BMW i8 put to the test: Genuine sports car or marketing vehicle?
We were initially sceptical, but the result surprised us in a positive way. The individual test reveals whether the BMW i8 with 362 bhp is really a genuine sports car and what it can achieve on the track.
My hand moves slowly to the start button of the BMW i8. There's a first time for everything. Today is my first time in a hybrid, or more precisely, a plug-in hybrid. A combination of electric motors and a three-cylinder engine awaits – certainly not a joyful day from a sports driver's perspective, or perhaps it will be? Until now, electro-hybrid tin cans had all of the charm of Birkenstock sandals. That said, I must be honest and say that up until now I have had as much of a clue about "electro" and "hybrid" cars as I have about carrier pigeon breeding. It's no wonder, on the tourist's car park at the Nordschleife the focus is on other topics. Prejudices form all the more quickly in the minds of die-hard sports car fans. "This is precisely why you are writing up the test," clarified my colleague Marcus Schurig immediately, as the BMW i8 rolled into the editor's garage.
BMW i8 with a 30-litre fuel tank
What the boss says, goes. And so, a follower of high-revving, naturally aspirated engines climbs into the BMW i8 and puts it to the test. Opposites are known to attract – initially, today they are more contrasting that North and South Korea. At least the new vehicle from Munich, which undergoes final assembly in the BMW plant in Leipzig, conquers the hearts of the sports car community immediately when it comes to looks. As a production car, the BMW i8 achieves the feat of coming intangibly close to the BMW Vision Efficient-Dynamics studies presented at the IAA in 2009 and 2011, and the i8 Concept.
Normally there is a considerable loss of 'coolness' between the exhibition stand and the series production-ready product. The futuristic i8-Design, in particular the rear of the vehicle, is radical, and the present day sports car community feels as though it has been transported a decade into the future.
It's not just the appearance - the 'ingredients' behind the BMW i8 silhouette sound like a large cinema-style sports car. BMW promises intelligent lightweight construction. The outer skin of the BMW i8 consists largely of thermoplastic polymers. Only the engine hood and the outer door panel are made from aluminium. Beneath the plastic housing of the 2+2-seater is a passenger compartment made from CFK, while the front and rear structure consist of aluminium.
With a full, 30-litre tank, our BMW i8 weighs precisely 1,486 kilo when measured during the test. We cast-iron fans can't have anything to complain about there – it does, however, immediately pose the following question: How light would the BMW i8 without the electric drive unit, but with a decent combustion engine instead? The electrical drive weighs around 200 kilos – hold on, let's give the sports car developed by the i-manufacturers a chance first. Other Munich natives deserve to be held back after class in this regard - we need only think of the M4 Cabrio with an incomprehensibly pathetic weight of 1,825 kilos.Climbing in feels like getting into the McLaren MP4-12C or 650S
Anyone who has not had a closer look at the BMW i8 in advance will almost tear the CFC and aluminium hybrid structure from its hinges when opening the gull-wing doors. The i8 door weighs almost 50 percent less than conventional door constructions. The weight of the doors is almost comparable to racing car doors, the door-opening mechanism resembles the butterfly doors of the McLaren MP4-12C or 650S. Foot forward, torso leaning slightly backwards – even the gymnastics exercise when climbing is reminiscent of the British sports car.
Click, shortly before the door engages with the lock, your attention is drawn to the visible carbon fibre structure of the passenger compartment and the door rims – the fact that here the lightweight construction has been finished with high-gloss, clear lacquer is a minor, yet elegant detail, which is lacking in the work of some other manufacturers. Start button, gear selector lever, iDrive-Controller, Sat Nav screen – in the BMW i8 interior, the modern driver will not be in for any initial surprises. The driver-oriented instrument panel provides just as little cause for criticism as the low seating position in the slimline sports seats with reasonable lateral support.BMW i8 with a spaceship-like sound
Pressing the start button: a moment that provides an acoustic reminder of the time machine from the science fiction film trilogy "Back to the Future". While outside the vehicle everything remains silent, inside the tested BMW i8 reports for duty with a spaceship-like sound. No lascivious cylinder roar, no spit from the exhaust pipe, no metallic drive noise – I would be lying if I said that I didn't feel that something was missing during the i8 start-up process. Fascination is a big word, but the hybrid BMW imparts a certain alterity of emotion as it starts up silently and then moves off electrically, with the barely audible hum similar to that of a tram.
