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Originally Posted by Boss330
Agree that it's not as simple as oversquare means low torque and undersquare means loads of torque.
However undersquare (with a large bore and short stroke) means the possibility to fit larger valves increasing flow.
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(I think you meant over-square)
... which would have come in handy on all BMW I6 engines in the recent past as well, including the S54 and other M engines. So, I stick firmly by my point that there is no compelling technical argument for avoiding an over square bore (and bore center increase) for so long. There may have been other reasons at play (costs of tooling or unavailability of more flexible tooling), sure.
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Agree that on a turbo motor many of the points above aren't that critical and a undersquare engine would have sufficed.
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Plus, 3L displacement is plenty for 430hp. If this were a 500hp engine, I would have already been reasonably convinced we have a larger block with more displacement, even though they've hit 3.2L in the past (using iron only, however) and even though Mercedes is now hitting 175hp/L in a $50k car.
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But, if bore/stroke info is correct, i give credit to BMW M for choosing a engine concept that is generally better for a high performance, high rpm engine. Especially given the work involved in this...
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For sure. Especially when I've believed all along they would go with the current I6 architecture to keep cost down.