With i8, BMW finally plugs in

The BMW i8 made its international motor show debut as a concept in Frankfurt in 2011. As such, the public has had plenty of time to ogle the coupe’s low-slung lines and try to reconcile its high-minded ecological attributes with its potential for hooliganism.

By the time the i8 hits showrooms in 2014, Formula 1 cars will be on track with strikingly similar propulsion systems to that in BMW’s first plug-in hybrid sports car: a turbocharged 1.5-litre gasoline engine backed by an electric drive and energy-recovery system. Though it does not field an F1 team, look for BMW to nevertheless try connecting the dots between racecars and the racy-looking $135,925 i8.

The i8, said BMW chairman Norbert Reithofer, will spearhead the company’s effort to become a leader in electric drive. “We will win significant market share,” he pledged.

The production car will have a maximum system output of 362 horsepower and 420lb-ft of torque, with 231hp alone coming from a tiny 1.5-litre turbocharged three-cylinder gasoline engine yielding a jaw-slackening 154hp per litre.

The gas engine sits at the rear of the car, driving the rear wheels through a six-speed automatic transmission, while the electric motor powers the front wheels through a two-speed gearbox. Together, they can launch the i8 from a standstill to 62mph in just 4.4 seconds, BMW claims. Keep a foot on the floor and the i8 will top out at an electronically limited 155mph using only the gas engine. Stay off the accelerator pedal and the i8 can travel as far as 22 miles on electric power alone with a top speed of 75mph. BMW pegs the i8’s combined average fuel economy at 94mpg (though the car has yet to be certified by the Environmental Protection Agency).

To convey the rear-drive sensation enthusiasts prefer, the i8 cuts power to the front wheels while turning, then returns the electric pull from the front as the steering straightens. The twin powertrains contribute to a 50/50 front-rear weight balance.

Like the i3, the introductory product from BMW’s i sub-brand, the i8 is made substantially of costly carbon fibre-reinforced plastic (CFRP), a material that weighs about half as much as steel of equivalent strength and is about 30% lighter than aluminium. The scale reflects a total curb weight of 3,285lbs, an impressively low number for a car carrying a battery big enough to motivate a machine for 22 miles alone.

Another weight-saving trick? Thin rear glass. Rather than using the usual thick glass, the i8 has two lightweight thin layers that are chemically hardened, like the Corning Gorilla Glass used for Apple’s iPhone screens.

Total driving range is rated at 310 miles, though travelling in Eco Pro mode, an efficiency-optimised driving setup, can add another 60 miles to that total. A full recharge of a depleted battery pack should take 3 ½ hours using regular 120v household current and 1 ½ hours using a 220v level 2 charger, BMW said.