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Discussion Starter #1
can anyone provide any documentation for tuning of the VPC? Everywhere i read all i see is "make sure you get this tuned by an experienced professional." I completely agree with that, but i cant even find anything on the "basics" of the VPC. Basically when i hook the VPC/AFC up it dumps a ton of fuel in and when i give it maybe 30%+ throttle quickly, it bogs down and sometimes misses. Can anyone tell me what i should adjust? or know what each knob on the VPC does? anything at all will help. thanks for you help.
 

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they are stock injectors. and as far as the chip goes. i have no idea what it is. or where to tell for that matter. im a noob when it comes to the vpc. plus i just bought this car so this is the first time ive messed with it. is there any kind of resistance chack that i can do for the chip when i find it to tell if it is bad? and for the wiring... it isnt the greatest. the previous owner didnt really do it as anal as i would have. you think i should solder everything just be safe? everything is spliced together. since the afc and the vpc have to go to some of the same ecu wires. they are all spliced into the various ecu wires with one splice. so theres like 3 wires for one splice. and the other thing i noticed is the grounds for the AFC should be atleast 1cm apart according the to MKIV.com write up on the installation. And they arent. they are both hooked to the ground wire with one splice. thanks for the link by the way, i think this will give me a better understanding of what this thing does. here is a general question...with stock injectors, and the VPC and AFC zeroed out, the car should run as if it were still running on the stock mass airflow sensor right? or would adjustments have to be made to get it to run like stock? Thanks for your help guys. really appreciate it.
 

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you have to open up the VPC to see which chip you have, there is usually a white sticker on the chip with some numbers. Write those down then go to HKS's website and try to match them up. With the VPC and AFC set to zero the car should run basically like factory.
 

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Just verify the chip, double check your wiring and redo them if needed, I also solder all my wiring. let us know how it works out.
 

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I have had this exact problem before. It is a loose/bad solder joint in the VPC circuit board and it is causing wild voltage fluctuations in the output. Usually a bad chip will make all the lights on the VPC light up weird or vpc won't seem to work at all, voltage will remain fixed no matter what usually at over 5V output on the maf wire. I ended up getting burned ont he VPC sale by a fellow member and having to replace the VPC at my own cost. The way you can tell is this. If you have an AFC installed with teh VPC you acn watch the air flow or sensor voltage on the AFC. If not you can get a multi meter and watch the voltage coming from the airflow output (maf wire). You will see the voltage wildly jump around when you pull on the cables or unscrew the PCB from the plastic casing and lightly twist the board.
 

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When your sure everthing is hooked up correctly and you have the correct chip in there.. Set all the VPC knobs at 12'oclock... and tune through the AFC... you'll have to make sure you setting are set correctly on the AFC as well..
 
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