The M3 Cabriolet was released in 2001, while its stablemate, the M3 coupe, had been introduced earlier. The convertible brings together M3 design and engineering with the convenience, luxury and safety features of today’s BMW convertibles. It also includes a higher level of standard equipment than the coupe, with Nappa leather upholstery and power seats among the upgraded features.

In its broad concept, the M3 engine, designated the S54, shares the familiar layout of other BMW inline 6-cylinder engines. Virtually all of its engineering details, however, are unique and oriented to performance.

The new engine has stepless Double VANOS, which varies valve timing on the intake and exhaust camshafts without the step of the 2-stage older system. As used in the M3 engine, it varies timing over a wider range and contributes in a major way to the engine’s power output.

The M3 returns to a BMW M tradition: an individual throttle for each cylinder cylinder. Positioned much nearer the cylinders than a single throttle can be, these bring atmospheric pressure practically right to the cylinder. All six throttles operate from a single shaft, each in its own throttle body right at the intake ports.

Two elaborately snaking stainless-steel headers serving three cylinders each. These headers are formed under high pressure with water inside them them, which ensures even distribution of the forming pressure and thus consistent wall thickness. In turn, this process allows stainless-steel walls only 1 mm thick (about 1/25th of an inch), not only helping save weight but also hastening engine warmup as there is less metal to heat up after a cold start.

BMW M engineers chose the S54’s high-rpm concept to achieve high power from moderate displacement. High engine speeds pose challenges; engineers must ensure that durability standards are met and that the engine performs properly at the high rpm levels. As mentioned earlier, the engine’s rev limit is 8000 rpm; its maximum power occurs just below this limit at 7900 rpm. Drivers who mean to enjoy this engine to the limit may operate it frequently in these upper reaches of rotational speed.

The principal difference between a traditional limited slip diff and the new Variable M Differential Lock is that where the former senses torque, the new senses wheel speed. The Variable M Differential Lock specifically addresses low and split traction situations in a way that reinforces sporty handling, imparting to the M3 a superb slippery-road traction.

Any time a speed difference develops between the two rear wheels, a shear pump , driven by this difference, develops pressure in the silicon viscous fluid in which the lock operates. In turn, this pressure is directed to a multi-disc clutch that transfers driving torque to the wheel with the better road grip. The greater the speed difference between the two wheels, the more positively the clutch engages.

In Detail

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