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Boost control diagnosis

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Hello all again!

As always I appreciate your time reading this topic.

I have a link g4x talking to a grimmspeed 3 port BCS and that controller is communicating to a tial 44mm EWG. We just overhauled the EJ25 that these items are living on. Everything is running very nicely as I’m breaking it in. I’ve had the car running on spring preassure (100kpa springs) for the initial miles of break in and all is going very well. Yesturday was time to turn up the boost abit so I planned to gently apply some WGDC on an open loop setup.

This is where I’m running into an issue. it’s behaving as if it’s not able to keep the diaphragm closed. It’s trying to as the boost increases about 2 psi over springs but then it’s like it’s loosing all of the back preassure against the diaphragm. I checked all the hoses to and from the controller to make sure no leaks. They all look good and hold air when I plug and blow into them. BUT! when I blow against the diaphragm through the hose it seems there is a slow leak. Should that diaphragm be 100% air tight? Do those diaphragms suddenly lose their seal? Anything else I haven’t though off I could test?

thanks all!


04 foz


There are multiple ports on newer gates so I'd make sure unused "bottom" ports are plugged and sealed.

The diaphragm won't seal absolutely perfectly in my experience, but perhaps it got caught during a spring change and has a tiny tear or defect and is leaking a bit more?

Hopefully you have big high flow fittings in the EBCS for EWG use and 5-6mm vac line, no restrictors in place, frequency set to 29ish Hz.

Did you verify logged WGDC was 100% when you only say 2 psi increase over spring pressure?

Is the WG fire ring fitted and properly seated? I've seen those forgotten many times so I have to ask.

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