hello, my st has been having some fuel air ratio problems for quite some time. i bought my st with an aftermarket cat and exhaust. the original owner had a tune on it but i have not tuned it and i bought it in 2020, i also moved to a much lower altitude from where the original owner had the car. i have an accessport, but know nearly nothing about tuning. what do i need to do? how/ where do i get it tuned? do i need to go in person or is this something i do online? any help is greatly appreciated!
DrakeFocusST
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1,180 Posts
Just wanted to throw out there, that I do appreciate the support, but I need to say that these cars run speed density and run full time closed loop fuel control under throttle/idle so having AFR issues doesn't seem plausible unless there's a mechanical issue like upstream o2 sensor, or injector/compression issues.
If you're not familiar with closed loop terminology it's a PID controller that takes feedback from sensors to make corrections real time. The car can correct +30% or -20% short term on top of long term trims.
How do you know there is an AFR issue? The vehicles should target an AFR value of 14.7 on the accessport at idle/cruise and when your pedal exceeds 80-90% depending on the tune threshold it should trigger power demand fueling and be in the 11 or 12's. When you let out of the throttle the injectors turn off and the AFR will hit 40 which is the highest the AP will read. This is all normal stuff.
If you're not familiar with closed loop terminology it's a PID controller that takes feedback from sensors to make corrections real time. The car can correct +30% or -20% short term on top of long term trims.
How do you know there is an AFR issue? The vehicles should target an AFR value of 14.7 on the accessport at idle/cruise and when your pedal exceeds 80-90% depending on the tune threshold it should trigger power demand fueling and be in the 11 or 12's. When you let out of the throttle the injectors turn off and the AFR will hit 40 which is the highest the AP will read. This is all normal stuff.
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