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 A4 TDI concept e technology concept has the agile handling characteristics typical of the 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.

The engine 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.

Other engine-related modifications include reduced internal friction, a new thermal management system during the warm-up phase and an electronically controlled fuel pump.

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 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 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 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 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 A4 TDI concept e reaches a top speed of 206 km/h (128 mph).