Revealed here in production-car guise for the first time, the new 425-hp M3. The engine will feature BMW's patented induction process known as M TwinPower Turbo. It uses two low-inertia turbochargers running a maximum 1.3 bar of boost pressure and fed by a innovative water-to-air intercooler system mounted atop the engine. Meanwhile, weight-saving features, such as a magnesium sump, see the new en
gine tip the scales 22 pounds under that of its predecessor, at a claimed 452 pounds. With 425 hp developed between 5,500 and 7,300 rpm and 406 lb-ft of torque between 1,850 and 5,500 rpm, the blown six delivers 11 hp and 110 ft-lb more than the naturally aspirated 4.0-liter V8 direct-injection gasoline mill it succeeds. An impressive 143 hp per liter -- some 38 hp per liter more than its predecessor through the effects of forced induction -- also gives it the highest specific output of any series production M division engine to date. With familiar M division technology, such as Valvetronic variable-valve timing and Double VANOS continuously variable-camshaft timing, the new six-cylinder revs to 7,600 rpm -- 600 rpm less than the V8 it replaces. While billed as the most powerful series production engine to find its way into the M3, the new inline six-cylinder, codenamed S55 B30, is the smallest capacity engine used by BMW's M division since the discontinuation of the first-generation M3's naturally aspirated 2.3-liter four-cylinder powerplant, the S14 B23, in 1991. In combination with BMW's efforts to pare weight from its new performance-car duo through the use of new lightweight materials, the added reserves help improve the power-to-weight ratio of the M3 sedan by 22 hp per ton over its predecessor to 280 hp per ton. The new M4 coupe improves by a similar 22 hp per ton over the outgoing M3 Coupe to 284 hp per ton. By comparison, the latest Porsche 911 Carrera S boasts 283 hp per ton. Channeling the drive to the rear wheels is a standard six-speed manual gearbox. The Getrag-produced unit has been developed from scratch and is claimed to be a 26 pounds lighter than the unit used in the outgoing fifth-generation M3. Among its features is dry sump lubrication, a double-plate clutch to handle the added torque loading, carbon-ceramic friction linings within the synchronizer rings and a blip function for downshifts. The individual ratios are shorter than before, with the final drive dropping from a previous 3.85:1 to 3.46:1 for added pace off the line. Buyers will also be able to choose an optional seven-speed M Double Clutch Transmission (DTC), again from Getrag, with remote-paddle shifters. A development of the M5, it allows the driver to choose between manual or automatic modes. More features include launch control and a smoky burnout program -- the latter permitting a degree of wheel spin while the car is traveling at low speeds. To help improve on-the-limit handling, it also receives stability clutch control, which opens the clutches when sensors detect a loss of traction to reduce drive and bring it back in line. Both gearboxes receive an automatic stop/start function, together with brake-energy regeneration and optimum-shift indicator. Despite BMW's earlier claims that the DTC unit is only 44 pounds heavier than the manual gearbox, the official weight figures reveal an 88-pound penalty.
