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Discussion Starter #1
Hello, I have the VPC "A" chip with 440cc injectors. No matter what I set on the SAFC, the ecu will override it or something so I heard.

I was told that under 4k (~closed loop), I should tune with the vpc. Above 4k (~open loop) is when I should tune with the SAFC. Anyways, so how do I tune the VPC? I know there are 4 knobs on it.

I have the "A" 550cc chip with 440cc injectors. So I guess I will have to richen it somehow.
 

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Discussion Starter #2
Just to make it easier, what I'm looking for is what are the knobs and how do they affect the fuel management?
 

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Discussion Starter #4
Thanks man. I searched and came upon endless threads about the vpc/gcc combo with the TT crew. The reason I think I need to tune the vpc is because no matter what I do to the SAFC, I still get 10 under wot.

I went from -25 to +25 (50% difference) and the fricking a/f is the same :dunno:

Hopefully I can learn how to play with the vpc and make it work.
 

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Put all the knobs straight up on the VPC. Use the FC to make fine adjustments. Must have a wideband.

The stock ECU will fight the VPC/FC in closed loop (under 4k rpm). So tuning here is not recommended.
 

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Moo
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How do you tune a vpc? You rip it out and replace it with an AEM EMS.

I assume you have an n/a otherwise you'd have 550 injectors. Set response knob to where the motor revs the best. Set idle to where it will idle (this will change every other day, see top line). Set gain to 0. Reset ECU. Adjust fuel pressure, idle bypass screw, etc to get a stable idle with little to no compensation from the ECU. From there tune at WOT with the afc. At this point it should be good. If you can't get a/f to change I'd look at your install of the afc and look at your fuel system. Mk3's have a restriction in the fuel return line that
can cause fuel pressure to rise when we install bigger fuel pumps. If your mk4 n/a has it, remove it.

From day to day you may need to adjust gain and idle on the vpc. This is why you tune with gain at zero by using the afc. To remedy this, see the top line.
 

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michaelvanle said:
Thanks man. I searched and came upon endless threads about the vpc/gcc combo with the TT crew. The reason I think I need to tune the vpc is because no matter what I do to the SAFC, I still get 10 under wot.

I went from -25 to +25 (50% difference) and the fricking a/f is the same :dunno:

Hopefully I can learn how to play with the vpc and make it work.
I hated the GCC in my old car, so I have the VPC/SuperAFR and we can tune that thing in 10 minutes. It's cake.

Zero all the knobs and do a WOT pull and use the GCC to tune the AFR's. If they won't adjust enough with the GCC, turn up the GAIN on the VPC and that will adjust the entire fuel curve, but you'll have to tune back down the rich spots with the GCC.

Mine on 30psi with 115 octane is at about 75 percent on the VPC gain, and then tuned with the SuperAFR and we see nice 11.5's across the board except for one rich spot that I am tuning out.
 

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CrouchingTiger
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Gcc

Hi, I'm a newbie and ofcourse have tons of issues. For starters I just bought a '94 TT that has a VPC and a GCC (PFC F-CON) in it. I found the information on the VPC through HKS. However they told me that the GCC was no longer made and as such they did not carry the manual on it anymore. Does someone have an old manual on this GCC (has 6 knobs vs. the new style having 5) and if so fax or sell me a copy of it? (HKS charges $5.- for a copy of their manuals) Any help would be appreciated. I can be reached directly at (832) 216 - 1302, Thanks
 

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Discussion Starter #9
Man, no matter what I do I'm still getting 10:1 under wot. I thought if anything I would have gotten lean since I'm running lower injectors than the chip is rated for.

I was told to make my fuel pressure lower. I don't have a fuel gauge, so I might look into that.
 
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