Crazyt

Well, the red beast is up and running again after I threw a couple hundred bucks at it. Only to relize that I now have a 12 inch crack in the windshield. Great, more money.

Anyway, I've run across a problem with my seven, it seems that after I get heavy into the gas (~8 psi of boost) and let off to cruise in the next gear, the engine just dies. It pulls great and will do if I keep shifting and flooring, but once I go into cruise the engine is kaput.

I'm thinking that the stock BOV relieves it's pressure and causes the AFM to shut. Now, the AFM controls the "opening circuit relay", correct? And this relay energizes the fuel pump? (I've rewired it so that the stock + for the fuel pump actuates a relay for +12V right from the battery to the pump (and a fuse of course). I've also wired another relay in so that everytime I wanted to start the car, I have to hit a momentary button to allow the relay that controls the fuel pump to function (after it's running the wire from the opening relay keeps this energized). When the car dies after boost, I just hit this button again and the car runs fine.

If the opening circuit was to deenergize, then my fuel pump would stop until I pushed the pushbutton I have installed according to my rewiring. My understanding is that the opening relay is not supposed to cycle. Am I right? Is the BOV capable of shutting the AFM?

I'm thinking of making a custom TID that has the BOV not pointed directly at the AFM. Does anyone have a good write-up for a DIY TID w/ a FMIC? (other writeups don't have FMIC piping to deal with:-) THanks for any help.

Car: S4 turbo, downpipe, presilencer, generic K&N intake, 720cc secondaries, Rtek 1.7, emissions removed, fmic

Crazyt

Forgot to add, the car did this even before I rewired the fuel pump.

HAILERS

To prove/disprove your idea, jumper the fuel pump check connector and go for a drive.

RETed

If you're not running any air filter, yes.
The air filter acts as a damper to prevent the AFM from slamming shut.


-Ted

NZConvertible

The AFM already has a damper in it, it's in the curved bit that sticks out the side.



A pod filter provides very little restriction, so I can't see removing one would make enough difference to cause a problem.

Plenty of people (including me) have run 8psi with the stock AFM, TID and BOV and no had and problems. I'd be very surprised if the BOV has anything to do with this. An easy way to test this out (as well as Hailers' suggestion) would be to disconnect and cap the BOV vac line and go for a test drive. No more theories until you've performed these two tests.

Crazyt

Well, I did what HAILERS said to do and it worked great. It's obvious that the opening circuit relay is cycling, now I gotta find out why. I haven't tried to disconnect the vacuum line yet from the BOV (not too keen on running without a BOV, even though I know okay for a short time). I'll try that tomorrow to see if the BOV has any affect. Thanks for the input.

NZConvertible

A test drive will do no damage. Unless you're running very high boost it would take months to do any real harm.

Crazyt

Okay, NZConvertible, your were right. Unplugging the vacuum from the BOV did not affect anything. I still had the problem, so it must not be the BOV.

Any idea's? Weak spring in the AFM? I got a NA AFM that I could use to test if it's the AFM itself, but I believe that would make my turbo run a little lean, correct? Thanks.

HAILERS

Your problem is really ODD. I put a hybrid in my car and had a problem when I let off the throttle. I could HEAR the vane in the afm clank when I let off the throttle. That problem only went away when I got a aftermarket BOV and a Greedy front mount intercooler.

So all those words above indicated my fuel switch in the afm should have been cutting fuel off momentarily each time. I never noticed any problem. Normally the ECU cuts fuel when you let off the throttle while driving, then injects fuel once more when the rpms drop to some low rpm level.

You could get radical and remove the black cover off the afm and tweak the fuel switch inside the afm. Heck. Try the other afm you have first , and see what happens.

Crazyt

It's more evident due to how I rewired the fuel pump (ghetto anti-theft wiring requiring me to press a button when starting the car for the fuel pump to run). If I didn't do it as I did, once the AFM opened up again the circuit opening relay would pick up and fuel pump will start running before the revs even came down, so the problem is pretty invisible. Beofre I rewired the fuel pump, I could here a relay clicking under the dash after getting off the gas (that's where the opening ckt relay is).