Quote:
Originally Posted by ZCP M3
God I am so addicted to this engine and its technical complexity. BMW needs to release some sort of video or animation showing how this system works!!!!
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Here you go
Quote:
Originally Posted by ZCP M3
The exhaust manifold feeds the two small turbos and they in turn feed the large turbo.
Here's how I envision this working....
Full throttle throughout.
From idle, the small turbo wastegates close, VTG goes to minimum diameter, and the small turbos spool up and provide boost. The large turbo's wastegate is fully open to avoid restricting the small turbos.
As the revs rise, the small turbo's VTG starts to increase it's diameter to maintain the proper turbine speed. Large turbo still not engaged at all.
At the point where the small turbos run out of breath, the large turbo's wastegate closes and it's VTG goes to minimum diameter. Small turbos wastegates begin to open.
Large turbo is up to speed and as it's boost pressure rises, the small turbos wastegates open fully to preserve the exhaust's energy for the large turbo and to cease providing boost to the engine.
Towards redline, the large turbo increases it's VTG diameter to maintain proper turbine speed.
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Good try, but quite wrong. I too am very much fascinated of this engineering masterpiece.
Idle-1500rpm: basically single VNT turbo operation (right one) Inlet air always flows through the large turbo compressor.
1500-2700rpm: exhaust gasses are going to the large (non-VNT) turbos turbine, adding boost to the small 1st turbo already working untill it saturates
2700-5400rpm: the second VNT turbo comes in to take the flow from the large compressor, and from here on all three turbo's sing to 5400rpm (previous biturbos only had the large one going once the small turbo saturated and was cut out). Two VNT's in the small turbos secure excellent throttle response.
Also, it seems this engine uses a top mounted water cooled IC, so no piping to the front, less volume, less flex, higher efficiency and therefore excellent response (alike the F10 M5).
What an engine
Oh and on the X-drive: apparently BMW did their best to make it handle predictably with a very clear rwd bias...
(Did I mention I want a M150d?)