The base six has a familiar BMW growl and builds even power all the way up its rev range; with a manual shifter, its acceleration and feel are pure classic roadster, not overwhelmingly exotic. It invites foot-to-the-floor driving, though it's by no means underpowered. The turbo version's more guttural and more of a high-speed-hammer drop-top, with effortless high-speed passing and strong power for sinewy mountain roads. In the sDrive35i, there's a rush of boosted power on tap even from low to mid revs, so revving it all the way up isn't rewarded in the same way.
A delightful six-speed manual gearbox is standard on both versions. A conventional six-speed automatic is available on the sDrive30i, while even enthusiast drivers are likely to enjoy the seven-speed dual-clutch automatic that's available on the sDrive35i; it includessteering-wheel paddle shifters so that shifts can be ordered up at the tap of a thumb (for downshifts) or fingertips (upshifts). The dual-clutch gearbox lets drivers choose gears and then reverts to an automatic shift mode, or it can be locked in Manual mode for all-paddle control.
The sDrive30i can dash to 60 mph in 5.6 seconds, while the sDrive35i can make it in 5.0 seconds. In sDrive35is models, an overboost function enables a temporary increase of 37 pound-feet of torque, and 0-60 times of just 4.7 seconds. Top speed is 155 mph.
The Z4 rides and handles very well. While handling purists will probably want to stick with the base suspension, all Z4 models are electronically influenced with the Z4's addition of Driving Dynamics Control. Three modes-Normal, Sport, and Sport+-are programmed into the car's electronic controls for steering feel, automatic-transmission shift speed, and stability control response. In cars equipped with the optional Adaptive M Suspension with Electronic Damping Control (part of the Sport Package), it also controls the suspension damping. With the adaptive suspension, the Z4 is remarkably flexible, if a bit digital, soaking up patchy bumps and even coarse, jiggly surfaces but tightening up for the esses and quick maneuvers.
In either of the Z4 models, the steering doesn't have the direct feel of the Boxster, and it's a touch too quick. Big, smoothly modulating brakes feel responsive but not touchy, firm but not unyielding.