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Discussion Starter · #1 ·
I'm BPU with VPC/SAFFC2. Just recently I started getting fuel cut in higher revs, say a little past 5K in 3rd or 4th gear, once it's been past 15 PSI (my max boost via HKS EVC5) for a second. I've searched SF for my symptom, and checked my ECU code, and sure enough, #34, fuel cut.

Seemed like the typical reason/fix for fuel cut with a VPC is a bad MAP sensor (HKS, not stock). I checked the voltage on my MAP sensors (HKS AND stock) less than 2 months ago, and it was fine. Assuming it hasn't gone bad since then, are there any other common issues with the VPC's FCD that bring this problem about? Thanks in advance.
 

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VPC has no bearing on fuel cut. You need the greddy bcc (boost cut controller) to prevent fuel cut. Check the online sponsor stores. It's usually around a hundred bucks.
 

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I am having a similar problem with my VPC it seems. The only thing is i am running really rich. The VPC voltage is at 2.3 i think and its suppose to be at 1.7 i believe. So right now my car was thinking that it had 2 psi of boost at idle and was compensating for it. I think it is a bad sensor. Well see tomorrow.
 

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Discussion Starter · #5 ·
Sounds like a bad sensor. Was that the MAP sensor voltage you were referring to? Where in FL you located?
 

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Maybe I am not reading the first post totally correct, but the VPC alone will not change the fuel cut...although the HKS fuel cut defencer will, or the more popular Greddy BCC will do it as well and it is the "correct" way of doing it since there are a couple things that it doesn't completely eliminate the way the HKS FCD will, but either will get the job done no doubt. There have been many discussions on this and you should be able to find it with a search.

There are real quick/cheap ways to get past the boost cut, but I wouldn't call it the "right" way of doing it by far. PM me if you really need to know how to do this real quick mod (if you don't already know) as I would rather this not be a mod that someone tried real quick after searching the forums one night.

FYI, I decided on the Greddy BCC when I modified my boost cut back when I had the stock ECU and all.


Take Care
 

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Discussion Starter · #7 ·
I know about the FCDs/FFCDs/BCCs, etc. out there, but the EVC5 guide made me think that the VPC had a FCD programmed in.
 

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Troux said:
I know about the FCDs/FFCDs/BCCs, etc. out there, but the EVC5 guide made me think that the VPC had a FCD programmed in.
VPC doesnt have an FDC programed into it. It just converts the type of airflow signal, and removes the MAF.

Get a BCC then :).
 

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Speaking only of the VPC itself, the GAIN control may cause fuel cut if mis-adjusted. I assume you know enough to keep that knob at 12 0'clock. There are a few threads on why this control is counter-intuitive when used on a closed-loop, feedback O2 system.
 

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As everyone else said you definitely need a BCC/FCD because the VPC has nothing to do with that. That would explain exactly why its cutting out when you go 15psi or more.
 

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Troux said:
I was under the impression VPC had software built-in (like the FCD) that prevented boost cut. Read #7 here:
http://mkiv.com/techarticles/hks_evc_ez/hksevc1.jpg
As I read #7, it seems like they're saying that it *doesn't* effect fuel cut at all, and are recommending one of their other products to take care of that.

FWIW, it's the Supra MAP sensor that determines fuel cut. I haven't put a VPC in, but I was under the impression that it used its own pressure and temperature sensors. If the stock MAP sensor reads 15 psi, it's going to cut fuel. That's why you need something like the Greddy BCC.
 
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