Ok so I took off my exhaust as i had a few leaks so I could weld it and was tuning my car open dp. Got it almost perfect one 1 or 2 counts of knock at most and afr 11.5-11.8. Then I put my exhaust back on now its saying I have 2,4,8,10,10 conts of knock starting around 5500rpm, I let off when the cel started flashing. But wtf I had done 5 back to back pulls with the open dp and only 1-2 counts of knock, then put the exhaust back on and now ZI have knock. Afr was a little richer too, 11.5-11 and hit 10.9 when the ecu pulled 4deg timing where it says i have 10 counts. So is this phantom knock? I believe it is just want a second opinion.

 

Probably because the back pressure changed causing different flow variations at a different RPM range? Or...the sensor is picking up harmonics from the exhaust pipe under the engine. How much clearance does your exhaust have under the oilpan?

 

you increased the backpressure of your exhaust system and youre wondering why you have knock now?

go retune your car, its not phantom knock

 

J.O.T. :Not that much maybe a inch or so, maybe less.



Just: The timing where the knock is occuring never changed from before I took the exhaust off, and there was only 1-2counts then. Actualy I believe I pulled a degree or two from before.

 

First one is open Dp second one is full exhaust. It was 12 counts not 10.