Well, you do get better acceleration out of a lightweight flywheel once you get past the any initial difficulty with launching. So I'm guessing that factored into Mazda's choice of flywheel weight. It's not like the car comes with a 332 hp V6, after all, so they need to squeeze performance out of wherever they can. Come to think of it, this logic may account for the flywheel weight of many 4-cyl cars.

its the best thing on the car.