Overview: Audi A1

Audi’s new small hatchback arrives with a choice of three power units — or four, if you include the 254cc Wankel, but we’ll come to that later. There are also three transmissions, one of which is electronically controlled, and one body: a cleanly-styled three-door. The look of the car follows Audi’s A1 project quattro design study from 2007. Audi quotes a Cd of 0.32 for the production A1, which is pretty good for a car of this size.

The A1’s dimensions place it neatly beneath the A3 and squarely in the four-metre class, though on-board technology makes it very much a ‘grown-up’ product. Notably, all variants feature a start-stop system and kinetic energy capture, as well as an electronic stability control system that comes with an electronically-controlled differential lock.

Audi A1 A3
Length (mm) 3950 4238
Width (mm) 1740 1765
Height (mm) 1420 1421
Wheelbase (mm) 2470 2578
Luggage volume (l) 267-920 350-1080

Two of the power units on offer are already familiar. The 1.6 TDI comes only with a five-speed manual gearbox, while the 1.4 TFSI can be had with a six-speed manual or VW’s seven-speed dual-clutch unit. It turns in its best figures with the seven-speeder. We can’t help thinking that the TDI deserves this unit, even if its plump torque curve means that it doesn’t strictly need it. As it is, the diesel comes with a five-speed box.

Entry-level A1s will come fitted with a new 1.2-litre TFSI motor. Like the TDI, this comes attached to a five-speed gearbox. Its fuel returns are no better than the 1.4’s — not surprisingly — and we suspect that the smaller engine’s driveability will be markedly inferior. A small turbocharged petrol engine isn’t often a pleasure to drive behind. Still, we shall see.

Audi A1 1.2 TFSI 1.4 TFSI 1.6 TDI e-tron
Power (PS) 86 122 105 61-102
Torque (Nm) 160 200 250 150-240
0-100km/h (s) 12.1 9.1 10.8 10.2
Maximum speed (mph) 111 124 116 80
Overall mpg 55.4 55.4 72.4 148.7
CO2 (g/km) 119 119 102 45

Running gear is standard Volkswagen fare, with MacPherson struts up front and a torsion-beam axle behind. The familiar Electronic Stability Programme (ESP) has been upgraded to include an electronic differential, which acts to divert torque from the unloaded inside driving wheel to the loaded outside one during cornering. The inside wheel can also be braked momentarily. This arrangement potentially reduces understeer — at least, up to a point. Torque vectoring, as it is known, has cropped up in several new cars announced recently, and it looks as though it will become fairly commonplace in a year or two.

The A1 offers three suspension set-ups according to which model you choose. An SE gets what Audi describes as ‘standard’ settings. The Sport model is predictably stiffer, with lowered ride-height, while an S-line car is more sporting still. All-disc brakes, ventilated at the front, are fitted as standard across the range. Power steering, which is also standard, is electrohydraulic.

The A1 will be available for British buyers to order from May, with the first deliveries expected in the autumn. Prices are expected to start at around 13,000.

Audi A1 e-tron

The A1 e-tron follows Audi’s extraordinary e-tron sports car concept shown at Frankfurt last autumn. Described by Audi as a ‘Mega City Vehicle’, the A1 e-tron is a series hybrid offering electric power for city use together with an internal combustion engine to act as a generator, extending the car’s operating range.

Audi A1 e-tron.

The A1 e-tron was designed specifically for use in European and North American cities, as well as the large and rapidly-growing urban areas of Asia and South America. The car is intended to drive on electric power wherever possible, with its internal combustion engine — which works only to recharge the battery pack — used only when needed.

The objective of any engineering system should be to use energy with the lowest possible losses. The interaction of components in a system and the management of energy flows should be designed primarily to achieve this. There are signs that Audi has paid some attention to these principles, not least in developing a thermal management system to keep the battery pack, the electric motor and the power electronics within their respective ideal temperature ranges. This is crucial with lithium-ion battery packs: they are prone to overheating, which affects efficiency and, in extremis, causes irreparable cell damage.

The synchronous electric motor of the Audi A1 e-tron is mounted transversely at the front of the car. Its low mounting position helps the car’s centre of gravity and reduces the tendency to understeer. Continuous output is rated at 61PS, with a peak output of 102PS available in short bursts. A minimum of 150Nm is available throughout the motor’s operating range, with a peak of 240Nm at low rotational speeds.

The electric motor sends its power to the front wheels by way of a single-speed transmission.

The power electronics are mounted in the engine compartment above the electric motor. The most important components are the pulse-controlled inverter, which serves as the controller between the electric motor and the battery; the DC converter, which connects the high-voltage network with the 14-volt electrical system; a breaker unit to protect the high-voltage components; and the charging module.

Audi A1 e-tron.

The socket for the standard charging plug is located behind the Audi badge in the car’s nose. At a charging station, a fully depleted battery can be recharged in roughly three hours from the 380-volt supply. An illuminated display adjacent to the plug-in connection shows the state of charge and the time required to complete the charging process.

The refrigerant compressor of the climate control system is powered by the high-voltage electrical system. The climate control loop also functions as a heat pump that regulates the temperature of the cabin and the battery pack: heat generated by the battery is used to heat the cabin, or dumped to the outside world by means of the climate-control system’s heat-exchanger.

An electronic brake system exploits the retardation provided when the car’s electric motor becomes a generator — capturing surplus kinetic energy on overrun and when the brakes are applied. In fact, the A1’s braking system is only partly hybraulic: a hydraulic fixed-caliper brake is mounted on the front axle, with two electrically-actuated floating-caliper brakes mounted on the rear axle. These floating calipers are actuated not by mechanical or hydraulic means, but rather by wire.

The T-shaped lithium-ion battery pack is mounted below the floor, in the rear section of the centre tunnel and the area in front of the rear axle where the fuel tank would normally be. The 380-volt battery has a nominal capacity of 12kWh. It comprises 96 prismatic cells and weighs less than 150kg.

The A1 e-tron has an operating range of 30 miles under electric power. On longer trips, the battery is recharged by a 254cc single-rotor Wankel engine mounted below the luggage compartment.

We are not convinced of the Wankel’s worth, particularly in terms of efficiency; but it is at least compact and light, and Audi is keen to stress that other power packs are possible. Nevertheless, the complete Wankel engine assembly weighs only around 70kg. This includes the power electronics, the intake, exhaust, cooling unit, insulation and subframe. Remarkable.

The Wankel runs at a constant 5000rpm, which apparently represents its peak efficiency. Electrical output is 15kW. Interestingly, the car’s electronics consider navigation data — such as the destination and intended route — and automatically activate the range extender as needed. The driver can also override the car’s decisions and start and shut off the generator manually. The fuel tank for the rotary pack holds 12l; Audi quotes a total operating range for the car of 120 miles.

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