Knock retard problems need some help.
Thread Starter
Teching In
Joined: Jan 2007
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Knock retard problems need some help. Howdy I need some guru knowledge, I have a 99 Z28 m6 with 5.3l stage 2.5 heads, a tsp 233/239 cam, long tubes basic other bolt ons. I had the car tuned by a local shop after which it ran ok but very rich after about 5000 miles the car started to hesitate under acceleration. I picked out hptuners and a lc-1 and started logging, after correcting some of the pig rich afr the car is still pulling timing when the MAP kpa is above 75. I will attach the log file of a quick wot run, this is after taking timing out of the spark table. Changes to PE and VE tables don't seem to have much effect on the knock retard that I am experiencing, and pulling timing out of the spark tables seems to make the car run worse and worse. Any suggestions where to go from here would be great, thanks.
Do you know what your static and dynamic compression ratio is? 5.3 heads will raise the compression. Were they milled? Do you know what the chamber sizes are? What octane fuel are you using. What kind of intake setup are you running. Reason I ask about the intake is your IATs are kind of high and your MAP is only at 92~93 KPA at WOT indicating maybe a restriction or if you are at a high elevation, that could explain it. Try adding some 100 octane unleaded and see if it goes away. That's the best way to tell if it is real or false knock. You may just need higher octane gas for your setup.
Thread Starter
Teching In
Joined: Jan 2007
Posts: 18
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the head are not milled but the 5.3L does bump up compression to 10.7 I believe. I am in phoenix 1000ft above sea level I believe, I have an ls6 intake and a lid stock TB and stock maf. I will try the higher octane thanks for the suggestion. If it is a real knock that appeared over time what is the cause and how is it corrected? The car used to run fine on 91.
