Help with KR
06-12-2006, 01:47 PM
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Help with KR Last year I installed a set of AFR 205s, a Comp 220/224 cam on XER lobes, and Yella Terra rockers. Ever since then I have had quite a bit of KR (between 9 and 10 degrees). The KR happens at 4200+ rpm mostly at high airflow (WOT). I thought that the SC that I had on the car at the time was causing it. It still does that same amount of knock in the same place now that I have removed the SC.
I can't imagine that it has anything to do with the heads or the cam. I suspect that it may be being induced by the rockers.
I just put some Sunoco 104 octane fuel in the car and it made no difference. Same knock same place. I have tried different timing maps and it made no difference. I have tried longer push rods for a little better lifter preload. No difference. It does it with the MAF connected and when in speed density mode. I run a catch can and have no oil in the intake system at all.
The car is a 2002 Corvette. Does anyone have any ideas? I want to get this sorted out so that I can install a SC.
I can't imagine that it has anything to do with the heads or the cam. I suspect that it may be being induced by the rockers.
I just put some Sunoco 104 octane fuel in the car and it made no difference. Same knock same place. I have tried different timing maps and it made no difference. I have tried longer push rods for a little better lifter preload. No difference. It does it with the MAF connected and when in speed density mode. I run a catch can and have no oil in the intake system at all.
The car is a 2002 Corvette. Does anyone have any ideas? I want to get this sorted out so that I can install a SC.
06-12-2006, 02:22 PM
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IF this is the same as the kr on the grand prix then it is false kr. False kr is ALOT of fun to find...NOT
It can be anything from bad motor mounts, to your exhaust heat shield being loose. At this point it doesn't sound like a chipped piston at all but most likely false kr.
It can be anything from bad motor mounts, to your exhaust heat shield being loose. At this point it doesn't sound like a chipped piston at all but most likely false kr.
06-12-2006, 07:16 PM
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I am certain that it is false knock. I am just not 100% sure what is causing it.
I have also changed out the entire exhaust system since I first noticed the knock. No difference there either.
I have also changed out the entire exhaust system since I first noticed the knock. No difference there either.
06-12-2006, 07:37 PM
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This is a common issue with 2002. Mine had it and a friend's car had it bad as well, both 2002's. Fortunately, we used the same tuner who also had a 2002 and he knew how to take care of it. Take a look at my stock curve below, before the header installation. Is that what yours looks like? Also note the final tuned curve, run #20, thats how long it took to figure it out!!!!
06-12-2006, 08:00 PM
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That is what my curve looked like with my original Vortech on it. It had the same dip at 4200/4300.
Do you know what the fix is?
I used my stock 02 timing map as a base and could not make any headway. I also tried a Z06 timing map and it did not change anything. I am convinced now that I ran the car on 104 octane that it is false knock.
Thanks.
Do you know what the fix is?
I used my stock 02 timing map as a base and could not make any headway. I also tried a Z06 timing map and it did not change anything. I am convinced now that I ran the car on 104 octane that it is false knock.
Thanks.
