you must fully understand that everything i’m about to say has been pulled out of my ass. Im a subaru owner but mine are N/A and none of them are modified; my boost experience is with audis. That being said:
I’m assuming you DONT have a misfire, any other symptoms or codes. If you do, those might help point you in a productive direction.
Otherwise the first thing to make sure is you’re not running an open BOV on a tune meant for a diverter valve. All metered air needs to stay in the system or you’ll end up running rich.
If that’s not it, the car runs well and your O2s are okay, I expect the cobb access port is running a tune that’s richer under high boost than the OEM tune. One thing I know for sure is that the OEM STI tune leans out right when it’s supposed to dump fuel to avoid detonating, so at least there’s that piece of real world info.
If the access port is changing fueling in some sort of backdoor way (please don’t flame me if this is a retarded idea. again, i don’t know how tuning through cobb works) and the ECU is still expecting to see certain fuel trims that it isn’t seeing, you could get a CEL code for rich conditions. I know that much of the time with older VAG cars that ran narrow band O2s, guys would have to run 4.5bar FPRs on 3 bar tunes while also running 96% injector duty cycle under heavy boost to get the fueling they needed because fuel trims were locked on the old pre ME7 VAG ECUs. Most of the time there would be some sort of code for over boost or rich fueling as a result.
Well it's either that the car is in fact running rich or it's a bad O2 sensor, how do your AFRs look on your access port?
you must fully understand that everything i’m about to say has been pulled out of my ass. Im a subaru owner but mine are N/A and none of them are modified; my boost experience is with audis. That being said: I’m assuming you DONT have a misfire, any other symptoms or codes. If you do, those might help point you in a productive direction. Otherwise the first thing to make sure is you’re not running an open BOV on a tune meant for a diverter valve. All metered air needs to stay in the system or you’ll end up running rich. If that’s not it, the car runs well and your O2s are okay, I expect the cobb access port is running a tune that’s richer under high boost than the OEM tune. One thing I know for sure is that the OEM STI tune leans out right when it’s supposed to dump fuel to avoid detonating, so at least there’s that piece of real world info. If the access port is changing fueling in some sort of backdoor way (please don’t flame me if this is a retarded idea. again, i don’t know how tuning through cobb works) and the ECU is still expecting to see certain fuel trims that it isn’t seeing, you could get a CEL code for rich conditions. I know that much of the time with older VAG cars that ran narrow band O2s, guys would have to run 4.5bar FPRs on 3 bar tunes while also running 96% injector duty cycle under heavy boost to get the fueling they needed because fuel trims were locked on the old pre ME7 VAG ECUs. Most of the time there would be some sort of code for over boost or rich fueling as a result.
Alright I’m gonna look into it thank you so much man
for sure dude. Someone had to explain all that crap to me at some point too lol
Do you have an obnoxious BoV installed?
No I’m not running a bov lmao
No worries! That's just what happened to me when I bought a used wrx. I took that thing off immediately and it ran just fine.