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Old 10-31-2007, 06:15 PM   #1
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Default after 4000RPM's running extreemly lean

I was at the dyno today trying to solve the fueling problem, and after 4000 RPM's the car started to run extremely lean. My setup is A BEGI stage 3 8 PSI, with Bipes and the BEGI fuel system. (FPR and Pierburg.) The car is a 96. Is there anything to help with this? I'm about to chuck the FPR and just go to an FIC if I can't get this to work.
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Old 10-31-2007, 06:43 PM   #2
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Injectors Clean?

Dual feed rail?

Is your fuel pump in working order?

You sure the FPR is getting a proper signal?

Heres a good question to ask. If your clutch was slipping that could potentially cause the turbo not to build boost and that would in turn not increase the fuel pressure causing a lean condition. Hmm, I wonder if thats possible.
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Old 10-31-2007, 06:51 PM   #3
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Not sure on how clean my injectors are

The FPR is hooked up acording to BEGI instructions

The fuel Pump is in working order

Everything was fine till after the car was driven with the o2 sensor in place.

I'm pretty sure the clutch isnt sliping because it does it in every gear, just when its under 8psi of boost
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Old 10-31-2007, 06:52 PM   #4
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id suggest strapping a fuel pressure gauge on there and making sure it's working properly.

did you adjust it form the get-go? tuning the FMU requires a bit of user intervension.
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Old 10-31-2007, 06:55 PM   #5
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It didn't need to be tuned too much till after all that started. (Which was after I put the o2 sensor back in) it was attempted to be tuned at the dyno, I have a Fuel pressure gauge, but its at a friends house
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Old 10-31-2007, 08:45 PM   #6
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it sounds like my Peirburg isn't working. It was working fine the other day, and my wiring looks good on it. The ground is still grounded, not sure what would have made it just not work anymore.
I dont hear it cut on any more. I need to get the car on a lift to check everything out. I may end out getting rid of the BEGI fuel system, and just getting a voodoo card or AEM FC/IC
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Old 10-31-2007, 10:58 PM   #7
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You could ditch the peirburg and swap in a walbro 190hp. It might be a good idea even if you buy the mspnp, I mean voodoo or FIC.
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Old 11-01-2007, 12:38 PM   #8
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If you go to an MS, FIC, EMU, or other big-injector piggyback, the stock fuel pump will be more than adequate.

Obviously you're on the right track with the Pierburg- it may very well be a loose wire somewhere. If it isn't and the pump is in fact dead, a Walbro 190 (not the 255 or the HP version) from lightning motorsports will be a cheap and easy alternative that'll get you back on the road quickly.
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Old 11-01-2007, 04:05 PM   #9
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The HP would only be needed if you still want to run high fuel pressures (90 to 130psi), sorry.
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Old 11-01-2007, 09:42 PM   #10
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Default open loop

the stock ECU goes open loop after 4k rpm ... look into it
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Old 11-02-2007, 02:57 PM   #11
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Quote:
Originally Posted by jif View Post
the stock ECU goes open loop after 4k rpm ... look into it
There is some truth to this, but it is not an absolute.

On the '90-'93 anyway, the decision to go open-loop is based upon load, not RPM. Since I have a WBO2 sensor, it is easy to see when the ECU is in closed-loop vs. open-loop. In the former, the AFR continually oscillates between about 14.2:1 and 15.5:1 or thereabouts. The exact numbers aren't so much important as the range and the pattern of oscillation. In closed-loop mode, the AFR settles into a stable value, usually somewhere around 13:1.

While it is true that this often tends to happen somewhere around 4,000 RPM, this is not a solid cutoff point. If you are operating at very high load (such as climbing a hill) then the ECU will go open-loop much earlier. By contrast, you can operate at very high RPM but very low load and still be in closed-loop. Anybody with a WBO2 can see this for themselves- go out on the highway and drive around in 3'rd or 4'th gear. Get the engine up to 5,000 RPM and just cruise steadily at that speed. Observe your WBO2 gauge, and you'll see that its oscillating as normal around the stoich point. Then depress the pedal further to accelerate, and once you cross a certain load threshold the mixture will drop down to around 13:1. Ease up on the pedal again, and it'll start oscillating again.
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Old 11-02-2007, 10:02 PM   #12
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I have pulled the pierburg, I have an ELF on right now to get me by. Next week I want to order an Xede With the 550's and all. It seems like the best emissions legal solution. And I'm tired of looking at a rat fucked wire harness going into my ECU. If DIY autotune has a 96 PNP MS out by mid NOV I will get that, if not I will get the Xede. I'm just tired of piggy backs and small injectors too.
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Old 11-03-2007, 01:37 PM   #13
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Fuel filter?
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Old 11-03-2007, 07:13 PM   #14
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Fuel filter is also brand new
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