Thread: boost lost???

let it warm up then hold it flat in most gears

or..... you could pull turbo apart and clean veins

Originally Posted by uninformed

thanks Paul, so do you think it would be safe to say, that if the rod fitting is set within 2mm of original postion and either way it was against that set stop, I should be ok...as I said I never touched this set stop and I dont think anything would have changed with it. My major concern was over boosting, but I think that max boost wont have changed. I think I will leave the rod set up so I have to put a small amount of pressure in the actuator to fit it up...that means at rest/idle the actuator spring is already compressed a little and should move off a touch quicker...the rod travel length lost here will only affect minimum boost at full extention


clear as mud

Provided the stop screw for minimum vane gap postion has not been moved (max boost) you should be able to adjust the rod length to achieve the original boost curve you had.
Err on the side of caution and start with the actuator rod resting on the stop and no pressure on the actuator (lengthened) then drive it and test loads (boost rate) if to much lag shorten the rod. The effects are much more dramatic than a wastegate adjustment so about half a turn at a time until you reach the boost rate you had (hopefully).

Cheers,
Paul.

Originally Posted by uninformed

how so?

with an old school turbo you were limited by the boost actuator opening the wastegate and how much fuel you could pour down its neck. the more boost it tried to make the wider it opened the wastegate.


with the VNT there is no wastegate turbine speed is controlled by where on the turbine wheel the gasses are directed by the vanes. [ame=http://www.youtube.com/watch?v=Gc2awh0O0Bc]VNT turbocharger cutaway animation - YouTube[/ame] here, more or less is the mechanical layout of your VNT in action. (this is a vacuum actuated unit)


at low exhaust pressure the vanes direct the exhaust gasses to the outside of the wheel where they can exert the most torque on the compressor wheel spinning it up. As the flow rate increases the gas is directed towards the center of the wheel

turbo de geometria variable - YouTube

heres a demo of what happens inside the turbo at varying exhaust flow rate.

once the vanes are all in, it comes down to how much fuels going in.\
]

thanks Dave, I kinda got that part, it was the "fueling from the pump that sets max boost" part I was lost with???

Cheif what part were you replying to

Paul, I have just returned it to where I believe it was originaly. Going by the clear line of soot above the lock nut on the actuator rod (it is clearly clean thread then black sooted thread). This was pretty close to where the nut had been left, Im pretty certain I hadnt moved it more than half a rotation either way during dismantling. I also feel I have the new drilled hole in the end of the actuator rod fitting pretty close to original. I dont have a boost gauge in the truck. Nor one to use for testing. I will go by the seat of my pants and EGT's....hell I dont think it is going to be worse than after last friday night when the pin must have finally broken free. Seeing this and how wollowed out the actuator rod fitting was, I think that may have lead to the lag "valve like" feel I explained in the begining of the thread.

Tommorrow will tell

You will be ok, it is not as though you have to set ip up from scratch.

The vanes I belive to be used to vary the size of the passage that the exhaust goes through, this in turn causes a higher gas speed when the vanes are towards the closed end of range of movement, higher gas speed causes turbine to turn faster.

any ideas on what torque value to do up the 10mm(OD shaft/thread) banjo bolt fitting that goes into the top of the turbo between the compresor and turbine?

Theoretically you should use two new copper washers (or whatever is used there) and at a guess the banjo bolt should be 25Nm or thereabouts.

It might pay to pull the connector off the IP solenoid and crank it till you get oil pressure, just to ensure the turbo has oil, then reconnect the solenoid and fire her up.