Car of the Year: Clever VW hatch ticks all boxes

Volkswagen Golf's twin-charge engine offers more power while using less fuel. Photo / Supplied

Another time, another place, the New Zealand Herald's Car of the Year might include technology three of our finalists bought to the market in 2009: power/fuel advances in a conventional engine, breakthrough crash safety, and a solar system for passenger comfort.

But until then, the twin-charge engine technology offered in the sixth-generation Volkswagen Golf ($46,590) is reason enough for the hatchback to qualify for the 2009 gong ahead of the Volvo XC60 and its "city safety"system, and the third-generation Toyota Prius' solar-powered ventilation unit.

Carmakers globally are turning to new technology to meet new emissions and fuel economy standards. All the vehicles launched in New Zealand this year indeed claimed improved fuel economy and exhaust emissions. Petrol and diesel will get cleaner but not any cheaper.

We placed a new emphasis on technology this year. Each of our 10 finalists - Audi Q5, Ford Fiesta, Mercedes-Benz E-Class, Mazda3, Nissan Qashqai, Nissan Maxima, Subaru Legacy/Outback, Volkswagen Golf, Volvo XC60, Toyota Prius - came with many strengths and few weaknesses. The E-Class, for instance, is the best for many years. The Mazda3 should be on everyone's shopping list.

But the VW Golf, Volvo XC60 and Toyota Prius introduced technology that defies automotive convention - new boxes to tick, new categories to consider, new thinking, new standards, new influences, new demands.

VW's twin-charge technology dominated this year's international engine awards, picking up three gongs: engine of the year, best "green" engine, and best engine in the 1- to 1.4-litre category.

A panel of 64 judges from 32 countries chose the 1.4-litre twin-charger stratified injection (TSI) petrol engine as its standout performer.

TSI uses a supercharger in tandem with a turbocharger and gives a small displacement engine like the 1.4-litre unit, the power of a 2-litre while retaining the smaller unit's better economy. In short, it offers more power while using less fuel.

"It is the future of smaller-capacity petrol engines as far as VW is concerned, something the Herald has recognised with the award for the Golf," says VW New Zealand general manager Dean Sheed.

"It helps to provide a solution to what is worrying the world - the use of fossil fuels and global warming from carbon emissions. It's what our customers want."

The twin-charge TSI engine is an option in the Golf and new Scirocco coupe, where it produces 118kW at 5800rpm and 240Nm of torque between 1500-4500rpm.

A seven-speed twin-clutch automatic transmission that shifts quicker than a manual channels drive to the front wheels.

It all started when VW set out to build a small-capacity petrol engine that provided performance and driveability that was about equivalent to the output of the carmaker's discontinued V5 2.3-litre, but with improved fuel consumption and lower emissions.

Using a turbocharger alone to get more air into the engine didn't produce what VW wanted. A turbocharger runs off the engine's exhaust gases. The upside is that it doesn't sap engine power. The downside is the delay - turbo lag - before exhaust gas pressure gets high enough to work the turbo to force more air into the mix.

A supercharger, on the other hand, runs directly on engine power and works instantly. But the higher the revs the more power it draws from the engine. Result: it isn't as efficient at the top end.

TSI combines the advantages of turbocharger and supercharger but leaves the disadvantages behind. It delivers a flat line of torque - at 1000rpm the engine is producing 175Nm - that contributes to improved driveability.

Between engine speeds of 2400 and 3500rpm, both the supercharger and turbocharger contribute to boost pressure.

At 3500rpm the supercharger is deactivated through a magnetic clutch, leaving the turbocharger working where it is most efficient - higher in the rev range. The transition between the boosters is seamless.

TSI also provides relatively low town-and-around fuel consumption - around 7 litres/100km (40mpg) in the Golf - and significantly cleaner exhaust emissions. The fuel-efficiency of the 1.4-litre petrol unit is one reason why VW has left a diesel engine out of its new Polo line-up for New Zealand: the diesel would struggle to compete.

Dr Ruediger Szengel, head of engine development for VW, says TSI technology has been hugely successful.

"Small engine capacity means low friction losses and high refinement," he says. "Induction boosting provides the ability to operate with long gearing, further benefiting fuel economy.

"Direct injection allows the use of a high compression ratio in conjunction with high boost pressures providing additional efficiency benefits.

"For similar reasons TSI technology avoids the need to inject extra fuel to cool the mixture at higher power outputs, providing TSI engines with a further fuel consumption saving over conventional, boosted petrol engines."

Volvo's city safety is an automatic braking system designed to prevent or minimise collisions at speeds under 30km/h, or in a typical rear-end crash.

It is designed to react to vehicles up ahead that are either stationary or moving in the same direction. It uses a windscreen-mounted laser sensor making 50 calculations a second to monitor closing speeds within 8m of the XC60's front bumper.

If a collision with the vehicle in front is likely, it pre-charges the brakes for the driver. If the driver doesn't act - and that happens in 50 per cent of low-speed collisions, says research - it jumps on the brakes instead.

City safety will also help to prevent an accident entirely, if the relative speed difference between the two vehicles is less than 15km/h.

At higher speeds, between 15 and 30km/h, city safety focuses on reducing speed as much as possible before impact to minimise damage and injury.

The laser sensor is linked to Volvo's standard restraint systems, which control the deployment of airbags and seatbelt limiters in accordance with the severity of the collision.

City safety is part of Volvo's "Mobility 2020" vision, a mission statement which states that no person should be fatally injured in a Volvo by the year 2020. The next version of city safety will recognise pedestrians.

Chief among the many technological "firsts" in the third-generation petrol-electric Toyota Prius is solar ventilation and remote air-conditioning, a system that cools the cabin of a car that has been parked in the sun.

The solar unit uses panels in the sunroof to run a fan that draws in cooler outside air and circulates it around the cabin.

The system works independently from the hybrid powertrain, unlike the remote air-conditioning which draws power from the hybrid battery for up to three minutes before the driver enters the vehicle.

It is activated by pressing the A/C button on the key fob for one second.

Both systems have been designed for comfort. The solar fan can cool cabin temperature quite considerably, so there is less need for the air-conditioning to be turned to full power on start-up.

The system can be activated as the driver leaves the car. One minute after the ignition is turned off, the air intake mode switches to "outside air ventilation" and the blower mode switches to "face" to ensure the most efficient performance.

To avoid cabin air that has already been cooled being vented straight away, the system starts operating after 10 minutes, continuing until it is switched off, or the ignition turned on.