BMW proves the German reputation for over-engineering by making the 2009 BMW Z4 sDrive35i the most complicated roadster ever. Unlike the very simple Mazda MX-5 Miata we reviewed recently, the Z4 sDrive35i is a technical tour de force. The engine sports not one, but two turbochargers. The transmission uses two clutches and a computer to move them. The suspension has different modes. And you could spend a couple of days going through the onscreen menus. But all of that technical wizardry results in extraordinary performance, a track-worthy roadster with few rivals.
The 2009 Z4 represents an update to the model, but BMW didn't make any radical changes to the exterior. The Z4 still has the long nose that bulges up, reaching above the level of the lower edge of the windshield, making it seem like you're piloting a World War II fighter plane. There are some refinements in the sheet metal, lines that break up the formerly smooth expanse of sheet metal down the sides.
BMW has gotten good at building cars with split personalities, reasonable everyday commuters that offer serious thrills on the weekends. BMW achieves this by the clever use of buttons around the cabin labeled Sport. The Z4 sDrive35i takes this idea a step further, not only having its various sport settings, but also using a convertible hard top. That top means security when parked in the city, real protection from the elements, and a little extra sound insulation. But it also gives you the option of wind-in-you-hair motoring on sunny days.
The convertible top tucks various panels underneath each other to stow itself away.
That convertible top does a peculiar little dance when going up or down, folding panels underneath each other and stowing its whole apparatus in the trunk. It's not particularly fast, and trunk space is compromised. The Z4 sDrive35i's LCD, mounted in a flip-up section of the dashboard, also stows itself away when not in use. We were impressed to see not only that LCD in a roadster, but BMW's up-to-date iDrive system, as well. The update to the Z4 extends to the cabin electronics.
As in the BMW 750Li we reviewed earlier, the Z4 sDrive35i's navigation system stores its maps on a hard drive, with enough capacity for rich detail. At 8.8 inches, the LCD is very wide, and presents beautiful 3D maps showing topographical features and the occasional landmark building. A 2D map is also available, but not as nice to look at. There's a reason why BMW uses such a wide screen: you can set it to a split view, using a portion of it as the main screen, and a smaller section as an auxiliary, useful for showing trip, audio, or route guidance information.
The Z4 sDrive35i is the third BMW we've seen with the new iDrive system, and it's still a relief from the old interface. But it's not without its problems, either. For one, it isn't always obvious which way to push the controller to back out of menus. Also, BMW offers a lot of customization options for its cabin tech, and you can drill down through quite a few levels in the settings menu. Digging into the Z4 sDrive35i's system, we made sure the navigation was set to automatically route around traffic problems.
Brian Cooley shows how to use the navigation system in a 2009 BMW 750Li, similar to that found in the Z4 sDrive35i.
Our Z4 sDrive35i came equipped with the dual-clutch transmission (DCT), which wasn't obvious initially as it has the same weird-looking shifter found in BMWs with automatic transmissions. The DCT, developed for the M3, shifts through seven gears, using two computer-controlled clutches for extremely smooth sequential changes. The DCT has automatic drive and sport modes, and a manual mode, controllable with the shifter or chunky paddles on the steering wheel.
Given the Z4's designation, sDrive35i, it should be obvious what sits under the hood. The Z4 sDrive35i is powered by a twin turbocharged 3-liter inline six-cylinder engine using BMW's Valvetronic system, for variable valve lift, and double-VANOS system, which changes the angle of the valves to enhance performance. The turbos each force air into a set of three cylinders, raising engine output to 306 horsepower at 5,800rpm and 295 pound-feet of torque from a low 1,300 to 5,000rpm.
This shifter is the same as the one used with BMW's automatic transmission cars, but in this Z4 it controls a DCT.
This complex power train results in some unevenness when driving the car around a city. At low speeds, acceleration becomes difficult to modulate. Applying moderate pressure on the gas pedal might move the car smoothly forward, or deliver a sudden burst of speed. In drive mode, the DCT tended to upshift rapidly, working its way up to fifth gear as we cruised at 30 mph. Fortunately, it was just as quick to downshift when we wanted power, being very responsive to accelerator and brake input.
This Z4 sDrive35i also came with the M suspension package, a button on the console letting us select Normal, Sport, or Sport Plus modes. Normal produces a comfortable ride, which gets noticeably harsher in either of the Sport modes. Taking a couple of quick turns around town, classic BMW handling became evident, the back end letting loose just enough to pivot the car.
After the less-than-smooth performance in the city, we were eager to see how the Z4 sDrive35i handled out where the wild things are. But first, we put on some driving music to check the stereo. As we would expect in a fully optioned up BMW, the Z4 sDrive35i didn't lack for audio sources. A port in the console was ready for an iPod or USB drive, the in-dash hard drive has room for MP3s, there's an in-dash single CD player, and the radio plays HD and satellite. Opting for the iPod, iDrive let us select music by artists, album, and genre, although its interface is a bit bizarre, requiring slightly more work with the iDrive controller than should really be necessary.
