BMW i8

	BMW i8
	Debut: 2014 Maker: BMW Predecessor: No

Published on 2 May 2014

In September 2009 our news section read as following:

The "Vision EfficientDynamics Concept" (a silly name, by the way) shown in Frankfurt is not destined to be a new-age M1. It is a demonstration how green technologies and sports car performance can come together. This mid-engined 2+2 sports car is powered by an unexpected powerplant - a 3-cylinder 1.5-liter turbo diesel engine, aided by two electric motors and Li-polymer battery. It is a plug-in hybrid car…

Will BMW put this car into production? Of course not. Its price would have been too expensive to do so. As a technology showcase, however, it is very successful.

I was wrong. 5 years later the concept car comes true, albeit with a smarter name, i8. We can't help praising BMW's courage and determination to put the high-tech concept into production. You know, concept cars involving tomorrow's technology have always been difficult to realize, because they take a lot of research and development and the bespoke components required could not be bought from mass production suppliers. Both drive up their costs to infeasible levels. That is why Jaguar cancelled the C-X75 supercar project after a hard study. We hold BMW in the highest regard for launching the i3 and i8. It takes a lot of good planning, investment and engineering to realize these cars.

Thankfully, the production i8 is remarkably close to the original concept, which means it looks amazingly sleek and futuristic on the road. Like the concept, it is a mid-engined 2+2 seating sports car (in Ferrari Mondial style). At 4689 mm long, 1942 mm wide and 1293 mm tall, it is about as long as a Nissan GT-R, but slightly wider and significantly lower, resulting in a supercar profile. When designed the car, BMW obviously wanted it to look like a modern M1, so it deliberately adopted a trapezoidal air outlet in the middle of the front bonnet. The doors are no longer transparent like the concept, but they still open in butterfly style like an exotic supercar should. The two-tone color, multi-layer surfacing and blade-shape rear fenders are carried over from the concept, and they contribute to a surprising family resemblance to the i3 city car. To accommodate a pair of child seats at the back and the mid-mounted engine, it adopts an unusually long, 2800 mm wheelbase, but the front and rear overhangs are short enough to keep the overall length relatively short.

An important design feature is the air channel that runs above the rear fender and beneath the lateral extension of C-pillar. It draws airstream towards and exit from the top of taillight, reducing both drag and lift. Thanks further to the streamline shape and unusually narrow tires (even the optional tires measure only 215/45WR20 up front and 245/40WR20 at the rear), the car returns a remarkable drag coefficient of 0.26, aiding its fuel economy a lot.

Before going on our technical analysis let's see its market positioning first, because that will influence the way we see it. Priced at £100,000 the i8 is just as expensive as a 911 GT3. In terms of outright power or performance – 362 hp maximum, 155 mph top speed and 0-60 mph in 4.2 sec – it is not exactly up to the level of Porsches, or Audi R8, or Nissan GT-R, or Jaguar F-Type R Coupe if you matter. However, neither these cars come close to its green credential or its relaxing driving manner in electric mode. If you have its battery fully charged at home, you will find its tailpipes emit only 49 grams of CO2 each kilometer on EU combined cycle, and the instrument reveals a fuel economy of 135 mpg! The modern, well-appointed cabin rivals luxury coupes, yet the latter have no hope to match its 1485 kg kerb weight or its mid-engined sports car agility. In short, there is nothing quite like the i8 on the market. Think a practicalized version of 918 Spyder, just at 1/7 of the price.

Porsche and Audi people should love the i8 very much, even though its dynamics are not necessarily as good. They should love its head-turning design, its sense of occasion, its advanced technology, its high build quality as well as high practicality. Swing up the butterfly door and you will know what I mean. Access to the cabin takes some skills, thanks to the high and wide sill of the carbon-fiber passenger cell, but that experience adds to the sense of occasion and reminds you that this is a real exotic rather than a hybridized 6-Series. Once inside, your head will be greeted with a low roof lining, and the view out from the steep windscreen is no less exotic. The prominent transmission tunnel exists not just for the sake of it, because inside there sits a big pack of battery which supplies the electric motor. You can't help feeling proud of its purity. There is no excess, no frills and no pretense in its design.

Some performance machines try to use carbon-fiber interior trims to lessen their guilt of weighing 1.7 or 1.8 tons. The i8 just won't do such silly things. Its owners know well that the whole upper chassis is made of carbon-fiber reinforced plastic (CFRP), so there is no need to emphasize anymore. The whole cabin is trimmed with materials that make you feel warm and comfortable, i.e. leather, eco fabrics, carpets and soft plastics. While the switchgears are not Aston-Vanquish bespoke, they look adequate for the price. The general interior styling is attractive, if not as special as the i3 with its furniture-like design. The TFT instrument looks modern. The front seats are comfortable. The rear seats are strictly for children. Considering the smallish boot located behind the engine compartment, it is not a bad idea to leave the rear seats for luggage.

Despite of the 200 kg electric propulsion system, the i8 weighs only 1485 kg in DIN scale (including water and oil), pretty light even by the standards of conventional sports cars. For example, a 911 Carrera 4S is only 20 kg lighter, while an Audi R8 V8 is a full 100 kg heavier. This must thanks to its innovative LiveDrive construction. Like the earlier i3, the chassis of i8 consists of two parts: an aluminum lower chassis ("Drive module") which carries all the mechanical components and crash structures, and a rigid CFRP passenger cell ("Live module"). This construction is even lighter than a full aluminum spaceframe chassis yet provides better protection to the occupants and battery. Outside, most of the body panels are made of glass-fiber reinforced plastics, with the exception of aluminum door skins. Thin tempered glass adds further lightness.

