overboost with mbc fitted

Fitted my Gtec 1 chip, boost gauge and manual boost controller now. I turned the screw all the way out on the boost control to start with and took the coupe for 5th gear run but its overboosting to around 1.4 bar, at that point i lifted my foot off the accclerator. I thought if the screw is all out then it runs base boost but doesnt seem to be.

So came back to disconnect the red and blue hoses from the manual boost controller and join them together to check what the base boost was and its a steady .5 bar

Could this point to a boost leak or faulty boost controller? Ive noticed on the side of this boost controller a small vent hole which wasnt on a previous controllers ive had on my last turbo coupes.

Anyone any suggestion to fix the problem or like to hazard a guess as to what could be causing the overboost?

The vent hole is normal and is needed to prevent the wastegate sticking open slightly once the valve is closed.

Have you got the hoses fitted correctly? Red hose should be from turbo outlet and goes to base of valve where it pushes against the ball/spring. Blue hose should come from side of valve and goes to wastegate actuator.

On the last valve I setup it had to be wound *way* out, almost to the point that the screw part came right out of the valve.

Also check that the ball and spring are moving freely, maybe something is jammed inside the valve?

Hi Graham, Its one of these mumby developements controllers. Ill check it again but i did notice it has a plastic ball in it and not metal which i thought was a little naff although its moving freely.

I took the screw out as far as is on the pic on the ebay sellers page just with a few threads left.

Yeh pretty sure the hoses are correct although certainly going to check again.

Oh very happy with the chip by the way... thanks for that
and once this overboosting problem is fixed it will be great

Going by that pic



The red hose (boost) would go to right side and the blue hose (wastegate) would go to bottom.

I checked the red and blue Hoses... all as they should be.

Then opened the valve and gave the internals a coating of oil put it all back together with the screw in just a couple of turns. Plumbed it back in the coupe and hoped it would give me base boost which turns out to be .5

So it seems you could be right about some of the valves needing the screw taken almost right out, I guess I just didnt expect that.

Now all I'm hoping to do is give it a little turn until I get 1.2 bar