rx7tt95

I'm at wits end trying to figure out a low boost situation on a friend's RX7. Here are the details:

street port engine (starts right up and runs well)

custom single turbo manifold, fully divided and custom downpipe

Master Power Turbo, believe it's a 60-1, might be a custom turbo with a master power compressor cover

TiAl V44 44mm wastegate, non adjustable, 8.5psi spring, vented to atmosphere.

GReddy Profec B Spec II.

We have tried two brand new Spec II's and cannot seem to get boost to function correctly. Here's how we have the wastegate and boost controller hooked up:

Positive boost comes off the compressor housing into a T. One T goes into the boost controller's solenoid , the NO port. The other end of the T goes to the bottom nipple on the TiAl. A vacuum line from the other side of the solenoid at the COM port goes to the nipple on top of the wastegate. The NC port on the side of the solenoid is open. Wastegate is vented to atmosphere. This is contradictory to what's listed in the GReddy manual.

The issue is that we are not able to adjust boost beyond wastegate pressure no matter what the settings. If we reverse the hoses, top to side, side to top, on the wastegate, boost is uncontrollable and shoots up quickly.

If I understand how the controller and wastegate works, the signal to the top nipple on the wastegate is manipulated by the solenoid. There's positive pressure to the side wastegate port which forces the wastegate open. By applying positive pressure to the top of the wastegate, it keeps the gate closed. The solenoid shuts on and off (cycles) to maintain boost at a preset, higher than spring pressure, limit.

I'm at a complete loss. We've hooked it up a dozen different ways and switched out all the components. The wastegate is the second wastegate (first was a Turbonetics) and was tested before being put on (it's brand new). All the Profec components have been swapped out for new ones.

Could it possibly be the manifold design or the turbo? Will the TiAl gate just not produce any more boost without being shimmed? Help appreciated! I'm trying to help out but I have my own car to put back together over the next two weeks so I don't have tons of time to devote to the other car. Thanks in advance!
Michel

books

iTrader: (8)

I have a Tial and Profec Spec II. The top of the wastegate goes to the COM port. I have my T (side of wastegate) connected to the port directly opposite of the COM port, I believe it reads NC. It is the port on the side where the wires exit/enter. The port which is perpendicular to both of those ports (labeled NO, I can’t see it to well) is open to atmosphere.

rx7tt95

Yep, exactly the same way I have it. I checked everything...even made sure the filter was installed in the right direction.

books

iTrader: (8)

"Positive boost comes off the compressor housing into a T. One T goes into the boost controller's solenoid , the NO port. The other end of the T goes to the bottom nipple on the TiAl. A vacuum line from the other side of the solenoid at the COM port goes to the nipple on top of the wastegate. The NC port on the side of the solenoid is open. "

according to your statements your connections differ from mine, NO vs. NC.....however I am having difficulty seeing the labeling clearly

rx7tt95

COM and NO I believe are parallel to one and other and NC is on the side. So my vacuum line with the boost signal goes straight through the solenoid so to speak, in-line. The third port is open and perpendicular to COM.

I guess I'm interested in the theory behind how the boost is controlled too. It seems that there's constant pressure under boost on the bottom side of the wastegate and the "balancing" force to keep it shut comes from the wastegate's top port which is regulated by the boost controller's solenoid. As the solenoid supplies boost to the top, it's boost + spring pressure keeping it shut. Remove boost pressure to the top and the boost pressure coming into the bottom port forces the wastegate open. The solenoid then cycles the top port's boost signal to keep a constant, higher than spring pressure boost level.

And there lies the problem. We don't get over wastegate boost when it's hooked up like that.

If anyone's familiar with the TiAl wastegate, chime in. It shouldn't matter what spring you have installed if a boost controller is present, correct? I.E. if I have the 8lb. spring in there and I want 12-14psi daily, the boost controller "should" be able to accomplish this, no?

rizzxx7

iTrader: (4)

yes it should.

rx7tt95

GReddy is under the assumption we have a defective unit. Not sure TWO units could go bad like that however...

The Wankler

iTrader: (14)

DId you use the same solenoid? Is the solenoid close to the WG? I do not run a external wastegate, but did just get my profec to work awesome.

books

iTrader: (8)

I removed my solenoid to get a closer look. The only port not connected is my NO port. My COM and NC ports are on the same axis. Perhaps they changed the configuration of the solenoid, or maybe the mounting plate is attached differently to the bottom of the solenoid. But it does seem yours and mine are connected differently.

With the Profec turned off, you will only get boost at wastegate level. Be sure that either hi or lo is displayed, if neither is displayed then your controller is in the off postion.

I thought you used to use the Apexi solenoid on your RX6 setup. I believe that solenoid and the GReedy are interchangeable.

btw, Your description of how an electronic bosst controller works seems accurate.

books

iTrader: (8)

Why don't you apply a boost source to the Profec to see if the solenoid will oscillate?