1997 volvo 850 t5 manual boost controller issues

bigty69 · Post by **bigty69** » 26 Sep 2016, 15:47

I recently installed a manual boost controller yesterday and while i was trying to tune it to around 13-15 psi of boost i encountered a problem no matter where i set it i cant get over 5 pounds of boost unless i set it fully closed then i can get over 20 pounds no problem. I know its a controller issue just w,ondering if anyone has any advice or has had thid happen to them. Yes my boost gauge is working fine and i am sure i have no vacuum leaks because it holds at about 20 INHG on the vacuum at idle.

Post by **scot850** » 26 Sep 2016, 16:06

Have you tried swapping the TCV? it could be it is failing. Also the Volvo TCV is only good for about 12psi.

Neil.

Post by **matthew1** » 26 Sep 2016, 16:57

Agree with Neil. It sounds like a 2nd component failing... TCV, wastegate diaphragm (not likely), or collapsing hose...

An MBC for a '97 is entirely mechanical, and either works or doesn't. And if you're seeing 20psi, it's working.

bigty69 · Post by **bigty69** » 26 Sep 2016, 18:39

I guess that i also should say that i originally had it connected from the tcv to the wastegate and it didnt produce over 5 psi so i saw this diagram from another thread and plugged my tcv lines and removed the hose off the compressor housing fitting and put a new one on then inserted my mbc then put the other end onto the wastegate yet i still have the same problem.

Post by **tryingbe** » 26 Sep 2016, 18:47

If you want to take your chances with a MBC, the end with the ball goes to the compressor outlet, the other end goes to the wastegate actuator.

But if your car didn't make 5psi with TCV, the issue probably is somewhere else, like the clip fell off at the turbine housing.

bigty69 · Post by **bigty69** » 26 Sep 2016, 19:11

Thats the problem the clamps never came off and just using my tcv like stock my car makes 8-9 psi surely its the mbc?

bigty69 · Post by **bigty69** » 26 Sep 2016, 19:14

Yet if i blow into the mbc while turning it i can feel it working it will regulate the air going through it its suck a simple design i cant see it failing.

Post by **tryingbe** » 26 Sep 2016, 23:44

bigty69 wrote:Yet if i blow into the mbc while turning it i can feel it working it will regulate the air going through it its suck a simple design i cant see it failing.

If you can blow to make the MBC work, is way lose.

The effective range of the MBC's adjustment nut could be very narrow, 1/4 turn could mean a jump from 5psi to 20psi.

bigty69 · Post by **bigty69** » 27 Sep 2016, 18:42

All right that did it thank you tryingbe. I turned it all the way closed and did even less then a quater turn now i got a comfortable 13 pounds of boost wide open. The car was fast before it is a monster now. Just waiting for my vag com cable to get here to convert the car to motronic 4.4 and we will be in buisness i also have a wideband gauge that should be here any day now. Thanks to all you guys for your help!