I have the Greddy T-78 turbo and wastegate on my car. I am having a problem with controlling the boost pressure.

All settings in the Power FC are o.k. (they're set at 10 psi). I removed the wastegate and disassembeled it to check for broken or clogged pieces. Everything is fine. When boosting the car, it will boost until it hits fuel cut (18 psi) due to the factory 2 bar map sensor.

What could be wrong? Could the lines going to the wastegate be cracked and allowing boost to leak, therefore not allowing the diaphram to be pushed open to relieve extra boost?

Any thoughts would be appreciated.

 

Roy,

How are you controlling boost? It sounds like you have no boost controller ('casue the PFC ain't controlling it...unless you figured something new out) and are just using the wastegate spring?

You need to join Scott (from Pitt) and Buckeye and get a profec B.

 

Roy,
Take a look at the top of the wastegate. There is a threaded bolt that needs to be unscrewed almost all the way out (Counterclockwise). That will keep your boost at around 10lbs. I have a feeling yours is screwed in to far.

Jason
www.rx7store.net

 

I have been controlling boost by setting desired boost in the Power FC. This has always worked. Jason, you are correct. The nut on the threaded bolt is all the way down. Do I need to loosen it to allow the wastegare spring to open easier? If I loosen the bolt, how do I get it to stay at the new position (will it not unscrew more without being held in that position?

I don't want to stay at 10 psi, I am going to run 17 psi. I just set the PFC to 10 psi for testing to get the boost to be controlled.

 

I also have the PFC Boost Controller.

 

Roy,

Can you elaborate on on the PFC controlling boost? How did you hook that up? I would be most indebted if you could teach me that. Thanks.

 

I bought the Boost Control Kit put out by Apexi. It comes with a 3 bar map sensor (which Ihaven't installed yet) a solenoid in which vacuum hoses run to the wastegare. The solenoid has a sensor that plugs into the PFC.

 

At lunch, I went and loosened the nut that is on that threaded bolt on the top of the wastegate. I
loosened it halfway and still can't control the boost. Right now, the only hose I have connected to
the wastegate is connected to the outlet on the side of the wastegate. We wanted to make the
wastegate operate at the factory spring setting (about 10 psi) but the boost still goes way high.

What should I check next? The hoses going to the wastegate. Think they may have a crack in
them allowing boost to leak out and not push in the diaphragm? This one problem is keeping me
from dyno tuning my car!!!

 

Roy,

If it is possible disconnect the WG line from point of "input" begining of the line where it gets the signal from. Connect a compresor to this end, before you do this "bleed the compressor down to 30 psi" pressure, now you can attach the pistol blowing bit with hose clams to the begging of the WG line.

Press the lever and feed 30 psi to the WG, you should be able to hear it click, it will be quite pronounced, try it a few times and you will hear it unseat and seat back when you let the pressure of, If you cannot hear it then you either have a leak in the line to the WG or the WG is sticking (this can happen !)

It is the way I test ALL WG's when I am doing work on customers cars and especially when I am setting manual boost via pre load on the WG spring via a screw compression set up, only problem is you need a compressor or have a friend with one.

Hope you find the problem.