I've been having a problem with detonation over 4,000 RPM at wide-open-throttle. But, when I hook up to AutoTap and record my runs, there's nothing showing up in the logs that would indicate detonation. At the most, I get 4 degrees or less of knock retard, and that shouldn't be enough to create audible pinging, which I can hear quite loudly over the motor.

So today, I hooked up with Brent and John (Pres and Vice-Pres of the West TN F-Body Association) and we logged a few runs. John is the AutoTap guru. We found a nice little road behind the Best Buy on Winchester where I could run full-throttle into 3rd gear and we started making passes. We noticed a few interesting things:

(A) When the car has been sitting and had a chance for the intake to cool down, the pinging isn't there at first.

(B) After a hard run, the pinging starts to be heard

(C) The more runs I make, the worse the pinging is heard, even though knock retard doesn't increase very much.

So ... it looks like it's a heat thing.

We went over the logs and the O2 sensors were close to being perfect ... if anything, they indicated that the car was running a shade rich, which doesn't seem to go along with the detonation. Detonation is usually caused by running lean.

So, for a test, we removed the Hypertech programming and I let the car idle for a few minutes, then drove slowly around to our designated "strip" and then opened up for a few runs. Again, there was no pinging on the first run. 2nd and 3rd runs had audible detonation, but not as bad as the runs with the Hypertech tuning installed.

When we went over the logs from those runs, we saw that knock retard was 2 degrees or less whenever it kicked in. But the kicker was the readings from the O2 sensors. They were PERFECT! Dead on .... exactly where they are supposed to be.

So ... here's the problem. As the motor heats up, I can hear pinging at WOT over 4,500 RPM, but when looking at the AutoTap logs, there is not enough knock retard to indicate any pinging that would be audible. What's up with that? Where is the detonation coming from?

Here are the mods on the car as tested today:

MTI air lid, Holley PowerShot filter, 160* thermostat, Flowmaster 80 muffler, Throttle Body coolant bypass, disabled skip-shift. I am running the stock MAF ends complete with the screen. Hypertech programming was installed for the first set of runs and removed for the second.

Here's what I plan to do for now: First, I reset the computer when I got home. I want to let it learn again without the Hypertech programming. Next, I want to mix some Toluene in the gas to increase my octane points. That should let me know if it's an octane problem and if I should look for a new source for gasoline. After that, I will add "Water Wetter" to the coolant to attempt to cool my motor down a little more.

Anyone else have some suggestions?

Roger

 

I've been having the EXACT same problem all summer long! I 1st noticed it in June. At the time the only intake mods I had were the Whisper Lid and Granatelli MAF. I thought it was the Granatelli MAF, so I took it off, but it still detonated. Here's what I've done:

-Went back to stock lid and stock MAF: Worked for the most part, but I've been running the Whisper Lid and Granatelli MAF since my '98 was new without any problems, so going back to stock was not an option I wanted to live with.

-Went back to the Whisper Lid, but kept the stock MAF.

-Used GM's Top Engine Cleaner.

I was still detonating after all that, so I decided to try something else. A member over at www.ls1.com said to check and see how much oil was getting into my intake. I checked the back of the throttle body and it was covered in oil. Apparently, the stock PCV valves have an "issue" with letting too much oil into the intake and GM has released a "revised" PCV valve to address this issue. I order the new PCV valve, part # 12572717, and installed it and also used another can of GM's Top Engine Cleaner. That seems to have stopped my audible pinging for the most part. While I was at it, I also ordered and installed an SLP 160 degree thermostat as well as the SLP fan switch. Yesterday, I installed new Bosch Platinum spark plugs. I was sure with all of the work I've done, I cured my problem because I no longer have an audible detonation. I then AutoTapped again yesterday and had the same results that you got...I get as much as 3.9 degrees of KR at WOT.

Just as you noticed, back when I 1st started detonating at the beginning of the summer, I could actually hear it, and all AutoTap had to say was 3.9 degree's of KR then too. All I can say for sure now is that I can't hear the detonation any longer and the car pulls A LOT smoother now after all I've done, but just like you, I'm baffled why I'm still getting KR.

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Black 1998 Camaro Z28 6-Speed: Whisper Lid, GMS MAF, SS Exhaust, BMR STB, SLP Shifter & ****, SLP 160 Degree Thermostat & Fan Switch, Baer EradiSpeed Rotors, 17x9 Firehawk Rims, 20% Tint, GTS Covers, MB Quart QM218.03CX Component Speakers, Kicker F6.5C Mid-Bass Speakers, Eclipse 8710.4 10" Sub In JL Audio Vantage Stealthbox, Orion Cobalt CS200.4 Amp, Orion Cobalt CS150.2 Amp.

-Best 1/4 Mile: 13.4 @ 106.0
-RWHP: 304.2 TQ: 314.3

Featured In:
-GM High-Tech Performance Magazine, 11/00 issue, "Street Heat" (Pg. 74)
-Chevy High Performance, 11/00 issue, "Chevy Showplace" (Pg. 126)

View:
www.banddirector.cz28.com

Previous F-Body: Black '96 Camaro 3.8 V6, 5 speed: RKSport/DynoMax Dual Exhaust, K&N Filtercharger, 16x8 5-Star Firebird Rims, 35% Tint, GTS Covers.