Boost problem. Specialists in SE?

[jameswrx]

Don\'t think it\'s something that basic to be honest.  I\'m pretty sure it\'ll be something related to the solenoid operation for the second turbo control or something like that.

I\'m new to these cars and their pretty unique turbo and solenoid arrangement.  Need to do some more research into how the solenoid control works.

Anyone know the exact timings (with reference to RPM increments) the turbo\'s produce their boost.  Is there a specific rpm the 1st turbo won\'t boost at?, for example if you are at 4,500 rpm on part throttle (no boost) and you floor it what happens?.

It almost seems to me there is possibly specific ECU controlled rpms where the 1st turbo will be operative and the same for the 2nd turbo using the various solenoids.

[clive]

Hi James, have a look at the pipes on the triangular  black plastic box in front of the plenem ( middle of engine) as l have known this symptom a few times if a pipe is off of this.

[Shark]

Hi James,

The sequential turbo system works as follows.

2krpm - first turbo spooled and at full boost
3krpm - some exhaust gas released to pre spool secondary turbo, but any pressure created by secondary is vented off while car runs on primary tubby boost only.
4.5krpm - secondary turbo venting ceases as now spooled, secondary is switched from venting to join primary and both turbos active from here to redline

Sounds to me like your primary is fine.
Rev (briefly!) to redline in neutral.  your should see about 0.4bar boost.  This will prove the primary fine theory.

Since you get bost properly at 2krpm, the deacrese your seeing is that reducing.  If you floor it at 3krpm, then it seems that the secondary is also managing to vent the primary.

Since your symptoms are the same as those I had a little while back, try this.
Lie down on the ground next to the car at the drivers side wheel arch.  You should be able to see an actuator under the turbopack.  The actuator has a rod comes out of it.  That rod has a small hole in the end of it and this should connect to a nother piece which is consequently moved when the control rob moves in and out of the actuator.  This could have become detached.  reattach (when cold!!!) if so, and see if that sorts your problem.  

attched turbo diabram with actuators so you know what it looks like.

[jameswrx]

Thanks guys will deffinately have a look at the probs stated.  The actuator sounds favourite (after reading a lot of threads last night).  

Appreciate the detailed responce Shark, thanks :cheers

[jameswrx]

actuator (turbo control) is attatched

actuator (turbo precontrol) is attatched

can\'t see the actuator (wastegate control) because of the heat shield

had a look at the pipework and can\'t see anything off:(

[jameswrx]

Right..

Just had a look under the inlet plenum and saw this little bugger off (see below).  Took some fiddling to get to and managed to pull it back through to an easier access point.  Trimmed back until it was an un perished part of the pipe, put a straight connector in and another bit of pipe to make up the length I\'d cut off, fed it back through and managed to ease the pipe on with some long nosed pliers.  Even managed to get some little zip ties on the pipes.



Also noticed there are a couple of metal pipes on there with nothing attatched to them, you can see one end of one of them in the pics (top pipe coming from behind where the bolt is).  It doesn\'t look like they have ever had anything on them (ie the pipes have the same aged surface corrosion allover, unlike the pipe which was hanging off which clearly is cleaner where the pipe should be).  Are ther some unused metal pipes under there?.

Going out for a spin now, wish me luck..

[jameswrx]

Right just been out and we have BOOST only now it\'s too much boost when the 2nd turbo kicks in it hits hard but it\'s boosting too much.

1st turbo spools to 0.7bar, keep foot in and revs a bit like this until 4,500 - 5,000 rpm then whoa boost comes in with 2nd blower.  Not sure how high it\'d go because I was well aware of any potential probs and set the defi to a warning if 0.95bar was reached and  I backed off the throttle when the 2nd turbo came in.

I tried a couple of partial throttle runs in 3rd and again 1st turbo spools as you\'d expect then 2nd comes in hard, I saw 1.15bar on partial throttle(peak recorded from defi\'s) and just backed off.  I have experienced of lots of turbo\'d cars and it felt like if I\'d WOT\'d it it would have gone off the boost gauge.  It almost feels like the wastegate on the 2nd turbo is stuck shut or something.

What I\'m wondering is if this pipe being off has meant no 2nd turbo exhaust feed at all?, I would think it\'s possible.  My theory is that this pipe (that I recconected) has been off a while and not allowed any spool of the 2nd turbo (hence no mechanical wastegate actuator movement needed to control boost level on 2nd turbo) therefore the actuator has possibly seized up?, either that or the 2nd turbo\'s actuator has a sh*t load of preload on the arm.