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| 2013 BMW ActiveHybrid 3. Click to enlarge. |
Together the inline 6 and electric motor combine for 335 hp (250 kW) and 332 lb-ft (450 N·m) of torque, an increase of 13% and 11% respectively. In addition to the boost available for the internal combustion engine, the electric motor is capable of powering the ActiveHybrid 3 in all-electric mode for speeds up to 45 mph (70 km/h) for distances up to 2.5 miles (four kilometers).
When the driver applies more throttle, the internal combustion engine is engaged automatically, then disengaged on overrun. During overrun and braking, the electric motor acts as a generator, converting kinetic energy into electrical energy, which is used to charge the battery. This is the same principle as the Brake Energy Regeneration function on the regular models, although on the BMW ActiveHybrid 3 the amount of energy recuperated by the electric motor is greater.
Under combined ICE/electric power, the BMW ActiveHybrid 3 delivers a 0 to 100 km/h (62 mph) acceleration time of 5.3 seconds. The sedan’s governed top speed is 155 mph (250 km/h) when equipped with performance tires.
TwinPower Turbo 6. The BMW ActiveHybrid 3 is the second hybrid model from BMW—after the BMW ActiveHybrid 5 (earlier post)—to use an in-line 6-cylinder engine in its powertrain. Also featured in the BMW 335i, this engine develops maximum output of 300 hp (224 kW) at 5,800 rpm and maximum torque of 300 lb-ft (407 N·m) between 1,200 and 5,000 rpm.
The engine has won the international “Engine of the Year” award two years in a row. The six-cylinder powerplant’s BMW TwinPower Turbo technology comprises a twin-scroll turbocharger, High Precision Direct Injection and VALVETRONIC fully variable valve timing. This technology package improves throttle response and revving ability as well as refinement and efficiency, while an aluminum crankcase also optimizes weight.
Electric motor. The BMW ActiveHybrid 3’s synchronous electric motor develops a maximum output of 55 hp (41 kW). As well as supporting all-electric operation around town, it can also provide a performance-boosting function for more powerful acceleration. In either case, the drive power is supplied instantly and without lag. Like all electric motors, this one develops its full torque of 155 lb-ft (210 N·m) from a standing start.
The electric motor is compactly integrated within the housing of the eight-speed automatic transmission, and is connected to the transmission by a clutch. Its operating temperature is controlled by the cooling system of the internal combustion engine.
With its eight speeds, the transmission combines a wide gear range with close ratio spacing. It also allows more use to be made of top gear, for a fuel-efficient, low-rpm driving style. The direct downshift capability and exceptionally short shift times can support very sporty driving, as well. A high-performance transmission controller matches gear changes to the driver’s demands and the driving situation.
Optionally, the BMW ActiveHybrid 3 can be supplied with a quick-shifting sports automatic transmission, the dynamic characteristics of which are emphasized by a customized selector lever and steering wheel-mounted paddle shifts.
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| Packaging of the battery. Click to enlarge. |
In addition to its conventional 14V electrical system, the BMW ActiveHybrid 3 is also equipped with a high-voltage electrical system with 317 volts. Linked by a voltage transformer, these two systems provide maximum electrical power throughout the operating range, for improved performance and comfort. Both the electric motor and the air conditioning compressor are powered exclusively by the lithium-ion high-voltage battery, via the high-voltage electrical system. This allows the desired interior climate to be maintained even when the internal combustion engine is not running—i.e. when the car is at a standstill, operating purely on electric power or in coasting mode.
Fully charged, the lithium-ion high-voltage battery provides an all-electric driving range of up to 2.5 miles (four kilometer) at an average speed of about 20 mph (35 km/h).
Since the lithium-ion high-performance battery is packaged under the trunk, the load capacity of the BMW ActiveHybrid 3 is reduced only marginally compared with other BMW 3 Series Sedan models. This space-saving integration allows for a completely level load floor and means the rear seat backrests with optional 40:20:40 split-folding remain fully functional. The positioning of the high-voltage battery near to the rear axle also contributes to the balanced weight distribution of the BMW ActiveHybrid 3.
