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Need help with V-AFC used with supercharger

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Old 04-15-2003, 05:04 PM
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Originally posted by Reignman
YS,

I didnt see all the settings while he was doing it but I remember that most of the settings were positive and not negitive (adding fuel). He also said that with the v-afc values all at zero that the A/F ratios were spiking around 6000rpm and it was running lean around there.
That is your problem. With a boosted application, your check-valve or ESM is keeping the ECU from seeing boost. The ECU has no maps for manifold pressure beyond atmoshphere (no boost/no vacuum). When your V-AFC is set to a positive value, it does this by tricking the ECU into seeing that there is more manifold pressure than there really is. So, if under boost the check-valve was holding you at atmosphere and the MAP signal going into the V-AFC was atmosphere, by adding fuel with the V-AFC, you showed the ECU boost. When you do that with a small number, the car usually just falls on its face. I imagine if you did it with a large number, it would trigger a CEL.

If you are going back to the same tuner, tell him he needs to add fuel with the FMU and pull it with the V-AFC.

Ray - can you confirm/clarify this in case I messed something up?

-YS
Old 04-15-2003, 05:09 PM
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[QUOTE]Originally posted by RT
[B]Oh sorry, you already answered some of the questions while I was snoozing (guess I should have hit refresh)
Old 04-15-2003, 05:17 PM
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[QUOTE]Originally posted by Yellow Streak
[B]

That is your problem.
Old 04-15-2003, 05:20 PM
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[QUOTE]Originally posted by Yellow Streak
[B]

That is your problem.
Old 04-15-2003, 05:27 PM
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[QUOTE]Originally posted by RT
[B]
Pete's 100% right-on here!
Old 04-15-2003, 07:05 PM
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Originally posted by Reignman


Thanks YS! Wouldnt I go about adding fuel by adjusting the FPR and then I could use negitive values on the v-afc?
Exactly

-YS
Old 04-15-2003, 07:45 PM
  #17  
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Harry's psuedo schematic is exactly what you want to do w/ the ESM, cut the V-AFC white wire and connect the ESM green wire toward the V-AFC and the Blue ESM wire toward the "harness" (MAP Sensor) .......

Hey Harry, long time no talk, hope all is well
Old 04-15-2003, 08:22 PM
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I hate that high speed sh!t (chirp chirp) ....... better safe than dead is my motto!
The weather is getting better up here, the Pac NW group hopes to get out to the track soon.
Take care and be careful .....
Old 04-16-2003, 03:24 AM
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Originally posted by RT
Harry's psuedo schematic is exactly what you want to do w/ the ESM, cut the V-AFC white wire and connect the ESM green wire toward the V-AFC and the Blue ESM wire toward the "harness" (MAP Sensor) .......

Hey Harry, long time no talk, hope all is well
Do you know what color wire would connect to the blue ESM wire?
Old 04-16-2003, 07:03 AM
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yeah, the other end of the white wire .............. if you cut into the white V-AFC wire you're going to be looking at the ends of two white wires ..... cut it between the vafc connector and the new harness. (Both the blue and green ESM wires will be connected to white wires, know what I mean?)


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