Test Car Specifications
Model tested: BMW i8 Roadster
Price: from £124,730 on-the-road
Engine: turbocharged 1.5-litre three-cylinder petrol engine mounted behind cockpit, plus electric motor over front axle
Transmission: six-speed automatic for engine, two-speed automatic for motor, four-wheel drive
Body style: two-seat roadster
CO2 emissions: 46g/km (VED is £440 per year)
Combined economy: 141.2mpg
Electric range: 33 miles
Top speed: 155mph (75mph on electric)
0-62mph: 4.6 seconds
Power: engine produces 231hp at 5,800rpm, motor maxes out at 143hp at 4,800rpm; total system maximum quoted is 374hp
Torque: engine produces 320Nm at 3,700rpm, motor tops 250Nm
Weight: 1,595kg
What's this?
The new BMW i8 Roadster spearheads the i8's midlife update, arriving in the UK at the same time as a new model year version of the i8 Coupe. Both share the same updated plugin hybrid electric vehicle (PHEV) powertrain. As before, there's a turbocharged 1.5-litre three-cylinder petrol engine mounted in the back making 231hp (though it has been updated to produce a sportier sound and now has a particulate filter). A six-speed automatic transmission is bolted to that and sends power to the rear wheels. Under the low nose sits an electric motor that exclusively drives the front wheels.
That motor has been upgraded to be more powerful than before, allowing the i8 to reach higher speeds (about 75mph) than the original car when running on electricity alone. Enabling that is a higher capacity battery pack, though no larger in physical size than the old one. This also allows a longer electric-only driving range (quoted as 33 miles for the Roadster or 34 miles for the Coupe). As before, the car defaults to hybrid mode and the driver can choose from Comfort or Eco Pro settings. To maximise electric running, there's an 'eDrive' button in either of these modes and the distinctly sporty Sport mode is accessible by moving the gear lever to the left. That alters the instrumentation appearance, transmission, throttle response, steering, engine noise and damping. It's still a two-setting adjustable damping system, though BMW has revisited its calibration, along with the power steering and stability control.
All this is controlled via a largely unchanged interior. The infotainment screen is new and there are new trim options, but that's about it. The Roadster has no rear seats and its new gullwing doors have no frames, but it's otherwise more or less the same as the Coupe inside. A button hidden in the centre console opens the fabric roof in 15 seconds, at speeds of up to 31mph, while another on the windscreen header allows you to open and close the small vertical window behind the cabin. This acts as an effective wind deflector at speed or allows a semi-open feel when the roof is raised.
The updated BMW i8 starts at £112,730 on-the-road, while the i8 Roadster is £124,730.
How does it drive?
The i8 Roadster requires a little structure stiffening to make up for the loss of a hard roof, but BMW has managed to keep the overall weight gain down to an acceptable 60kg. On paper, that blunts performance a fraction and makes the Roadster a smidgen less efficient, but the gaps are so slight that different driving styles are likely to make more of a difference in the real world. So, while we've not yet driven the updated i8 Coupe, we expect it to feel much the same as this car. And that's a very good thing indeed, as BMW's engineers have enacted a series of subtle, but highly effective, changes on the i8's chassis, resulting in a car that is much more satisfying to drive, more like that of a traditional BMW, oddly.
While the damping still has two settings, it has been altered and, in conjunction with the updated power steering calibration, it helps the nose of the i8 feel far better planted, with less bobbing about on the entry to a corner, for example. On the exit of a bend, it has less of a tendency to push on than before, too, which makes for a more satisfying driving experience. To get the full effect, you need to switch the dynamic stability control fully off, as then you can sense the modest torque vectoring going on at the back axle, giving the i8 a 'pointier' feel than before. In the dry, it takes quite a lot of provocation to unstick the rear tyres, even in really tight corners, but it's possible, for a short amount of time, before the front-mounted electric motor pulls the car out of the bend.
That motor also helps make the engine feel much larger and more powerful than it ought to, just as in the original i8. The extra chunk of performance is welcome of course and in Sport mode in particular the car feels fast enough for any needs. It's not a hardcore sports car for track use, but it copes well with the rigours of a 'spirited' drive on a twisty mountain road, with good brakes, quick steering, a fast transmission and great response. Now you can have all that with the wind in your hair and unhindered access for your ears to the exhaust and engine behind.
Verdict
It's of no surprise to hear BMW UK predicting that three quarters of its sales of the updated i8 will be of the Roadster. Sure, it's a tad heavier, a fraction less efficient and less practical, but it's effectively the same as the i8 Coupe with an extra dollop of crowd-stopping style. Along with all that, the chassis updates make the i8 a more engaging car to drive. Not that BMW had any genuine direct rivals to begin with...
Exterior Design
Interior Ambience
Passenger Space
Luggage Space
Safety
Comfort
Driving Dynamics
Powertrain
