Many engines in many Audi models operate in conjunction with a standard start-stop system. In terms of drivetrains, there are practically no limitations: manual transmissions are just as well suited for this technology as automatic transmissions.
When the Audi comes to a stop, at a traffic light, for instance, the control unit shuts off the engine. The driver must keep the brake pedal depressed (automatic transmission) or release the clutch pedal (manual transmission). A powerful starter energized by a heavy-duty, deep-cycle battery restarts the engine quickly and easily when the driver releases the brake or steps on the clutch again to engage a gear.
The start-stop system is highly effective. It is only inactive during the engine’s early warm-up phase, on roads with steep gradients and in extremely cold temperatures. In the Audi A8, for example, it lowers fuel consumption in a standard driving cycle by approximately 8 grams of CO₂ per kilometer (12.87 g/mile). In everyday city driving, the system has the potential to achieve far higher efficiency.