Pre-control Problems?
 

I'm currently seeing 3-4psi under about 3500 RPM and when I shift out of this boost, I hear what sounds like surging, but it seems to be coming from the US driver's side of the engine. If I creep up to about 3500 RPM and then jump on the throttle, I often get full boost, but only after a lagging transition through the same 3-4psi mark. Mods are limited to aftermarket downpipe, PFC, Knightsports EBC. It should be noted that boost was perfectly fine with these mods before.

This leads me to believe that the pre-control is acting up. I get no movement of the actuator arm on KOKO tests, and am wondering where to go from here. I searched for "pre-control" and found tons of random threads. Perhaps Mr. Links can help me to an answer that's already there, but I assume this isn't an uncommon problem. The issue came on gradually over the course of a couple days... the boost seemed to "stick" to 3-4psi before shooting up, but now it's impossible to build more boost under the magic 3000 RPM mark.

Are there any solenoids or other lines I need to check? I've already been under the UIM and Mazdatrix replaced everything under there when the engine was rebuilt about 5000 miles ago, so I'm very doubtful that anything is wrong with the rat's nest.

Any help is appreciated.

The pre-control and wastegate control solenoids are right in the front of the intake manifold.

Some things to check:
1. Make sure they're connected both electrically and hose wise
2. Get some banana clips and a 12V source to make sure they are coming on
3. Make sure the hoses are on both the wastegate and pre-control wastegate
4. Make sure the e-clips for the actuators are on and that the rods are connected to the pins
5. If all those check out, bust out a mity vac and test the actuators manually to make sure they are moving

Do those tests and let me know how it pans out. Although you said the actuators didn't work via the KOKO test, another thing to check is the short primary intake hose leading out of the airbox. It often collapses, leading to symptoms like these.

helpful link: http://autosportracetech.com/RX-7/Tu...erOverview.htm

I'll keep an eye on this thread. Best of luck to you.

Thanks for the suggestions, WaLieN! Problem is solved.

The charge control actuator diaphragm seemed to be torn. There were a couple indicators for this. First, the lever/pin that limits the movement of the charge control valve would "float" neither open nor closed on idle. At my -18inHg vacuum, that was a red light. The mity vac proved the actuator faulty, and when I replaced the valve with a known working one, I got enough pressure to get the secondary spooling again.

However, I have run into another issue: I no longer get full boost until redline on the secondary. I replaced the turbo control actuator, but the problem persists. Clues point to a leaking one-way check valve. Here's hopin'!

Well, I'm glad that it was a simple fix!

To tell you the truth, I never got full boost until redline. It would taper off once I got closer and closer to redline, and as far as I know, I thought this was common amongst FDs with a reasonable exhaust.

On a side note, IIRC, you're a teacher. How do you feel about the dramatic changes in the structure of schools these days?

I used to see 10psi right through to redline, but I understand that it was not unusual for boost to drop to 8psi at around 7000rpm. Perhaps that was what was happening to yours?

Yes, I'm a teacher. I can only speak to what's happening at the high schools, and I could still go on for hours about the restructuring of schools these days; it's a complicated issue. Suffice it to say that I don't believe anyone at national, state, or regional levels - not the politicians nor the teacher's union - is looking out for the students. Luckily, we've got a lot of really great teachers who do. As long as we don't lose sight of and support for that, we'll be okay.