But it is in particular in pure electrical driving mode that the BMW i8 causes contortions in all passers-by during the test, as if the eighth wonder of the world is floating past them. Meanwhile, the Sat Nav screen, with symbols for the fuel and electrical charging stations, reveals that down-town Stuttgart is already well equipped for plug-in fans and electric travel.
In everyday driving, the suspension of the BMW i8 is comfortable compared to most sports cars, without attempting to be a saloon. The standard equipment includes adaptive dampers, which adjust the suspension depending on the selected drive mode. Five different drive modes are available. Alongside the Comfort and Eco-Pro modes, in which both combined driving with the electric drive and combustion engine and pure electric propulsion (eDrive) are possible, Sport mode can also be selected.
It is difficult to see why Sport mode cannot be activated via the Driving Experience Control as is the case in all other BMWs, but rather can only be selected by jolting the gear stick to the left. Why is BMW hiding its Sport mode? Is the BMW i8 then ultimately to be viewed not as a sports car, but with the focus instead placed on the much-cited sustainable production and efficiency?
Using only the electric drive, the BMW i8 accelerates from 0 to 100 km/h in 11.1 seconds
We are more interested in the drive performance. Using only the electric drive, the BMW i8 accelerates from 0 to 100 km/h in a valiant 11.1 seconds. The maximum speed is 120 km/h. But that's enough of the silent electrical drive. While in pure electric mode, the BMW i8 is driven by a 96 kW hybrid synchronous electric motor at the front axle, with the eDrive button deactivated it also attacks the road with the support of its three-cylinder engine with 231 bhp, which drives the rear axle. The system performance of 362 bhp really leaves no cause for complaint.
The developers cleverly conceal the turbo lag of the BMW i8 (max. boost pressure of 1.5 bar), the maximum torque of which is only reached at a later stage, by means of a 15 kW starter generator, which is positioned directly at the combustion engine and provides support by means of power boosts (eBoost).
Why is the electric motor on the front axle not sufficient? Its power is not sufficient for dynamic driving, with just one gear transmission ratio or for speeds of over 200 km/h. BMW reaches into its bag of tricks and thus uses a two-speed transmission system that is unusual for electric motors and should enable more even power distribution.
Granted, the BMW i8 is no high-revving wonder machine, but nonetheless, it does impress with its good torque over the full range of speed. It feels like it is revving at higher than 6,500 rpm, which is also down to the fantastic background noise of the three cylinder. The fact that I am actually writing such a sentence is something that, prior to the i8 test, I would have considered a utopian dream, as likely as my favourite local team winning the German Championship. Unlike the driving three-cylinder parking space that is the Smart car, the straight-six engine that has been cut in half, with a litre capacity of 154 bhp, emits a dirty roar that stands in contrast to any eco-friendly image the vehicle may have, especially when in Sport mode.Robust bursts of sound when double-declutching
If anyone then wishes to manually gear down through the steps of the six-speed automatic transmission using the steering wheel paddles, the BMW i8 throws robust bursts of sound past their ears when double-declutching. Resourceful engineers have given the plug-in hybrid a remarkable sound. Of course, at this point we could once again dig out the god of naturally aspirated engines, the M3 E46 CSL, but no-one expected the i8 to be a natural vocal performer without playback anyway.
And how does the BMW i8 drive? Thanks to the Launch Control, it accelerates to 100 km/h in 4.4 seconds in Sport mode. After 15.2 seconds, 200 km/h is history. Here a Porsche 911 Carrera S will also have to go full throttle in order to keep up. The BMW i8 sprints effortlessly to a top speed of 250 km/h, which can also be achieved and sustained by the combustion engine alone. One fact that fascinated our M135i driver, following in the slipstream during our motorway test drive with the i8 and later at the petrol station during a joint pit stop, was this: "I would never have imagined that this vehicle could manage such a speed!"
At the fuel pump, the difference between sports car visuals and fuel consumption almost caused the filling station attendant to pass out. However, the BMW i8 is not the fuel-efficient miracle that the theoretical NEFZ consumption value of 2.1 litres per 100 kilometres would have you believe. That said, the minimum consumption of 7.2 litres that we calculated, along with the average test consumption of 9.2 litres are out there on their own when it comes to the sports car segment.
