Thread: Still getting knock with 3.8" pulley and exhaust mods

Recently installed K&N intake, PLOG, and ZZP 3" Catless DP on my 1999 GTP. There are no vaccuum leaks or anything like that and I replaced all the vac/boost lines to be sure. I have a lower temp T-Stat and the stock 3.8" supercharger pulley. Did some data logging yesterday and I am still seeing ~2 to 3 degrees of KR at WOT at different places in the RPM range. Anyone know why this is the case? Have you seen this regularly on stock GTPs with exhaust mods?? Figured I would have 0 KR after those mods without running more boost...

Originally Posted by coolone

It happens... New plugs? Wires?

New ZZP 10.5mm wires. Not new plugs. I have AL104s to put in though. bad to run those without added boost though??

Originally Posted by Fivefingerdeathpunch

If this was the HP Tuners website, I'd say post the tune and scan so we can take a look at it.

But you can't paste those on the this forum. Without seeing the tune, there isnt anything I can do to suggest.

Understandable. The tune is pretty much stock as far as AFRs go, PE tables, MAF, etc.

LTFTs are a consistent +3.1% under WOT...

Not that uncommon. I'd switch to e85 or intercool it.

Originally Posted by Fivefingerdeathpunch

I'm sure if he lowered the timing by 2 degrees to around 13-14, most of it would be gone.

True. I haven't seen the timing go below 14.5 with my KR and that was shifting at 5,750 rpm.

Originally Posted by 91parkave

Why wouldn't you add a little more fuel for your pe and see if the knock goes away first

Think I should try that even though it's a stock pulley? I was under the impression they run them a little rich from the factory. Guess it would be a quick change though in the PE table and see how it works.

Originally Posted by wa04compg

Stock tune 3in dp and stock pulley I saw up to 5 degrees of kr I wouldn't worry about it


Sent from my iPhone using Tapatalk

Did you do anything to get rid of it? Think it is worth me dropping pulley size if I am already seeing KR with the stock pulley?

Good deal. Thanks for the info!

As of this afternoon, just saw up to 5.7* KR at WOT around 5,300 RPM.... Target AFR is 12.2 (set by me) in the PE table. I still need to swap plugs to see if that helps but gosh, 5.7* ?!?!?! Fuel trims are zero all the way across. Can plugs get rid of ~5* of KR? Maybe I should target lower AFRs in my PE table??

That's just target. I left the stock adder vs. time/RPM alone.. I'm tempted to zero out that table and make the target lower. Going to change plugs this afternoon and change the target and see how it does.