This is the single oddest boost problem I’ve heard of. I’ve tried everything in my small amount of knowledge to figure this one out.

Here’s the deal. When I do a WOT run in...well any gear, say from 3k to 6k I have no boost below the 4.5k anymore. On the initial run its fine. .8 bar all the way. But once I get past the transition and ride it out for a bit then just cruise, I have 0 bar boost until after the transition, then back to full boost.

Now, if I stop the car, turn it off and let it sit for a bit, crank it up, I once again have full boost below 4.5k.

There is a loud exhaust note once the problem is there while cruising below 4.5k.

This problem has been going on for a long time now and its driving me up a frikkin wall. If I drive around shifting below 4.5k, boost remains ok, Its become worse as of late, if I just lightly accelerate past the transition, its begun to have the problem now too, but after cruising for about 5 min it will go away.

ARGH! Anyone got any ideas about this one. Don’t notice any boost leaks, all rubber connections are fine. I thought it might be the actuator in the y-pipe (Think that’s what its called) was getting stuck open/closed but it “seems” to be working properly.

So in # form: boost pattern.
First run, 12-10-12
Next run after first, 0-0-12
Turn car off let sit. 12-10-12

 

maybe your wastegate is sticking open? It would explain the change in exhaust sound.

 

Wastegate is my last hope i think. Thats what my brother thought it was, however I dont know how to find/fix that. Anyone got some helpful links to that?

Thanks Wicked.

 

Yeah, I would check your wastegate actuator, and the hose connections.

 

I would guess that it is the turbo control actuator getting stuck open for some reason. The would explain the noise. Might be a mechanical issue, or it could be a bad check valve / solenoid / hose /etc. Check out the various turbo system troubleshooting web sites and go to town.

-Max

 

Humm, gonna have to try to check that also, I thought thats what I checked the first time. But unless im reading the map wrong now, I guess that was the Charge control actuator.

Now whats the process for checking these? (wastegate/control actuator) Is there a way to correct the problem or are these things something that will need to be replaced?

Oh, forgot to mention this is my system now. Simple

 

Like maxcooper said, it's probably the TCA. That or the CCA (the actuator you mentioned first).

Here is the bible for learning how to debug the turbo control system:

http://www.autosportracetech.com/RX-7/rx7stuff.htm

 

AH, great link LAracer. Thanks.

Gonna take a bit to figure all that out.

 

Hot damn. Heading in the right direction.



Now, as the blurry lil...err BIG picture demonstrates, the Turbo Control Actuator is jammed...uhh..open? or closed..whatever. Picture is from under car laying beside the passanger side front wheel.

After trying to pry it free to see if its mechanical or whatnot, it will comeout but once i stop prying on it, it will move right back in.

So this would mean? Its being held closed by pressure i would think, witch leads me to think that there is something wrong in my plumbing right?

Or would there be another reason for it staying like that?

I figured if it was mechanical once I pryed at it, it would snap to the correct posistion. Right?

And VERY sorry for the size of the pic, my picture editor was lost after reinstall.

 

Unless I'm mistaken... And, going by your picture, I believe your picture is showing the Precontrol linkage for your second turbo... you'd have to remove the heat shielding to expose the actuator linkage for the waste gate, which controls the exhaust flow to the front or primary turbo. Based on your original discription of your problem, sounding like an exhaust leak... that is typically the sound you'd get if the waste gate were jammed in the open position. The retainerclip will come off and the linkage rod from that actuator has a tendancy to drop away slightly and they the next time you would boost, the rod will move just enough to jam the waste gate door in the open positon. Result? Shitty performance... Loud exhaust leak like note and no performance below 4,500RPM...Check it out... If that clip is missing, and I'm betting it is, you can get replacements from Malloy Mazda...

Good luck,

Rich
Let us know how you make out!

 

The picture is of the Turbo control actuator. Its directly below the wastegate and the turbo pre-control actuator. If you look at the "simple" link with the hoses you can see it at the bottom.

