1992 UD 1800 nissan 6.9l turbo diesel overboost valve question

[Bigbluechevy]

Hey guys, I am at a dead end. Here is the story

I have a flatbed, and I was having boost leak issues, so I installed a boost gauge to see where I was at. I put a new gasket between the exhaust manifold and turbo because it was leaking. Then I sealed all the piping from the turbo to the intake plenum. Now I get 10psi at WOT. Still feels like a loss of power from when I bought it.

Tested the waste gate and it holds vacuum, so I rev it and it works as it should when I let off.

There is a valve on the plenum section(see image) that bends down to the throttle body, and this valve is spring actuated to release excess pressure when the throttle body closes I think. Or its spring is set to open the valve when it reaches a certain pressure. The mating surfaces do not seal well, and the way it is build allows it to sometimes not even seat all the way and as I continue into the next gear I can hear it leaking under my seat. Once I shift, it might seat and seal, or it might hang up. I believe that I need to replace this part in order to get to the next step in getting everything correct on the intake side.

This valve is threaded into the plenum elbow and is something like 27mm across the threads. Does anyone know what this valve is called, or if I can buy an adjustable one? I cant find anything online, and my alldata only has UD trucks from 1998-up.

Any help would be appreciated.


I sent my employee to get the valve and he came back with this diagram. It is the part in the upper left corner that has the arrow drawn to it. Now I am looking for online it and he has no more info that is helpful.

 

[Bigbluechevy]

After much research I found a few others removing these overboost valves on all types of diesel motors without problems. since there is no throttlebody butterfly I dont think I will have a surge to worry about. Any opinions on this statement? I wont be messing with it until monday when I get to work.

And, If my map sensor reads more boost than stock will it compensate with diesel or would running more boost need a tune to be set up correctly?

Thanks, Connor.