Cascade Crew

aaron_sK · Posted: Mon Feb 02, 2009 4:40 pm Post subject: Knock count issues

I've got a pretty serious mystery on my hands with the IROC knock counts.

Ever since I started datalogging the car I've noticed that any revving in neutral, or going WOT in gear will set off knock counts and spark retard. Not a lot (maybe 2-10 counts per instance) but enough to make me worry. Being unable to tune it away in the past, I basically ignored it, but I've been working on eliminating it recently:

-BLM's are fine when the sensor goes off. Always right in the 126-128 range. The O2 readings vary, no consistent rich or lean condition.

-Tried tuning it out of the timing table with no luck. I even tried pulling the table down into the 8-20* range and still knocked.

-Bought a brand new Delco sensor, no change.

-While hunting through TGO I found an old post Paul made like five years ago with AE changes for an HSR. Figuring that was enough overkill to test if it was a lean pop issue, I tried his changes. That had it running so rich on acceleration that it smelled worse than the Merc, but still it knocked just the same.

-Running out of ideas, I tried disabling the DFCO, decel lean, and rev limiter; no change.

-I then tried pulling the EST connector entirely, and running it at 6*. The thing ran like crap, and STILL the ECM was trying (unsuccessfully) to pull timing.

The only thing I can think of is that the exhaust is setting it off. Do you guys have any other ideas before I try writing it out of the chip?

Twilightoptics · Posted: Mon Feb 02, 2009 5:55 pm Post subject:

That's not very much knock at all. For all you know it could be natural in the motor itself. If I were you I'd reduce the amount of timing the ECM pulls out for knock, and increase the recovery rate.

Then I'd verify my timing is set right with the light, and watch my desired spark at those counts. If it's within reason, I'd run a step up in octane and ignore the counts.

You can also unscrew the knock sensor a little. if they are in too far they become hyper sensative.

aaron_sK · Posted: Mon Feb 02, 2009 6:17 pm Post subject:

Good deal Paul. I have been running only 91-92 octane in it for awhile now, so there's not much to change there.

When I installed the new sensor, I just ran it in till it was barely snug. I had heard about the overtorqueing problem before.

All my ESC rates and limits are still stock APYP, so I'll have to start fiddling with those.

Thanks man. Thumbs up