I put a UEGO on my '99 with just an RB headerback exhaust, I've always been curious to see what Mazda seemed to think a good tune was. I figured I'd share incase anyone else was interested and had never bothered to try it.

I guess the results weren't all that surprising but it did make me want to look into a cheap piggyback to pull some fuel and see if I could improve my gas mileage a bit. The tune actually looked like a good boost tune to me. It ran 14.2-14.7 at cruise. When I made a pull it would start in the high 12's and taper to 11.5 by redline.

I've never messed with tuning an NA car but it looks like they can tune to high 13's at WOT, I'm kind of curious what kind of gains that would give.... Awww man, that was a horrible idea it was to put a wideband on the daily

 

Thanks for the info. i don't know if it makes a difference because of ecu but mine in my 90 with stock ecu fluctuates between 13.8-16.2 at cruise. I am running a turbo so it may be that.

 

Yah I was very suprised when I put a wideband on my 99 when it was stock, they just tune 'em rich from the factory.

 

My '02 will hit low 10's and 9's on the top end, stock. It would be an ok boost tune, however, it really needs to go open loop sooner than 4500 rpm.
Stephanie

 

Stock AFRs on miatas at WOT are very very rich for an NA car.
On my 94 1.8 and my friends 91 1.6, both cars run around 11:1 at WOT after it goes open loop.
To make matters even worse, on a hot day when your coolant temps and intake air temps are high the ecu even runs richer and you can hit 10:1 and even 9:1 AFRs.

I thought that this was only done on the pre 99 miatas that didnt have knock sensors built in. I didnt know that even the newer cars with a knocksensor from the factory still run as rich as the earlier cars.

If you can tune the car to run around 13:1 at WOT you probably would be able to squeeze some more power out of it.

 

I will be installing a wideband with my 1.8 swap into the 91, it will be interesting to see how the 1.6 ecu runs on the 1.8. I wonder if I can add a few MPG's once I add the MS. I am planning on running the car NA for a few months before getting a turbo kit so I can figure the miata out with MS. This might be the wrong forum to ask but do the guys that MS naturally aspirated miatas see any gas miliage gains? I have some MS experience but only on american V-8s and they were all only for fuel controll.