No boost on primary, 4-5 psi on secondary
 

Yesterday I did a few WOT runs and suddenly had less boost from the primary turbo. Normally I got around 10psi up to 4500rpm, when I realized the problem it was maybe 4 to 5 psi. With every WOT try (I think 3-4) it got less, ending up with 0 psi. Problem exists in every gear.

When I go over 4500 rpm, the boost goes slowly up to 4-5 psi.

I think the car has also getten louder (Exhaust, in the engine bay I hear no other sounds than usual).

I'm still hoping that its only a hose or something. I will try to check all the components of the turbo system, any specific advise on where to search for a leak? Or shuold I just pull the turbos?

Sounds like a vacuum leak.
Checked all the pipings, hoses, couplings, etc.?
If it's stock, I would start with intercooler pipes or y pipe.

Sounds like you have a split coupler. Remove all the rubber couplers and sqeeze them to check for cracks.

Could also be collapsing primary inlet as well.

I'm not sure what you mean, but I think its not OEM anymore, or is it?

just looks like upgraded intercooler pipes, turbos are on the other side

I don't know where the primary inlet is located or what it is so I guessed. So its the inlet to the turbos?

Sorry that I am that uninformed, but my engine bay is pretty much stock, so I cannot see anything related with the turbos. Other than that, I am no native speaker and with some terms I'm not familiar yet.

I will be at the garage later this day and have a look at all the mentioned spots.

One more thing, if it was a vacuum leak, wouldn't the vacuum reading on the boost gauge be lower than normal? Its 6psi as before, but was fluctuating a little bit sporadically when idling.

Your vacuum/boost gauge is reading after the throttle body. Even if you had no intake (or a huge vacuum leak) before the throttle body you would get similar vacuum readings because your throttle body controls manifold vacuum. Your -6 psi is low vacuum by the way, which points to a tired engine on top of your turbo control issue. So, you probably need a rebuild.

You should download the factory service manual; it's free.

Turbo/vacuum diagrams:

https://drive.google.com/open?id=0Bz...1MydGJoc2I2eFU

https://drive.google.com/open?id=0Bz...UUyVndCZUU4SFk

https://drive.google.com/file/d/0Bzh...ew?usp=sharing

Thnx for the diagrams!
I checked all the couplers and the hoses I could see, nothing obvious.
Seems like all couplers where upgraded at some time.
The inlet to the primary turbo is pretty sturdy.
Then I checked if the charge control valve and the turbo control valve (I think, please see the attached pic) move when the engine is started.
The first moves when the engine starts, the second doesn't.

I removed the upper hose from the air intake to the secondary inlet, but other than that I don't see much quickly removable parts for further investigation. Only thing I would remove would be the UIM for checking the rats nest.

I think the next step after that would be removing the turbos, or do you guys see another option?

Does anyone have another idea what could cause the problem described?

Since all "big" hoses seem ok and the problem seems to be only with the primary turbo, there has to be some way to check it, doesn't it?

The only thing I could do now would be further breakdown of the system, but where would be the best place to start? UIM?

But if I dissassemble the system I loose the possibility to test things with the engine running..

I'm pretty helpless now and would appreciate any help!

Did you check all the couplings and hoses/piping or just intake hose for secondary turbo?
Sounds like the problem is all across the board due to the fact that secondary turbo only gets 4-5 psi.
crossover pipe does get split since it is made out of plastic.

I checked all the couplers, but I only removed the upper intercooler coupler. The others I checked by sight. Since they are all aftermarket, they are all in good shape.

I hoped because of the pretty straight forward symptom (zero boost up to 4500rpm, some boost afterwards) it could be narrowed down to only a few originators.

Could it also be a control valve (i.e. turbo control valve or turbo precontrol)? Can I test them while in the car?

I will start further breakdown this afternoon and will start with the IC pipes and the crossover pipe.

Troubleshooting

There are some good info. you can look through.

Already reading on that page, thank you anyway. Its hard to understand but I will try.

I checked the charge control valve today, when I put vaccuum on the right port it moves and when I put pressure on the left port its moving, too.

Where is the vaccuum chamber located? I would like to test this with vacuum, too.

