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Help with V3 showing feedback knock


Richard Nixon
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Hey all,

Some advice needed please. When going up a somewhat moderate incline in 5th gear around 2300-2500 rpm the feedback knock gauge on my accesport registers up to -9.00 at times. Monitoring it shows this only happening in 5th gear which seems odd as this is not a steep hill, but merely small inclines on 94 in minneapolis if anyone is familiar. I have done quite a bit of research and it seems like as long as the DAM registers at 1 which is constantly is I should be ok? Also, fine knock learn is showing -1.40 max, usually less than -1.00 to 0. I don't think downshifting should be neccessary this many times over on the highway, though when I see the knock registering and down shift it does egual out to 0.00 almost instantly. Just looking for a little reassurance from anyone who has seen this before. Thanks in advance for any help. I did add a couple logs incase anyone is willing to help take a look.

 

09 Legacy gt 5mt

Cobb stage 1 91

Filling up with 92 from costco

 

Highlited lines 75-179 this is on somewhat hilliy WI roads where knock registered around 2400 rpm up the incline, short drive

 

https://docs.google.com/spreadsheets/d/1KMmAkIpaL4BJWNeX9kj1lpUw0_9XPqEcfiRAklpUnoo/edit?usp=sharing

 

Below is an hour drive to work with the conerning area around line 9811, all highway

 

https://docs.google.com/spreadsheets/d/1Z903kDpiIG3SaATIGoa8GNXZBXte9iiTblMFMJ5xSxY/edit?usp=sharing

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  • 1 month later...
You have nothing to worry about. You are logging a parameter you do not understand. Stop downshifting. If IAM/DAM is 1 and flkc is less than 2.5 carry on.

 

Heres one for you guys.. im recieving a sensed knock anytime i put a load on the vehicle while in neutral/parked e-brake up (2005 GT 5MT) i.e depressing the brakes, turning on my headlights, or even dropping the e-brake lever. Please note this is after a cold start, to op temp warm up before readying the car to move. Once op temp hits ill USUALLY recieve a knock sense after i turn my headlights on. Or with the ebrake still up ill depress the brakes and a knock is sensed also/again.

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Ok then leading to my next question.. how hard does any sort of striking force need to be for a knock to BE sensed.. i have like 2 brackets not attached to anything that hold wires(the brackets are metal) but i cant imagine these brackets have enough “swing” room to make a hard enough impact against the motor block to sense a knock ...
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You would be surprised. The knock sensor is just a microphone bolted to the block over cylinder #4. If the sensor is orientated in a direction other than 10oclock it will read incorrectly If it is over-torqued, it will read in correctly. If it is under-torqued, it will read incorrectly. I have personally had a set of Perrin spherical bearing front end links that were wearing out and those caused enough chatter for the knock sensor to pick up the noise and register false knock.

 

 

 

The knock sensor is finicky and very LOW tech. The ECM takes every noise heard (feed back knock) and then checks against the crank and cam sensors. If the crank and any cam is within +/- 15deg of top dead center the ecm considers this to be a firing condition. Firing condition and noise is knock. No firing condition and noise is just noise. Fine Learning Knock Correction is the ecms learning of what it determined to be true knock in the same rpm and load range. You see the amount of timing pulled to reduce/eliminate the knock.

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