Originally Posted by
AndyGrove
Hello. I would greatly appreciate some insight and experience. I have a 68 C10 w/ a stock internal LQ4 (minus Tooley double valve springs), solid motor mounts, rubber trans mount, 2002 Silverado ECU, GT45 Turbo, 4L80E w/ stock TC, 3.08 gears, and 295/55 MT tire, running 91 octane. I have read multiple forum posts on this site and others regarding knock sensitivity, but am still confused, so decided to make a forum post to see if others had already been through and had experience w/ my issue.
I recently got my truck running a couple months ago and have slowly but surely been tuning it. My VE was way rich to begin w/, so it took me a bit to get that dialed in. As of a couple weeks ago, I had it tuned to 5 psi w/ good results (power and data) and currently am at 8 psi. Everything w/ the tune has looked great, except for periodic Knock Retard when at WOT. This is NOT Burst Knock, as I have that disabled. In looking back at all of my logs, the knock has occurred all over the timing map, but of most recently has been occurring at around 3500 RPM, 4 lbs boost, at .91 g cyl airmass, wherein I am commanding 14 deg of timing, which I viewed as pretty conservative. I am not "hearing" any knock. I have only a downpipe and one exhaust pipe to deal w/ and it is secured well and not interfering w/ the frame. Today I tried to reduced timing by 5 deg in the area of the map that has recently shown issues, and I still saw Knock Retard (this was at 11 deg of timing at 3400 rpm and 4 lbs of boost). I also disabled the Tip In Knock by setting my min threshold to 10000 RPM, and again still saw knock. I have NOT changed any of the knock sensor setting except for the recover rate, wherin I multiplied the stock values by 3, and knock recovery is now much quicker. I do not have easy access to high ocatane fuel / race gas, but Im guessing that is probably my next test to try to determine if the knock is fake or not.
I visited w/ a friend who has turboed a 1/2 dozen or more LS engines very successfully, and he mentioned that he doesnt install Knock Sensors anymore, and that I would be chasing my tail if trying to utilize them, as he has experienced the same issues as I. I dont have access to E85, cant afford a dyno, and dont want to hurt the motor, so I initially was very intent on trying to utilize the knock sensor for tuning, when I get to a point of fine tuning the timing.
Sorry to ramble... just wanted to provide all the pertinent details. I would like to know if there are any others out there w/ a similar setup as mine, w/ a LQ4 w/ stock Knock Sensor sensitivity settings that went through similar issues as I? Given the information provided, do you feel it is fake knock? If it is fake knock, Im guessing Im either going to have to change the "Knock Sensor Level vs. RPM vs Cyl" table or the "Knock Sensor Global Gain vs RPM vs MAP" table. Does anyone have experience which table/s to change and by how much?
I appreciate your taking the time to read of my issue, and thank you in advance for any advice you could give.
THANKS
ANDY