After countless spy shots, BMW has pulled the covers off open-top version of their plug-in hybrid sports car, the i8 Roadster. At the same time, the German automaker has given the i8 Coupe a major technical update, enhancing the car's hybrid system.
The roadster retains most of the design features seen in the hard top. That means it gets the slim laser-powered headlights, the signature kidney grill and the aggressive front bumper treatment. One minor change made to the car is its hood, which has been lowered. It's at the rear where most of the changes are with a 'flying buttress' taking the place of what was supposed to be the rear windshield.
Despite the loss of the roof, the open-top two-seater still comes with frameless gullwing doors. These panels are made from CFRP (Carbon fiber reinforced plastic) with an aluminum outer shell, while the windscreen frame is made entirely from CFRP. CFRP is also used to manufacture the side skirts with their extra-large cross section. Additional struts and panels in the front and rear axles also help to maximize the body’s rigidity, says BMW. The roadster's top meanwhile is made from a unique fabric material.
For its hybrid system, the i8 Roadster packs an updated version of the lithium-ion battery specifically developed for the car. According to BMW, its cell capacity is up from 20 to 34 Ah and gross energy capacity rises from 7.1 to 11.6 kWh. All of which means the electric motor has more energy at its disposal. The electric drivetrain alone provides 143 PS and can go up to 105 km/h before the internal combustion engine kicks in.
The gas engine on the other hand is a 1.5-liter turbo engine with three cylinders. It makes 231 PS and 320 Nm of torque on its own. Combined with the revised electric drive system, peak power is rated at 374 PS although torque was not mentioned. It lays down the power through all four wheels with the electric motor providing power to the front wheels and the turbo gas engine sending drive to the rear.