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Feedback Knock

8K views 8 replies 4 participants last post by  Jackstand Johnny 
#1 ·
So I finally found my balls an drove the car to the gas station an back. On the trip everything sounded/felt ok for the most part. The new Megan racing motor mounts definitely sent more vibrations throughout the car. The lightweight flywheel is very easy to adjust to.

So the issue I came into is randomly for the split second I touch the gas or quickly let off the gas I saw feedback knock. But then it would instantly go away. I have read that with lightweight flywheels and crank pulleys they have a tendency to show false knock. Pulley's due to not having the dampening rubber built into the OEM pulley. And with the motor mounts being stiffer I would only think that all of this would be worse when combined.

Does anyone have any input from experience? Or have any ideas? My tuner thinks that's it is most likely a false reading. But I just want to get the topic going in case someone else any possible input.

Thanks!
 
#2 ·
what engine management are you running? are you able to calibrate knock threshold?

false readings can come from all over the place, but if you able to single out the exact frequency range of your knock then you know you'll only get knock warnings when you have knock.

if this was not done properly (or at all) and your frequency range it too large then the sensor will pick up other sounds that are not knock and read them as knock giving you false knock readings. which yes could be the pulleys or flywheel.

i have read reports of a driveshaft every so slightly hitting the exhaust as is spins. during heavy accel when the exhast vibrates, the spinning driveshaft would kiss the flange or a bolt sticking out (cant remember exactly) cause a fals knock reading.

also there was a dude i think on these forums who was getting false knock from a bolt or washer he had dropped and neglected on top of the engine block under the intake manifold. i think it worked its way under the coolant passage. either way it was also causing false knock.
 
#3 ·
Thanks titter. I am tuned with the Cobb AP an my tune is locked by the tuner. I had a loose bolt create false knock way back also but I made sure this time I put 1 bolt/nut on at a time. I wish the tune wasn't locked but I get why they do it. They don't want their hard work just given out to everyone.
 
#6 ·
Im sure you don't care about some of these parts but it was a quick copy an paste so I didn't have to think. Few more parts on her than whats listed

Grimmspeed EBCS
PTE 6262 turbo
1000cc injectors
Full exhaust
Tial EWG
Lightweight Crank and alternator pulley
PS and AC delete
Oil Catch Can
Outfront Motorsports V3 closed deck EJ205 case
Manley Turbo Tuff rods
Manley Extreme Platinum Pistons
Manley 79mm Lightweight Crank
King STDX bearings
Cometic Gasket set
11mm Oil Pump
STi Oil Pan
Killer B oil pick-up tube
STi dipstick
Gates Racing water Pump/timing kit
Lightweight XTD Flywheel
Stage 3 XTD Clutch
 
#7 ·
You mentioned these knock events happening wen you plip the throttle and quickly let off. Does it matter where your engine is revving or how fast youre going? I get knocks between 1700 and 2200 rpm but also u der that same throttle load like when Im cruising on the highway and going up a hill to maintain speed.

My soon to be tuner told me they came tune them out for the most part. This is probably the kbock threshold that the above poster mentioned. Have you talked to your tuner about this? It sounds like youve got a pretty rigid drivetrain and other parts like the crank pulley. If your knock threshold is setup for a wrx with stock much softer components then it would stand to reason that this is whats causing more k ock events. My knocks stay longer and slowly workback down to 0 for what its worth. This is also with a 2002 WRX but with ots stage 2 and 4eat auto trans. Sorry I cant be of more help.
 
#8 ·
Thanks Johnny. Yes I had been talking with my tuner but I also like to hear from the forum as someone else might have something random that help. It had been determined that it is a false knock. I and my tuner are hesitant to change the threshold because I don't want to take the chance we go to far and then when there is real knock it doesn't show. So I watch it like a hawk an know its habits now.
 
#9 ·
No problem at all. I know exactly how you feel and that advice put my mind at ease. Smart move man. I do the same thing. Also I should note that as things like modifications, climate, etc change, so can the knock patterns. I just this past week installed a cobb sf intake and airbox, post maf hose and a custom 3" catback and after the Vishnu method of resetting the ecu, Im noticing different trends. Im hoping MY tuner can mitigate some of this. Id be happy with my feedback knock and fine knock learning showing anything less than -1.0. Today my feedback knock jumped to -5.xx but Ive seen it hit -10.xx and my bugeye is still going.

Just imagine if you had an accessport for your body after a night of drinking or binge eating taco bell.
 
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