No boost

[vrinner]

Had the race car out a couple weekends ago at Cal Speedway and prior to that at Vegas. After some tweaking to the vacuum line routing the car was only making about 5psi boost after Vegas. I put the plumbing back on the Gillis valve and was making a steady 10psi.

Previous thoughts were that the Gillis valve was shot but it's cranked fully shut.

I verified that the waste gate actuator was set correctly.

No exhaust leaks.

Got rid of blow off valve and put in re-plumped for previously working bypass valve and plumbing.

Vacuum line runs from vacuum tree to Gillis then out of Gillis to waste gate actuator (validated it is not backwards). no change...10psi boost
Then I ran the line from vacuum put a tee in it splitting between at the bypass valve to the Gillis....no change...10 psi boost
Crimped the vacuum line from the Gillis valve to the waste gate actuator and the car would spike to 15psi then fall back down to 10psi.
Other than Megasquirt everything else is the same but I dont think that would cause any sort of low boost issues.

Car has never really run right with the new exhaust and new intercooler. Think maybe one of those is causing issues?

Any thoughts, comments, suggestions would be appreciated.

[Mike S]

My guess is the diaphragm in the WG is shot and you are getting the 10psi of boost based on the spring. With the gillis screwed all the way in, you should have been spiking boost until you let off the gas.

[MikeFleming]

Using a regulated air pressure source, apply pressure to the WG diaphragm and see how much it moves with 5, 6, , ... 10 PSIG applied. It (a new WG) should not move at all and 9 psig nad move 0.015" with 10 PSIG applied. And a whole bunch more with 11.

The springs get weakened with temp exposure, so the WG opens early. if the diaphragm is ruptured or torn, and the tear is large enough, it will never open. Which means uncontrolled over boost.

You should be able to get a new T3 WG assembly for ~$100. They usually come with an adjustable rod end and a locking collar clamped on. It should come already set for 0.015" movement at 10PSIG so you bolt it to the turbo comp housing, adjust the arm length to fit tightly over the flapper arm stud, lock in place with safety war or the Jesus Clip and then take the collar off.

Consider them part of the yearly consumables.

[FoxBuddy]

You should be able to get a new T3 WG assembly for ~$100. Consider them part of the yearly consumables.

Do you have to get this from a specialty store or are they readily available?

[MikeFleming]

I would expect the turbo suppliers and rebuilders to have them available. A quick Google found he following:

http://www.treadstoneperformance.com/view.phtml?f_cat=Wastegate+Actuator

http://www.turboneticsinc.com/store/index.php?route=product/category&path=46_76

Remember ottget one set to 10 PSIG. 7 is too low and 18 is too high.