It's appropriate that BMW has bestowed perhaps the most extreme example of its ridiculous new naming convention upon the most extreme version of its Z4 hardtop roadster, the sDrive35is. Suffice it to say that the "s" at the end of the newest Z4's name stands for "sport" and is accompanied by a lot more than a cute little body kit.
As you might recall, the current-generation Z4 debuted a little over a year ago with the top model -- called the Z4 sDrive35i -- featuring BMW's venerable 300-hp, 3.0-liter twin-turbo in-line six code-named N54. The sDrive35i, unlike other "35i" vehicles, stands pat for the 2011 model year and doesn't get BMW's new N55 single-turbo 3.0-liter straight six. Instead, the Z4's powertrain news for '11 is that the new sDrive35is edition gets a more powerfully boosted version (14.5 psi of peak turbo boost versus 8.7 psi) of the N54, which results in jumps of 35 hp and 69 lb-ft of torque ... it also results in the front end of the car jumping upward during hard acceleration like that of an old-school big-block American muscle car at the drag strip.
It's therefore easy to believe BMW's claim that the Z4 sDrive35is (which we'll refer to as "35is" from now on to save precious Internet ink) will blast from 0 to 60 mph in 4.7 seconds -- 0.3 second quicker than the sDrive35i (henceforth "35i") with a dual-clutch automatic. The transmission qualifier is important because, while the 35i can be fitted with either a six-speed manual or a seven-speed dual-clutch unit ("DCT" in BMW-speak), the 35is comes only with the DCT. That may sadden traditionalists, but we find some consolation in the fact that the transmission is very responsive and well-matched to this upgraded engine. It is unfortunate, however, that BMW designed each column-mounted shift paddle to handle both upshift and downshift duties, rather than the more traditional left-for-downshift, right-for-upshift approach. While test-driving the 35is on rural New Jersey back roads, I quickly gave up on those shifters in favor of the console-mounted shift lever's manual control, where pushing forward intuitively (at least to this reviewer) actuates a downshift and pulling back cues an upshift.
Once I was behind the wheel of a 35is on New Jersey Motorsports Park's lovely Lightning Raceway, though, I was content to toggle the Z4's standard Driving Dynamics Control to its Sport Plus mode and let the transmission manage gear changes automatically. I found this especially helpful since the 35is can be a bit of a handful to drive quickly on the track (especially compared with the other BMWs that I sampled at NJMP, including the glorious M3 and the physics-defying X6 M). The hottest Z4 certainly has plenty of power and nice steering, but it can feel unstable under braking, particularly unforgiving of hamfisted inputs, and extra challenging at times in the hands of relatively inexperienced track drivers like myself. It's much easier for a novice to play Lewis Hamilton in a more balanced-feeling Porsche Boxster S. Not only is the Boxster S less powerful by 25 horses, its normally aspirated urge comes on buttery smooth and predictable. Of course, it can be more rewarding to get a more powerful and anxious car like the Z4 working well on a track, but when you're limited to just a few laps in a car, it's sometimes preferable to enjoy yourself instead of frighten yourself.
The buzz around the paddock at NJMP was that the 35is might ultimately represent the most powerful E89-chassis Z4; M editions of the last-generation Z4 roadster and coupe -- a.k.a. E85 -- were part of that vehicle's swan song. The rumor that the E89 will top out with this 35is model could be supported by the fact that BMW worked so hard to differentiate it cosmetically from its lesser siblings. To wit, the 35is features M-badged items including its steering wheel, dead pedal, and doorsills along with its front and rear fascias; a lowered adaptive suspension is also sourced from BMW's legendary M division. The sideview mirrors are capped in silver (à la Audi S4), and the cabin also features gray-faced gauges and cool carbon-fiber-look aluminum trim on the dash, center console, and door panels. The 35is's exhaust system was specially modified for this engine's tuning, and the aggressively refined result is music to our ears. The 35is also gets unique wheels, whether the base five-spoke eighteen-inch design or the very attractive split-five-spoke nineteen-inchers, which are a worthwhile $1200 option.
Speaking of money, the Z4 sDrive35is is on sale now and has a base price of $61,925, which is a $9150 premium over the 35i model and $15,050 dearer than the base 30i version of the Z4. BMW claims that the 35is, despite its higher-strung engine, gets similar mileage to the DCT-equipped 35i, which is rated at 17 mpg in the city and 24 mpg on the highway.
We'd still love to see an M edition of this Z4 (maybe they'd call it simply "Z4 M" ... wouldn't that be novel?), but the new sDrive35is is a suitable flag-waver, no matter what, if anything, comes next.