2QYK4U

I am having an issue controlling boost since having my new turbo kit installed. I have the GM boost control solenoid, and use it in conjunction with my EMS to control boost. My EMS is currently set to limit the boost to 10 psi. I have a Tial 44mm wastegate with a .5 bar spring it in (which means the least amount of boost it will make is ~7.25). My boost solenoid is hooked-up in accordance with this picture:



Specifically, the connections are as follows:

1. Pressure source = turbo charger outlet
2. Vacuum line from pressure source to t-fitting
3. Vacuum line from one end of t-fitting to

2QYK4U

No suggestions?

Spec_Ops2087

Although I probably won't have any useful answers, it would help to know what the actual problem is. You never mentioned it in your post aside from "I am having an issue controlling boost since having my new turbo kit installed."

2QYK4U

According to my EMS, boost is supposed to be limited to 10 psi. However, my S is trying to boost to 18 psi or so!

Spec_Ops2087

hmm, thats def not boost creep as its way to much overboost.

Check all the vac lines and check the wastegate for any air seeping out of the sides (where it shouldn't be).

2QYK4U

Thanks for your suggestion.

My plan is to bypass the boost controller and see if the wastegate itself is functioning properly.

2QYK4U

Well, the wastegate itself is functioning properly. We bypassed the boost controller and the wastegate held the boost to ~7.5 psi. So, one of the following is causing the problem:

1. Poor pressure source
2. Ruptured vacuum line
3. GM boost control solenoid has gone bad
4. One or more of the wires to GM boost control solenoid are unhooked
5. Programming in the EMS is wrong

We are going to change the pressure source (currently the turbo outlet) to the intake manifold and see if that resolves the issue. If that doesn't work we'll address the other potential causes.

AusS2000

I had exactly the same issue and it resulted in a blown engine.

Periodically the boost would not be limited and would climb to over 20psi. I knew this and was generally careful but got carried away one day racing a Ferrari.

I have the engine out of the car at present and have disassembled the wastegate. It looks fine.

Do we have any details on how reliable these GM Boost Solenoids are?

geists2k

^^That is a really good question.

When I first put my turbo kit on, boost control was perfect. After about 1500 miles I started boost creeping big time. Never enough to blow the motor, but enough to make me wonder why I was set at 14 psi and was easily going to 17-18 psi.

I replaced all my vacuum lines and it seemed to make it better but about a month later it was over boosting again.

I am in the process of putting in a new InlinePRO built motor and head (just because I can ) and I will be replacing my plastic GM boost control solenoid with a new metal AEM piece.

I have no doubt this will make a difference.

2QYK4U

So, you are going with the AEM boost control solenoid? If I recall correctly, some members on this board have had problems with that solenoid. Anyways, I am thinking about going with the Greddy Profec Spec 2 boost controller.