Audi A4 TDI Concept e

Efficiency is the way into the future - Audi is introducing the current state-of-the-art for its fuel-saving technologies at the Paris Auto Show. The Audi A4 TDI concept e technology concept has the agile handling characteristics typical of the Audi A4, but requires just 3.99 liters of fuel per 100 kilometers (58.95 US mpg). This exemplary result was possible through the concentrated use of innovative efficiency modules.

Audi is committing major resources in order to continue improving fuel efficiency and reducing emissions. The brand is introducing a trend-setting technology concept at the Paris Auto Show: the Audi A4 TDI concept e offers the typically agile experience of driving an Audi, yet it uses just 3.99 liters of fuel per 100 km (58.95 US mpg), which corresponds to a CO2 output of only 105 grams per km (168.98 g/mile). With this near-production study, Audi demonstrates the great potential of the technologies in its modular efficiency system.

The powertrain of the Audi A4 TDI concept e uses a direct-injection TDI engine with an output of 88 kW (120 hp) and 290 Nm (213.89 lb-ft) of torque. It propels the sedan from 0 to 100 km/h (62.14 mph) in 10.7 seconds, and tops out at 206 km/h (128 mph). An entire array of details - from soft springs on the intake valves to a new thermal management system - improves fuel efficiency. Intelligent technologies are used in the engine's functional environment as well, such as on the fuel pump and on the automatic air conditioning's compressor.

The recuperation system is another fundamental component for improving fuel efficiency. It recovers power when braking and coasting to a stop, and temporarily stores it in a battery. A start-stop system switches the engine off when the vehicle comes to a standstill. Magnesium was used to reduce the weight of the six-speed transmission, which received an insulating cover for faster warm-up and modified gear ratios.

Audi uses an electromagnetic servo assembly for steering; electrically actuated brakes are fitted at the rear. The 225/45 R17 tires have been optimized for road resistance. Sophisticated fine-tuning measures have improved the aerodynamics of the body. Two types of support are at the driver's fingertips: he can either call up an economy training program, or have the navigation system calculate the most fuel-efficient route to his destination.

The heart of the sedan is a direct-injection diesel engine - a 2.0 TDI with output of 88 kW (120 hp), just as for the A4 production models. From 1,750 to 2,500 rpm, the four-cylinder engine produces a constant torque of 290 Nm (213.89 lb-ft), which generates impressive acceleration. The piezo injectors in the common-rail system inject the extremely finely atomized fuel at a pressure of up to 1,800 bar, and the special piston geometry provides ideal thermodynamics in the combustion chambers.

The 2.0 TDI also features a comprehensive package of additional efficient technologies. The oil cooler, the oil nozzles for cooling the piston crowns, the oil pump and the water pump have been designed so that they can be switched off - when inactive they do not require any power. New piston rings resulted in lower tangential forces, the spring pressure on the intake valves was reduced slightly, and the vacuum pump for the brake booster received a new actuator. These measures as a whole reduce emissions by 5 grams of CO2/km.

Just as in the production version, Audi is using a thermostatically controlled cooling circuit with an internal heat exchanger for the automatic air conditioning system. It responds in a highly efficient manner - the system uses 20 percent less fuel than its predecessor. The Audi A4 TDI concept e uses a new controller: the engine disconnects the air conditioning system's compressor from its drive whenever possible.

Like many Audi production models, the Audi A4 TDI concept e uses a recuperation system that converts the energy of motion during deceleration into usable electrical energy. In the deceleration and braking phases the Audi A4 TDI concept e operates with increased secondary voltage. At this point, it is able to convert the kinetic energy into electrical energy; it is buffered in an absorbent glass mat battery, which is a robust battery with a long life. Whenever the sedan accelerates again, the battery feeds the energy back in, thus reducing the load on the alternator.

Efficiency and agility are inextricably linked at Audi - as proved by the basic data for the Audi A4 TDI concept e. The sedan sprints from 0 to 100 km/h (62.14 mph) in 10.7 seconds, and accelerates from 80 to 120 km/h (49.71 to 74.56 mph) in fifth gear in just 10.9 seconds. The Audi A4 TDI concept e reaches a top speed of 206 km/h (128 mph).

The transmission is coupled to a start-stop system that switches the engine off whenever the sedan comes to a standstill. The TDI is deactivated whenever the Audi A4 TDI concept e comes to a standstill, the shift lever is in the neutral position, and the driver's foot is off the clutch pedal. It starts up again as soon as the driver steps on the clutch - a specially developed starter handles this in around two tenths of a second, which is faster and smoother than a traditional component. While the driver puts the vehicle in gear, the TDI speeds up; as he takes his foot off the pedal, it drops down to idle speed.

The start-stop system improves the exemplary fuel efficiency of the Audi A4 TDI concept e still further, meaning that 5 grams less of CO2 are produced per 100 kilometers - as measured on the dynamometer. And in actual terms this reduction may turn out even higher, as many trips to work are less than ten kilometers long and are frequently interrupted by traffic lights.

Another important feature is that an electro-mechanical part replaced the electro-hydraulic power steering. This yielded a further reduction of 4 grams of CO2/km. It does not have to circulate any hydraulic fluid, nor absorb any energy while the vehicle is traveling in a straight line - its electric motor which provides power assistance only kicks in if the driver turns the wheel.

Source: Audi press

Gallery: Audi A4 TDI Concept e