BMW has only just officially revealed its electric i3 city car, but already the German automaker seems ready to tease us with its i8 plug-in hybrid sports car.

The company has released further details on the i8's plug-in drivetrain, with detailed images showing some of the i8's more intimate workings.

We already know the i8 will feature BMW's latest generation of three-cylinder turbocharged engine--set to appear in MINIs and BMW's other smaller models over the next few years.

High output, high economy

1.5 liters in capacity, the TwinPower turbocharged unit develops 231 horsepower and 236 pounds-feet of torque, the highest per-liter rating of any engine BMW has produced for the road. It's paired with a 96 kW (131 hp) electric motor, with 184 lb-ft of torque.

Total system output is 362 horsepower and a hefty 420 lb-ft of torque--the latter figure contributing to the car's strong acceleration. 60 mph can be reached in "under 4.5 seconds", and a similar time is all it takes to hit 75 mph from 50 mph.

Top speed is 155 mph (like many BMWs, presumably limited) while the i8 should do 75 mph on electric power alone. A six-speed automatic gearbox provides access to all this performance, with different driving modes allowing manual control, improved efficiency or maximum performance.

The i8's lithium-ion battery pack is good for around 21-22 miles on electric power alone, and total range between the two powerplants is "over 310 miles". Combined economy is pegged at "around 95 mpg", though like always, this figure is subject to driving style, time spent in electric and gasoline modes, the alignment of the planets and more.

The now-familiar ECO PRO mode could boost this by up to 20 percent however, and allows for all-electric running until provoked by a request for more power or low battery capacity.

Engineering highlights

It's surprisingly light weight--at 3,285 pounds, the i8 weighs little more than a Nissan Leaf thanks to the its carbon-fiber reinforced plastic and aluminum structure. Using lightweight magnesium and foam plastic interior structures has allowed BMW to shed dozens of pounds from the interior, compared to a car like BMW's own 6-Series coupe.

BMW has worked hard to attain its traditional 50:50 weight balance front to rear, with electric components close to the front axle, engine in the rear and the batteries centrally mounted

Slick aerodynamics also feature, with a drag coefficient of 0.26. That suggests the i8's dramatic lines (as yet unrevealed in production form) aren't just for show, but aero efficiency too.

Other technical highlights include 50 percent lighter chemically hardened glass (inspired by the glass used in smartphones) and aluminum screws and bolts, saving 45 percent off the typical steel equivalents.

We won't have to wait long to experience the i8's high-tech approach for real, though--it's set to debut at this September's Frankfurt Auto Show, before cars hit showrooms in 2014.


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