BMW i8 RoadsterDecember 4, 2017
The BMW i8 is now available in a Roadster body style, with sub-50g/km CO2 emissions and a longer, 33 mile electric range.
Following the world premiere of the i8 Roadster at the Los Angeles Auto Show 2017, the order book will open in January 2018. The Roadster will be joined in showrooms by the mid-life update of the i8 Coupé.
The i8 Roadster has an all-season fabric soft-top with electric operation, allowing the roof to open or close within 16 seconds and while travelling at up to 31mph.
An updated version of the BMW i8’s lithium-ion battery provides improved emission-free range. The high-voltage unit is located centrally under the car, its cell capacity is increased from 20 to 34Ah, and the cell configuration allows a 12hp increase in peak output to 143hp.
The improved technology means the i8 Roadster can cover up to 33 miles with zero emissions, while the i8 Coupé can achieve up to 34 miles.
The new BMW i8 Coupé and new BMW i8 Roadster are powered by a hybrid synchronous electric motor and a three-cylinder petrol engine with BMW TwinPower Turbo technology. The engine’s power is fed to the rear wheels through a six-speed Steptronic transmission, while the electric motor propels the front wheels via a two-speed automatic gearbox.
The extra energy reserves have made it possible to raise the electric motor’s peak output by 12hp to 143hp, generates its maximum torque of 250Nm from rest.
The battery cells’ higher capacity means that the proportion of all-electric driving can be increased substantially, even in hybrid mode. With the default driving mode engaged, both the new BMW i8 Coupé and new BMW i8 Roadster are capable of pulling away and reaching speeds of up to 65mph purely on the electric motor’s power. And if the eDrive button is pressed, the all-electric threshold of both models is increased further to 75mph.
The new high-voltage battery benefits the electric range of the two plug-in hybrid sports cars too. In the EU test cycle, the new BMW i8 Coupé achieves a maximum range of 34 miles – around 50 per cent more than before – while the figure for the new BMW i8 Roadster is 33 miles.
The i8’s combustion engine has also undergone further improvements. The turbocharged three-cylinder unit featuring direct injection and VALVETRONIC variable valve timing extracts a maximum output of 231hp from its displacement of just 1.5-litres, plus peak torque of 320Nm. The engine also runs more cleanly, as it now comes equipped with a particulate filter as standard that effectively absorbs all the particulate matter contained in the exhaust gases.
The system output produced by the electric motor and engine acting in unison has increased to 374hp. The new BMW i8 Coupé accelerates from zero to 62mph in 4.4 seconds, while the new i8 Roadster takes 4.6 seconds. Both models have an electronically limited top speed of 155mph.
Combined fuel consumption, as calculated in the EU test cycle for plug-in hybrid vehicles stands at 149.8mpg for the BMW i8 Coupé and 134.5mpg for the BMW i8 Roadster – which equates to petrol CO2 emissions of 42 and 46g/km respectively – plus 14.0kWh of electricity for the BMW i8 Coupé and 14.5kWh for the BMW i8 Roadster. In everyday driving, both models return fuel consumption and emissions figures that undercut those for conventionally powered sports cars with similar outputs by around 50 per cent. A typical commute through city traffic and along country roads can be negotiated with fuel consumption of over 56mpg when using both drive units. On long-distance journeys with prolonged sections of country and motorway driving, the intelligent energy management ensures that average economy betters 40mpg.
In hybrid mode, the electric motor provides a power boost to assist the engine when vigorous acceleration is required. The electric motor is also able to recuperate energy and feed it to the battery on the overrun and under braking. The petrol engine’s high-voltage starter-generator can similarly generate additional reserves of electricity, thereby ensuring that sufficient energy is on tap at all times.
The unladen weight of the i8 Roadster is 1,595kg, just 60kg more than the Coupé.
On sale from January 2018, prices for the BMW i8 Coupé starts at £112,730 and the Roadster is priced from £124,730.