BMW M5

Courtesy of Road and Track

The tach steadily marches up past 7000 rpm, 7100, 7200... When it reaches 7400, the speed limiter quietly steps in and holds us comfortably, almost leisurely, at 155 mph. Freed of its electronic tethers, the 2006 BMW M5 would be capable of supercar numbers, topping out at nearly 200 mph. This, from a midsize sedan with four doors and none of the wings, scoops, flares or carbon-fiber bits normally associated with such vision-blurring speed.

How does the M5 do it? How else? Horsepower: 507 to be exact, generated by a silky-smooth 5.0-liter V-10 that loves to rev (redline is 8200 rpm) and, when combined with BMW's third-generation 7-speed sequential M gearbox (SMG), serves up instant acceleration with the flick of a steering-wheel-mounted paddle. Yet like the V-8-powered car it replaces, this fourth-generation M5 effortlessly blends sports-car performance with commuter-car comfort.

Naturally, as the only sedan on earth to feature a V-10 and a 7-speed sequential transmission, much attention focuses on the M5's high-tech powertrain. As well it should because they work exceedingly well together. The 90-degree V-10 is a clean-sheet design, engineered specifically for this car (and the forthcoming M6) and not based on any existing BMW powerplant, including the BMW Formula 1 engine. It's also normally aspirated, unlike the competing Audi RS 6 and Mercedes-Benz E55 AMG powerplants, meaning it generates power through high engine rpm and its 10 cylinders rather than turbos or superchargers.

Accomplishing such output without forced induction is no small feat, requiring some sophisticated engineering, especially in a V-10 that revs so freely. Like the M3, the M5's engine employs individual throttle valves for each of its 10 cylinders. They're tied to an electronically controlled throttle-by-wire system that ensures immediate response and adjusts each throttle butterfly individually in as little as 120 milliseconds. This works in concert with BMW's bi-VANOS variable valve timing for seamless power delivery anywhere in the rev range. To cope with the extreme heat and combustion pressure associated with high-rpm loads, the crankcase utilizes a racing-derived bedplate design that integrates cast-iron inserts into the aluminum casing for improved stiffness.

Also helping produce those 507 horses and 384 lb.-ft. of torque is enough computing power to put an M5 on the moon. The ECU alone contains three 32-bit processors that perform a staggering 200 million calculations per second, controlling anything and everything related to engine performance. This includes, among other things, the throttle valves, bi-VANOS, fuel mixture, emissions and spark. Plus it acts as the central portal for all information traveling between the engine and smaller control units managing systems like SMG, Dynamic Stability Control (DSC), ABS and Electronic Damper Control (EDC). An added benefit of all this computerized wizardry is the console-mounted Power button, which serves up three settings: P400 for just 400 bhp, P500 for the M5's full 507 bhp or P500 Sport for 507 bhp accompanied by noticeably quicker throttle response.

The other half of the M5's 1-2 powertrain punch is the new, third-generation SMG. Like the V-10, this 7-speed unit, which is the only transmission available, is all new and built just for this engine. As such, it's not hampered by the limitations of converting an existing manual gearbox to SMG (as is the case with the current system), allowing engineers to optimize it for faster, smoother sequential operation without sacrificing automatic mode driveability. Like the M3, the M5's SMG offers drivers 11 different Drivelogic shift profiles to choose from (six in manual, five in automatic) based on how aggressive or sedate they like their shifts.

Some die-hard manual fans may take issue with the M5's SMG-only status, but after some time behind the wheel, only the most stubborn will miss the clutch pedal. The performance of this latest iteration has been improved significantly, delivering 20 percent faster upshifts during hard acceleration, while also smoothing out shifts at lower speeds or in stop-and-go traffic. Gone is the occasionally unpredictable behavior in automatic mode, replaced by noticeably smoother clutch engagement regardless of engine revs. And for Formula 1 wannabes, all downshifts are accompanied by perfectly synchronized throttle blips in both manual and automatic modes.