 

I've had this same EXACT problem for a while. Also, while the primary would boost I would here a metal rattling noise at idle and close to idle, and when i wasn't getting boost the rattle would be gone. Never figured it out because I just ripped the whole sequential system out. Good luck

 

I had a similar problem and found it to be the vacuum chamber check valve, 12-10-12 1st run right after I started the car, 0-12 @ 4500 everytime after till the car sat. The turbo control actuator uses both vacuum and pressure to work more quickly. Once you are in boost, it uses vacuum stored in the vacuum chamber buried near the alternator, purple in the vacuum diagram. http://www.autosportracetech.com/RX-7/vacuum.jpg
When my check valve was bad I would get pressure to both sides of the turbo control actuator causing it to be stuck at least part way open.
If you look in the rats nest 2nd from the front of the car on the drivers side, the vacuum chamber hooks to a y, one right above one another. The lower line is the vacuum chamber and the upper line has a check valve pointing toward the UIM and hooks to one of the nipples on the front of the UIM. The passenger side of that tube in the rats nest feeds the turbo control acuator nipple that is further back on the TCA.

Just something to check.

 

Just so we are all on the same page on things:

TCA = turbo control actuator = the actuator on the big door that opens to run the secondary turbo at full speed after the transition (pictured above)

PCA = pre-control actuator = actuator on the little door next to the turbo control door that pre-spools the secondary turbo before the transition

Wastegate = the door that lets exhaust exit the manifold without going through either turbo, shares responsibility for controlling boost with the PCA before the transition, solely responsible for boost control after the transition

It sounds like checking the clip on the wastegate door would be a good idea based on the experiences posted. It would affect boost (before and after the transition) and would affect sound level. The fact that you can eventually build some boost makes me think the problem is something besides the wastegate, though.

The pre-control actuator could be missing the clip, too, and it would affect the sound and kill boost before the transition. This sounds more in line with your symptoms.

The turbo control door would affect the noise and boost level before the transition, so it is also worth some investigation. Bad check valves or other control problems could be responsible, or it could be the wastegate clip or some other mechanical problem. I do think it might have some kind of home position, though, so the fact that it wants to return to that position on its own doesn't necessarily mean there is a problem.

-Max

 

not to hijack this thread, but I just had my car tuned at RP and Chris couldn't get the primary to boost past .75+- bar. He suggested that the primary turbo is bad (only 21,000 miles) I suppose a faulty wastegate could be the culprit, right? I heard they were pretty reliable though.

Also my car only made 280hp where Chris says he usually sees 300hp with my mods. Any suggestions?

Mods include: cb, hiflo cat, dp, pfc, greddy smic, efini pipe, apexi intake

 

Wow, I never ansered this once I found the problem. So for future referance...

The TCA was indeed being held open. After tracking down what lines could hold pressure that would directly relate to that TCA, i disconnected the hose that connected to the solenoid that was supposed to control that actuator.

Pressure was released and the actuator on the TCA returned to the correct position.

The small solenoid was sticking, once it allowed pressure in it was stuck in the on/off position thus holding the pressure when it should not have.

Replaced the solenoid and everything worked properly.

Resurected to close it.

 

Got a qurestion about this... I just drove my 7 today for the first time in a while, it was boosting fine all day until the past few hours. All of a sudden louder and deeper exhaust sound then no boost even when I shift to 3rd. Were these the exact same symptoms? I tried shutting the engine off and on few times to see if there would be a difference but it was the same everytime. I'm assuming there are two options on this, disconnect the actuator control or check if the vacuum chambers are leaking?

 

The end all symptoms seem the same. Only thing was that I would get boost after the transition. 4.5k boost would come in full. No boost before that.

If you let the car sit for awhile, 30 min or so, does it have a full boost pattern? After going above 4.5k does the problem start?

Also, while the problem is happening, look under the car and try to locate that TCA, if it's sticking out even after the car is off, then yeah, you got the same issue.

My tempoary fix was a check valve and a restrictive bleed off filter on the other end untill I got the solinoid. Pressure would bild up to actuate the TCA, then slowly bleed off to let it return.

 

Do you think my problem could be a TCA? The car boosts fine at any RPM in a single gear, but if I redline that gear(or just pass the secondary turbo transition point), I only get 2psi on the next gear. Could it still be a turbo control solenoid problem?

 

anyone have any idea as to what the home position of the tca is on idle..
rod extended (closed) or rod retracted (open).....