BMW comes closest to capturing the bugs-in-the-grin roadster ambiance of yore. One sits tall in the saddle, with less car up around the shoulders. It's easier to hang an arm out the window of an M or Z3 than in any of the others here. Our editors who own a Jag E-type and a Sunbeam Alpine roadster felt right at home--that is, until they tromped on the go pedal.
The rush of 315 horses twisting their way through five short gears (at the beckoning of an exquisite shifter, we add) with only 3141 pounds' worth of momentum resistance makes for quite modern acceleration indeed--the quarter-mile flashes by in just 13.1 seconds at 109 mph. (That qualifies as third best in this test, but only by an eyelash.)
This marvelous M engine whips up 1.6 horsepower per cubic inch--an impressive figure for a naturally aspirated engine. The intake system is fully machined for optimal flow, and the pistons compress the combustibles at a lofty 11.5:1 ratio (highest in any BMW street-car engine). Direct-acting finger followers help lighten the valvetrain by 30 percent, permitting a higher (7600 rpm) maximum engine speed, and the VANOS system varies the intake- and exhaust-valve timing by up to 60 and 46 degrees, respectively (well up from 40 and 25 degrees in the Z3 3.0). The combined effect feels just like more cubes or a supercharger, but in our foot-to-floorboard test, flogging four cars of similar weight equally hard, BMW's high-tech approach yielded the best trip fuel economy (20 mpg). Our only small gripe with the engine is the metallic rasp that attends its thrust, which sounds as if every exhaust heat shield were loose and vibrating. No kid will duplicate it.
In the Sohio whoop-de-dos, the M roadster exhibited go-kart responsiveness. The driver sits way back near the rear axle for nearly perfect weight distribution, so there's a sense of swinging the nose into turns. The steering is kart quick, too, but most testers felt it offered insufficient heft and feedback, leading some of us to overcontrol the car. Add to this a rear suspension that dates back two generations of 3-series and offers less sophisticated wheel control, and the combined effect is a choppy ride and a somewhat nervous feeling at the (admittedly quite high) limit.
On bone-dry roads, the immense torque constantly threatened to overpower even the beefy 245/40ZR-17 Michelin Pilot Sports, resulting in frequent intervention by the now standard DSC stability-control system, despite its high-performance recalibration. When the car keeps suggesting you're out of control, you start to believe it. The gigantic brakes, however, inspire huge confidence with a firm, communicative pedal and superb, indefatigable stopping power that whoaed our M in 162 feet from 70 mph (tying the Vette for best).
The elemental character of the M roadster does bring with it a few inherent niggles. For one, the cockpit felt a bit tight for taller members of the group, and several carped that every surface an arm might rest on was hard. The BMW also provided the fewest features, although it's not exactly a stripper, and it was the only convertible with a softtop boot cover to fasten on.
In this rarefied company, those few nits account for the M's five-point deficit relative to the winner, despite the fact that for some this fantastic engine makes up for almost any complaint. For those who need a brand-new car to transport them back in time while it's rocketing them from point to point, this is the obvious choice.
http://www.caranddriver.com/comparisons/bmw-m-roadster-page-2