This seven-band equalizer lets you fine-tune audio reproduction from the impressive sound system.
Those audio sources are played through an optional premium audio system in our Z4 sDrive35i, which uses an amazing 14 speakers complemented by two subwoofers. Did we mention this is a complicated car? Those speakers are powered by a 650-watt amp, and, as part of this optional system, you also get seven-band equalizer on the LCD, with which you can really fine-tune the sound. We took the easier route, adjusting the treble, bass, and mid controls, and the system produced excellent audio. The instrumental reproduction came through with clarity and fine separation, letting us hear snaps from snare drums, twangs from guitar strings, and background sounds that often get lost in multilayered recordings.
We found it very convenient to use an iPhone with this car, plugging it into the iPod port and pairing it up with the Bluetooth phone system. We've been pretty happy with BMW's phone systems for some time, as the company early on had the technology to transfer a phone's contact list to the car, making it available on the LCD. The system in the Z4 sDrive35i provides that same functionality, and it's only eclipsed by the Ford Sync and Kia's new system, both of which let you dial by speaking the name of a contact rather than having to look it up on a screen.
With the navigation system showing us where to go, and loud music blaring from the speakers, it was time to get the Z4 sDrive35i into the fun stuff. We suspected that, with plenty of room to run, any unevenness in throttle modulation would disappear, and the car satisfied us in that regard. Powering around on the freeway, the Z4 sDrive35i proved exceptionally maneuverable, small and nimble enough to take advantage of openings in traffic, and powerful enough to pass just about any other car. The only thing to watch out for was getting too far over the speed limit.
The fun stuff
Taking the Z4 sDrive35i onto one of our favorite routes in Northern California, a good run of twisty roads without a car or house in sight, we found out how well the Sport mode on the transmission works. Through the first set of twists, the Z4 sDrive35i was in its natural element, easily negotiating these corners at speed, immersing us in sublime BMW handling. With the suspension in Sport mode, the car showed tremendous poise, with a willingness to be thrown around.
These controls come with the M suspension option, letting you select from three suspension modes.
Letting the transmission's Sport mode pick the gears showed the near-miraculous nature of the DCT. On the straights, it jumped to an appropriate high gear, fourth or fifth, but not too high to get out of the power band. Braking before a corner made the DCT quickly downshift, so that when we were ready to get on the gas again, the car was in second or third, offering plenty of power to shoot into the next straight.
Depending on the speed we entered the corner, the rear of the Z4 sDrive35i would come out in a predictable and controllable manner, letting us keep the nose pointed exactly where we wanted it. Putting it in Sport Plus mode, we found that the car loosens up the traction control substantially, but doesn't turn it all the way off. In this mode, we felt the rear end start to slide out pretty far in the corners, but then the traction control came on to reel the car back in.
We stop for a photo break on a twisting, country road, taking in a view of rolling hills.
Although the gearbox is filled with technical wizardry, manual shifting resulted in quick, tight gear changes. It would take racing driver reflexes to make shifts even close to this quickly. The DCT also accomplishes these shifts smoothly in automatic mode, matching the gear to the revs to keep the car from bucking.
The engine's 306 horsepower is enough to make the Z4 sDrive35i a powerful sports car. BMW claims 5.1 seconds to 62 mph with the seven-speed DCT, and 5.2 seconds to 62 mph with the six-speed manual. We didn't perform any timed runs, but on our various fast starts, the Z4 sDrive35i shot forward, making a satisfying exhaust blast with each gear change.
The DCT also helps the Z4 sDrive35i turn in decent fuel economy. Although hours of hard driving in the hills resulted in only 18.5 mpg, our overall average was 21 mpg, which isn't bad considering the big engine in this car. The EPA rates the Z4 sDrive35i at 18 mpg city and 25 mpg highway.
The 2010 BMW Z4 sDrive35i proved to be a spectacular tech car, from its performance gear through its cabin tech. The twin turbo engine and twin clutch transmission deliver a spectacular driving experience, helped by the adjustable suspension. The cabin tech also offers a lot of practicality, with traffic avoidance integrated with the navigation system, along with full-featured Bluetooth phone and iPod integration. The audio system also delivered excellent sound. The only thing really lacking are other useful information feeds, such as weather, and driver aid technologies, such as blind spot warning. As for design, the Z4 sDrive35i is a good-looking car, but, although iDrive is substantially improved from its previous incarnation, it's still less than perfect.
|Model||2010 BMW Z4|
|Powertrain||Twin-turbo 3-liter inline six cylinder engine|
|EPA fuel economy||18 mpg city/25 mpg highway|
|Observed fuel economy||21 mpg|
|Navigation||Optional hard drive-based, with traffic|
|Bluetooth phone support||Optional|
|Disc player||Single CD, MP3 compatible|
|MP3 player support||iPod integration|
|Other digital audio||HD radio, Satellite radio, USB drive, auxiliary input|
|Audio system||Optional 16 speaker, 650 watts|
|Price as tested||$66,195|