The chassis layout can be seen easily from the pictures below. The internal combustion engine is mounted transversely right between the rear wheels. On the other hand, an electric motor sits at the front axle, allowing the car to claim 50:50 weight distribution. By placing the 98 kg, 7.1 kWh lithium-ion battery inside the transmission tunnel it also achieves low center of gravity and low polar moment of inertia. This is very important because with those narrow tires (to enhance fuel efficiency) the i8 really needs perfect balance to compensate for the lack of grip.

Good suspension should help handling, too. The Drive module rides on aluminum double-wishbones up front and 5-link suspensions at the rear, both are fitted with electronic adaptive dampers that link to the driver control system.

One important factor contributing to its remarkable lightweight and fuel economy is the small, 1.5-liter three-cylinder turbo engine – can you imagine a sports car like this employs a 3-cylinder motor? It is not the turbo diesel perceived in the original Vision EfficientDynamics concept, but a petrol engine developed primarily for the consumption of Mini Mk3 and the next generation front-wheel-drive 1 and 2-Series. Predictably, it has all the sophisticated technology to make it powerful yet fuel efficient, such as Double-Vanos, Valvetronic and direct injection. Vibration is taken care by a balancer shaft and multi-stage damper. With higher boost pressure than other applications, this version produces an incredible 231 horsepower and 236 pound-foot of torque. Sitting next to the compact engine is a 6-speed automatic transmission, which sends power directly to the rear wheels.

Meanwhile, the front-mounted synchronous motor produces another 131 hp and 184 lbft of torque to the front wheels via a GKN 2-speed gearbox. The low ratio is designed to serve EV driving mode, where you can drive up to 75 mph and, if more relaxingly, for a range of 22 miles. The high ratio serves hybrid modes. Maximum combined output is 362 horsepower and 420 pound-foot of torque.

There is also a starter-alternator motor mounted next to the engine, which can supply another 8 hp. Its extra torque can fill the torque gap before the turbo is spooled up.

Consequently, the i8 can be either FWD, RWD or 4WD depending on driving modes. In pure electric mode, it is driven by the front wheels only. Cruising on highway, it is driven by the engine and rear wheels only. In hybrid modes where more power is required, it is driven by all four wheels. As the front and rear power sources are independent of each other, it takes engineers a lot of fine tuning to achieve a consistent torque split, otherwise the handling could be unpredictable. Now let’s see how the car drives on the road…

On the Road

As expected, the plug-in hybrid sports car starts off in EV mode with near silence. It feels very relaxing to drive, not just because of the lack of noise and vibration but also the surprisingly light steering and the effortless performance provided by the electric motor. Change to Comfort mode, the superb refinement remains until the car passes 40 mph, when the engine at the back fires up. Even then, the power transition is smooth, and the 3-cylinder exhaust note is subdued.

However, since this is a sports car, Sport mode is the one to have. With it engaged, the steering weighs up immediately, the dampers get firmer, throttle response gets crisper, the exhaust noise gets louder and, oddly, sounds like a large-capacity straight-six! Thanks must go to the sound synthesizer that overlays the 3-cylinder exhaust note with an artificial soundtrack through audio speakers. The small engine works well with the 6-speed automatic to deliver respectable punch, especially in the mid-range. In addition to the extra electric power, the car feels quick in straight line. Probably not as quick as a Carrera S or R8, but more than enough to beat a Carrera 3.4 or Cayman S. In corners, you will appreciate the instantly accessible electric shove that helps to mask the torque gap and pull the car quickly out of corner.

The handling is pretty good. Response and feel of the electrical steering rack is decent, if not exceptional for a sports car. The suspension is quite firm in Sport mode but it keeps the car flat in corner. Thanks to the low center of gravity and good balance, the i8 feels light and agile in the twisty. It is an easy car to drive fluently on challenging roads. However, if you push it harder, you will find the skinny front tires give up early, turning into understeer easily. This is what separates the green sports car from its rivals, and it could be frustrating to committed drivers. No matter how hard you try, it just refuses to oversteer. If the i8 had electric torque vectoring between the front wheels like 918 Spyder, it could have avoided this problem. As it doesn’t, it is not a great driver’s car. Drive it up to 7/10 or 8/10 and it feels superb. Beyond that level and its fundamental problem is revealed. For a sports car with this performance level, its cornering limit is too low.

Not just the chassis, its hybrid powertrain also fails to catch the hearts of keen drivers. While its mid-range punch is admirable, it lacks an enthusiastic top end to please. Output of the turbocharged 3-pot tails off beyond the 5800 rpm peak, and the gearbox changes up automatically at 6500 rpm. After all, this is a fuel-sipping small car motor rather than a true product of M division.

Make no mistake, the i8 is not set to be a high-performance sports car in conventional sense. BMW could have sacrificed some efficiency, fitted it with beefier rubbers and a bigger engine to make it more appealing to committed drivers. That would be easy, but that is not the intent of the new i-brand or the Megacity project. If you understand its concept, you may agree that it is time to change the form of motoring to suit the new world orders. The i8, like i3, is fundamentally a green car. It just wants to prove that a green car can also be fun to drive, albeit in a slightly different way to conventional sports cars. From this point of view I would say it has achieved that target in style.

Verdict: