Knock/Detonation with SCT Tune?

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01-22-2010, 03:16 PM

#21

ski

4th Gear Member

Join Date: Mar 2006

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Posts: 1,470

Quote:

Originally Posted by replica

Ok, just got back from some "testing." I basically drove on empty exit ramp roads in second gear and went WOT from about 30 MPH until about 4,500 rpm. The suspected "knock" is quite fussy around 4,000 RPM. I could repeat it. If I wasn't at WOT, it wouldn't happen. Then I switched to the 87 octane tune and I could not create the "knock" with the same testing method. Then I went to the 91 octane tune and the knock doesn't really seem present either.

Kind of a bummer I can't use my 93 octane tune. It's disappointing that the 93 tune is so temperamental. The sound I was hearing that I'm calling knock may actually have not been knock. Without some data logging or something I can't stop putting quotes around the words "knock" until I know for sure.

I really don't think I have significant carbon build up with only 35,000 miles. I also have the stock intake so a loose CAI isn't the issue.

Don't give up on the 93 tune just yet. If your car is still using the same tank of gas, then no noise with the 87 and 91 tunes does not eliminate any of the original possible causes(too much lower octane gas remaining in the tank when you initially filled up with 93, a bad load of 93, or carbon build).
FWIW, my 05 GT was pinging with only 17K miles on the clock, and a can of Seafoam cleared it up after only 200 miles. These engines are notorious for building up carbon, especially under the right conditions, e.g., using poor quality gas from Mom & Pop stations, doing a lot of stop & go driving, doing a lot of "cold engine" operation by not driving with the engine at normal operating temperature for at least 15-20 minutes, etc.