Hybrid-specific auto start-stop function and coasting mode. The specially designed hybrid auto start-stop function ensures that comfort is not affected even when the vehicle is stopped in traffic for longer periods, because the automatic climate control and the on-board electrical system are powered by the lithium-ion high-voltage battery. On moving off again, when the driver releases the brake, the vehicle will restart on either the electric motor alone or the electric motor and the engine, depending on the high-voltage battery’s current charge level and on how much power the driver wants or needs.
ECO PRO mode, which can be activated via the Driving Experience Control switch, supports a particularly fuel-efficient driving style in the BMW ActiveHybrid 3 and makes more frequent use of all-electric mode. ECO PRO mode modifies the characteristics of the powertrain, including the transmission, while the electrically powered convenience functions are programmed for optimal energy efficiency.
Coasting mode, a new development for the BMW ActiveHybrid models, boosts efficiency by shutting the internal combustion engine down not only when the vehicle is stationary, or when driving in town.
Coasting mode switches off the gasoline engine and disconnects it from the driveshaft. From this point on, the BMW ActiveHybrid 3 coasts soundlessly, with zero emissions and with no engine braking effect. The efficiency improvements are further enhanced by reduced rolling resistance tires.
In ECO PRO mode, the coasting function is available at any speed up to 100 mph (160 km/h), while in Comfort mode it operates between 37 and 50 mph (60 and 80 km/h) when the brakes are applied lightly. In Sport and Sport+ mode the coasting function is not available.
Even in coasting mode, all safety and comfort functions remain fully operational. When the combustion engine is shut down at a standstill, as well as during all-electric operation and in coasting mode, the electrically powered stationary climate control continues to maintain a pleasant interior climate. The stationary climate control can also be used to cool the interior before getting into the vehicle.
Intelligent energy management with proactive analysis. In addition to coordinating the operation of the internal combustion engine and electric motor based on the current driving situation, the advanced-design power electronics also support proactive, forward-thinking analysis of the driving situation for even more efficient energy management.
To achieve this, the power electronics can be linked up to the optional navigation system. When a destination has been input and route guidance is active, the electronics can then access and analyze data that can take advantage of an upcoming change in external conditions or driver requirements. Based on this analysis, and subject to the quality of the navigation data, the vehicle can be prepared in advance for imminent requirements so that all powertrain systems and the onboard electronics can be managed appropriately and in such a way as to make the most efficient possible use of the available energy.
Factors that may cause a change in powertrain operating strategy include the topography of the route and speed limits. For example, if the system knows that a downhill stretch is coming up soon, the BMW ActiveHybrid 3 can wait to recharge its battery and invest all the high-voltage battery’s electrical energy in providing supplementary driving power, since the battery will be recharged during the forthcoming descent at no cost in terms of fuel consumption.
On longer downhill sections the electric motor’s generator function, too, can be enlisted to recharge the high-voltage battery with no loss of speed. The operating strategy can also be managed so as to achieve, as far as possible, optimal charging of the high-voltage battery when nearing the end of the journey, thereby increasing the electric driving range on the “last lap”.
The operating status of the powertrain components is shown in model-specific displays in the instrument cluster and in the Control Display of the BMW ActiveHybrid 3. As well as the energy flow and energy recuperation display, these include a further gauge next to the rev counter which shows the boost effect being provided by the electric motor during acceleration.
A model-specific menu in the iDrive operating system provides a variety of information—for example on the lithium-ion high-voltage battery’s charge level and the power sharing between the internal combustion engine and the electric motor in the course of a journey. A fuel consumption history can also be displayed, which not only shows fuel consumption history for the previous 15 minutes and the extent to which the electric motor of the BMW ActiveHybrid 3 has been used.
Source: Green Car Congress
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