98Zheadsncam

iTrader: (26)

Well, I had a great tune...but, I just had to get rid of my pace setter 1 3/4 headers, and install some TSP 1 7/8's. Now, I'm getting knock at WOT in the 4000-4800 rpm range.

I already checked the header clearance and ground down the k member a bit. I don't think they're hitting the chassis anywhere else.

Basically, my question is, where should I start? Should I pull timing in the high octane spark table where the ECM is picking up knock?

Or, should I richen up that RPM range?

The Banish book mentions that sometimes knock can be encountered when there isn't enough timing...so could I also try adding timing in those specific areas?

I'm including my tune and a log I just took. I set notes at each of the places I did a WOT run.

Any thoughts will be appreciated.

jimmyblue

iTrader: (11)

If you're convinced it's real knock, then you want to
revisit your WOT fueling and spark. Better headers
-can- (not to say, -did-) improve cylinder scavenging
and thus filling with fresher charge, so more knock
prone if the original tune was at all edgy. Whether
you want to fix this with fuel or spark, wants some
cut-and-try. If you are speed density only, then the
headers additionally may change relation of air mass
flow to manifold pressure with no clue to the PCM -
so if you depend at all on the VE table (and you will,
tip-in at a minimum still falls back to it - "unsteady
MAP") that may want a look first, delivered AFR vs
commanded.

98Zheadsncam

iTrader: (26)

Afr at wot seems to be hovering in the high 12's. I know that the 98 ecms are known for false knock as well...the car didn't experience any knock before the new headers, though. At any rate, thanks for the advice.

superbean

98 ECM works fine, it's the early 98 model specific knock sensors that need updated. (Or just tuned out all together if you're comfortable doing so)

gagliano7

Make sure your headers or exhaust aren't touching anywhere causing false knock.

98Zheadsncam

iTrader: (26)

Yep, I have the updated knock sensors installed already.


I'm fairly positive what i'm seeing is, in fact, false knock. I desensitized the knock sensors via the "knock sensor multiplier B (cylinder mode) table. I'm getting no knock at WOT now, however, the scanner shows sporadic knock when I start the car. from 1 degree all the way to 8. My wideband is showing about perfect at WOT - 12.7 -12.9. I'm not too worried about it.


Thanks for the input.