BMW i8 on the Hockenheim circuit
Even with your foot to the floor on the motorway, the hybrid sports car consumes no more than 16.9 litres on average. For conventional bhp heroes sometimes like to indulge in a double helping of high-octane energy, or even more. However, consumption and range depend on the charging cycles at the grid. The BMW i8 can also charge its 5.2 kWh lithium ion battery independently by means of thrust recuperation when in Sport mode or energy recuperation when braking.
But that's enough for newfangled technical details: how does the BMW i8 perform when pushed to the limit on the Hockenheim circuit? BMW confidently promises "exceptional drive dynamics". With the tank full, and 100 percent charged – it's time for a first hesitant lap of the Hockenheim short circuit with the i8. While in everyday driving the modulation of the brake pedal requires a certain acclimatisation period, on account of the interplay of the purely electrical generator brakes for the energy recuperation and the mechanical deceleration, the i8 impresses when pushed to the limit, with an easy-to-modulate feel on the pedal. The electrical power steering also requires a little getting used to. In the Comfort or Eco-Pro modes, the power steering is synthetically light. In Sport mode the whole feel of the steering is much more firm. Around the central position, however, the steering could do with a little bit more precision on the track.Faster on account of wider tyres?
More interesting than the steering ratio (16.0:1) is the question as to how the slimline format of the tyres works from a lateral dynamics perspective. The standard tyres on the BMW i8 (195/50 front and 215/45 rear) really reminds me of my time learning to drive, in a Golf III, prior to the turn of the millennium. In any case, in the test, our BMW i8 is fitted with the optimal mixed set of tyres with 215 tyres and 245 tyres on the front and rear axles respectively (subject to an additional charge of 1,500 Euros). According to BMW this should "ensure a high curve dynamic and superior traction".
In spite of the narrow tyres, the BMW i8 carves through the racetrack with astonishing agility. If you avoid over-exerting the front tyres by braking into the corner late, the hybrid sports car rewards you with direct handling. To those who are a little too fond of the accelerator, the i8 responds in a disgruntled manner, understeering as it enters the corner. It responds to load changes by adjusting the handling to promote lateral dynamics, provided the air pressure is higher at the rear axle than at the front. On the short circuit there is a half-second time difference when using "normal" air pressure, which provides for an almost identical fill value at the font and rear axles, and air pressure for "full load" (2.3 bar at the front, 2.8 bar at the rear).
The traction of the all-wheel-drive hybrid varies greatly depending on the steering angle. The BMW i8 pushes anyone who likes to put there foot down early with a small steering angle at the apex of the curve away via the front axle. In tight corners with a larger steering angle, the i8 does not release all of its power immediately at full load, and in spite of the deactivated DSC, the engine noticeably regulates itself. Inside the hybrid sports car there is a host of different driving aids at work, such as the Cornering Brake Control (CBC), Dynamic Brake Control (DBC), the ADB-X (Active Differential Brake) and the drive torque control (FAV).
Rolling movements? The well-adjusted chassis barely has any tendency to roll. On the contrary – the BMW i8 moves nimbly, as though is has a great deal fewer than its 1,480 kilos on its bones. Entrance to the motodrome, Sachs corner, dip, southern corner – where does the BMW i8 lap time place it in the rankings? With a surprisingly fast time of 1:15.0 minutes, the hybrid sports car places well in the ranking, between the Porsche Boxster (1:14.9 min), the Lotus Elise S Club Racer (1:15.1 min) and the Jaguar F-Type (1:15.2 min). With wider tyres, the i8 could certainly threaten some of the more established 'top dogs'.Fast lap in Hockenheim
However, the limiting feature on the racetrack is not so much the slipping tyres or the braking system, as is often the case in other vehicles, but rather the deteriorating performance of the electric drive. Calculating the lap time in the BMW i8 was more like a superpole time trial, whereby only one lap was taken as the best time
1:15.0 min, 1:15.4 min, 1:15.6 min, 1:16.0 min, 1:16.2 min – within five laps it was not only the charge status that had dwindles from 100 to 3 percent. On account of the proportion of the lap driven at full throttle, performance also falls noticeably, as evident in the deteriorating lap times. "Electronic scrap", yells a colleague from the next room, as I put down the last few lines of this text. The BMW i8 is anything but. However, I did also confirm some electric vehicle prejudices.
Date5 February 2015