Automatic versions of the latest economy focused Audi A3 models are the first in the premium sector to benefit from the latest engine start-stop technology, which has already helped to cut emissions in manual transmission TDI versions to a sector-leading 109g/km. The new highly efficient 1.4 TFSI petrol and 1.6 TDI versions of the Audi A3 equipped with the acclaimed S tronic twin-clutch automatic transmission will spearhead the new technology, which also goes hand-in-hand with a recuperation system to harness braking energy.
In its newly developed form for automatic applications, the start-stop system cuts engine power when the car comes to a standstill at traffic lights or in queueing traffic - the engine then remains dormant as long as the brake pedal is depressed and then restarts in just two-tenths of a second only when it is released in readiness for take-off. With the system's help, economy is boosted and CO2 is reduced by approximately 5g/km, but if required it can be deactivated at the touch of a button.
The start-stop system is also supplemented in these models by recuperation technology, which provides further fuel and CO2 savings by recycling a proportion of the wasted kinetic energy generated under normal braking and normally dissipated as heat, and storing this temporarily in the vehicle battery to reduce the engine load when the car subsequently accelerates again. With its help, fuel usage is reduced by as much as three per cent in the Audi A3.
Advanced electro-hydraulic controls and the alternate use of two clutches enable the S tronic gearbox to deliver lightning fast automatic or manual shifts via the gear lever or steering wheel-mounted paddle controls with no interruption of the engine's power delivery across seven ratios.
The first of the two clutches serves the odd-numbered gears and reverse, and the second the even-numbered gears, so when the A3 is travelling in third gear, for instance, fourth is already pre-selected in anticipation. As soon as the shift command is given, the first clutch is disengaged and the second engaged in just a few hundredths of a second, virtually seamlessly.
Despite this transmission's distinctly sporting slant, it can actually improve economy and reduce CO2 output while at the same time quickening acceleration. This is true of the Audi A3 1.4 TFSI S tronic with start-stop, which reaches 62mph from rest 0.1 seconds more quickly than its manual counterpart at 9.3 seconds, and has a 3.7 mpg advantage over the manual option in the combined cycle economy test, recording 53.3mpg to its 49.6mpg. CO2 is consequently also down at 124g/km, versus the manual version's 132g/km. With or without the S tronic option, the Audi A3 1.6 TDI remains the most economical and efficient model in the Audi range, with a combined economy figure of 67.3mpg (manual 68.9) and CO2 output of just 109g/km.Published 20 October 2009