In this case, the German automaker is developing a so-called "coasting" hybrid, which is a variation of the stop-start feature being included in an expanding stable of vehicle models. In fact, the system is similar to what we saw on the Volkswagen Golf Twin Drive in 2008, but Audi uses a three-cylinder gas-powered TFSI engine instead of the four-cylinder diesel that was found in the Golf. A version of Twin Drive was developed for the Audi A3, as well.
The iHEV (Intelligent Hybrid Vehicle) is now being developed for the Audi A7 sedan, though the automaker hasn't said anything about timeframe, cost or availability. Still, the company came out with a nifty video (see it below), complete with computer-created graphics showing the car climbing and descending hills with the help of the hybrid system.
The video's explanation was minimalist, but UK's Autocar laid out the details of the system, which includes a 48-volt electric motor powered by a 48-volt lithium-ion battery that, unlike current stop-start systems that cut the engine when the car is at a standstill, actually cuts or idles the engine when the car's in motion in order to save fuel. In other words, it can coast. Audi goes one step further by equipping the A7 with a navigation system that collects data on the inclines and declines down the road (literally) and uses the information to speed up, slow down or shut down the gas engine appropriately.
The upshot is that the car, when tested on 38 miles of winding country roads, was able to shut down its gas engine during 28 percent of the journey and boosted fuel economy compared to a conventional A7 by about 10 percent.