DubbyZ28Camaro

Okay, here is the deal...last year I was trapping at about 105-106 in the quarter mile. I just went to the track last night and I am trapping at 102-103 on slicks and 104 on DR's. I only ran a 13.3 and was expecting to hit a 12.9X. I took the car down to the shop today and I was getting a consistent 2-4 degrees of knock retard at wide open throttle.

Is this normal behavior???

We were just talking about this last week in school and the GM cars are designed to have as much spark advance as possible, so much that they are always on the verge of detonation and it is done to squeeze the optimum amount of performance from the vehicle. Is 2-4 abnormal or is this just the nature of the beast...where am I losing MPH from?? Also, the last time I checked it out I could have swore that I was only getting about 1 degree of KR every so often, not consistenly. My A/F was also right at 14.7:1, I did notice that the LT fuel trim data was at -15% on both banks, BUT they weren't changing at all, maybe because I have the rear 02's disabled or what???

Anyways, since I have trapped at 105-106 last year, I have gone through an optispark (changed it), added a Meziere electric H20 pump, and added a 1LE driveshaft...what is my problem or where should I look???

Thanks

Josh-'04 GTO

No way! When the PCM pulls timing out it kills power.

First, since I see you have headers in your sig, I would buy an LT4 knock module and see if that helps. You could be experiencing false knock. That should help cure it if that is the case.

If you are still having this problem, I would run down the gas tank very low and put in some 100 octane unleaded and see if you are still seeing knock retard.

DubbyZ28Camaro

I've got the LT4KM...but at WOT there will almost ALWAYS be some knock retard because these cars are always on the verge of detonation. My question was referring to if 4 degrees of knock retard is normal, because I don't know what is normal as far as pulling timing is when it is about to detonate.

I am trying the 100 octane trick tomorrow...gas tank is nearly empty, but the problem is that I need a scan tool to monitor KR because I can't feel the power loss, I can only see it in my timeslips.

Anybody else??

Buttercup

Uh, no there shouldn't be knock retard at all, even at WOT. Best ignition advance should yield maximum cylinder pressure, but if the fueling is correct this is usually a few degrees before incurring any knock.

You said your AFR is 14.7. I'm assuming this is at WOT? How was this measured (with a true wideband O2)? If this is true you are running too lean. The rear O2's have nothing to do with fuel trims. If everything is running correctly I prefer to tune my car so that it runs just slightly rich fuel trims at cruise to insure no fuel corrections at WOT.

I would make the necessary changes so that you have proper fuel trims at cruise. Definitely run some higher octane fuel to rule out false knock.

johnpsz

Ok I don't know if this will help or not but, I was consistantly getting knock retard pulled, about 4-5 deg. above 4000 RPM's and sometimes more. I fixed it but don't really know how what I did fixed it, and noone really could help me with finding out how it really worked. Injuneer did chime in with some good info for me though.


http://web.camaross.com/forums/showt...threadid=98685
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http://www.fbodycentral.com/phpBB2/v...030&highlight=


Like I said before I don't know if it will help you or not!

DubbyZ28Camaro

14.7:1 was at idle. I used a GM scanner (Tech 2) to monitor this. At WOT, the O2 readings were around 950mV and 942mV...

I appreciate the help on this guys...I didn't have time to try the race gas trick, but I will either tomorrow or tuesday and get back to you...thanks for the help!!