bobbybouchet

I recently picked up a 96 miata with a begi system IV turbo kit with #1 intercooler running 5 psi. The previous owner installed this kit in 2002 and daily drove it up until last year.

I hooked up a wb02 to it yesterday to check the AFRs and it was running very lean, 15:1. So I checked the fuel pressure gauge and it was running 120+ psi under boost! The onset was set to 70 psi, so I reset that back to 50 psi. The max fuel pressure was still hitting close to 100, but still ran lean.

What could be causing the car to run lean? I checked the timing and it is set to 8. Recently changed the fuel filter and fuel lines. Could there be a problem with the injectors?

18psi

iTrader: (76)

it was running 15:1 IN BOOST?

Braineack

iTrader: (62)

stock injectors running 120psi should have more than enough pressure behind them to support 5psi. I've run 12psi (200rwhp) with 305cc injectors with just around 90psi of fuel. are you sure your wbo2 is calibrated corrected, that engine wouldn't last long with AFRs like that in boost.

bobbybouchet

Yes, it was running 15:1 under WOT and 5psi

bobbybouchet

Could the injectors be damaged from running 120 psi fuel pressure, causing the leaness? The wb02 works fine on other cars and was showing stoic while cruising.

18psi

iTrader: (76)

as brain said, either your wb02 is off or you'd have blown up

dustinb

Bad o2 for the loss. Actually, what are your AFR's not in boost, and where did you position your wideband sensor?

bobbybouchet

AFRs were ~14.7 off boost. The wb was in the downpipe o2 bung right behind the turbo.

dustinb

It could be it's too close to the turbo and isn't reading properly / damaged. The wideband should be quite a ways downstream.

18psi

iTrader: (76)

DEFINITELY sounds like a faulty wb

Braineack

iTrader: (62)

The position of the sensor is not for readings, but too much heat.

if it's idling at 14.7:1 chances are it's outputting correctly, just doesn't sound right as 265cc injectors with 120psi of fuel behind them should be plenty for 220rwhp.

falcon

iTrader: (13)

Megasquirt.

Sparetire

My guess is that the WB02 is fine at idle when your EGTs are probably sitting around 250 F post turbo. When you floor it and they start cranking along at 1200 F plus at that spot, the sensor has problems. My bet is that it starts getting wonky under any conditions within a month or two.

Having said that, you could actually be running that lean. Dont boost it untill you figure this out. Its pretty amazing how long an engine will run with detonation sometimes. Other times it will just fly apart pretty quickly. Long story short, dont assume your WB02 is off, even if it almost certanly is.

falcon

iTrader: (13)

I killed my WB02 on my rotary in a month.

Move it like 5 feet down stream. Get a new bung welded in. Make a copper heatsink as well.

Is it and LC1?

bobbybouchet

It was an innovative LM-2. It was temporarily screwed into the dp and was also placed at the end of the exhuast. When it was post cat, it was running slightly richer, but still showing lean.

bogly

iTrader: (5)

Is it possible that you are locking up the injectors (100% duty cycle)?

I had something similar just a few weeks ago with a non-intercooled shanghai.
After the stock injectors were replaced with tan tops, the AF improved drastically. I am now running 11.xx under boost versus 12.xx that would occasionally dip to 13.xx.

If I increase the pressure on the AFPR, it can get the AF to 10.xx under boost (I had this for a few days when we were in the 90's here and I thought I heard some pinging under WOT).

bobbybouchet

I'm leaning towards the injectors. I will probably pull them and have them cleaned and tested. I've been reading a lot about megasquirt, so I may go that route.

Stephanie Turner

I am pretty sure you have an exhaust leak. If there is extra air is being sucked in, it will read lean.
Stephanie

1909miata

I read thru half the thread and got bored. Ifi repeat I'm sorry. Exhaust leaks can give a false lean reading I battled this. I also batlled my begi being stubborn. Then I bit the bullet and got megasquirt. I hotly recckmend it takes away your head ache

1909miata

Also only running 5 psi I would get somw 1.8 injectors and thow them they go right in, inspect the orings for cracks or you'll have a leak....