Unforgiven1

iTrader: (5)

Alright, just read a decent article over knock/detonation. Covered the bases pretty well to me. If you're curious...

http://zhome.com/ZCMnL/PICS/detonation/detonation.html

I'm getting a very audible knock right at around 5300 RPMs +, so it's only occurring during performance driving. I would really like to remedy this because I like taking the car down the strip and want to keep damage to a minimum. Has anyone experienced this before? I haven't really done anything to combat it, with the exception of running an fuel system cleaner though it. I'm thinking that if I upgrade to a CAI kit and run some octane boost that would help also. If you have experienced this before were you able to correct it by changing the spark advance/timing? Besides the things mentioned I'm out of ideas. Your help is appreciated. TIA.


Justin

P.S. In Oklahoma, most stations premium/super/ultra is 91 grade. 93 grade is a diamond in the rough.

jimmyblue

iTrader: (11)

With 91 you probably want either more top end
enrichment, or less spark. On a '99 you have the
the little injectors and if you haven't changed a
fuel filter on this car you might oughtta. If you
had scanner access you could look at whether
it's short fuel delivery or excess spark. And I
reckon no programming means hot fan settings.
You need to find a local '99 buddy with HPTuners
I think. Or be him.

M6HuggerSS

id ay good tune-up first
then octane booster
then maybe a dyno tune?....they could check your AFR and make sure your not deadly lean! ...but fix it fast!

soundengineer

iTrader: (16)

go to a performance shop and have the engine properly re-tuned...away from the factory tune...
you should have no problems on 89 octane if you tune it properly...

typpically the times you are up high in rpm you are at wide open throttle(which ignores your 02's) and the stock tune is not that great for wide open throttle high rpm... you dump in more gas..and it will fix that problem....


and dont buy octane booster....it only raises up your octane .3 at the most....not enough to help...
find someone who sells race gas(100 octane or higher)...and mix it in... do some math...

10 gallons 91 + 6 gallons 100 = 94.375 octane....
mix more race gas...get a higher octane

you can also use xytelene(basically a paint thinner) in smaller quantities(20% or less) to boost octane.....but thats a whole other topic...and you should not experiment without a little more research...

you can get an extra 20 hp out of a good tune

FinalTA

iTrader: (1)

I recommend an oil catch can inline with the PCV system (AMW makes a good one). I would also run a top end engine cleaner (Seafoam is good) through a vacuum line on the motor and let it sit overnight. I have done thise 2 things when I had the same issue and it is now gone...

-Jason

CHRISPY

colder thermo and fan programming
good gas
verify fuel pressure and injector sizing is adequate
"slightly" richer AF
reduced timing
properly setup PCV
proper maintenance (clean injectors etc)
Good tuning!

Hope this helps, there is more you can do as well

Mike K.

just like the others have said, get more fuel in there somehow.

BriancWS6

iTrader: (18)

I was getting the same thing around 5500 up with the hpp3 tuning installed and I just dumped in a bottle of octane booster with a 1/2 tank of fuel and it completely went away.

Unforgiven1

iTrader: (5)

Hey guys,

I know it's been a while but I just wanted to say thanks for the replies. I'm definitely going to be doing a catch can and running some top end cleaner through after that I'll go for a tune somewhere. Anyone in the central OK area that could help me with that? Once again, thanks your help is always appreciated.



Justin

TKGN1

give us a shout on a catch can, so far we have had excellent reports stopping oil contamination on the LS1s due to the pcv system.

Unforgiven1

iTrader: (5)

You bet! Haven't heard or seen anything but good about your product. Will place my order in the near future hopefully. Glad to hear that business is going good for you guys as well. Peace.

Justin

HITMANSS

There is an easy way to check if you are getting oil contamination. Pull off the bellows in front of the TB, open the butterfly, and feel behind the blade. Chances are it will be covered with dirty oil.

The catch cans work great, but can be expenisve. A cheaper alternative is to use a Campbell Hausfield air compressor filter, plumbed in-line before the PCV. The filter is designed to trap oil & water vapor into a clear bowl. You'll be surprised how quickly the oil will start accumulating in the bowl.

With Sea Foam, all you need is a short piece of hose that you can fit over the PCV inlet nipple. Just turn the engine on, slowly suck in half a can of Sea Foam, then turn the engine off, & let it sit for an hour. Plug the hose end, and re-start the engine. It will make smoke like you won't believe for 2 -3 minutes, then clear up. Repeat the process with the remainder of the can, then remove the hose, & replace the PCV fitting. Change your oil and filter immediately. The oil will be really black and nasty looking.

jyeager

Just thought I'd chime in with my perspective. You've got a stock motor which is well-known to run really rich at WOT. You will not fix your problem with tuning because the stock tune is very conservative. Tuning typically leans you out which would make your problem worse.
How long does your knocking persist when it happens? The knock sensors should detect it and pull timing to take care of it. But the PCM can only pull so much timing (is it 6 degrees?) and then can do no more.
Because your symptom is knocking at higher RPMs then the most likely culprit is oil contamination. One of the previous replies recommended a top engine cleaning and somehow stopping the PCV from sucking in oil. That's what you need to focus on. It's hard to say at this point if the oil being sucked in is causing the knock, or if there's been a bad buildup of carbon from previously consumed oil.
I'd start with the top engine cleaning which is super simple. Buy the can from a GM dealership and follow the directions.