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Old 02-11-2008, 12:12 PM   #1
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Default False Knock at what RPM?

I spent most of Saturday on the dyno and one of the hardest things to deal with was the false knocks showing up through the knocksense LED. It was really unnerving to see that blue light and stay into the throttle.

We had 2 widebands running...one in the header, one in the tailpipe. AFRs were in control. I had a set of det cans on while tuning, and no prevalent knock was present. But it was really hard to tell with all the blower noise.

The knocksense LED was lit up like a Christmas tree around 5k rpms. After analysing the datalog numerous times, we determined that it was just noise, be it valve train or blower.

I have a 2000 engine so I have solid lifters. Has anybody else running a 99-00 engine determined where engine noise prevails as knock?

I plan on inducing knock at a low rpm/kpa range and setting the sensitivity of the knocksense to the point where it just sees that knock. I don't know if that will clear out the false knock up top, but it's a starting point.

I like the idea of the knock LED, but if it becomes something that I see all the time, the warning aspect of it becomes worthless.

If the sensitivity adjustment doesn't work, I have thought of installing a window switch that basically turns off the knocksense at a given RPM.


Whatcha think?
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Old 02-11-2008, 12:23 PM   #2
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Have you not messed with the sensitivity adjustment at all? I found that if i adjusted it so that when i took the car to redline out of boost that it showed no knock it worked well. My timing is super conservative and i have low comp pistons though and I still see false knock one every blue moon when i actually have the unit turned on.
With the solid lifters we have to "shim" them to keep them in spec. It's possible tightening up that tollerance will remove some of that noise.
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Old 02-11-2008, 12:36 PM   #3
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I doubt that the valve train will make so much noise that it will be picked up as knock. Is it more present when the engine is cold and the clearence to the cams therefore larger?
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Old 02-11-2008, 12:41 PM   #4
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Yes, I have played with the sensitivity settings, just not too extensively. I will play with them this week.

I was just curious if there was a rpm point where valve noise was seen as knock. I have a feeling that the noise I was picking up was through the blower not the head. It was impossible to hear anything through the det cans once the blower started whining.
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Old 02-11-2008, 12:45 PM   #5
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Your are using the stock NB knock sensor right?
Are you running cold side or hot side? Might need to move the sensor from one side to the other.
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Old 02-11-2008, 01:59 PM   #6
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To tune the sensitivity just right, what i would do is fill up your tank with the highest octane gas you can find (like 104 if you can find it). then tune the sensitivity just so the light doesnt come on at all when driving the car. this way with the high octane, you know for sure you can't be knocking, and once you start driving with normal 93 (or 91?) and see the light come on, something may actually be wrong
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Old 02-11-2008, 02:37 PM   #7
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I have the blower coldside and the knock sensor in the stock location on the 2000 block (between 2 & 3). I am using the bosch knock sensor from DIY.

I may have to try putting the sensor on the hotside engine mount. I know I am getting blower noise as knock, but I hate to turn the sensitivity down too far and mask the knock as well as the blower noise.
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