overboosting

[smcnairn]

Hello I suspect my actuator is shagged but before i go and buy a new one i would like to confirm this. It all started when i raised my boost to just under a bar using a bleed valve. It was ok for a few weeks untill i went to overtake and the boost shot up to well over a bar! From then on it does not allow me to put the foot down with out over boosting! ive had my inter cooler off checking all the vacuum and boost pipes the all seem ok I also removed the bleed valve. Is there any way of making sure it is the actuator that is the problem??

 

[MarkTurbo]

I doubt its the actuator

If that was shagged you'd be getting the opposite problem (it wouldnt be holding boost) It sounds like a pipe has come off somewhere Check them all again.

 

[Rishi]

Yeah if the actuator was shagged then you'd end up with less boost...

Could be as mentioned a hose thats come of or it could be an air leak from a damaged hose...

Check everything...



Rishi

 

[donpulsar]

Include the hose coming into the top mount underneath, and the one that comes out from the top to the plenum / inlet. ( if y'still running a top mount that is )

 

[smcnairn]

yes but if the actuator was shagged it wouldnt open the wastegate and exhaust off the excess boost pressure? is this right?

 

[smcnairn]

Yeah i checked that two small pipes to the the top mount too?

 

[nismoboy]

remove the bleed valve and see if it get rid of the over boosting?

 

[smcnairn]

Yeah bleed valve is off. just the same overboosting.
Running out of things to check now! :x Has anyone had this problem im thinking the actuator again.

 

[Fast Guy]

Just how much is it over boosting? What psi/bar are you running and what does it go upto then back down to when over boosting? and is it over several 1000s rpm or a very short range?

 

[nismoboy]

Could have lost the restrictor out of the vacum pipe? check the vacum pipe for the actuator, its located on the side of the inlet manifold.I think the pipe a has a grenn band on it where the restrictor should be?

 

[ram5ay]

yes but if the actuator was shagged it wouldnt open the wastegate and exhaust off the excess boost pressure? is this right?

Depends how it is knackered:
If the actuators diaphram has a leak in it then this would apply, you will get overboosting because the boost pressure will not act on the diaphram to overcome the actuators spring. You could test this roughly by fitting a longer length of pipe onto the actuator and blowing/sucking through it...... it should hold pressure if it is ok.
If the actuator rod has broken or become dissconected from the wastegate, then the exhaust pressure should simply overcome the wastegate and the turbo wont develope boost.

As previously suggested, I would double check all of your pipes running to the actuator and through the factory boost solenoid, making sure there is no air bleeding anywhere, as this is the most likely cause of your prob.

 

[Fast Guy]

Could have lost the restrictor out of the vacum pipe?

That would cause lower boost

 

[smcnairn]

Thanks for the suggestions. The overboosting happens over a short range of rpm. The vacuum pressure is ok. Im gonna do the check on the actuator pipe from the inlet manifold and the actuator tomo il let yous know how i get on. thanks.