No it's not an amazing sound but it sound's good. My post was just to show that just because it's a diesel doesn't mean it has to sound like a tractor. I don't feel any BMW has an amazing sound anyway's.
Also thank you Niky, I kept getting an empty white box.
Well, electric is most likely the future of motoring. If they make an electric M-car, which will probably happen eventually, then make it a good M-car. After all, it's not about the fuel, it's about the car you're putting it into.
Honestly, it's a great idea to combine diesel engine with M performance. I just wonder if those cars make any good noise. Audi with their latest 3-litre biturbo had proved that diesel can sound like a proper petrol engine.
It's because it's two-stage compression, i.e. the output of the larger compressor feeds the intakes of the other two, with an inter-cooler in between (and after). It could have been two large turbos feeding each other instead of one large and two small, but BMW wanted the low-speed response which necessitates the use of a smaller turbine (ideally closest to the engine, so the high-pressure stage).
When the engine gets into the higher revs, the throughput begins to overwhelm the first small unit, so the second one is brought online to take up the rest of the flow being discharged from the larger (low-pressure) compressor. The same is true on the turbine side, except the two smaller units feed the larger one.
Two-stage compression with inter-stage cooling implies some serious boost going on. Then again, so does 740 Nm from 3 litres.
