Boost pattern issues
 

My mods (stock sequential turbos):
- DaleClark check valves
- downpipe
- PFC
- St. May's exhaust
- all aluminum radiator
- Dual Hallman's (currently using stock solenoids, though)

A little history: While I was driving my car at college one day, I went over a bump, and my car took on a notably louder and ricier sounding exhaust note. Long story short, I took my car back home to Houston and had Chuck Westbrook look over the car with me. It turned out that one of the nuts on the front compressor housing had worked itself out, causing a pretty bad exhaust leak. So, we took the turbos off, Chuck redid all the nuts, I replaced exhaust gaskets, etc.

Before this, I had been having a boost issue where my car would trail off boost pressure in the higher rpm's if I gunned it in a gear, but once I shifted to the next, the car would hold 10 psi steady.

Now the car will not maintain 10 psi at all. It always trails off to 7 psi (wastegate). Chuck and I have been having a hard time trying to get it working correctly. Firstly, we noticed that the previous owner had hooked up the precontrol and wastegate hoses near the solenoid rack incorrectly, which we remedied. This had essentially no effect at all. Then, we tried hooking the stock solenoids back up, but because I don't have the restrictor pills anymore, it will only build 7 psi. AND, the pressure still trails off at about 5200 rpm.

Any ideas about what could be wrong? We should be doing the poor man's non-sequential sometime solely for the purpose of testing wastegate boost control. I haven't gotten around to verifying the rest of the hoses, but I will.

I had a similar problem awhile back with boost. The remedy... MBC on the wastegate and pre-controller. This has kept my boost rock solid....

http://robrobinette.com/boost_controller.htm

I had been using the two hallmans beforehand all of this with the same results: 10 psi before transition, only to trail off.

The previous/second owner had replaced the engine and turbos because the first owner had trashed the engine. He installed twin Hallmans for the stock ECU but hooked them up wrong. There are a couple of turbo control hoses that look like they may be kinked. There were a few other items of improper care.

We fixed the Hallman install and the other noticeable items except the posible kinked hoses under the UIM. Boost still drops off around 5200 rpms from 10 psi to 7 psi. Enthalpy then pulled the Hallmans and hooked up the boost control system back to stock. The boost drop off remains even after he adjusted the boost control values.

We plan to pull the UIM and check everything on the rats nest.

Before you go to all that trouble, check the Turbo Control Actuator. The turbo control actuator could have a slight leak on the boost pressure side. Use a Mighty-Vac (or similar instrument) to check that the controller holds pressure and vacuum. The actuator rod should remain steady and not return/move once actuated with pressure or vacuum. See service manual, pg. F-86 for test procedure details.

If you have loss of secondary boost in 1st or 2nd gear, this is indicative of a bad turbo control actuator. Use this link from the "FAQ" section for trouble-shooting if you don't already.

http://www.autosportracetech.com/RX-...leshooting.htm

Well, it turns out the problem was that one of the hoses on the turbo control solenoid was pinched. I put a new hose in this weekend, and now the pattern is perfect, and it holds boost to redline.