage into the LO table from the HI. eg, if KLF=0.13 then you'll be 13% of the way from the HI into the LO table settings.
Short term knock retard is still dealt with based on the Knock Retard settings.
That's how I've understood all the mumbo jumbo anyway.

That is my understanding as well....the "learned values" are there to handle long term knock situations like a bad tank of gas, mechanical issues etc. so the timing is reduced and not dependant on actual knock sensor activation...much like you would do to "de-tune" a 93 octane file to use 87 octane fuel.....

To me there is no reason to make the 2 tables the same (except gen III Speed Density), for if you do, you have other problems you need to address...it is just a band aid in my thinking....

Ed M

[ericwilloughby]

So if the Hi and Lo tables are the same, then if KLF=1.0, there is no way for the computer to deal with knock---correct?

I'd like to know this also.
And how do I force the ecm back to the hi table

[Ben C]

If the tables are the same the computer can still pull timing based on kr, but can?t reduce timing to prevent kr.

[ericwilloughby]

Looks like flashing the modified low octane table reset the klf. Thanks anyway. 1st I've heard of klf. Was it also on the Gen 3 ecm? I thought timing just switched between the 2 tables not a mixture

[GHuggins]

Think of it like already pointed out - short terms and long terms where short terms are your knock settings pulling immediate timing and then on the other hand long terms via the knock learn factor starting off with lower learned timing... KLF will learn down to the low octane values quickly - usually already pretty much there if it sees 5 or 6 degrees of timing being pulled via short terms... However, KLF takes about 1 whole week of driving without knock to learn back to the high octane table... STILL, just like fueling - having long terms and short terms just adds that much more safety into the equation such as hitting a 6 degree max setting on the short terms and then pulling a few more degrees via the long terms for when that watered down tank of junk gas was purchased at that last station you hit

[ericwilloughby]

K.. Thanks.. 95% of the time I buy E85 but I found 87 octane for $2.20 since I'm not FI I went for it. Didn't know it had pulled timing from 26 degrees down to 16 until I happened to log. I'd never heard of KLF.

Does the E40 ecm have that also? I've only tuned an E40, 411, and my current E38

[ericwilloughby]

Also.. Does klf apply to the entire table or is the table divided into cells and a different KLF for each area?