2021 BMW Z4 M40i Reviews 2021 BMW Z4 M40i Reviews– The Z4 comes in two classes: sDrive30i and sDrive M40i. Those numbers are mostly meaningless as the base car has a 2.0-liter turbo-4 which is rated at 255 horsepower while the M40i pulls even harder with its 3.0-liter turbo-6 which is rated at 382 hp. […]