mentalasanything

Evening all,

I finally got round to fitting a wideband controller to my cabby last week. Now I don't know an awful lot about AFR so please go easy on me. After a bit of a poke around I came across some other RST owners readings and mine didn't seem that far off.

Bit of background: EFi turbo CVH, OFAC, Powerchips 195 chip, beiges, ported and polished head, FMIC, Mongoose, 10PSi boost, idles lovely.

I oberved the following readings:

Idle: 13.2
Normal Driving: 14.2
Boost: Ranging between 12 and 13 with WOT and full boost.

Which don't sound too bad, maybe a tad rich?

The reason I got round to fitting it was a concern it may be a bit lean. It's started to pop a lot more off throttle or decelerating and become a bit jerky when slowing down. When off throttle or decelerating the gauge goes off the scale, it hits 22.3 and stays there, is this a normal reading? I'd have expected it to settle somewhere nearer the idle reading?

Lee

matthart

Idle is fine (they idle happier a bit rich), normal driving is fine, boost is maybe a bit lean at 13 but 10 PSI wont kill it (just dont turn it up).

22.3 is just clean air, so off throttle it's not injecting at all.
Some manufacturers purposely map cars like that for fuel efficiency but I've no idea whats in an OFAC or a 195 chip.
Get it on a dyno to confirm your readings, but for OFAC issues you're going to need an OFAC wizard as they are total arse to diagnose.

studabear

The engine becomes a big air pump when you let off the accelerator, so it going really lean is normal, the ecu won't be injecting loads of fuel while on over run/decelerating. As long as it richens up as soon as you accelerate/apply a bit of gas I see no issue here.

matthart

Lean on overrun is normal, but not 22.3, that's no fuel whatsoever? I admit I don't know if the OFAC does fuel cut but that's not going to lead to a very nice driving car.

I had my megasquirt configured to cut out fuel on overrun and it just caused a massive jerk as soon as i touched the throttle.

mentalasanything

Cheers gents!

Should explain it starts at 13 and works its way down to 12 as boost increases, it sits in the very low 12's on full boost.

It does richen up instantly

Pretty much what it's doing, but it never used to do it. I'm not so bothered by the lean off throttle reading as this sounds normal from the research I've done, more the jerkiness and unusually excessive popping.

I'm slowly adding the tools and components to go OFAM. Maybe I'll stick it on my Christmas list and my problem will go away.

Lee

fraser9764

iTrader: (3)

Then it wasn't mapped correctly.
Fuel cut on overrun is completely normal In most cars. Why would you want to pump fuel into an engine which is required to make no torque?
Again I don't know how OFAC behaves normally, it's pretty old tech now so may cut or may not.
I'd start with checking for air leaks and check tps calibration.

mentalasanything

Resetting the ECU and letting it re-calibrate the sensors was going to be my first move. After that maybe checking base base idle reference for the ISCV.

Cheers,

Lee

Nosmonkey

I had the same problem with my S2, albeit on MFI. lots of popping on the overrun, turns out the manifold bolts were loose and letting air in.