crf538

iTrader: (3)

im getting knock retard up to 4 degrees while on boost. afr is 10.8-11.5 and IAT is 60 degrees. im curently only on 4 pounds of boost and i have pulled timing all the way down to 6 degrees trying to avoid it. i set my meth to come in earlier to see if it would help and it didnt change a thing. ive looked the car over and havent found anything that might be hitting to cause the problem. is it a bad idea to turn down knock sensitivity ? do many people have to do this?
the car seems to fall on its face a little when it starts making boost and miss, i would imagine this has to do with the 6 degrees of timing but i am scared to turn it up till i figure out whats causing the knock

thanks

ForcedInduction

iTrader: (2)

sounds like "phantom knock" the knock sensor(s) are either bad or have water intrusion(assuming a Gen III) or the knock sensors are picking up some kind of vibration or noise. More info on what this motor is/in?

I had a max of 8* of KR being pulled from my truck on the dyno from 4500rpm+. All caused by a bad u joint and pinion flange.

Louis

iTrader: (7)

What year car? Does it do it cold, and hot? Throw in some 100 octane and if it is still there, mostlikely false knock

crf538

iTrader: (3)

its a 99 t/a
home built tc 76 kit
air to water IC
stock long block with springs and pushrods
ls6 intake
60 lb mototrons
i havent really seen any trends as far as when it does it, it will just spike up for a couple of cells and then be gone.

assuming it is false knock how should i do away with it withought doing away with the real thing?

i havent heard it spark knock once

WS6HUMMER

iTrader: (19)

I dont know alot about tuning FI right now, I just got my car running but I have heard if the timing is too low/retarded it will break up in the higher RPMs, I'm sure when it breaks up the knock sensors would pick it up. I have stupid low timing for my base tune and I'm running 9-11* in the higher RPM range. Either that or it could be burst knock.


BTW I didi have alot of trouble with false knock on a 99 silverado I tuned, I went crazy trying to figure out if it was real or not before I doubled the attack and cut the gain in half. I just dindnt want to assume it was false before I desensatized the knock sensors.

Slowhawk

iTrader: (12)

Sounds like false knock which is very common on alot of FI cars. It's up to you if you make them less sensative or even shut them off.

On my personal Vette with a stock motor and 14lbs I shut off the KR sensors because sometimes it would KR like crazy for no reason.Drove/raced the car for a long time like that. My Avalanche truck with a stock 5.3 and turbo also had the KR sensors shut off and was like that for 35k miles,even while towing and it still has the same motor today.Both vehicles tuned OLSD

The point is- KR sensors are over rated IF you know your tuning and can sence a problem with the car if something is wrong.

crf538

iTrader: (3)

i zeroed out the burst knock once to see if that was it, still happned.
once i backed it off to 6 degrees around the torque peak and it took out 4 still.

thanks for the input guys, i might try to make it a little less sensitive tommorrow, i dont see how there is any way im getting real knock at 4 psi with a 10.8:1 afr and meth.

anyone know how much i should cut it back so that it still will catch real knock or have a better idea?

BuffJoeyD

iTrader: (2)

Had a turbo car of similar setup have false knock forever - Only way to get rid of it was to change the PCM - same tune, diff pcm no knock. Changed back, car knocks again.

Make sure its false- then figure out how to tune it accordingly.

Louis

iTrader: (7)

can you take a screen shot of the KR on the logger? I recently had a car do it when I blipped the throttle at idle. Instant 8* KR

crf538

iTrader: (3)

yeah ill have to do it tomorrow though, i saved the log to my thumb drive and then left the thumb drive with the car 45 min away

WS6HUMMER

iTrader: (19)

Thats burst knock right? Thats a different PID right?

Louis

iTrader: (7)

Yes and no, Ive fought every KR table, every AFR and every advance like the OP. Its not uncommon to desensitize or completely disable KR like slowhawk said. Rick at Synergy confirmed my thoughts, as did a few others.

There is a lot of stuff moved, changed, close quarters to and in with a turbo kit. 5 pounds of trash in a 1 pound bag. Phantom knock is bound to happen. Hell, it happened with the factory Y pipes banging on the floor board!