As well as providing a power boost to assist the petrol engine during acceleration, the electric motor can also power the vehicle by itself. Top speed is then 120 km/h (approx. 75 mph). The BMW i8 has a maximum driving range in this emission-free, virtually soundless, all-electric mode of up to 35 kilometres (approx. 22 miles). The motor derives its energy from the lithium-ion battery which is centrally mounted underneath the floor of the vehicle. The model-specific version of the high-voltage battery was developed and produced by the BMW Group. It has a liquid cooling system and can be recharged at a conventional household power socket, at a BMW i Wallbox or at a public charging station. A full recharge takes less than three hours at a household power socket and less than two hours at a BMW i Wallbox. The BMW i8’s vehicle concept and powertrain control system mark it out as a progressive, revolutionary sports car. The BMW i8 always achieves the optimal balance between performance and efficiency, whatever the driving situation. When power demands allow, the high-voltage battery is recharged by the electric motor. The high-voltage starter-generator, responsible for starting the engine, can also be used as a generator to charge the battery, the necessary power being provided by the BMW TwinPower Turbo engine. The battery can also be recharged via the electric motor during overrun. These various processes help to prevent depletion of the BMW i8’s battery in order to maintain the electric drive power. The all-electric driving range is sufficient to cover most urban driving requirements. Out of town, the BMW i8 offers impressively sporty performance which is also very efficient thanks to the power-boosting support for the petrol engine from the electric motor. With such versatility, the BMW i8 belongs to a new generation of sports cars which unites exciting performance with cutting-edge efficiency – to enhance both driving pleasure and sustainability.
Driving Experience Control and eDrive button: a choice of efficiency and performance characteristics – at the touch of a button. The rear wheels of the BMW i8 are driven by the petrol engine via a six-speed automatic transmission. The front wheels are driven by the electric motor via an integrated two-stage automatic transmission. Combined maximum power and torque of 266 kW/362 hp and 570 Newton metres respectively provide all-wheel-drive performance which is as dynamic as it is efficient. The BMW i8’s intelligent powertrain control system ensures perfect coordination of both power sources. The variable power-sharing between the internal combustion engine and the electric motor makes the driver aware of the sporty temperament of the BMW i8 at all times, while at the same time maximising the energy efficiency of the overall system. Utilising both power sources, the 0 – 100 km/h (62 mph) acceleration time is expected to be less than 4.5 seconds. Linear acceleration is maintained even at higher speeds since the interplay between the two power sources efficiently absorbs any power flow interruptions when shifting gears. The BMW i8 has an electronically controlled top speed of 250 km/h (155 mph), which can be reached and maintained when the vehicle operates solely on the petrol engine. Variable front-rear power splitting in line with changing driving conditions makes for excitingly dynamic cornering. On entering the corner, the power split is biased towards the rear wheels to improve turning precision. For more vigorous acceleration out of the corner, the powertrain controller returns to the default split as soon as the steering angle becomes smaller again. The BMW i8 also offers the driver unusual scope to adjust the drive and suspension settings of the vehicle in order to adapt the driving experience to his or her individual preferences. As well as the electronic gear selector for the automatic transmission, the driver can also use the Driving Experience Control switch – a familiar feature of the latest BMW models – or, exclusively to the BMW i8, the eDrive button.
Using the gear selector, the driver can either select position D for automated gear selection or can switch to SPORT mode. SPORT mode offers sequential manual gear selection and at the same time switches to very sporty drive and suspension settings. In SPORT mode, the engine and electric motor deliver extra-sharp performance, accelerator response is faster and the power boost from the electric motor is maximised. And to keep the battery topped up, SPORT mode also activates maximum energy recuperation during overrun and braking: for this, the electric motor’s generator function, which recharges the battery using kinetic energy, switches to a more powerful setting. At the same time, gear change times are shortened and an extra-sporty setting is selected for the standard-fitted Dynamic Damper Control. Also in this mode, the programmable instrument cluster supplies further driving-related information in addition to the rev counter display.
The Driving Experience Control switch on the centre console offers a choice of two settings. On starting, COMFORT mode is activated, which offers a balance between sporty performance and fuel efficiency, with unrestricted access to all convenience functions. Alternatively, at the touch of a button, ECO PRO mode can be engaged, which, on the BMW i8 as on other models, supports an efficiency-optimised driving style. The powertrain controller coordinates the cooperation between the petrol engine and the electric motor for maximum fuel economy. On overrun, the intelligent energy management system automatically decides, in line with the driving situation and vehicle status, whether to recuperate braking energy or to coast with the powertrain
disengaged. At the same time, ECO PRO mode also programs electrical convenience functions such as the air conditioning, seat heating and heated mirrors to operate at minimum power consumption – but without compromising safety. The maximum driving range of the BMW i8 on a full fuel tank and with a fully charged battery is over 500 kilometres (310 miles) in COMFORT mode. In ECO PRO mode, this can be increased by up to 20 per cent.
The BMW i8’s ECO PRO mode can also be used during all-electric operation. The vehicle is then powered solely by the electric motor. Only if the battery charge drops below a given level, or under sudden intense throttle application (kickdown), is the internal combustion engine automatically activated.
The driving mode selected at a given moment is indicated to the driver on the programmable instrument cluster by a distinctive colour and by a different, mode-specific set of driving information. The three-dimensional appearance of the display adds to the futuristic look and feel of the vehicle as a whole.
High-quality chassis technology, DSC and Dynamic Damper Control as standard. The high-end chassis and suspension technology of the BMW i8 is based on a double-track control arm front axle and a five-link rear axle, whose aluminium components and geometry are specially configured for intelligent weight savings. The electromechanical power steering offers easy manoeuvring in town and typical sports car-style high-speed steering precision. Also standard is Dynamic Damper Control: the electronically operated dampers change their characteristics according to the selected driving mode to deliver the desired vehicle dynamics.
The DSC (Dynamic Stability Control) stability system includes the Anti-lock Braking System (ABS), Cornering Brake Control (CBC), Dynamic Brake Control (DBC), Brake Assist, Brake Standby, Start-Off Assistant, Fading Compensation and the Brake Drying function. The push button-activated Dynamic Traction Control (DTC) system raises the DSC thresholds, allowing some controlled drive wheel slippage for easier start-off on snow or loose ground, or for extra-dynamic cornering.