Hi everyone, new here.


I've got a s14 sr20det and im having some issues getting an accurate boost reading. The boost gauge is running from one of the vacuum ports under the throttle body at the intake manifold. I got it tuned only 2 months ago on 19psi but the tuner said that my boost gauge is reading inaccurately, reading 16-17psi instead of 19psi full boost.

It's got a GFB manual boost tap supposed to be bleeding to 19psi to open the wastegate

I have tried it under load in all gears and only get upto 16-17psi in 2nd 3rd and 4th gear.

I have tried replacing the Vacuum line and tried 2 different boost gauges and got the same reading of 16 maybe 17psi at full boost.

I don't know much about the tuning side but it was tuned with a Nistune board on the factory ecu I believe,

What I want to know is does the factory boost sensor give a psi reading to the ecu therefore getting a different boost reading to the boost gauge?

Does anyone know the most accurate vacuum source I should tap into to get an accurate boost reading? would it hurt to take off the vac line to the factory boost sensor and run my gauge of that to test for a better reading? or should I try Tee off the fuel pressure regulator, is this a safe place to Tee off long term?

Essentially I need to get an accurate boost reading to ensure whats going on, if it is only making 16 psi then I can wind it back up no troubles but I don't want to wind it up if its reading inaccurately and lead it out.

Has anyone had any experience with GFB manual boost taps slowly reducing the amount of boost its bleeding?


Any insight appreciated, I'm stumped

cheers.

A manual controller maybe the issue. Boost is going to taper off in the higher RPM. You may hit 19 and by 5-6k rpms is will start falling off. Have you checked the BOV for any leaks.