Vacuum chamber is on the front of the engine near the power steering and A/C bracket

You need to figure out why your vacuum at idle is so low first. You have way bigger problems than boost right now... if those compression numbers are right.

Thats absolutely clear. I want to rebuild shortly. But what I don't want is taking everything out, not finding anything, rebuilding the engine, put everything back together and having the same problem again. I'm not sure wether to go single now, depends on money, so I want to find the error now.

Ok, but just to be clear; if you are on the verge of losing an apex seal and it finally breaks it will trash both your engine internals and turbos.

I love the twins, but I can understand the appeal of single turbo for track use or high power applications.

If you tear it down now, are very meticulous, compare everything to the manual, and check all the solenoids/actuators/check valves/etc you should be able to find the issues during the rebuild and put it back together properly.

You will need a mityvac with pressure and vacuum ability. There is a write-up thread on here about checking all your solenoids.

Ok, made some final tests..

Used some new vacuum hoses and some new screw clamps where there where loose old normal clamps.
Tried to find the vacuum chamber for testing it for vacuum leak, didn't find it..
Then I put everything together and made another testdrive. Still, no boost from the primary. I then tried to accelerate, go off the throttle and go quick back on the throttle. No boost.
At last I fixed the charge control valve in the pulled in position, no boost. I didn't go over 4500rpm.

Whats strange is that I hear the BOV (aftermarket) when I go off the throttle below 4500rpm, but it is much much quieter than normal.

Well long story short, car is in the garage in the "pull the engine" position. I also ordered a cheaper version of the mityvac and hope to find the error.

Thank you guys so much for hanging in there with me so long! :)

You should check the compression like alexdimen mentioned above.
Vacuum reading seems very low.

Oh, I forgot to mention, I will pull the engine for a rebuild. ;)

Since the chain hoist I ordered for pulling the engine is defective, I decided to remove the UIM in the meantime, like I planned all the time, and look what I have found:

https://cimg6.ibsrv.net/gimg/www.rx7...35ec750a32.jpg



Here is a picture for better overview, the mark is where the blown hose is:

https://cimg7.ibsrv.net/gimg/www.rx7...42fcce34dc.jpg

It looks like is the hose is coming straight out of the block, but I'm not sure.
Would you say this could be the reason for the problems I described?

Which hose is this, where is it coming from and where does it go? (Or whats the solenoid on the second picture with the blue hose on it?)

How do I best get to the hose, I assume the LIM has to come off?

The solenoid with the blue hose is Solenoid A Fuel Pressure regulator, that orange plug that is not plugged in goes to it. Also that vacuum hose in your first picture feeds the fuel pressure solenoid.
You do not need to take the LIM off to service those hoses mainly the rats nets and ACV. There are some very good posts on doing a vacuum hose job (I am doing one now). I would recommend buying a silicone vacuum hose kit and doing that job as you are part way there anyway and a lot of those hoses look pretty brittle.
Here is a link to some vacuum diagrams, the hose that is broken is the Teal one going to Solenoid A
https://www.rx7club.com/3rd-generati...-turbo-749702/
Here are some links on doing the vacuum hose job,
Dale Clark's
https://www.rx7club.com/3rd-generati...our-fd-904277/

Another to give you some more information
Rx7 Projects: Vac Hose Job
I just went off the diagrams on mine.
One last thing the vacuum chamber is located between the power steering pump and alternator

Hope that helps
Mike

Thank you for naming the solenoid and the links. The last one isn't working though, temporary problem?

I removed some vacuum hoses yesterday for testing the vaccuum, they are VERY brittle! Needed lots of WD40 and a screwdriver to remove them, they instantly cracked.

I would really like to simplify the whole system, so I'm thinking going non-sequential.

Back to the turbo, how would the symptoms be if the primary turbo would be mechanical defective? I assume I would have no boost from the primary turbo and some from the secondary, right? My hopes that this is a turbo controlling issue are thinning out..

The reason for this is mainly the closing charge control valve, when the engine starts. When I understand the system right, the only way then for no boost on the primary turbo would be a boost leak, but then why is the boost rising at 4500 rpm?