Merc takes an eco-friendly approach

The second-generation Mercedes-Benz A-Class, bigger inside and out and better all-round than the outgoing car, is an adaptive mix of high-tech and natural components, each working to produce more efficient motoring.

Flax fibres are mixed with plastic in the seats. The exhaust uses olive wood for the charcoal filter which absorbs harmful hydrocarbons and is self-regenerating.

Fibres from the abaca plant, which is the strongest and longest natural fibre in the world, are used in the sandwich-style floor. Such material could replace glass fibre as a strengthening agent in plastic parts for car bodies thanks to the exceptional bending and tensile strength. Natural fibres also stand out from glass fibres with their lower weight, ease of use and suitability for recycling.

Mercedes-Benz says the increased use of high-quality natural materials, recycled components, low pollutant emissions systems, and fuel-efficient engines and transmissions make up the template for more eco-friendly vehicles.

The new line-up of petrol and diesel engines for the A-Class consume 10 per cent less fuel and emit fewer global-warming carbon dioxide exhaust emissions, says the company.

Other emission pollutants have been reduced: nitrogen oxides by 17 per cent; sulphur dioxide by 6 per cent; volatile hydrocarbons by 8 per cent; other waste materials by 10 per cent.

The manufacturing process of the car is cleaner - during the vehicle's planned life cycle the factory will produce around 9 per cent fewer greenhouse gas emissions.

Primary energy consumption has been reduced by roughly the same degree, falling from 522 gigajoules for the first-generation A-Class to 479 gj in the new car. This equates to the energy stored in 1300 litres of petrol, says the company.

The number of approved recycled components is also more than three times higher than the outgoing model.

Mercedes-Benz says the improvement in fuel economy has been helped by the use of a constantly variable transmission (CVT), in this case a seven-speed unit called Autotronic that has a manual function.

CVT, which has been around for about 110 years, has mostly been used in running lathes or drill presses. Netherlands company DAF pioneered its use in vehicles in the 1950s. Subaru used a CVT unit in its all-wheel-drive Justy in 1990. Cars with engines larger than 1.2 litres were considered incompatible with CVT, mostly because of its inability to cope with high torque output. But with advanced hydraulics and high-speed sensors and microprocessors, it can be coupled to more powerful engines.

A typical CVT unit includes: a high-power/density rubber belt; a hydraulically operated driving pulley; a mechanical torque-sensing driving pulley; microprocessors and sensors.

Essentially, it operates by varying the working diameters of the two main pulleys in the transmission which in turn varies the transmission ratios. A bit like a "derailer" shifts the chain on bicycle gears but without the obvious steps. The "stepless" nature allows the CVT unit to constantly change its gear ratio to optimise engine efficiency. The result is lower fuel consumption, less greenhouse gas emissions and better performance. Research shows that CVT uses between 10 and 18 per cent less fuel than a 4-speed automatic transmission.

The CVT unit is standard across the A-Class range for the New Zealand market. A brief drive in Wellington showed it to be most effective, especially with the manual mode.

The new five-door compact rides and handles better than its predecessor, has more room for occupants, improved safety equipment, is better built, and its styling gives it a stronger presence.

Mercedes-Benz broke technological ground with the first model, after the infamous "moose" incident in Sweden. The new model does, too. It comes with the choice of three petrol - one 1.7- and two 2-litre options - and two 2-litre diesel engines. Prices start at $44,900.