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Old 09-23-2016, 03:48 PM   #1
86Dreams
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What is this? An
injector laying contest?

Default Desensitizing the Knock sensor

Does anyone have experience 'tuning' the knock sensor for elevated levels of ambient noise? After all the modifications, I have ended up with -1 in fine knock learning in 2800-3600 RPM ranges despite adding fuel or pulling timing or both. I am 99.99999% certain it is from elevated levels of noise.Even going back to the stock tune (a version adjusted for maf wgdc and dam) the knock is present in the same places.

Using Accesstuner Race under the knock sensitivity tab, I am thinking I should potentially adjust 2 tables: "Knock threshold/filter final Limit" and "Knock Threshold weighting factor (RPM)".

But I am not 100% certain of this decision.
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Old 09-23-2016, 04:24 PM   #2
Shiftace420
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You are correct.

Increase the weighting factor in the corresponding RPM range a few percent.

Then you will need to adjust the final limit ceiling the same amount.

It only takes about 10% to quiet down a very noisy engine build. You only want to raise the threshold as much as needed. More and your risking unchecked detonation. I suggest starting with about 2-3% and trying it for a while before increasing any more.
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Old 09-23-2016, 05:44 PM   #3
86Dreams
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I had adjusted to about 7%. I scaled it back to about 3% now. will report back if it blowsup
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Old 09-23-2016, 10:08 PM   #4
Shiftace420
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Should be fine.

I did it a little different

At low loads, I adding a couple degrees of timing until I knew the knock is real and can be corrected by removing timing.

I then removed 5 degrees of timing from the point where I know it knocked.

From there added 1% at a time to the knock threshold tables until the false knock went away.

Probably not perfect but it worked for me.
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Old 09-26-2016, 10:27 AM   #5
86Dreams
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Thats a good sounding procedure Shiftface420. After the weekend I find that some of the knock returned, but i feel like a lot of it has quieted down. I might try tweaking timing again to see if I can get a little more efficiency. then after tweaking timing Ill try your procedure.

It still managed to pick up a knock at high load in one region so i think its still working correctly.

Last edited by 86Dreams; 09-26-2016 at 10:37 AM.
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Old 09-26-2016, 11:20 AM   #6
Shiftace420
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It can be a bit of trial and error for sure. I would not try to make it knock on purpose at high loads but if it does knock, you can kinda do the same procedure for knock at high loads.
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Old 09-26-2016, 05:46 PM   #7
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Quote:
Originally Posted by 86Dreams View Post
Does anyone have experience 'tuning' the knock sensor for elevated levels of ambient noise? After all the modifications, I have ended up with -1 in fine knock learning in 2800-3600 RPM ranges despite adding fuel or pulling timing or both. I am 99.99999% certain it is from elevated levels of noise.Even going back to the stock tune (a version adjusted for maf wgdc and dam) the knock is present in the same places.
In my experience the easiest way to figure out if knock is real or from engine noise is to just try running a tank of 100+ octane through

Run to near dry, then fill up half-way with straight 100+. Cheapest way - if you can do it yourself and really want to save that extra ~$30 - would be to drain your fuel lines and tank and all that and just run 4 or so gallons.

If you don't drain the tank and lines, drive until you've consumed ~1.5 or 2 gallons. From what I've seen that's usually the point where the engine is only burning high octane, but I'm sure this varies car to car.

Run on your most conservative timing map (if you don't have something like a break-in map, you can always pull a few degrees of global timing). From there, you should be able to tune out any knock that's truly due to engine noise. You should not see knock at all if you're running a map built for 91 or 93 on 100 octane with global timing pulled
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