So I was going to work this morning and was trying to pass someone on the interstate and I punched it in 5th @75mph @ 4200rpms, and the car (via Accessport) started showing some crazy knock. I only was on it for a sec when I let off because of it but it peaked out at 12.7CA, AFRs were at mid 11s. This is not the first time this has happened, it has happened a hand full of times before. It would happen once or twice then not happen for a while then just pop up again.

All other gears are fine and WOT from 4th going to 5th it doesn't happen.

Any ideas? I think it maybe related to the ECU transitioning to the WOT at speed.

 

Could be your timing or it could be rolling into boost at a low rpm in a high gear. Although I would think 4200rpm would rule that out. Are you running a custom tune through your AP or a generic one?

 

Off the shelf (generic)

 

That's common though I've never really heard of a solution or reason why. It was common in my WRXs and the MS3. I was always told never to go WOT in the top gear at any RPM.

 

You can WOT in 5th after you hit redline in 4th.



Check common stuff like relay, FPR vacuum line....

 

lol yeah all that stuff has been checked. Even changed to a new set of spark plugs (OEM) didn't do anything.

 

Its not uncommon for the timing used in 3rd/4th that is knock-free to be an issue in 5th. Especially since boost can creep higher in 5th. Try to lower the timing in the problem area by 1* and see if its more consistent.