While a 2006 redesign moved most of BMW's 3-Series vehicles to a new E90 platform, the M3 convertible remained on the previous-generation platform (E46). Changes to the M3 convertible involved only new option packages. What remained the same was its spectacular level of performance.

At the heart of that performance spins the M3's S54 engine. Although a traditional BMW six cylinder, it is a unique powerplant engineered for the highest level of performance. For example, while current BMW sixes feature an aluminum block, the S54 uses iron in order to maintain its 3.2-liter displacement without increasing size and to make it strong enough to withstand the demands of its incredible output: more than 100 hp per liter.

To achieve those numbers, BMW uses its VANOS variable cam phasing system to control the engine's 24 valves, which are activated by dual overhead cams and assisted by one of the most free-flowing production exhaust systems. The S54 makes 333 hp at 7,900 RPM on the way to its 8,000-RPM redline, with 269 ft-lbs of torque at 4,900 RPM.

Power flows to the rear wheels through either a short-throw six-speed Getrag manual or a Sequential Manual Gearbox (SMG) transmission that employs electro-hydraulic shift control to achieve Formula One shifting speeds. As a result the M3 coupe does the 0-60 jump in a quick 5.4 seconds. Yet with this older high-performance technology, you'll pay at the gas pump - estimates are 16/22 mpg, with one reviewer observing 16 mpg average.

The M3 rides on a high-performance version of BMW's Macpherson strut front and multilink independent rear suspension. Yet, like the S54 engine, the bits and pieces of that suspension are unique to the M3. The suspension components are stronger and calibrated for a firmer ride. Reviewers, however, found the ride, "comfortable enough, in a sports way," meaning you could use the M3 as a daily driver and autocross/time trial it on the weekends.

The handling is benchmark for its class, and the convertible's extra 365 pounds over the coupe doesn't slow it down much. The Auto Channel reviewer wrote, "If the M3 coupe is a laser scalpel for the carving of corner apexes, the convertible is merely a finely-honed conventional surgical scalpel. Sharp enough, and then some."

The convertible top with heated rear glass is fully automatic. With the push of a button - no manual latch - it folds out of view. Reviewers reported "insignificant cowl shake - only on the poorest and roughest of roads."

The interior, like the powertrain and suspension, supports the car's high-performance objectives. Heavily bolstered front bucket seats with 10-way power adjustments hold occupants firmly when indulging in "spirited" road workouts as the driver grips the M's thicker sport steering wheel. Gauges provide quick and easy reading, with the tachometer featuring a variable warning segmentation - based on oil temperature, the LED display illuminates amber from 4,000 to 8,000 rpm, shutting off in 500-RPM segments as the engine warms up.

The BMW 3-Series has achieved a "Good" rating in the 40-mph frontal-offset crash test. The M3 has stability control, four-wheel ABS disc brakes, front side-impact airbags, and a Rollover Protection System with two sensor-deployed rollbars behind the front seats.

The M3 convertible remains a benchmark car for its class. Reviewers consider it a sports car with a backseat, usable trunk, and plenty of fresh air.