Audi's TDI power is going green with the launch of an environmentally-friendly A4 concept car at the recent Frankfurt Motor Show.
The A4 TDI e Concept consumes 4.9 litres per 100 km.
CO2 emissions for the vehicle are 129g/km, which is less than the limit that the European Union aims to introduce for fleet vehicles from 2012. The power output is 105 kW, and torque is 320 Nm.
A common rail injection system supersedes the unit injection pumps used to date, its piezo injectors supplying fuel with a pressure of up to 1 800 bar, allowing extremely fine atomisation in the combustion chambers.
This improves fuel combustion and smooth running.
Modified piston geometry improves the thermodynamics in the combustion chambers. Other measures to reduce internal friction and for temperature management further increase fuel efficiency.
There is also an ultra low emission system.
Engine power is transmitted onto a newly developed six-speed manual gearbox that is characterised by greatly reduced internal friction.
Another important contribution is made by the start/stop system. It avoids the engine running inefficiently when the vehicle is stationary.
As soon as the vehicle comes to a standstill, the gear lever is moved to neutral and the driver takes his foot off the clutch, the TDI is automatically switched off.
The engine is restarted when the driver depresses the clutch. The TDI runs up while he is engaging the gear. It has reached idling speed by the time he releases the pedal.
According to Audi a specially developed starter motor turns the engine in little more than two tenths of a second ? this is apparently 60% faster than a conventional part.
Furthermore power is transmitted onto a newly developed six-speed manual gearbox that is characterised by greatly reduced internal friction. It has been specially tailored for the high-torque of the special TDI engine.
Also, the recuperation system on board the TDI e Concept converts kinetic energy into useful electrical energy as the vehicle decelerates. An innovative gel battery is used as the power source for the vehicle electrical system. This is extremely robust even at high loads and when it is heavily discharged, allowing it to achieve a particularly long service life.
When the car is coasting or braking, the secondary voltage from the D/C converter is run up. The alternator is then able to convert the kinetic energy into electrical energy that is temporarily stored in the gel battery. When the car subsequently accelerates again, the battery feeds the energy back, relieving the load on the alternator.
The power steering has also been thoroughly modified ? its effectiveness has been improved by around 50% because it is now fed hydraulic energy by a demand-controlled vane-cell pump. In contrast to conventional power steering pumps, which constantly recirculate large volumes, it only pumps as much oil as actually needed at that very moment.
Audi has also reworked the automatic air conditioning system to use less fuel.