Boost problem... please help

[Shark]

Right, apologies for the length of this post but I want to get all the info in so that (hopefully) you can help me.

I have lost boost on the secondary turbo of my FD.
Only mods on the car so far are PFC and remap from RE:Worx

I lost boost pressure about a week ago and on inspection (and advice) found that the rearmost hose (facing the front of the car) had popped off the pressure chamber in front of the plenum.
I replaced it and got boost pressure about halfway through the secondary turbo range then it fell off again not to return.  I checked the same hose and found the one at the front to be loose... it popped off with a release of pressure as soon as I touched it.  put that back on and still no joy.

I have checked all the vacuum hoses to the best of my ability and found no cracks or leaks.  :confused:

The car holds full boost pressure of 0.9 bar up to 4,500 revs.  When the secondary turbo should kick in at 4,500 the pressure falls off to about 0.1 bar by 6,000 revs.  It then holds at about 0.1 bar.  I take this to mean that if there is a leak in the system then it can only be introduced when the secondary turbo is brought into the picture.  ...but I am not aware of any hoses used only for the secondary turbo??

I\'m going to take the plenum off this weekend and look at the solenoids to see if that is where the problem lies (hopefully I\'ll be able to figure out what I\'m looking at!)

If anyone has experienced or heard of this before, please let me know what it was and how you fixed it.

[Also posted on FDUK]

[eatmyrx7dust]

Sounds like the waste gate is opening !! to lose that much pressure. You will need to take of all hoses to get down to the actuator rod assy.
There are also two blow off valve which only open on -ve pressure in y-pipe. Check the brown coloured one at the rear of engine bay. I suppose if this was stuck open you may get similar symptons, but you would hear whoosing noise when 2nd turbo kicked in.

Adrian

[Shark]

Originally posted by eatmyrx7dust
Sounds like the waste gate is opening !! to lose that much pressure. You will need to take of all hoses to get down to the actuator rod assy.

booger.  That\'s a big job, but I suppose an opportunity to put some decent hoses on.

Originally posted by eatmyrx7dust
There are also two blow off valve which only open on -ve pressure in y-pipe. Check the brown coloured one at the rear of engine bay. I suppose if this was stuck open you may get similar symptons, but you would hear whoosing noise when 2nd turbo kicked in.

No whoosing noise, - Always had a lovely whoosing noise on both turbos, now only on the first which holds pressure and a screaming engine in the absence of the second.

If a BOV was stuck open, wouldn\'t it vent pressure on the primary turbo as well as the secondary?

[Shark]

BTT

Hoses all seem okay but the secondary doesn\'t seem to be spooling.

Can anyone tell me how to test the following?

Charge Relief Valve (in case it\'s not closing)
Charge Control Valve
Actuator (Charge control)

and in case that\'s not the source of my problems...

How to check these items on the secondary turbo...
Can I get at these?

Turbo control valve
Turbo precontrol Valve
Wastegate valve
Actuator (Turbo control)

[bobster]

Hello mate.... this sounds very familiar

Right bear with me here..... when you do a WOT run from low revs the boost falls away at the transition? Thats if it ever generates it. (if you change up gear and keep your foot in you should still get no boost)

I would hazard a guess and say that it is more likely to be the actuators. Possibly the Turbo-Control or Pre-Control actuators. I would check that the actuator rods are still connected to the arms. The C-clips may have fallen off.

You can get to the Turbo control actuator from underneath the car ... you just have to bend the little heat shield out of the way. This was my problem....the rod was caught over the arm... but not properly located in the hole.... Also happened another time with the wastgate rod.... wastgate was just flapping about so no boost at all.


A very useful guide

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

Hope this helps

[Shark]

Excellent!  Thanks!!!

I found this write up on scudericiani (sp?) but without the diagrams I was having a little trouble.

Any idea where I could get a vacuum tester and how much they cost?

[bobster]

I never bothered with the vacum tester as I couldn\'t find one either..... :rollin

I would also invest in some very long nose pliers.

[Shark]

Cheers bud.

Will get the undertray off and make sure I didn\'t cause the whole damn problem with some careless fitting shenanigans!!

Have been reading through that site and this sounds like it would cause my problems if it were stuck open...  If it seems to be working then I can work back to the vacuum chamber , but the question is would the primary run such low pressure if the secondary was coming in or is the 0.1 bar I\'m getting too low? (implying the primary being allowed to leak pressure above 4500 revs?)

The actuator rod being the bit coming out of Chamber B, yes?

Charge Control Solenoid / Actuator
The Charge Control Valve controls the transition from Primary to combined Primary and Secondary Turbocharger operation. When ever the pressure applied to both Chambers of the Charge Control Actuator are equal, the spring force of the Charge Control Actuator will open the Charge Control Valve.
Below 4500 RPM this actuator is ON, (actuator rod pulled in), this closes the valve between the Primary and Secondary Turbochargers. This valve seals the air passage the same way as a throttle butterfly valve.
A simple test for the Charge Control Actuator is to start the engine and let it idle, the actuator rod will be pulled in. Stop the engine and remove the hose from Chamber A and the actuator rod will be out, see also Boost Test Step 5.
Chamber B is always connected to the Primary Turbo Compressor and normally will have 0 to 12 psi of boost pressure applied. Chamber A is connected to the Charge Control Solenoid, from 0 to 4,500 RPM a vacuum, from the Vacuum Chamber is applied, above 4.500 RPM the Secondary Turbo Compressor is applied to chamber A.
From above 4,500 RPM with Secondary Turbo Compressor applied to Chamber A, when the Secondary Turbo is producing the same or more Boost than the Primary Turbo, the Charge Control Actuator\'s spring will allow the Charge Control Valve to open, allowing the both the Primary and Secondary Turbo provide boost.

[bobster]

You should be able to see that actuator without pulling the car apart...

You can get to the turbo control without taking the undertray off... when under the car just follow the exhaust back towards the turbo and you might be able to see it on the underside of the turbo pack.... You shouldn\'t even have to take the tray off.
I think this is more likely to be the problem.

[Shark]

hehehe    It\'s fixed now!!!     :cool :cool

You were right bob, the turbo control actuator rod had popped off!
A bugger to get back on and I\'ve burnt me fingers being too impatient to wait for it to cool down properly but it\'s back on and working.

Question is, should there be a split pin or suchlike holding the rod in place?  You mentioned a c-clip - can you elaborate on what that might be???

[sadgoth]

hehehe It\'s fixed now!!!      

Excellent news mate! Glad you have your turbos back online!

[Donato]

Hi Gregor,

Glad you got it fixed mate. There should be a c clip holding on the actuator rod on (they rust and fall off). If you phone one of the tuners they will be able to pop one in the post for you, i have some kicking about if you get stuck i can post you one.

Donato

[Shark]

Cheers mate.

I\'ll get on the phone on Monday and probably get a spare or two at the same time just in case.

It;s gonna be an expensive trip next time I head north.  I already owe you a beer or two Donato, and I think I owe Bobster a couple too now :rollin

Edited to add - Thanks go to Clive for spending the better part of an hour on the phone rekindling my enthusiasm to fix this myself when I was ready to book it into someone.  
Turbo problems not being fun, I have some nice new hoses coming from SHY to put in at my leisure.

[bobster]

Glad you got it sorted....If it\'s any consolation, I burnt my fingers too

The rats nest is alot of fun....Enjoy.