Car is a 2000 t/a, on3 kit and 78/75. Manual boost controller.
Tried to turn the boost up a little bit from 12lbs.
Turned the **** on the boost controller in and was not seeing any gain.
The boost controller is completely closed, not letting any air to the wastegate…yet boost still peaks below 13 psi.

So how is the wastegate still opening..back pressure? Or something else is going on?

 

Put an EBC in it.
I used the Cortex in my last car and with it tied into the engine RPM and speed sensor in the transmission I could do boost by gear and boost by speed, worked really well.

 

Again, with that 3” exhaust you’re probably building a ton of backpressure and it’s pushing the gate open. a stiffer spring will help, but the real fix is opening up the exhaust.

 

What spring do you have in the wastegate? Typically you are only going to be able to double whatever spring is in the gate with a controller like that.

 

Had this problem with my last car which had a full 3" exhaust with a cutout under the driver floorboard.
I tried using a 3-4 lb. spring but the BP would push the gate open, had to step up to a 7 lb. spring to get control back.
Even with the cutout open I still couldn't run that light of a spring.
This was on gate only as well, I never tried going back to the lighter spring when the EBC went in.

 

Try disconnecting the bottom port to the wastegate (plug that line). You should see more than 12psi. Boost applied to under the diaphragm will help open the gate... even if you remove the top line its still assisting. remove the bottom line and keep an eye on the boost gate it will def go up. Likely its BP pushing the gate open... its worse the bigger the gate is and the pre turb BP. I have 21psi worth of springs in a 60mm summit WG (piston style) to get 7psi of boost out of a 5.3 with a 2.5" crossover and a VS billet 70/70 turbo with a 3" down pipe. I know its 21psi bc I bench test the cracking pressure and open pressure. On my other car with a 60mm HKS knock off WG with basically the same combo I saw 2.5-3:1 on the BP pre turbo so at 7psi of boost that was 18-21psi pre turbo pushing on the gate piston. Also its not a 1:1 ratio as the bigger the WG piston the more air the pressure has to push on it which means bigger WG will open easier than smaller gates as they have more surface area. If your getting 12psi on spring with a MBC or EBC you should be able to effectively double that pressure as it cancels out the pressure being applied to the underside of the diaphragm (bottom port).

Also you didn't say if your referencing to turbo compressor housing, intake pipe, intake manifold? You need to measure the pressure drop if your using anything after the intercooler. Basically if your compressor housing sourced you could have 12psi at the housing and only 10psi in the intake... so the gate is reacting to the 12psi source not the 10psi your seeing.

 

Definitely backpressure blowing the gate.

I had a 3584rs turbo on my setup last year and with 14 psi worth of spring it made only 8 with the ebc off. And I could hardly get over 15psi with the controller on due to the backpressure that was over 3 to 1

Swapped the turbo over the winter for a g42 and with the same spring setup I can make much more boost. Haven't measured backpressure on this setup yet