Is it normal

[BMWM3]

NOTE:....
Normal driving conditions for both:

Noticed on my Saleen supercharged mustang the Airfuel ratio stays a constant 14.1 or 13.9 when cruising in 4th at a speed of 65mph .. when I throw it into neutral for getting to ready to come off of expressway to stop light the air fuel ratio jumps as high as 14.9 or 15.1 for a spilt second then at full stop and sitting at the light the air fuel ratio will hover around 14.6 to 14.7 at idle.

However on my prochargerd p1sc mustang the air fuel ratio stays around 14.4 or 13.4 when cruising on expressway at same speed same conditions... the air fuel ratio of the procharger when throwing into neutral will jump as low as 18.7 to 19.1 and read lean for a about a second or two then idle out at red light around 14.4-14.9

Is the procharger air/fuel anything I need to be worried about.
should i get a retune?

 

[BAKnBLK2010]

Nothing wrong. It's not unusual to see a spike like that just for a split second.

 

[stkjock]

Mine does the same


consider the scenario - when you let out - the PCM reads 0% pedal, it stops adding fuel and spark to the cylinders - the air keeps coming due to the RPM, so the AF leans out. There is no load on the motor at that point - so you're fine.


At least that's how I understand it

 

[BMWM3]

Mine does the same


consider the scenario - when you let out - the PCM reads 0% pedal, it stops adding fuel and spark to the cylinders - the air keeps coming due to the RPM, so the AF leans out. There is no load on the motor at that point - so you're fine.


At least that's how I understand it

Gotcha

 

[waldogt07]

Mine does the exact same thing.....That is normal.....

 

[BMWM3]

I was just skeptical since my saleen doesn't do it and my procharger I finally installed gauges on it and was wondering whats up.

 

[gtmiller1001]

Same here on my NA set up. I have an Aeroforce Interceptor gauge and it leans all the way out to 29.29 when letting off the throttle and "engine braking". I understood it the same way SJ explained it, no fuel coming in, just air. If anything I'd think this would create a brief cooling affect on the motors guts. As long as the motor is not under load the AF doesn't really matter...to an extent.