Power for the 2006 BMW Z4 M Roadster comes from a 3.2-liter, 24-valve, dual overhead cam, inline six-cylinder engine that generates 330 horsepower. Managing that output is a standard six-speed manual transmission or an optional six-speed Steptronic automatic with steering wheel-mounted paddle shifters. This powertrain allows the M Roadster to hit 60 mph in only 4.9 seconds, with an electronically-governed top speed of 155 mph.