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Old 11-26-2018, 04:39 AM
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wpoll wpoll is offline
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Quote:
Originally Posted by Clunk84 View Post
hi thanks I'll check that post out now,
I was concerned that a flake of metal was missing from the inner skin of the manifold at the point at which it would meet the turbo probably about 10x13mm but he said he had checked the turbo for damage and it wasn't and it all span freely and all was ok ... I'm now thinking is this piece jammed in the nozzle ring somehow... it is however boosting hard when all is well and at them moment I only feel the loss of power top end and the howl when cold and at idle when the vacuum hit -18

also vacuum hoses have been replaced and apparently intercooler and exhaust checked for blockages/leaks.

my gut feeling is that it the turbo and I'm really fed up as I only changed this about 3yrs ago / probably 28,000 miles! and also if it is it could have been replaced easily and with the same labour cost as when the cam cover was off and the manifold out!
Pretty frustrating to have done all that and still have issues.

If there is a piece of manifold missing, then where is it? It sounds too big to have passed through the turbo... You might be right about it jamming the nozzle ring, although if the nozzle ring was jammed the actuator rod (plunger) wouldn't move.

That's the exact reason I changed my manifold as soon as the cracks started - they are known to fall apart if left too long.

In my vacuum test, it took about -15psi on the VGT actuator to move the actuator to it's full limit. My measurements weren't exact but it all works very well. I wouldn't think -18psi would be an issue. In fact too much vacuum in itself cant cause any issue, as the nozzle ring will just hit an end stop and not move any further.

What CAN cause issues is too much vacuum at the wrong time. And the amount of vacuum applied to the actuator is only controlled by the pressure modulator, hence why I think it needs to be checked out.

The vacuum supply is from the vacuum pump, via the main vacuum manifold, to the vacuum reservoir through the pressure (vacuum) modulator and then to the actuator.

The correct way to check this system is to check the DDE for errors related to charge pressure control deviation. Any errors noted should be followed as per the diagnostic steps provided by BMW.

There's some ore info. on turbo issues here...

https://www.newtis.info/tisv2/a/en/e...ntrol/EIDTjVEl

and here...

https://www.newtis.info/tisv2/a/en/e...ntrol/EIXiL8xM

HTH...
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