at first when I installed my hallman i had thought that the boost was rock solid to 20. but just recently i noticed that boost is fallin to like 17. It is not fallin fast like before without it, but around 7300rpm it starts to fall to 17. I had read a previous post about using the heavy spring, so installed the spring and I am still getting some tapperage (haha..is that a word) anyways, i have tighten all my connections and it everything checks out. ANY ideas?

 

My guess: Boost leak. Pressurize your intake tract and if you've got a leak you'll find it pretty quickly.

 

Everyone I know that has the Hallman MBC still has some taper about 1.5 to 2 psi drop in higher rpms.

 

Tighten your BOV hosses and I/C hosses. Hopefully this helps. I am running 1.4-1.5bar to redline consistantly. It doesnt drop unless you let off the gas(well according to my boost gauge anyways).

 

Mine does the same thing. Doesn't start to drop untill after 5K rpm. Falls to 17 just like yours. I'm pretty sure I read a few other post around here, of others with the same prob.

I took it apart and put it back together again, making sure everything was tight... no change.

I might try a 1g bov, or the Tomei one.

 

I am running Turboxs HPmbc by the way. I personally think it's a better MBC. When I first set it up it was holding 1.4-1.5 bar(whichever I set it to) and would drop to 17 by redline then I started messing around with the fine tuning side and now holds 1.4 or 1.5bar to redline. It's a little more expensive then the Hallman but its worth it.

 

thanks for help everyone.

I will try and see if there is a leak.

 

Yea, there has to be a leak somewhere!. I could boost in excess of 1.5 bar all day long if I wanted to.

I love turbo cars, but unfortunately, almost all of them at one point suffer from boost leaks. It can be quite a challenge sometimes to track them down, especially if pressurizing the intake yields no leaks.