Better still, the SMG also features Launch Control, a no-brainer electronic aid that does a better job of launching the M5 from a standstill than any human could. Activation requires that SMG be in its most sporting position (S6) with DSC off and the console-mounted gearshift lever held in the forward position. From there, all it takes is pushing the gas pedal to the floor, letting the system hold engine revs at 4000, then releasing the gear shift. What happens next is pure computer-controlled bliss as the rear tires spin just enough to ensure optimal traction, the SMG shifts automatically at precisely the right revs and the M5 rockets away. Using Launch Control, expect 0-60-mph times somewhere in the neighborhood of 4.5 seconds and the quarter-mile around 13 flat.

Move to the open road and the M5's V-10/SMG combo really comes into its own, easily disposing of any stretch requiring serious acceleration. The SMG's ultra-quick shifts make it a breeze to choose gears, ensuring the rev-happy engine is always generating maximum thrust. Run up through the gears out of a slow corner and the engine pulls with a smoothness that easily rivals the current M5's engine, arguably one of the finest V-8s around. Compared with competitors like the supercharged Mercedes-Benz E55 AMG and turbocharged Audi RS 6, the M5 gives up a measure of torque, but between the snappier shifts and the intoxicating V-10 exhaust note, BMW's latest delivers a decidedly sportier driving experience.

This more sporting nature certainly owes much to the engine and gearbox, but neither would be worth the aluminum they're cast from if they weren't bolted to a highly competent chassis. In the case of the M5, electronically controlled shocks and 3-mode DSC get the job done, helping keep the chassis sorted and delivering a wide range of driver-adjustable damping settings to choose from. The shocks have three EDC modes (comfort, normal, sport), which determine the electronic damping parameters in which the suspension will operate. In all three settings, the shocks continuously adapt to changing surface conditions and chassis loads, but can also be more narrowly focused if softer (comfort) or firmer (sport) performance is desired.

Also helping maintain control are huge ABS-assisted 14.7-in. front and 14.6-in. rear vented/cross-drilled rotors that confidently slow the M5 all day long. DSC is equally accommodating, offering full yaw-control functionality, none at all, or better still, M Dynamic Mode (MDM), a sport-tuned setting for aggressive driving that steps in only when the car is really out of shape. Driven in any of these modes, the M5 exhibits excellent poise and a surprising willingness to be tossed around. It's by no means light on its feet, weighing in at more than 4000 lb., but at the same time, the steering and chassis remain highly communicative, telling the driver what the car is doing and how it likes to be driven.

With so many individual power, suspension, SMG and yaw-control settings to chose from, it could take quite a few button pushes to switch from a comfortable commuter configuration to a more aggressive back road or racetrack setup. Not so with the M5's steering-wheel-mounted MDrive button, which allows the driver to instantly switch to personalized settings for power, EDC, SMG, DSC and the optional head-up display. It's as simple as storing individual preferences in the MDrive memory (accessed through iDrive), then pushing the MDrive button to activate the customized setup.

Mechanicals aside, the M5 further distinguishes itself with subtle styling touches that differ from the standard 5 Series just enough to communicate its more sporting intent. The front fascia has been massaged for better high-speed aerodynamics and improved brake/engine cooling, a re-sculpted rear end now sports four exhausts and the fenders have all been flared slightly to accommodate the larger 19-in. double-spoke wheels. And like the M3, M-specific mirrors and a pair of side gills adorn the M5's flanks.

Inside, not too much differs from the standard 5 Series. M-specific leather surfaces and trim accent the interior for a slightly sportier feel. The speedometer and tachometer are new (black dials, white numerals, chrome rings) with the tach featuring a yellow-to-red oil temp-dictated rev limit similar to the previous M5. The biggest news in the cockpit is availability of an optional head-up display which, in addition to showing standard vehicle information, can also be configured to act like a race car's shift light that turns color, then flashes as redline is reached.

Sadly, we won't see the M5 on North American shores until late 2005 at the earliest, so get your order in now and be prepared to pay close to $90K for the privilege. This puts the sticker price nearly 20 grand more than the previous model, but given its significant improvements in both performance and driveability, it's hard not to want one anyway.

With its fourth-generation M5, BMW not only vaults back to the top of the super-sedan ranks, but also proves that ultra-high technology and driving excitement can indeed coexist in the same vehicle. Few, if any, cars have the wealth of electronics helping them get down the road, while at the same time proving equally entertaining to drive. The M5 does just that, wrapping sports-car performance in a sedan body, then letting the driver decide which of the two it really is.