AFR issues. Please help.

[makulit054]

Setup:
Sr20det with FMIC
T25
Greddy type rs bov(recirculated after the maf, before the turbo)
MBC set to 10psi
Innovative wideband:
Idle/crusing at 14.2 afr
WOT 11-12 AFR
When I coast and I let my rpms drop, the afr shoots to 22. Which is a lean condition. It will either come back to 14 on it's own but sometimes afr's will stay that way until i either put it back in gear or brake. I've also noticed when I parked and I rev as soon as my rpms hit about 2k rpm the afr's shoot up to 22 afr but when it returns to idle it will be back to 14afr. I hope I am making sense.

[OfourTHREEfive]

When I got my car dyno tuned my tuner was primarily concerned with my WOT afr. I asked him about my coasting and idle and he said its not a concern. Hope that helps.

[mifesto]

my friend had an issue with PLX device wideband "sticking" like how you described. it turns out the soldering on the circuit board was bad and it needed resoldering. PLX fixed it for him.

[krazydriver]

that's standard on almost all cars.

Off-throttle fuel cut.Think of it this way. If RPM > 1500, Throttle <5% there's a good chance your coasting and there's no point in burning gas. So the ECU cuts fuel.

If your revving it, soon as you release the gas pedal the fuel cut will occur once again going to 22 full lean/fuel cut.

So it's designed to save gas by not burning it when you don't need it.

[makulit054]

Thanks for all your replies. The reason why I am concerned is because it was not doing this before but I see your point. I know when I had my blitz bov which wasn't recirculated my afr was real rich.

[mifesto]

to add to "krazydriver"'s comment and my own, yes it is normal for any car to hit a lean spot as you let go of the pedal after a rev. but yeah if the wideband AFR is taking time to come back from a lean spike because you let go of your throttle quickly, your wideband could be sticking. but yes the leanspot itself is normal.

[makulit054]

Are you talking about the sensor itself of the control unit.

[krazydriver]

Read my first post. I've got an lc-1 it does the same thing, that's how the car runs.

The wideband would not be sticking. The AFR will read full lean until usually < 1500 RPM. At this point fueling is required for proper idle/low speed afr.

Downshifting would increase RPM which would make the ECU increase fueling because the engine is accelerating. Braking would affect load/decelleration on the engine resulting in a change to the map/maf reading which would affect what the ECU does for fueling.

In other words, your car is fine, your wideband is fine, and there is nothing to worry about.

[makulit054]

thanks. I also have the LC-1. Thanks for the replies.