· Twin turbo V-8 engine (550i) delivers 400 hp and 5.4 second 0-60-mph time, plus silken refinement and impressive fuel efficiency considering the performance.
· All-new turbocharged inline-6 engine (535i) delivers 300 hp and 6.2 seconds 0-60mph time with excellent fuel efficiency.
· New 8-speed automatic transmission (535i and 550i) contributes to performance and fuel efficiency.
With the 5 Series Gran Turismo, BMW lays the cornerstone for a new type of automobile – while also demonstrating BMW’s traditional mastery of an all-important aspect of automotive performance: the powertrain.
The Gran Turismo debut model is the 550i, powered by BMW’s stunning 4.4-liter, 400-hp twin turbocharged V-8 engine. Compared to BMW’s normally aspirated V-8, displacement is reduced from 4.8 to 4.4 liters, and incorporates twin turbochargers and High Precision direct injection. In quantitative terms, the new engine delivers 400 hp and does so over a range from 5500 to 6400 rpm. Maximum torque is 450 lb-ft., and available over the extremely broad range of 1800 to 4500 rpm. The result is greater power and torque delivered over a wide range of operating conditions with greater fuel efficiency. Aside from the dramatic thrust that drivers will notice subjectively, the objective data are dramatic too: 0-60 mph in just 5.4 seconds and a top speed when equipped with the Sport Package of 150 mph. For models equipped with all-season tires the maximum speed is limited to 130 mph.
Through its unique reverse-flow layout, the 550i’s V-8 engine is able to achieve even higher performance without correspondingly higher fuel consumption. In technical terms, the approach involves some very new design details. For the first time, twin turbochargers and the exhaust-cleansing catalytic converters are placed between the V-8’s two cylinder banks. In turn, this required the exhaust camshafts and valves to be inboard so that the path from cylinders to turbochargers (which are driven by exhaust gas) would be efficiently short. A key benefit of this layout is a more compact engine package. This is the reverse of a traditional V-8 layout, and opens a new era of V-8 engine development potential.
A key feature of the engine is BMW’s High Precision direct injection. Positioned centrally in the combustion chambers for optimum combustion, the injectors deliver fuel at very high pressures. To meet BMW’s ambitious performance/efficiency/emissions goals with the necessary long-term durability, a “stack” of piezo crystals reacts lightning-fast to impulses from the Digital Motor Electronics, governing the injector needle’s opening stroke and duration for ultra-precise control. This contributes 2-3% fuel savings and reduces emissions by 20%. The engine (also as featured in the new 7 Series and BMW X6) meets U.S. ULEV II (Ultra Low Emissions Vehicle) limits.
Playing a Supporting Role: Innovative New 8-speed Automatic Transmission
The 5 Series Gran Turismo’s innovative character is further supported by its all-new 8-speed automatic transmission, which brings smooth shifting, sportiness and efficiency to a new level of perfection. Compared to the exemplary 6-speed automatic offered in most current BMW models, the 8-speed’s “taller” cruising gears make a significant contribution to reduced fuel consumption and carbon-dioxide emissions as well as quietness. And its wider spread of ratios from lowest to highest gear enhances acceleration and response across the range of driving speeds.
Technically speaking, this new automatic’s attributes have been achieved via an innovative concept that provides the two additional ratios (7 and 8) with no increase in bulk or weight. In an arrangement not heretofore employed in an 8-speed automatic, four planetary gearsets and five clutch packs are controlled in a way that no more than two of the five clutch packs are freewheeling at any given time. The modest increase in the number of mechanical elements allows the new transmission to achieve unusually high efficiency: the so-called “gearing efficiency” is higher than 98% in all eight gears. In 6th gear, it’s highest of all because that is direct drive, with no gearing at all. Combine this with reduced friction and the ability to keep the torque converter “locked up” more of the total driving time, and you have a transmission that is very much a part of the 5 Series Gran Turismo’s overall efficiency concept.
Two additional gears mean threefold progress: quicker shifts, greater smoothness, enhanced efficiency.
The wider spread of ratios allows the engine to run at lower speeds, mainly in the “tallest” gear, 8th. Yet even with this wider spread, the steps between adjacent gears are reduced; in turn this means a stronger, smoother flow of power during acceleration.
And for the same reason, faster shifts are a further benefit because only one clutch pack is disengaged to shift up or down by one or two gears. On the other hand, downshifting more than two gears is accomplished as a direct shift. For example, a downshift from 8th to 2nd gear is made with only one clutch pack disengagement, and thus occurs without stepping down through the intermediate gears. Thus at one instant the driver can be enjoying the quiet, fuel-efficient low rpm of 8th gear, and in the next instant getting maximum acceleration.
Brake Energy Regeneration: an Energy-Saving Innovation.
For the first time in a U.S. BMW model, the new 5 Series Gran Turismo is equipped with BMW’s Brake Energy Regeneration system.
To save energy and reduce the vehicle’s fuel consumption, this system controls the times at which the alternator charges the battery. Conventionally, a car’s alternator runs continuously and thus charging is always available to the battery; in the Gran Turismo, it charges only when the vehicle is decelerating or braking; otherwise, it freewheels, drawing virtually no power from the engine. An electronically controlled clutch, somewhat similar to that used with the air-conditioning compressor, is added to engage and disengage the alternator.
Accommodating the less frequent charging is a special, more powerful battery that can satisfy a contemporary vehicle’s high electrical demands without access to continuous charging. The battery uses a technology called “glass mat,” in which its internal plates are separated with saturated absorbent glass-boron silicate rather than the usual liquid electrolyte. This construction sharply reduces the battery’s conversion of charging energy to heat, and can provide the necessary electrical power for longer periods between charges.