Divided turbine housings don't normally bypass 1/2 of the exhaust gasses from the turbine.
The division is to prevent low pressure pulses from some cylinders interfereing with high pressure pulses from others - normally with a 6 cyl engine the front 3 are divided from the rear 3 in the manifold and the housing keeps them separate until the turbine.
As others have suggested, the turbos are back to front. With compounds, the small turbine is closest to the manifold, and the larger turbine closer to atmosphere - tubines operate with an expansion ratio (opposite compressors, which have a pressure ratio for boost), the gasses expand through the 1st turbine stage as some of their energy is transformed to mechanical work, so a larger turbine is required for the 2nd turbine stage.
On the air side, the large compressor is closest to atmosphere (1st stage compression), and the 2nd stage compressor (near the engine manifold) needs to be smaller.
Usually you size the compressors so the operating pressure ratio of each compressor more or less equally contribute to the overall pressure ratio (need compressor maps for both to determine what this will be). If required overall pressure ratio is to be say 4, then PR for each can be 4/2 = 2 (PR1 X PR2 = overall PR). Because the inlet air density for the 2nd stage is greater, the torque will be greater and if shaft strength is a concern then lower the PR of the 2nd stage (and increase PR of 1st stage).


 
						
					 
					
					 
				
				
				
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  Reply With Quote Originally Posted by DRanged
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