While we have yet to see a production model, BMW‘s newly formed “i” sub-brand continues to expand its range of concept cars with a third study for a roadster version of the i8 Coupe.

Given the close relationship with the coupe model, it’s very likely that the i8 Spyder will receive the green light for production as well with a possible market launch to follow within the next two to three years. The i8 Spyder will make its world premiere at the Auto China Show 2012 in Beijing in late April.

While it shares its basic platform architecture and plug-in hybrid powertrain with the coupe, the Spyder is a strictly two seater model and has a slightly shorter wheelbase and overall length.

Other changes include the solid doors, which keep the ‘butterfly’ design swiveling upwards, the new colors and materials inside, and the redesigned rear-end that now features a transparent engine cover.

BMW doesn’t say or show if and what kind of top is provided to keep passengers protected from the elements of nature.

Like the coupe, the Spyder is based around a lightweight carbon-fibre-reinforced plastic structure with the same material used for the outer panels.

The i8 employs a plug-in hybrid powertrain combining two different power sources. The primary unit is a 1.5-liter turbocharged three-cylinder gasoline engine with 220HP (223PS) and 300 Nm (221 lb.ft) positioned behind the passenger cabin that’s linked to a dual clutch transmission driving the rear wheels. The second power source is an electric motor delivering 129HP (132PS) that turns the front wheels.

The two power sources can work independently to drive the vehicle or in tandem, in which case, they generate an aggregate system output of 349HP (35PS) and peak torque of 550Nm (405.6 lb.ft).

BMW says that the i8 Spyder passes the 100km/h (62mph) yardstick in 5.0 seconds after take-off (i8 Coupe: 4.6 seconds), on its way to an electronically governed top speed of 250 km/h (155 mph).

The two-seater model is claimed to return a combined fuel consumption of just 3.0lt/100km, equivalent to fuel economy of 94.2mpg UK or 78.4mpg US, in the European test cycle.

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