The i8 is a drop-dead looker, and a scintillating-driving 4WD sports car. It’s also a fuel-sipping plug-in hybrid. In a mid-mounted position behind the cabin is a 1.5-litre three-cylinder petrol engine, highly turbocharged for 231bhp.
That’s hooked to a small motor-generator, and then to a six-speed transmission driving the rear wheels. But the front wheels have their own 131bhp electric motor. A battery sits in the spine of the carbon fibre body.
In Sports Hybrid mode, the petrol-driven rear wheels and electric-driven front wheels get it from 0-62mph in 4.4 seconds. The complex electronics manage the split of effort across the two power sources to give it a helpful torque split for fast cornering. Regeneration happens when slowing down, or indeed when spare engine power pushes against the front wheels. At the other extreme of its astonishing repertoire is Electric Mode.
Starting with a fully charged battery from the mains, it will manage about 15 gentle miles before the engine kicks in. For max economy, the body is light (thanks to carbon fibre) and low and very aerodynamically slippery. The i8 even uses ‘Gorilla Glass’ for the side windows, the same as used for phone screens, because it’s thin and light. The tires are surprisingly thin, helping aerodynamics, but four-wheel-drive compensates.
The powertrain all seems very exotic, but actually BMW is being canny in spreading out the technology across its model range – by running it back-to-front. Seethe new4WD, PHEV version of its 2-series Active Tourer people carrier, called the 225xe.
The three-cylinder engine is moved to the front and drives those wheels, while the main electric motor is at the back. Again it allows electric drive or hybrid. The same system will also be introduced soon on two of the firm’s SUVs, where the 4WD aspect will be a big draw.