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Speed of course, you don't have a Karman sensor anymore (otherwise you did something strange).
 
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It should still be set-up for Karmen I think. I don't remember me changing that setting on the AFCwhen I put the VPC in. Works like a champ too.
 

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Right, you will not see any change in the behaviour when changing the S-AFC setting.
 

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I have the VPC and S-AFC in it......

When i first got it hook up at AAM in MD.They still use the KARMAN it runs good,no problem with idle and it runs great too.But the only down fall it trigger my check engine light on:(.

After the rebuilt the shop that work on my car change the wirring and now it running speed density it shut my check engine light off which is good.But the only down fall now is that everytime i shift fast at WOT the car studder(hesitate to response right away),everytime the throttle close its dumping too much fuel.The injectors i have in the car is 720cc and HKS only make 550cc chip for our car,duty cycle is the same as its running 550cc.


If i can start over again i will defenatly go with the real stand alone system.I think you should too;).
 

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You need to set it to Karmann. The VPC is speed density system, but remember what it does is take the temp and pressure readings and CONVERT them to Karmann to send them to your ECU so your ECU thinks the VPC is your MAS sensor. So to say again, your VPC is a Karmann MAS emulator, the output of it is Karmann frequency. You then wire your AFC in to further modify this emulated Karmann signal. Got it?
 

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Jim,does the karman vortex air flow meter really restrict the air enough to justify a vpc ? does the VPC respond as fast as a Karman Vortex air flow meter ? Have there been any tests done the you know of ?

Frank Martin
 

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GCtech Motorsports
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Discussion Starter #8
i called HKS and APEX-I and both said to select pressure sensor,,unless im hooking the afc before the vpc to select karman other than that pressure

thanks
Gilbert
GCT automechanic
racing engneering
 

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I believe the MAS is a major restriction, plus by eliminating it you can run a HUGE K&N airfilter that flows over 1000 CFM rather than the small oval one designed for use with the MAS.

With a VPC, you can also vent your BOV to atmoshpere for those that like the sound.

I have had no problems with it response time or tuning wise. The main reason for using it is of course to alow for adequate tuning of bigger injectors. An AFC by itself is inadequate as far as I'm concerned, it only allows you to tune based on RPM, wheras a VPC or ARC II allow you to tune based on actual airflow.

The other small benefits are just gravy!
 

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TTGTO whoever you talked to is WRONG. You definitely select Karman for the reasons I stated in my earlier post.

Also, it is IMPOSSIBLE to hook up the AFC BEFORE the VPC. The VPC is using its own seperate harness and pressure and temperature sensors. The MAS is off the car, the wires are left unplugged. I guess if you really wanted to you could hook it into the VPC's pressure sensor before it gets to the VPC, but then you would select PRESSURE.

Doesn't anyone else know how this stuff actually works and want to chime in here?

For a final time - the VPC takes its own pressure and temperature readins and converts them to an emulated KARMAN signal that your stock ECU then reads. Hence the name - Vein Pressure Converter. Think Vein = intake in Jinglish, just like your bodies veins. It basically is intake pressure converter. Your ECU does NOT understand pressure signals, it is designed and programmed to work with a KARMANN MAS!!!!

Trust me i am an electrical engineer for DaimlerChrysler and have shop specializing in 3S/DSM/MOPAR as a side business. I have had the exact setup we are talking about in my 550HP 11 second Stealth for several years now. You talked to some customer service phone answering boys at HKS and Apexi.
 

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Thanks Jim,
So the VPC is a MAP sensor and a temperature sensor with the electronics to simulate the frequency output of the original Karman Vortex air flow meter. Do you know what type of map sensor they use ? is it a Ford (where the output is a variable frequency) or is it an analog 0-5vdc output ?

Frank Martin
 

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Great question. i have my car apart right now to do the six speed conversion. I will have to measure and find out, but I suspect it is a 0-5V not a variable frequency. It is really small, 3 wires, looks like a diapragm and transducer in there.
 

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A standalone is great, but remember - they are:

1) More expensive
2) Require more expertise to tune properly
3) Sacrifice driveability, civility of factory ECU (see number 2)
4) Increase chance of damage due to incorrect A/F or TIMING
 
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