BMW has revealed the i8 in production for the first time at IAA in Frankfurt, the 1,490 kg (3,284 lbs) plug-in hybrid adopts a 2+2 configuration and boasts a carbon fiber reinforced plastic passenger cell and an aluminium frame for the combustion engine and electric motor, the battery pack and the suspension.
The doors are made up of a CFRP inner structure and an aluminium outer skin and weigh 50 per cent less than a conventional construction. The intelligent construction of the magnesium instrument panel support brings a weight saving of around 30 per cent compared with the BMW 6 Series, for example. In addition, the high structural rigidity of the magnesium support structure The revolutionary character of the BMW i8 is emphasised by a further innovation: the use of an internal combustion engine which is making its debut in this model.
The BMW i8 is the first BMW production model to be powered by a three-cylinder petrol engine.
This highly turbocharged unit is equipped with latest-generation BMW TwinPower Turbo technology. It is exceptionally compact and develops maximum power of 170 kW/231 hp from its 1.5-litre displacement. The resulting specific output of 113 kW/154 hp per litre of displacement is on a par with high-performance sports car engines and is the highest of any engine produced by the BMW Group.
The new three-cylinder engine derives its typical characteristics from BMW’s six-cylinder in-line engines, to which it is closely related and which are noted for their eager power delivery, revving ability and refinement.
The three-cylinder’s BMW TwinPower Turbo technology comprises a high-performance turbocharging system and direct petrol injection with high-precision injectors positioned between the valves, along with VALVETRONIC throttle-less load control, which improves efficiency and response thanks to seamlessly variable valve lift control.
Like a six-cylinder engine, the three-cylinder unit is free of first and second-order inertial forces. The low roll torque, a typical feature of a three-cylinder design, is further reduced by a balancer shaft, while a multi-stage damper integrated in the automatic transmission ensures very smooth and refined running at low rpm. BMW TwinPower Turbo technology and low internal friction improve both fuel consumption and torque characteristics. Accelerator response is sharp and the three-cylinder unit quickly reaches its maximum torque of 320 Newton metres (236 lb-ft).
The car’s second power source is a hybrid synchronous electric motor specially developed and produced by the BMW Group for the BMW i8.
The motor develops maximum power of 96 kW/131 hp and produces its maximum torque of around 250 Newton metres (184 lb-ft) from standstill. Typically for an electric motor, responsive power is instantly available when starting andthis continues into the higher load ranges.
Credit for the linear power delivery, which extends right up to the high end of the rpm range, goes to a special motor design principle exclusive to BMW i. BMW eDrive technology refines and improves on the principle of the permanently excited synchronous motor with a special arrangement and dimensions for the torque-producing components. This results in a self-magnetising effect normally confined to reluctance motors.
This additional excitation ensures that the electromechanical field generated when current is applied remains stable even at high rpm. As well as providing a power boost to assist the petrol engine during acceleration, the electric motor can also power the vehicle by itself. Top speed is then 120 km/h (approx. 75 mph).
The BMW i8 has a maximum driving range in this emission-free, virtually soundless, all-electric mode of up to 35 kilometres (approx. 22 miles). The motor derives its energy from the lithium-ion battery which is centrally mounted underneath the floor of the vehicle.
This model-specific version of the high-voltage battery was developed and produced by the BMW Group. It has a liquid cooling system, offers a maximum usable capacity of five kilowatt hours and can be recharged from a conventional household power socket, at a BMW i Wallbox or at a public charging station.
The rear wheels of the BMW i8 are driven by the petrol engine via a six-speed automatic transmission, while the front wheels receive their power from the electric motor via a two-stage automatic transmission. Combined maximum output of 266 kW/362 hp and combined peak torque of 570 Newton metres
provide all-wheel-drive performance which is as dynamic as it is efficient. The BMW i8’s intelligent powertrain control system ensures perfect coordination of both power sources.
The variable power-sharing between the internal combustion engine and the electric motor makes the driver aware of the sporty temperament of the BMW i8 at all times, while at the same time maximising the energy efficiency of the overall system. Utilising both power sources enables a 0 – 100 km/h (62 mph) time of 4.4 seconds.
The BMW i8 has an electronically controlled top speed of 250 km/h (155 mph), which can be reached and maintained when the vehicle operates solely on the petrol engine.
The BMW i8 is also the world’s first volume-produced vehicle to be equipped with chemically hardened thin glass. This innovative technology, so far used mainly in smartphone manufacturing, lends the material impressive strength. The partition between the passenger compartment and boot of the BMW i8 consists of two layers of chemically hardened glass, each of which is just 0.7 millimetres thick, with acoustic sheeting sandwiched in between. In addition to excellent acoustic properties, a further advantage of this solution is a weight saving of around 50 per cent compared with conventional laminated glass.
The design of the BMW i8 body is as groundbreaking as the plug-in hybrid sports car’s concept as a whole. Hallmark BMW dynamics, lightweight design and efficiency are all expressed in the car’s proportions, lines and surface design.
The 2+2-seater is immediately recognisable as a BMW i model and a new-generation sports car. The structure of overlapping and interlocking surfaces – lent additional emphasis by the car’s colour concept – also contributes to the unmistakable appearance of the BMW i8. This layering principle allows aerodynamic forms to be wrapped up in a progressively styled package, while powerfully formed wheel arches draw attention to the wide track of the BMW i8.
The compact construction distinguishing both the electric motor and combustion engine allows the front and rear sections of the car to be particularly low-slung and thus accentuate the car’s dynamically stretched flanks. The doors, which open forwards and upwards like wings, add extra intrigue to the sports car design of the BMW i8. A signature feature of BMW i cars is the “black belt”.
On the BMW i8, it emerges in a “V” shape from the bonnet and extends back over the roof into the rear section of the car, where it frames the centre section of the rear apron. At the front end, the black belt is framed by the body-coloured apron and side panels, while at the rear it is overlapped by the “floating” roof pillars, which extend over the rear lights. Another element of the standalone BMW i design language is the “stream flow” contour of the side window graphic.
On the BMW i8 the stream flow also determines the path travelled by the air between the falling roofline and the character line rising through the rear section of the car’s flanks towards the rear spoiler lip.
The three-cylinder combustion engine in the BMW i8 develops 170 kW/231 hp and drives the rear wheels, while the 96 kW/131 hp electric motor draws its energy from a lithium-ion battery, which can be charged from a conventional domestic power socket, and sends its power to the front axle.
This bespoke plug-in hybrid system, developed and produced by the BMW Group, enables a range in everyday driving of up to 35 kilometres (approx. 22 miles) and a top speed of 120 km/h (approx. 75 mph) on electric power alone, coupled with a “glued-to-the-road” all-wheel driving experience headlined by powerful acceleration and a dynamically-biased distribution of power through enthusiastically taken corners.
The more powerful of the two power sources drives the rear wheels and uses the electric boost from the hybrid system to deliver hallmark BMW driving pleasure while at the same time offering groundbreaking levels of efficiency. The sprint from 0 to 100 km/h (62 mph) takes just 4.4 seconds, yet average fuel consumption – as calculated in the EU test cycle for plug-in hybrid vehicles – stands at 2.5 litres per 100 kilometres (113 mpg imp) from launch. CO2 emissions come in at 59 grams per kilometre.
