Automotive Intelligence - the web for automotive professionals and car enthusiasts
October 10, 2007
The first M3 produced 192 hp from its 2.3-liter four-cylinder engine during its 1988-1991 model year run. A legend was born and Americans embraced the high-rpm, naturally-aspirated M concept. The next generation arrived in 1995 with a 3.0-liter (and later, 3.2-liter) 240-hp inline-six powerplant. In 1997 the first M3 Sedan joined the family and the first M3 Convertible followed shortly thereafter. The most-recent version, available as either a coupe or convertible from 2001-2006, again was offered with six-cylinder power, this time providing 333 hp from its 3.2 liters. This vehicle was BMW’s first use of SMG (Sequential Manual Gearbox) for the US market.
The all-new 2008 M3 Sedan and M3 Coupe that arrive in spring 2008 will feature the first V8 in a series-production BMW M3. It will also feature driver-adjustable settings for crucial dynamic controls including steering, damping and stability (and an available steering-wheel-mounted “MDrive” button to store the preferences) and a sumptuous interior that can be optimized to a driver’s desires including the comprehensive entertainment/navigation system operated through BMW’s latest iDrive controller.
The move to eight cylinders in the fourth generation BMW M3 provides a powerplant offering the seemingly disparate characteristics of more power, increased efficiency and reduced weight when compared with the previous six-cylinder M3 engine. Displacing 3,999 cubic centimeters (4.0 liters), the new light-alloy engine produces 414 hp at 8,300 rpm and 295 pound-feet of torque at 3,900 rpm with 85 percent of the maximum torque available consistently through 6,500 rpm. This power output represents a 15-percent increase over the six-cylinder from the last generation M3 and it comes with an eight-percent fuel-economy improvement when compared to its predecessor. Compression ratio is dialed in to 12.0:1 and redline is set at 8,400 rpm.
The V8-power unit within the engine compartment of the new BMW M3 Sedan boasts the company’s variable double-VANOS camshaft management. Offering extremely fast and responsive valve timing, this technology reduces charge cycle losses and improves the output, torque and response of the engine, with a positive influence on fuel economy and emission management.
A separate throttle butterfly for each cylinder – eight in this instance – is a feature adapted from BMW M’s racing heritage and provides immediate reaction to the gas pedal at all times. Two stepper motors operate the four throttle butterflies on each row of cylinders, giving the engine a particularly sensitive response at low speeds together with an immediate reaction whenever the driver presses down the accelerator for extra power and performance.
A volume flow-controlled, pendulum-slide cell pump supplies the engine with lubricating oil, delivering the quantity required by the engine. Wet sump oil lubrication, optimized for dynamic performance, ensures consistent oil supply to the high-rpm engine at all times, particularly in extreme braking maneuvers. The system features two oil sumps—a small oil sump in front of the front axle subframe and a large oil sump behind it.
A new, comprehensive electronic management system coordinates all engine functions with optimum efficiency and maximizes operational integration with the clutch, gearbox, steering and brakes. In addition, the engine control unit performs a wide range of on-board diagnosis functions and masterminds the ancillary engine units.
A highlight of the engine management system is the use of ion-current technology to determine engine knock as well as misfire and poor combustion events within the cylinders. Contrary to conventional methods, this monitoring and control function is performed precisely where the phenomena occurs—within the combustion chambers. The spark plug in each cylinder senses and controls the risk of knocking, at the same time monitoring the correct ignition and recognizing any misfiring. In other words, the spark plug acts as an actuator for the ignition and as a sensor monitoring the combustion process, and is therefore able to distinguish between a misfire and poor combustion. This dual function of the spark plugs facilitates the diagnostic procedures required in service and maintenance.
And the increased performance with better economy comes from the lightweight engine. At 445 pounds, it is seven percent or 33 pounds lighter than the previous model’s Inline-6. Lightweight components do not stop with the alloy engine block. The crankcase is made of a special aluminum-silicon alloy eliminating the need for cylinder liners. Despite the need to resist high combustion pressures and engine speeds—this is the “fastest” production engine ever produced by BMW as it can reach 8,400 rpm—the engineers managed to keep the compact and rigid crankshaft weight down to 44 pounds.
Manual transmission, twin-disc clutch and Variable M Differential Lock Power from the BMW M3 Sedan’s V8 is transmitted to the rear wheels through a close-ratio six-speed manual gearbox. The performance parameters of the M3 dictated heat management as a key design factor for both the transmission and clutch. The transmission features integrated temperature-dependent oil cooling management, while internal ventilation maximizes heat dissipation for the twin-disc clutch.
The new final drive comes with a Variable M Differential Lock generating up to 100 percent locking action with fully variable action whenever required, ensuring optimum traction on all road surfaces.
Engineering a chassis which is “faster than the engine”
Providing sure-footed responsive handling for a high-performance, powerful and luxurious sedan, while keeping mass under control, presented numerous challenges for the BMW M3’s engineers. The result is a new, aluminum chassis developed specifically for this model. The design begins with placing components in such a way as to create a 50/50 front/rear weight balance.
(October 6, 2007)