I'd be surprised if BMW would bother with a V8 turbo diesel in these times of environmental and fiscal responsibility, but I may be wrong. The 40d is as good if not better most of the V8 turbo diesels anyway. But you're right, given the same specific power/torque as the 40d, you would be looking at 330kW and 880Nm for a 4.4-litre V8 td.