SFMU Fuel system help

[cs82685]

Here's the background if you're interested, just got the car back after quite a while. I took it for a little boosting and it was running much leaner than usual. NBO2 gauge was reading .82 volts. This is with stock injectors idle fp 55psi.

I've got my brand new 30# accels laying around so I put them in change to 2.72" disc and largest ring w/dark spring. I drop the idle fp down to 26-28 (as low as it will go with -4an return line) Take it out for a spin, immediately when the engine starts seeing boost the a/f gauge nose dives 50...30...20...let off. WTF

Ok well people have used the largest disk with no ring and a bleed valve with 30# injectors before so I switch back. Take another test drive and back to .80-.82 under boost. Still way low, my car has always run around .88-.90 and run wonderfully at that amount.

Checked the sfmu with an air compressor so I could watch my fp gauge and got it to rise to 100psi. Also put a new vaccuum line on from the intake manifold to the sfmu.

At this point I should be running incredibly rich with the largest disk and no bleed valve and yet I'm not. I'm racking my brain here and can't think of what the problem may be

When I get time I'm gonna take the hood off and have someone watch my fp gauge while I'm driving, but I guess for now I'm just gonna have to either raise the idle fp or take out my wastegate spring.

Any suggestions anyone my mind is going in circles so I could use some new ideas. Only other thing I can think of is to check the connections for my a/f gauge, but I feel like that's probably not it. I'm also getting a code for the IAC and have a crappy idle, but I don't see how that would effect anything at WOT.

Oh and last thing, the car sat for three months I drained out most of the gas and refilled with 93 which cleared up my idle quite a bit, could it be that what was left was bad and is screwing up my a/f mixture?


TIA to anyone that can give some insight to this.

 

[selmerguy]

The big disk in the sfmu is about 12:1 right? If the sfmu is working right you should be pig rich under boost. Also you need a wideband if you want to tune. Your narrow band could say .90 and you can be lean. It is just not accurate. How does the car feel under boost? How much boost are you running?

I have been playing around alot with my logger and my wideband with my 1g and the narrow band is pretty good at idle but with throttle you see some funny numbers. Good luck and I hope you car runs right.

 

[cs82685]

The big disk in the sfmu is about 12:1 right? If the sfmu is working right you should be pig rich under boost.

That's what I thought and was expecting to see.

Also you need a wideband if you want to tune. Your narrow band could say .90 and you can be lean. It is just not accurate. How does the car feel under boost? How much boost are you running?

I'm afraid to go over a few pounds of boost, I've been driving around at 25% throttle. I don't know if this will sound weird or not, but under lean conditions prior to this, I've always smelled something distinct for a couple seconds afterwards, and I did this time too, I don't want to push it without being able to keep an eye on my fp's. I really do wish I had a wideband for tuning, but currently I don't.

 

[cs82685]

Well I feel like an idiot. I had the top screw too far out. I discovered this when I went to check my static pressure and discovered it wasn't any higher than idle. So I decided I would turn the top screw in until it started to increase my fp, boy I had to turn a long way. Once I got there and idle rose a couple psi, I tested static again, and it shot right up, took it for a test drive and bingo, problem solved.

Anyways, I'm now happily boosting with my nbo2 gauge reading .90 volts. Which is a little above what I used to see, but I still expected much more considering I've still got the largest disc in, no bleed valve and 30#'ers. Oh well I'm happy.

To top it off, I went cruising around and found a dude with a 1g awd, with 20g aem standalone, etc. Nice, a running car, and a new DSM buddy