2012 BMW Z4 sDrive28i

For over a decade, only one premium automaker has offered a four-cylinder in the U.S. And while the recent rise of Audi in the States isn't solely because of its 2.0T engine, it's obvious that luxury buyers are finally coming around to the idea of a fuel-sipping four-pot. As a matter of fact, they're starting to demand it. And BMW is heeding the call.

Next year, BMW will begin offering its turbocharged and direct-injected 2.0-liter inline four-cylinder engine on the 3 Series and 5 Series, matching Audi car-for-car in the entry-level and mid-size segments. But before the sedans arrive on U.S. shores – nixing the naturally aspirated 3.0-liter inline-six in the process – BMW is slipping its TwinPower four-cylinder into an unlikely host: the 2012 Z4 sDrive28i.

Why unlikely? Just look at the length of that hood. It was designed from the onset to house one of BMW's venerable inline six-cylinder engines, but by lopping off two cylinders, BMW almost made a front-midship roadster.

The mounting points used to fit the outgoing six-cylinder and the current turbocharged 3.0-liter are the same that hold this TwinPower turbo four in place. The byproduct is an impressive weight balance of 47.3/52.7 front-to-rear, an improvement – depending on your perspective – from the 47.9/52.1 of the six-cylinder model.

The new N20 four-cylinder is the first engine to benefit from BMW's recently revealed modular engine program, and it's the same mill we sampled earlier this year in the not-for-U.S.-consumption X1 xDrive28i. Power remains almost unchanged in the Z4, with 240 horsepower coming on between 5,000 and 6,500 RPM and 260 pound-feet of torque available from 1,250 and 4,800 revs. While the new N20 is down by 15 hp compared to the six, torque output is up some 40 lb-ft. And the extra juice is evident the moment you mash the throttle.

Fitted with the six-speed manual, BMW claims the Valvetronic-equipped four will hit 60 mph in 5.5 seconds, while the new eight-speed automatic gearbox does the deed in 5.6 seconds – a decrease of 0.1 and 0.4 seconds, respectively, over the six-cylinder. And as you'd expect, overall weight is down as well, with the new four-cylinder Z4 tipping the scales at 3,252 pounds, or about 33 pounds less than the outgoing sDrive28i.

Predictably, that minimal weight loss can't be felt from behind the wheel, but the extra grunt is front and center. There's a hint of turbo lag below 2,000 rpm when you're lining up for a pass, but as soon as the single, twin-scroll turbo starts huffing and puffing, the Z4 accelerates more authoritatively than the six. Driving the old and new models back-to-back, we also noticed slightly less dive and squat from the mildly reworked suspension (BMW isn't saying what's been done, aside from tweaking the springs and shocks for the new weight balance), but that's probably more a product of the box-fresh four-cylinder compared to the slightly abused previous generation tester.

We also sampled both the manual 'box and new eight-speed automatic transmission, and while we're partial to choosing our own ratios through the slick stick, the auto's quick changes and steering wheel-mounted paddle shifters trade a modicum of engagement for a healthy dose of convenience. It's one of the few times we wouldn't fault buyers for choosing the slush box, and considering the average Z4 owner, we're sure it'll be the most popular transmission.

Naturally, you want numbers, but BMW is only giving one for now: $48,650 (plus $875 for destination). That's an increase of $1,200 over the outgoing model, but for 2012, Bluetooth and USB integration, along with trunk-through loading and an alarm system, all come standard, so the price bump is nearly a wash with the new equipment. As for the other figures you're after, well, BMW isn't giving up fuel economy estimates just yet. With the (surprisingly abrupt) start-stop system fitted to the Z4 sDrive28i, BMW claims that fuel efficiency is up by 20 percent over the six-cylinder in the EU test cycle, but that could go either up or down when the EPA estimates arrive later this year. Figuring the outgoing model managed 18/28 mpg city/highway, it's safe to assume the four-cylinder should ring in around 22 mpg in the city and 33 on the highway.

More importantly, the character of the Z4 is completely unaffected by the new engine. The six's sonorous tones have been replaced with a hint of turbo whistle and a thrum from the exhaust, but the overall experience remains surprisingly unchanged. Grunt is up, fuel consumption is down and top-down cruising is just as good as it ever was. The replacement for displacement is here, and if it's executed this well, we'll gladly give up a liter or two for the privilege.

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