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Getting cleaner and greener
Audi's electric-driven turbocharger a game-changer
MUNICH, Germany — The road to the future is paved with uncertainty. Specifically, what will power the shift away from the world's dependence on oil?
Audi has a number of ideas that will come to fruition in the coming years. While most of the solutions revolve around Otto’s 136-year-old cycle, hybrids and, ultimately, electric vehicles, will become the driving force.
One of Audi's solutions involves using turbocharging. While the primary source of forced induction on Audi’s 3.0-litre V6 turbodiesel remains the conventional exhaust-driven turbocharger, there’s a twist. The drawback to any turbocharged strategy is lag time — the momentary lag between the demand for power and the time it takes the turbocharger to spin up to the speed required to service that demand.
Audi's solution involves a second turbocharger — one driven electrically.
Under normal circumstances, the exhaust gas is routed around the electric turbocharger. However, at low engine speeds, when lag is at its most evident, the electric turbocharger kicks in and counters the lag. It banishes all and any hint of the lethargy that plagues so many turbocharged engines. It also gave the test riders here a very swift kick in the pants when the A6 test car was hoofed off the line!
The unspoken bonus? The electric turbocharger is driven by the electricity harvested during braking, so its input and the tremendous effect it has on low-end torque is basically free.
In the mid-term, Audi plans to roll out a number of hybrid vehicles. The Audi A3 e-tron is still a conceptual parallel plug-in hybrid at this point, but it will go into production in 2014, followed shortly thereafter by plug-in versions of the Q7 and A4.
The long term involves the further electrification of the automobile. By 2020, Audi wants to be the leading premium manufacturer of electric vehicles with annual sales reaching six figures.
One of the vehicles that will lead the electrified charge is the range-extended A1 e-tron. This is the second-generation range extender that operates in both series and parallel hybrid modes — the gasoline engine is used to charge the battery and drive the car.
As for the techy bits, the A1 e-tron features two electric motors, a 1.5-litre three-cylinder turbocharged gasoline engine and a 17.4-kilowatt/hour lithium-ion battery. The gas side produces 127 horsepower and 147 pound-feet of torque, while the main electric motor chips in with another 113 hp and 184 lb-ft of torque.
The second electric motor, which is rated at 67 hp and 155 lb-ft, is normally used to start the engine and act as a generator to recharge the battery. However, if the driver goes to wide-open throttle, it joins the main electric motor in powering the A1.
With all three sources giving their all (the so-called boost mode), the A1 e-tron puts a net system output of 175 hp at the driver’s disposal.
Where the A1 differs from many hybrids is that it uses a single-speed transmission — the lone gear is roughly the same ratio as sixth gear in Audi’s twin-clutch gearbox. As such, the engine only drives the A1 at speeds above 55 kilometres an hour. The reality is that this does not affect the way the car drives at all — the main electric motor begins to twist out its peak torque the instant it begins to turn. In the lightweight A1, this brings a spirited launch off the line and a run to 100 km/h of less than nine seconds.
The driving range is remarkably good. The A1 e-tron can travel on electricity alone for up to 90 km. Beyond that, the extended-range portion provided by the gasoline engine delivers a total driving distance of 600 km. In the end, the A1 e-tron consumes just one litre of gasoline for every 100 km it's driven!
Driving the A1 proved just how integrated the extended-range system is in operation. The transition between all-electric and extended-range modes is completely seamless. In fact, the only thing that gave the game away was the noise of the three-cylinder engine — engines with an odd number of cylinders tend to be less than harmonic in the sound department.
That said, the noise level is suitably subdued even when the driver goes into the boost mode. As such, the A1 e-tron drives and sounds very much like an all-electric car. I coaxed it up to 100 km/h on electric power alone. It will run at up to 130 km/h electrically and has a top speed of 180 km/h.
The other bit of good news is that the system is entirely scalable, which means that it will work equally well in the larger A4 or A6.
Going one step further is e-quattro. As its name implies, it’s an electric all-wheel-drive system. Taking the A1 e-tron’s basic powertrain and adding two more electric motors to the rear axle not only gives an on-demand system, it also allows torque vectoring — driving the outside rear wheel faster than the others points the car into a corner with much less understeer.
Audi also revealed the all-new A3 Sportback, a car that, sadly, will probably not make it to Canada. Along with its cleaner styling and Audi's signature LED daytime running lights comes a significant stretch in the wheelbase — the additional 58 millimetres brings noticeably more rear-seat leg-room.
The display car also featured Audi's TCNG powertrain, which can run on gasoline or compressed natural gas. The latter is housed in two tanks that are mounted aft of the rear axle beneath the trunk floor.
The need to develop cleaner transportation is underscored by one statistic. In 1800, there were but three cities with more than one million inhabitants -- Beijing, London and Tokyo. Today, there are 442 such cities, and counting.
— Postmedia News
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