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Discussion Starter · #1 ·
Quick question, I have tested my BPC by doing 2 tests. On test 1 i disconnected the BPC electronically and took it for a drive. I was getting 1 pound. Then i plugged it back in and took the 2 bottom hoses and spliced them together. I took it for a drive and i was getting 6-7 pounds. Is that whats suposed to be happening? I did thise because i have a issue on full throttle where my car jerks violenty under acceleration. I have a stage 1 JZW tune on the viggen.
 

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Disconnecting it electronically should give you base boost (6 psi on my car), not 1 psi!

I don't remember what order the hoses are in -- which did you splice together in the second test? The compressor and wastegate?
 

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What does the boost pressure look like without any changes to the BPC? What pressures are you seeing when the jerking happens?

The stage 1 tune should have removed the fuel cut at 15 psi, so that probably isnt' it...
 

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what is the boost like when the BPC is plugged in electronically?

when you spliced the two bottom hoses together that's exactly what's supposed to happen 6-7 pis

i think your BPC is stuck open, that's why you are getting overboost
 

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Discussion Starter · #6 ·
When my car is cold it runs fine! I can gun it and everything seems to work fine. After a little bit it starts doing it and it gets worse and worse every time I accelerate. When my car I cold and seems to run fine I get 20 pounds and then when it starts to happen it starts from anywhere between 14 and 17 pounds.


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When my car is cold it runs fine! I can gun it and everything seems to work fine. After a little bit it starts doing it and it gets worse and worse every time I accelerate. When my car I cold and seems to run fine I get 20 pounds and then when it starts to happen it starts from anywhere between 14 and 17 pounds.


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try a brand new BPC
 

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i seem to have a very similar issue. once things heat up my boost goes down
 

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Discussion Starter · #10 ·
Any suggestions on to what I should do? I did play around with the noise reduction valve and I noticed when I unplugged it it was making my bucking ALOT WORSE. Just a piece of information for you guys!


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Discussion Starter · #12 ·
It's the one that connects the 3 vacuum line. 1 line from the diverted valve 1 line from the throttle body and 1 line from the intake manifold. The sensor sits on the back of the engine bay right next to the brake fluid container.


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interesting. that thing controls the by pass valve only.

i by passed that thing on my car. i just have one hose going from throttle body directly into the by pass valve
 

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Discussion Starter · #14 ·
It's the one that connects the 3 vacuum line. 1 line from the diverted valve 1 line from the throttle body and 1 line from the intake manifold. The sensor sits on the back of the engine bay right next to the brake fluid container.


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Do you have NGK plugs gapped to around .035"? I have a JZW stg 4 tune on mine and it jerked violently at WOT until i gapped my plugs to around .035" and they were at .039" IIRC
 
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