Quote:
Originally Posted by gt90stang
I’ve been fighting a over 4500 RPM detonation problem at full throttle in 1st gear only. I tried TTNOV pulling timing and it worked but performance really suffered so it wasn’t acceptable. The most timing I could run in the WOT spark advance vs RPM function was 21*, but I still got detonation over 4500 RPM in first gear.
I got to thinking about what was going on, looking over the datalogs and nothing made much sense (looked ok). So I decided to back up a bit and remove the tweak I did to the spark advance rate vs RPM function. When I originally did this my thinking was to allow the PCM to remove timing faster.
The spark advance rate vs RPM function settings I was using:
0, 0.5 992, 0.5 3008, 0.375 4000, 0.125 8160, 0.125
Versus the original of:
0, 2 0, 2 992, 2 3008, 1.5 4000, 1 8160, 1
So basically 4 to 8 times faster advance rate than stock. So when I went back to the original spark advance rate vs RPM function I am now able to run 23* in the WOT spark advance vs RPM function with no detonation. All I can think of is that the PCM can’t deal with the higher slew rates of the modified spark advance rate vs RPM function. Datalogs before and after these changes are virtually identical. Anybody have any insight here?
Gt90stang, Don
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Wow, you run more timing than I do and I have Meth/H2O injection. You do have lower compression and boost though. Good you were able to fix it, though I never messed with that function so I can't help you. I am seeing about 20.5 degrees max above 4500 RPM. I do pull timing via TTNOV to keep tire spin away at launch, but I pull most of it (6 degrees) @ 3000 RPM and am only pulling 2 @ 5k & none @ 6k, so I don't think it hurt performance that much. Did you use the same amount of timing pull in all cells? I pull more if the load goes down because that means the tires spun. Anyway, that's the way I use TTNOV. it may be that the datalog does not catch the timing changes due to how fast you rev out in first. It is known that the TwEECer does not log a lot of data at fast rates of change (like in 1st gear in a blown car). Anyway, sometimes success is the best explanation and the only one you need
