What gives knock sensors

[Bartly]

Just like everyone responded so far it's centri cars, and Lund jr said the same thing. My personal theory is it's blower gearbox noise, and the belt buzzing. Since they're hard bolted to the motor it gets picked up because the knock sensors are so damn sensitive.

Thanks for sharing your thoughts.

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[JPSTANG]

Just like everyone responded so far it's centri cars, and Lund jr said the same thing. My personal theory is it's blower gearbox noise, and the belt buzzing. Since they're hard bolted to the motor it gets picked up because the knock sensors are so damn sensitive.

I see your point and believe this to be some what true, but why do some of us only have it in certain gears? Any other gear in my car it will pull like a freight train as soon as you shift to 4th and stab it, knock. You would think it would be the same through the entire RPM range for all gears if it was just the head unit and belt. Starting to think its the transmissions rattling in certain gears...

 

[ahl395]

Yeah, I’ve lost count who’s many times I’ve crawled around my car/engine looking for anything rubbing on the engine or any hard parts mounted to the block. Seems if something was rubbing or vibrating it would occur just as much whether I stabbed the gas peddle or eased into WOT. But, I can see an impulse triggering it so maybe stabbing the gas peddle would make it show up?

Stabbing the pedal could make the motor torque more than easing into the throttle maybe?

Somewhere I just found false knock was the plate between the trans and motor, if your auto check there.

 

[watisthis]

Have the same problem, as well as, just cruising in 6th around 2500 rpms just randomly see spikes of small knock. Figure I only see these things happen when I hit bumps, aggressively torque the motor, or sitting in 6th. Chalked it up to false knock, hopefully be going to e85 soon anyhow.

 

[Bartly]

Just like everyone responded so far it's centri cars, and Lund jr said the same thing. My personal theory is it's blower gearbox noise, and the belt buzzing. Since they're hard bolted to the motor it gets picked up because the knock sensors are so damn sensitive.

So I was thinking about this a bit. If it is related to having a centri type blower it would actually be false knock because it’s noise coming from the head unit vs the combustion chamber. You would think all the E85 guys with centri would be seeing it just as often as well, maybe they just don’t bring it up?
Also superchargers like Whipple, Edelbrock, TVS etc are also hard bolted to the engine, have gear boxes and a belt that could have the same type of noise. Just spitballing, no matter either way, just thoughts I had.

 

[Jay-rod427]

So I was thinking about this a bit. If it is related to having a centri type blower it would actually be false knock because it’s noise coming from the head unit vs the combustion chamber. You would think all the E85 guys with centri would be seeing it just as often as well, maybe they just don’t bring it up?
Also superchargers like Whipple, Edelbrock, TVS etc are also hard bolted to the engine, have gear boxes and a belt that could have the same type of noise. Just spitballing, no matter either way, just thoughts I had.

Yes it's false knock. And mine was on E85 from initial install and was doing it until desensitized. Whipple's doing the same thing was mentioned above. Could be the crank transmitting belt vibes to the block and/or the headunit/manifolds. Any kind of blower it appears they are seeing noise ford never intended.

 

[Bartly]

Yes it's false knock. And mine was on E85 from initial install and was doing it until desensitized. Whipple's doing the same thing was mentioned above. Could be the crank transmitting belt vibes to the block and/or the headunit/manifolds. Any kind of blower it appears they are seeing noise ford never intended.

Sorry I missed the part about you being on E85. Well that settles that, thanks again for the info.

 

[ahl395]

So I was thinking about this a bit. If it is related to having a centri type blower it would actually be false knock because it’s noise coming from the head unit vs the combustion chamber. You would think all the E85 guys with centri would be seeing it just as often as well, maybe they just don’t bring it up?
Also superchargers like Whipple, Edelbrock, TVS etc are also hard bolted to the engine, have gear boxes and a belt that could have the same type of noise. Just spitballing, no matter either way, just thoughts I had.

Whipple/PD guys have false knock issues too, but it does seem more common on centri cars. I was told this is often because of the intake piping routing where the PDs don't have this. On Prochargers especially look at the intake pipe running next to the AC line that you're supposed to bend out of the way. Mine was making alot of contact there.

 

[Bartly]

Whipple/PD guys have false knock issues too, but it does seem more common on centri cars. I was told this is often because of the intake piping routing where the PDs don't have this. On Prochargers especially look at the intake pipe running next to the AC line that you're supposed to bend out of the way. Mine was making alot of contact there.

Yes I can relate on that AC line area and the metal tube. Pretty tight fit area. On that note I always kind of thought that false knock mostly related to metal on metal to the engine. The Procharger intake piping is somewhat isolated from the engine hard parts either by the silicone hose at the throttle body or the rubber hoses at the head unit. So at either end there is either a rubber or silicone connection. Just something I had dreamed up in my head on why the AC lines and the metal tube shouldn’t cause false knock. Does that make sense?

 

[ahl395]

Yes I can relate on that AC line area and the metal tube. Pretty tight fit area. On that note I always kind of thought that false knock mostly related to metal on metal to the engine. The Procharger intake piping is somewhat isolated from the engine hard parts either by the silicone hose at the throttle body or the rubber hoses at the head unit. So at either end there is either a rubber or silicone connection. Just something I had dreamed up in my head on why the AC lines and the metal tube shouldn’t cause false knock. Does that make sense?

True. The line does go to the AC compressor though which is mounted to the block. Not sure if theres a rubber hose in between or if its a straight metal line. Also not sure if the knock sensors can pick up noise from things tapping on the chassis or not but I'd expect it to have to be alot worse for that to occur.

 

[Bartly]

True. The line does go to the AC compressor though which is mounted to the block. Not sure if theres a rubber hose in between or if its a straight metal line. Also not sure if the knock sensors can pick up noise from things tapping on the chassis or not but I'd expect it to have to be alot worse for that to occur.

Lol, your right I spaced that the AC line goes to the compressor, woops I hadn’t thought of that.

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