Ground-breaking hybrid supercar in open-top form
At first glance, BMW’s i8 Coupé and its Roadster stablemate look like typical supercars. They have head-turning style, with ground-hugging, two-seat bodies, a mid-engine layout and even gullwing doors. But in one vital respect they depart from the traditional supercar template. In place of the traditional supercar V8 or V12, the i8 has a three-cylinder, 1.5 litre petrol engine. Because as well as being a supercar, the i8 is also a plug-in hybrid, combining conventional internal combustion with a powerful electric motor and battery. Originally launched in 2013 in Coupé form, the 2018 line-up now includes a Roadster for the first time. It was worth the wait.
The i8’s futuristic lines adapt well to the Roadster version. As with the Coupé, the LifeDrive body architecture is constructed of carbon-fibre reinforced plastic, with a windscreen frame also made of the same material. The Roadster’s frameless doors open gullwing style, giving easy access to the seats – not something all supercars can boast. Despite additional strengthening to compensate for the absence of a roof, the total weight penalty for the open-top has been restricted to just 60kg. The new soft-top roof stows away under the rear deck in just 15 seconds, at speeds of up to 31mph. With the roof stowed, the rear buttresses and rear window remain, creating an open-top cockpit that’s free of wind buffeting.
With a BMW electric motor at the front and a three-cylinder 1.5-litre petrol engine at the rear, the i8 Roadster, like its coupé cousin, offers a total power output of 374hp, enough to power the Roadster from 0-62mph in 4.6 seconds. However, press the eDrive button and you can enjoy virtually silent, emission-free motoring for a range of up to 33 miles at speeds of up to 65mph. Compared with the first-generation i8, the new model’s battery capacity is up from 20Ah to 34Ah, while the maximum output of the electric motor alone is now up to 143hp. While the EU combined test cycle figure of 156mpg might be hard to achieve in real-world conditions, BMW suggests that a typical commute combining city traffic and country roads could return around 56mpg in hybrid mode. Compared with the Coupé, i8 Roadster has model-specific tuning for the springs, damping and Dynamic Stability Control.
From its lightweight body construction to its advanced plug-in hybrid powertrain, the i8 is a technological flagship for BMW’s iSeries cars. The standard specification for both models includes BMW’s Professional Navigation system, BMW Display Key and Driving Assistant including Surround View. The BMW Connected personal mobility assistant includes intelligent route planning (with refuelling stops at a charging station or filling station), current trip status and personalised in-car displays. Options include BMW Head-Up Display, non-dazzling BMW Laserlight with BMW Selective Beam, and acoustic pedestrian warning.
BMW Driving Assistant includes city collision warning with a braking feature when pedestrians are detected to be on a collision course with the car. The optional BMW Head-up Display puts all relevant information, including sat nav instructions and speed, directly in the driver’s field of vision to improve concentration on the road ahead.
Verdict: hybrid power has appeared in several high-performance sports cars recently, from McLaren to Ferrari. What makes the i8 genuinely different is that the electric motor isn’t simply there as a top-end power boost to a thirsty V8 or V12, but instead offers true zero-emissions motoring in town with the prospect of thrilling sports car performance on the open road. In Roadster form, ownership of this future-ready sports car is enhanced by the joy of wind-in-the-hair motoring.