LA MOTOR SHOW: BMW i8 Roadster revealed

The BMW i8 has gone topless.

The German manufacturer used the LA motor show this week to unveil the long-awaited two-seat Roadster version of its pioneering electric sports car, along with running powertrain and cosmetic updates to the existing two-plus-two i8 Coupe.

Arriving five years after the unveiling of the Coupe, the Roadster’s roof mechanism and structural reinforcements add a respectable 60kg to its kerb weight, rated at 1595kg.

The extended gestation of the Roadster is owed in part to its roof, which has been redesigned from earlier concepts to fully retract into the car’s rear end.

“A unique mechanism allows the soft-top to be folded into a compact package and stowed away in a perpendicular position, creating around 100 litres of additional storage space behind the seats,” BMW says.

“The all-electric roof opens and closes very quietly in 15 seconds, a process which can be initiated while travelling at up to 50 km/h. Dropping down the roof raises the rear window by around 30 millimetres into a comfort position, where it can serve as a draught stop.”

BMW has modified the i8’s windscreen with a strengthened frame and beefed-up quarter windows to accommodate the moving roof structure. The Coupe’s side windows have been eschewed for new black and aluminium panels bearing the word ‘Roadster’.

The drop-top employs an updated 11.6kWh battery pack, up from the outgoing 7.1kWh unit used in the Coupe. The battery works in concert with an upgraded electric motor that produces 105kW and 250Nm (up 9kW), driving the front wheels.

BMW claims a top speed of 120km/h in pure-electric mode and a pure electric driving range of 53km from its topless electric car.

A familiar 1.5-litre turbocharged three-cylinder petrol works in conjunction with the electric motor, offering carryover 170kW/320Nm outputs and driving the rear wheels. In total, the combined hybrid system output is 275kW, BMW says.

The same upgraded battery system, internally referred to as Gen IV, features in the 2018 i8 Coupe. A lighter kerb weight means it boasts a slightly longer electric driving range of 55km and a more effective 0-100km/h time of 4.4 seconds (versus 4.6 seconds in the Roadster).

Inside, the Coupe and Roadster sport an updated dashboard design with the latest version of BMW’s iDrive6 infotainment system. New seats, an optional head-up display unit and new trim options are also included in the update.

Also new to the i8 is BMW’s 360-degree charging system. Used in combination with the car maker’s I charging station, it can provide a claimed 80 per cent state of charge in less than three hours.

The i8 Coupe and i8 Roadster are due to reach global showrooms in May, 2018. Australian arrivals have been slated for later in the year.

In a coup for Australian enthusiasts, BMW will hold a private viewing of the i8 Roadster for special guests in Sydney on Thursday evening.