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Old 09-25-2012, 07:43 PM   #24
Scooby Newbie
Member#: 317488
Join Date: Apr 2012
Chapter/Region: International
Location: Adelaide, Australia
1995 GC8C WRX import


Originally Posted by pmugabi View Post
It will be a real big surprise to me if a fuel filter sock or pump change will fix this. A cut that sudden is electrical. Testing the MAP sensor as suggested takes 2 minutes max. The fact that you have a one way valve shows that you've had similar issues before.
The reason for the valve is to remove the factory overboost fuel cut. There were no issues before installing it, I just wanted to run more boost than the Z4 ECU would allow

Originally Posted by pmugabi View Post
Just to confirm, are you sure what the MAP sensor looks like? Are you sure that your one way valve works at 15psi?
Yes I know what it is :P And I am positive it works at 15psi because it worked for a couple of months with the car at 16-17psi. The current issue is not an overboost fuel cut. Though originally I suspected it was.

Originally Posted by rob View Post
Which GFB valve exactly? I did not see any bypass valves for the GC8 on their website.
I am using a GFB Mach 1. It's not listed for the WRX because it's a universal valve that I simply made fit. It's a Blowoff valve that can also be run recirc (as I am doing).

Originally Posted by rob View Post
Explain specifically how your one-way valve on the MAP sensor works.
It's a very simple little trick (thought it was pretty common?). You put a one way valve in the vacuum hose that goes to the MAP sensor. By doing this, the MAP sensor can sense vacuum (if it even does that), but it is unable to sense boost, because the one-way valve prevents any boost from reaching the MAP sensor. This therefore eliminates overboost fuel cut because the MAP sensor isn't detecting any boost. This method works brilliantly. And before you ask, yes I have the valve the right way, and yes it is working :P (have tried another new valve). But my issue isn't overboost, as I am now running 3psi less than the Z4 fuel cut.

Here is my setup. You can see both my bypass valve and the grey one-way valve on the MAP sensor hose in this pic.

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Last edited by Merko; 09-25-2012 at 07:49 PM.
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