Who did it?

 

Any update on this? My 535d would appear to have turned into a single turbo ; it's a dog below 2500 rpm but seems OK after that. It's as though the small turbo's wastegate is stuck open and not generating any boost. No funny noises, smoke or warning lights, just a slug of a car at low rpms. And since the gearbox software expects big torque at low rpms it doesn't downshift unless you just about floor the throttle.

 

hello

just to let people know that ALL turbos on the 5 series are built by Garat via honeywell

thanks

 

In reading up on the operation of the 535d sequential turbos it would appear that all intake air passes through both turbos, first through the large one and then the small one. There's no wastegate on the small turbo, only on the large one. A computer controlled valve distributes the flow of exhaust gases between the two turbos; I guess this is effectively the wastegate for the small turbo. I find it interesting that all air flows through the small turbo; I would have thought that the compressor wheel would add significant resistance.

So my issue sounds like it might be one of the exhaust distribution valve being stuck in one position.

 

Hi Phelix
Good research there. I recall a technical cut-away diag. of our engine, but it was about the launch time.
As you know, the units fitted to this engine are much simpler than the variable-vane one so prone to failure on the smaller output, single turbo cars. In my view this should make ours more reliable!
Still, not much confort if you've problems. I'd say you've probably narrowed it down well in terms of the exhaust gas distribution. Its could be that you've popped one of the hoses off or got a boost leak somewhere.
Is your car re-mapped? - could increase liklihood of hose coming of or leaking IMO.
Good luck with fixing ASAP - keep us in the loop.

 

Happy to post whatever else I can find out and what the solution is. My engine is unchipped.

Here's a good cutaway of the turbo system


And I was wrong with what I posted earlier; when the large turbo is at full boost inlet air no longer flows through the small turbo.

So guessing some more; perhaps the flap that allows air to bypass the small turbo is stuck open.

 

That sounds right now.
Hope its just the actuator/flap rather than an exchange turbo(!)
Don't want to jinx things, but it would be the first failure I've heard of, and there must be lots of 100k+ mile examples of the 535d now.

Hope its a quick(cheap) fix.

 

Tis sorted. I took the airbox out to get a good look at the arrangement of the turbos and the various flaps and noticed that the vacuum line that controls the exhaust distribution valve was badly chafed where it runs across a sharpish corner. I couldn't get a replacement piece before the local dealer closed so shortened and re-routed it and put everything back together. All's back to how it was before.

 

Good work! - glad yr sorted, and @ ?0 too.

 

Sorry to dig this one up again.
Do you know what the actual issue was? Do you know what they replaced and did the warranty cover it?
Thanks!