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Old 07-08-2001, 06:10 AM   #1
wigglesxjr
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2002 WRX
Midnight Black Pearl

Default Correction of MBC Rich Condition

After viewing the posts depicting WRXs running rich after an MBC is installed, and the subsequent damage (degraded rings, poor oil quality, etc.) connected to the rich condition, it made me ask if anyone has done anything to correct it?

I was thinking along the lines of an Air/Fuel controller like the Apexi S-AFC, but after considering the price of that particular unit and seeing an article about the HKS AFR (somewhere in the June Import Tuner), I was wondering if either of these units could correct the engine dumping too much fuel for ignition.

so basically, my questions are:

1) will an air/fuel controller (ie. APEXi S-AFC) correct the richness of the engine after MBC install?

2) will the HKS AFR suffice for this same purpose?

thanks for the responses in advance.

-Joseph
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Old 07-08-2001, 06:30 AM   #2
Imprezer
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MBC causing rich condition? Can someone explain why it happens?
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Old 07-08-2001, 07:00 AM   #3
wigglesxjr
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i'm not really clear on how exactly the MBC will cause the engine to run rich, but according to this post, it does happen...

http://www.i-club.com/forums/showthr...light=MBC+rich
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Old 07-08-2001, 09:37 AM   #4
Shik
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I think some people may be getting the wrong idea. The MBC itself does not make the car run rich, it's what the MBC is doing the can possibly make the car run rich.

One result of people adding an MBC(or any controller for that matter) is raising the boost. The WRX's ECU does have maps to operate above the stock boost level, but as was mentioned, these maps are there as a "fail safe". If the ECU begins to see boost levels raising above stock, it figures either the boost control solenoid or wastegate itself has failed or some other problem has caused boost to rise(like adding a boost controller ) so the ECU tries to save the motor by dumping in a ton of fuel based on it's "fail safe" maps.

So really, it's the ECU's maps that are rich at higher boost levels. How you get to those maps really shouldn't matter(MBC, EBC, bleed valve, etc.)

Another difference is that with the stock set-up, the ECU decreases the boost in higher rpms, dropping it in some cases back down to single digits(correct me if I'm wrong, I don't have my boost guage installed yet). With a boost controller, the boost stays where you put it as you deleted the ECU's ability of decreasing it(boost solenoid). So it may be possible, that even the ECU's maps for 13-14psi are quite rich, but as it is stock, you don't stay there long enough to notice it since the boost drops. Put a boost controller on and run at stock level all the time and it may run a bit rich.

This quote however has me puzzled:
Quote:
hey, i noticed the black smoke(rich) ,so I got an Apex-i AVC-D Boost controller and I am running 15.5psi now, it leaned it out some,
Not sure what set-up he was running before hand, but as far as I know(the experts can correct me if I'm wrong), the factory boost solenoid, or aftermarket boost controller has no direct effect on the ECU adjusting it's maps to make it run leaner or richer. The boost solenoid, I believe, is there simply to perform an action which the ECU tells it to, which is bleeding away boost from the wastegate actuator to make it open or close, thus varying boost levels. The boost solenoid does not relay info back to the ECU in order to adjust it's maps. So simply by adding a different kind of boost controller shouldn't cause anything to "lean out some". Different boost levels may, but not different boost controllers.

The question of "how to compensate for the ECU's rich maps" may be the better question to ask. Then again, I could have just wasted a minute of your time and been wrong about everything
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Old 07-08-2001, 09:45 AM   #5
Baluchitherium4
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Two ways to cure it, add more air, or take away fuel. Either would make more power, but adding more air to take advantage of the extra fuel would add the most. Now if I could only figure out how to do this without spending a substantial amount of money.

Trust me on this, you would much rather run a little RICH than to be running LEAN. Lean=melt pistons or burnt valves=very bad.

Later,

Dale
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Old 07-08-2001, 01:05 PM   #6
wigglesxjr
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so, back to my questions

will using either the Apex'i S-AFC or HKS AFR/SAFR cure the rich condition?
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Old 07-08-2001, 03:07 PM   #7
Baluchitherium4
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I used to have an AFC on my Eclipse. Yes, you can lean the mixture out with it. I'm not sure about the AFR. I'm not familiar with it. With the AFC, you tap into the MAS signal and adjust the readings the ECU gets from it. I.E., you fool into seeing less air coming into the engine, therefore it gives it less fuel. The AFC has high and low throttle settings and you can adjust the reading in 500 rpm increments. You can also tap into the O2 sensor wire with the AFC and read O2 voltage. This can give you a more exact idea of your air/fuel ratio. EGT is the best device to tune with though.

Later,

Dale
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