Ive installed the wideband and tuned the car now it runs in the 12s almost all the time. I see 12.6-12.8 very often, sometimes 13.0-13.1 (rarely). I set the rail return style with an FPR set to 50 psi.

Only problem is that when braking, the AFR goes to 17:1, sometimes 18. Could it be how my PCV valve is setup?


BTW, the car is MUCH faster now, probably as fast as it can be with the stock 240 exhaust system. Top end is nuts.

 

I presume you are off the gas when braking. When decelerating like that (no load), you are in open loop and IPW is reduced, so of course it will read lean. That is normal.

My PLX displays AIR on the screen when I am decelerating.

 

Yep that's normal. With stock injectors and fuel pressure your AFR would read 21+ on decel

 

Hehehehe...I figured you'd already know that JClaw. But yea, what they said. Injector pulsewidth is drastically reduced when coasting in gear.

 

Ditto, fuel is cut on braking and coasting.

 

Well its the first time I use a wideband. And the reason I was asking is that with the car just sitting there, at idle (not coasting or anything) it will read lean when I press the brake, indicating the vaccum has to do with the fluctuation. Moment I release the brake (still sitting in the driveway), it goes back to normal.

The source for the brake booster vaccum line is directly in the plenum, drilled a hole with a fitting on the side of the intake.

 

Like I said, this is not decelerating, this is sitting at idle in the driveway and simply pressing the brake pedal.

 

Ahhh...i see what you're saying now. Sounds to me like the brake booster is leaking vacuum and letting unmetered air into the intake manifold.

 

What if we put the vaccum source for the booster somewhere else.

Were gonna need to test that booster though.