The second in BMW’s new i brand of vehicles, the i8 plug-in hybrid-electric (PHEV) sports car was a central highlight in the automaker’s display at the recent Los Angeles International Auto Show. Like the i3 compact electric vehicle (EV), which will be in U.S. showrooms in spring 2014, the soon-to-follow i8 has a carbon-fiber body structure, aluminum chassis, and lithium-ion batteries—all based on the same technology but in different sizes and shapes for a different target customer base.
The i8 electric motor (driving the front wheels through a two-stage automatic transmission) is the same as the one used in the rear-drive i3, but it has been “tuned” for lower power (96 vs. 125 kW), Jose Guerrero, BMW North American i Brand Product Manager, told AEI on the LA show floor. Torque is the same at 250 N·m and comes instantly. The motor power level in the i8 is optimized for integration with other elements of the powertrain and the overall vehicle, including a new BMW-developed 3-cylinder internal-combustion (IC) engine displacing 1.5 L and employing BMW TwinPower Turbo technology to drive the rear wheels through a six-speed automatic gearbox. Engine output is 170 kW (231 hp) with maximum torque of 320 N·m (236 lb·ft).
The new IC engine is the first 3-cylinder to power a BMW production model, and it has the highest specific output of any ever made by the automaker: 113 kW/L (154 hp/L).
Acceleration in the i3 is impressive (as experienced by AEI on a ride-and-drive of that model as part of the automaker’s LA Auto Show activities), but BMW promises even greater acceleration in the i8, which rockets from 0 to 62 mph (100 km/h) in just 4.4 s. The figure for the i3 is 7.2 s (7.9 s for the i3 if ordered with the optional range-extender IC engine).
Together, the i8’s motor and engine generate 266 kW (362 hp) and maximum torque of 570 N·m (420 lb·ft). The usable capacity of the Li-ion battery is 5 kW·h.
Also enabling great acceleration is the car’s lightweight body, which like the i3 consists of a body structure made primarily of carbon-fiber-reinforced plastic, along with replaceable outer body panels made of thermoplastic. Curb weight is 1490 kg (3285 lb).
Aerodynamics play an important role in acceleration as well, with an i8 Cd value of .26.
As quick as the car is, it gives nothing away in terms of efficiency. On the EU test cycle, fuel consumption overall is 2.5 L/100 km with CO2 emissions of less than 59 g/km. The driver can choose all-electric mode, which provides 35 km (22 mi) of range. Five driving modes are available; “comfort” provides the optimum balance between fuel efficiency and driving dynamics. Combined range in everyday driving conditions is 500 km (310 mi).
Torque distribution is geared toward optimized driving dynamics.
One of the more interesting innovations is the partition between the passenger compartment and the trunk. In a world-first for a volume-produced car, the partition is made of special glass that is chemically hardened—similar to what is used in smart phones, says BMW. Two panes, each of 0.7 mm (0.03 in) width, sandwich a layer of acoustic sheet. A conventional laminated glass partition would weigh 50% more, says BMW.