Ok Ive been having a problem lately with my secondary boost. I will get primary up to about the transition point and then it will either gradually lose boost or break up and lose boost. When it breaks up it sounds like a door is being partially opened and closed. This leads me to believe its the charge control actuator. I did the test to see if it was open when off and pulled in when started and as far as I can tell it is. Is there anything else that would present this problem, and or do you think it might be the solenoid or a line going to that solenoid? I would like to figure this out pretty soon so I can get a run in at a track to see what my ET with proper boost would be.

 

bump.

 

So I take it your boost pattern is something like this 10-5-0?
Take a look at this site for turbo troubleshooting tips.

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

 

No its more like 12-10-falls slowly while hesitating and finally reaches usually around 3 to 5 right before i hit redline.

Ive read that page numerous times but cant pin point which one would cause the problems Im having. Thats why I am asking for some advice on here

 

Sounds like your Charge Relief Valve is open when the secondary is online....it should be closed.
Problem for you is that the CRV itself is pretty durable and probably still works fine....it could be the Charge Relief Solenoid, which requires UIM removal, ugh. Either that or a popped hose in that vacuum circuit.

 

I'm having the same problem..

 

I don't think there is a way to pin point turbo problems without doing
some testing. (g)
Especially secondary problems.
Does your problem happen in all gears?
Have you checked your check valves?

 

Yea it happens in every gear, Ive checked all the one way check valves. I have put vacume to my BOV and CRV but havent put pressure to them to check. I just put on block off plates and I didnt see any lose vacume lines, but I didnt check under the rats nest. The problem was happening before i put on the block off plates.

 

I had a similar problem with my 93. This thing dogged me for weeks while I checked every line, solenoid and actuator both statically and dynamically (and monitored with a gauge) while driving. Primary boost was fine until transistion. After the transition, boost would decline and sometimes not build past 6# at all. Strangely enough, sometimes it worked ok. It certainly appeared to be a control system problem, but nothing was wrong with the controls that I could find.

One day I was under the car checking something on the suspension when I noticed a couple of loose bolts on the turbo assy--the ones that run through the access plate that also attach the turbos to the exhaust manifold. There was also evidence of an exhaust leak. As it turns out, as soon as the precontrol valve (the primary's wastegate) started to open, it was venting exhaust out the leak and the secondary could not prespool properly.

Tightened everything up. Problem gone--period. Full boost throught entire range and almost no transition lag. Now that I look back it makes sense, the problem started gradually and got worse over time. I had even considered the possibility that the secondary turbo was failing. Guess not. These turbos have over 110k miles on them and still make > 15# no problem.

Moral: Periodically check for exhaust leaks, it does not take much of a leak to make a big difference in boost. Hope this helps.

 

Ill check it out this weekend. Ill also test the Charge relief valve.

Mine was different then your problem though because it doesnt just smoothly loose boost its more of a sputtering/hesitating type of boost lose.

 

Mine would do that hesitation thing too, particularly once it got really bad. Though it wasn't always consistent. What got my attention is the sound that you describe as a door opening and closing. Mine would make that noise every time and it got progressively worse. I didn't recognize it as an exhaust leak, but it went away completely once I tightened everything up.

BTW: I think there is a small aluminum heat shield that covers the bolts I'm referring to. I was able to get to everything easily from below with the car jacked up. Took about an hour to fix.

 

Well I just went through and problem with my secondary and it
turned out to be the turbo control solenoid on the ACV.
But my boost pattern was a little diffrent than yours. 11-5 -5 and dropping
and no secondary boost in 1st and 2nd gear.
The first time I removed the UIM I replaced the TC solenoid on the ACV with a
bad one and my boost pattern was 11-5-3 and dropping in all gears.
The second time I removed the UIM and replaced that solenoid with a good one
my boost problem was solved. Ah the joy's of troubleshooting turbo problems. (g)

 

Yea ive alrdy tried that. I have a brand new one on there.

And the heat shielding you are talking about Speed of Light. Is that over a stock dp?

 

It's not over the DP. If I remember correctly it's about, say 4" x 4" and is held on by two nuts (10mm end wrench required). It's under the downpipe and in between the oil return lines--very easy to spot from below. The precontrol actuator runs to a pivot shaft just below it. The plate itself is held on by four larger bolts, two long, two short, I think.

The key here (to me, at least) is the sound it's making. You shouldn't be able to hear any of the valves operating. What sounds like a valve operating was, at least in my case, the exhaust flapping the loose cover plate on the turbo's.

I hooked a pressure gauge to about 8ft of tubing so I could watch it in the car while I drove. At the exact point that the charge control valve opened (under load) is when the boost would start to collapse; even though prior to switching, the pressure on the secondary turbo (only) seemed normal. What apparently was happening is that when the CCV opened , the boost would be unstable or break up because there was not enough exhaust to drive the secondary turbine and it would start to stall. I also check the charge relief valve to no avail. (by pinching the large hoses off at the air box).

Note that the CCV opens at the same time the Turbo Control valve in the exhaust manifold switches. If they don't switch together, you will have a problem. The TC valve is controlled by two solenoids--the one that's on the ACV and one on the solenoid rack. I originally changed the one on the rack, but it did not help. Since I had already verified the actual operation of the CCV and CRV, I was beginning to think there was a tubine problem, not to mention getting really pissed. I never suspected an exhaust leak, I only found it by accident.

 

bump. did ya find out anything?

 

I looked at it yesterday, but didnt have that much time. I didnt see any loose bolts around the turbo area. I did find a cracked vacume hose going from the pressure regulator. replaced it but didnt affect anything. I plan on taking a closer look at it on Sunday.

 

What kind of intake hoses do you have?

 

everything from the turbos on is stock as far as intake hoses.

 

You need to take a look at your intake hoses. The stock hoses have a issue with collapsing under boost when they start to age. Give them a squeeze with your hand in the center. If you can make the sides touch with little effort that could be your problem. If you are not sure, discounted them from your intake/filters and make a quick test run. Make sure nothing is restricting the opening of the hoses when you do this.

Hope this helps.

 

Durable, yes, but it could still have a problem. See if it snaps shut nice and tight with the hoses disconnected. I found that mine didn't, and I took apart the valve, cleaned it, and now it's nice and snappy.

Dave

 

Keep looking. One cracked/leaky hose leads to many.

Dave

 

I have replaced those with hard pipes so I know thats not a problem.

 

Well I switched the BOV with the CRV for testing and I didnt see any difference in the way the car acted. The only thing I can think of left is the charge control actuator or something that controls it.

 

That's why I asked what type of intake hoses you had

 

Well I am replacing my ignition wires this week so the UIM will be off. I will be looking for any kinked or cracked hoses under the rats nest. If its there is nothing going on there Im going to assume its a soliniod or the charge controll actuator