David Galloway

Hello, little about the car first, 1998 rhd, stock 99 spec parallel twins, hks downpipe, stock midpipe w/ cat, hks hi-power catback, street ported, microtech lt9c, turbosmart boost controller 12psi but with no boost gauge.

Was running 11.5 afr at idle, about 11 afr at wot under boost and about a 12 before boost kicked in at 3000 rpm or simply street driving.

Just installed downpipe and catback a month ago, hasnt been re-tuned since. But have been driving it perfectly fine since then. Problem happened day after i installed a new aluminum AST (which it seems would have nothing to do with it.) But after the installation, my idle afr is 11.8, 10-10.5 afr at wot under boost and 12.5-13.5 at 1/4 throttle or just driving it around.

Any ideas? gonna check my wideband sensor today, but i have no idea. This happened directly after changing out my AST but i did not touch any vacuum lines etc.

Dvst8

iTrader: (6)

I wouldn't call avg 11's afr lean. Seems like you're running on the rich side.

ZoomZoom

iTrader: (2)

Idle is def Rich but I'm no tuner.
You may want to take it to a professional experienced with rotary tuning. It's supposed to be leaner in vacuum and at idle and rich once into boost and then slightly leaning out after torque peak.

Other than your idle I would say it's fine. But I'm not tuner.

13 is lean for a rotary. You never want to see 13's in boost on a turbo rotary. Especially high boost.
So I'm not sure where the poster above is getting this info.

14 is prob good for idle. No one is blowing a motor at idle.
Only thing I would do is lean out your idle. Don't do anything on your own.

Also we don't know how good or accurate your wide band sensor is that you are using.

David Galloway

I'm using the Bosch 4.9 Wideband sensor that came with my aem AFR gauge. I just was worried that my numbers were off, it used to run a lot richer, right after the Downpipe and catback install it would idle around 11. Never would see anything above 13.5 unless decelerating. Now that I know as long I'm below 13 in boost I'm safe that's good. I think above poster is just giving a general example of the stoich afr #'s being 14.7 even and anything below is considered rich. Closest rotary tuner to where I live is 4 hours away lol.
Should my idle afr be bouncing around in between 11.5-12.5? It used to stay pretty even at 11.5 and now it seems to have a mind of its own lol

ZoomZoom

iTrader: (2)

As long as you are in mid to low 11's in boost you are safe to up around 14 to 15 psi but it's not the only factor. 13's in boost will blow your **** up.
Take the car to a pro. Don't take advice from the forum as it's worth what you are paying for it.