Nock Sensor on LS3..!! Need help Please.!!
 

Yesterday I was trying to tune my car with HP Tuner but the weird thing is that with stock tune I have knock 3 to 6 from 4100to 6000 RPM..!! and the timing was 21 degree.

We have changed the knock sensitivity to 260 and I still have the same thing. Can I go lower than 260? I think it was false knock coz I did not hear any knock from the engine neither see any smoke coming from the exhaust.

We also could not change the cutoff limit from 6200 to 6600..!!

Mods that I have: ARH LTs 1 7/8, Borla axel back, Airaid CAI and Eibach lowering spring.

Thanks.

First. What fuel are your using? 91 or 93?

LS3's can knock on 91 from the factory. We never touch the knock retard settings in any tune. They are there for good reason.

Also, the LS3 RPM limiter is 6600 from the factory.

Be careful, programming software that gives full access is powerful and causing engine damage is easily done if you are not careful.

I have been told that we can go up to 260..!! I will try to do another run with 93 and see the result.

P.S. would the headers cause this knock? it could be touching underneath the car and that is causing the knock?

Yes an exhaust contact can easily cause a false knock. Should be no reason to mess with knock sensing or the rev limit. Anything less than 93 can also cause real knock. You won't be able to hear it. The computer senses it way faster than a human ear can pick it up.

It use to be a few years back, you could hear a burst of detonation - then the computer would pull the timing and eliminate it. These latest gen of computers though are so fast, they pick up knock in a split second and dump the timing to eliminate it before you even here the slightest bit.

I'd tinker with 93 from a different station, and some octane booster, and eliminate all exhaust contacts....leave the knock sensing alone, and then see if it is still pulling the timing. I bet it won't be.

May also help to put some miles on the CAI and headers so it self adjusts as much as possible. I've seen where putting a CAI in, during those first couple of drives, the car was showing quite a bit of knock activity. Then after some miles of driving all was back to normal.

Yesterday I added some octane booster and did a test, there was not any knock above 1 which is good but the timing was 25 all the way up to 6200 rpm

So, is 25 degree ok for my setup? or can I go higher 28-30?

Thanks,

Timing should not be a set number across the board.

I find the best power running 22-24º around peak torque, and ramping up to 25-27º at peak horsepower on Gen IV engines. After peak torque, it's good practice to drop off a degree or so by redline. Your cylinder air mass and operating conditions change at different RPM... you shouldn't just run the same timing across the board and call it good enough.

Thanks for the info, I will try to play around and see how it goes.

unless you are a well seasoned tuner, I would highly suggest that you don't "play" with any settings. listen to Kirk on this one, you can damage your engine quite easily...

If you leave knock settings alone, it's actually pretty hard to blow up an engine.

I notice a difference with this. I usually fill up at Chevron but the last tank I had to fill up a a Circle K, and about a 1/4 tank into it, I noticed it seemed to run a bit rougher than it does with Chevron gas.

That's all well and good, unless you live somewhere where there is no 93...such as Utah. Highest octane gas you can buy is 91.

Now, the engineers claim it's due to our altitude, the 91 is equivalent to 93....is it? Who knows, but there is no such thing as 93 octane gas in Utah.

I wouldn't decrease the sensitivity of the knock sensors but you can make them less intrusive by increasing the decay rate and reducing the attack.

Another thing I wouldn't do is try to tune the spark on the street with the knock sensors. . .

Also keep in mind that from the factory these cars are over-sparked around .2g/cyl and below in the high octane table.

Wow, I wish I knew what you guys were talking about :(

Wouls anyone mind giving me quick lesson?