Engine: T5: over boost issues

[wise old monkey]

v70 t5 2006. I've had over boost issues for a while, I've replaced tcv, map, maf, intercooler, all vacuum pipes and a new actuator.
but still have over boost, yet if I boot the car and the boost goes to 2bar its fine, the moment I hold it at 0.5bar it over boosts.
any ideas people.

I fone a smoke test yesterday and there is no air leaks on any of the pipe work.

[davebb]

Hi , what tools have you got, have you got vida,
with the ignition on but with the engine not running, look at the MAP reading VS the ECM Atmosphere sensor it should be the same,
The 2 bar you take the boost to ,is this including the atmos psi,
is the car re-mapped for this psi, when you changed all of these sensors , are they all original, or cheaper ones,
look at wiring for any damage, at/from sensors
test that all sensors are working as they should,
is the TCV actuator working correctly, i fitted a new one, cheap from china that worked very well, but then parked the car up for some time (a few weeks) and
when i went to use it , i had no boost control, and i could only get a small bit of boost at higher revs, i tested the TCV actuator and it was not moving, it was stuck at no boost, it could had been the other way,
so i fitted a original one, and all is ok,
can you pressurise the intake and read the MAP Pressure is reading the same,
Thanks and good luck,
Dave

[wise old monkey]

all new sensors are bosch, wiring is fine, been on vida everything was fine.
it's a expolice training and mapped by frf swansea for the police, I've had the car for ten years

[richmac]

That's a lot of boost!

How does the car actually drive? Does the ECU throttle it back or does it just feel/ look wrong? Did it suddenly start doing this or was it progressive?

It sounds like a wastegate issue. Basic checks that I suspect you've already done so apologies in advance:

1. Is it the correct Pierburg TCV? Correctly plumbed in? Are the lines good quality/ right size?
2. Is it the correct wastegate actuator?
3. Is your wastegate free to move?
4. What preload is set on the wastegate actuator?

[wise old monkey]

1. yes
2.yes
3. yes
4. 7.5psi
going to try another actuator tomorrow

[richmac]

I assume the car came with the actuator set at his PSI to go with the tune and it moves correctly when pressurised (guessing you have Mitivac or similar).

You could try carefully running at the overboosting threshold with the yellow clamped off to see if it behaves the same without the TCV controlling the wastegate, ie: is the TCV actually opening it. Don't boot it, however!

How's your bypass/recirc valve?

[wise old monkey]

stripped it all down again this morning, the hose under intake on the turbo had come off, swapped the actuator out for my expensive forge motor craft actuator, now its got no over boost, but won't go over 0.5bar, so I guess I need to setup the actuator.
can not get to the recirculating valve to check it

[precisionguesswork]

Originally Posted by wise old monkey

stripped it all down again this morning, the hose under intake on the turbo had come off, swapped the actuator out for my expensive forge motor craft actuator, now its got no over boost, but won't go over 0.5bar, so I guess I need to setup the actuator.
can not get to the recirculating valve to check it

The gate should be set to 7psi cracking pressure
Preload should be 3 turns on the nut then snugged down.
TCV will handle the rest.