Quote:
Originally Posted by CanAutM3
For a given displacement, a longer stroke does not mean more torque. While it is true that a longer arm means more torque for a given force, this is offset by a smaller piston area on which the cylinder pressure is applied therefore yielding less force.
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I had crafted a fairly involved response to this, but realized that it was more complex than I thought at first.
But, in short, cylinder count plays a role because, while it does not change total piston area, it does effect area per combustion event. So, assuming we have two engines with the same displacement, same stroke, same effective RPM range, but different cylinder count, the one with fewer cylinders theoretically has the torque advantage. This could partly explain why Porsche's H6 (in its most evolved form) has higher peak torque than BMW's S65 V8 at similar RPM.
But yes, generally speaking torque is displacement-bound (while power is RPM-bound). Most naturally aspirated production cars make somewhere in neighborhood of 75-85 ft-lbs of torque per liter at peak, whether they are econoboxes with tiny three or four cylinder engines or supercars with huge V12s.