Originally Posted by kapolani

I would like you all to help me understand this principle.

It is my understanding that if the ECU see's excessive knock counts timing will be pulled.

Would the following example qualify as timing being pulled:


9,9,9,8,8,8,7,7,7,8,8,7,7,7,6,6,7,7,8,8,7,7,6,6,6, 5,5,5.......

But, what if you see knock counts via EvoScan and timing doesn't look like it's being pulled. For example:

Say you have knock counts of 5ish 6ish and the timing remains flat:

4,4,4,4,4,4,4,4,4,4,4,5,5,5,5,5,5,6,6,6,6,6,7,7,7, 7,7,7,8,8,8,8,.....

and progressively ramps up as boost builds.

What does that show?

Can you have knock counts and the ECU NOT pull timing?

Thanks!

Originally Posted by chmodlf

Yes you can have knock count and not pull timing. Sometimes the ecu keeps the timing number rather than decreasing if it is seeing knock. By using the load and rpm you can pretty well judge what is going on.

There are a few parameters that the ecu is using to modulate the timing (in addition to knock). To my knowledge no one has yet figured it out completely. It will be soon with the ecu disasembly that is currently going on.

Originally Posted by kapolani

Say you have knock counts of 5ish 6ish and the timing remains flat:

Originally Posted by mrfred

I have yet to see a situation like this with my car. A KS of 3 definitely pulls one deg of timing every time with my car.



At WOT, a flat timing curve vs rpm is not common. The timing adv curve usually starts up around 15 to 20 deg at 2000 rpm, drops rapidly to 0 to - 3 deg by around 3500 rpm, and then gradually rises up to around 10 to 12 deg by 7000 rpm. A steadily increasing knock sum count after 3500 rpm will give a flat effective timing curve.

Originally Posted by mrfred

I didn't mean to peg all Evo's with that timing curve. It was just an example to show how a steadily increasing timing adv curve combined with a steadily increasing KS could result in a flat timing curve. FWIW, the story on EvoM I've seen with the IX is that increased cylinder pressures in the IX are the reason the lower timing adv at high rpm.

Originally Posted by nj1266

Maybe your experience is Evo 9 specific. On my 8 I have logged timing getting pulled with as little as 1 ks and timing NOT getting pulled with a sequence of 3 ks. Also, on my 8 the max timing w/o knock ramps up to 18*. I have no idea why the 9 runs so little timing up top. But I would really like to know.

Originally Posted by l2r99gst

nj1266,

I have seen you make this statement countless times. Just because you see an increase in ignition advance, it doesn't mean the ECU isn't pulling timing.

The ECU is still going to follow your timing profile based on your ignition maps and what RPM/load you are at. It's just that the the ECU will subtract timing from the value that it should be.

For a quick and completely arbitrary example, let's say that your timing should ramp up like this from peak torque:

3 5 8 10 14 18 (completely arbitrary just to prove a point)

Let's say that you get 6 counts of knock where the 14 and 18 were. Then your timing will look something like:

3 5 8 10 12 16

Of course the ECU will still advance timing. It will just apply the knock correction to it. I just keep seeing you say that you see the ECU ADD timing when there are knock counts. Sure....it is just following the timing maps and correcting as needed.

Also, what was posted about the DSM ECU is incorrect.

The DSM ECU will pull .35* of timing for every 1 count of knock. The 1G ECU pulled a maximum of 15* (43 knock counts). The 2G was slightly lower than that, but I forgot the number.

But the DSM ECU would pull timing exactly proportional to knock counts, starting at 1. Roughly 3counts of knock to 1 degree being pulled. I don't believe that we have found out the exact formula for the Evo ECU yet.


Eric