The coasting function works between 34 and 100 mph (55 and 160 kph) to save precious fuel.
Ahead of its highly anticipated reveal set for next month, the all-new Audi A8 is back in the news yet again as the peeps from Ingolstadt have decided to spill the beans about the flagship sedan’s green credentials. Standard across the entire range will be a mild hybrid system consisting of a water-cooled 48-volt alternator starter mounted on the front side of the engine and complementing the regular pinion starter. Audi points out the latter will only kick in during cold starts. Also part of the mild hybrid setup will be a lithium-ion battery pack mounted in the trunk with a 10-Ah charge carrier capacity and a 48-volt system.
The full-size luxury sedan will be equipped with a highly advanced coasting function available from 34.2 to 99.4 mph (55 to 160 kph) once the driver takes his foot off the accelerator. In this speed range, the A8’s engine will be completely shut off whenever possible to save fuel and it will remain that way for up to 40 seconds. After the driver presses the gas pedal, the combustion engine is activated immediately without any delays in acceleration. This will be possible thanks to the aforementioned 48-volt belt alternator starter (BAS) permanently connected to the engine and ready to fire it up right away at all times.
Gallery: 2018 Audi A8 New Spy Photos
Audi’s engineers have also come up with a clever start/stop system active from 12.7 mph (22 kph) and incorporating a new function dubbed “predictive convenient starting.” Once the A8’s front-mounted camera and sensors detect the car in front starts moving, the engine is automatically turned on even if the driver still has his foot on the brake pedal, so that he’ll be able to drive off quicker and consequently improve the flow of the traffic. The onboard tech will also be smart enough to detect if the posh sedan is dangerously getting too close to the car behind it while in coasting mode.
Thanks to the mild hybrid system and the clever powertrain management, Audi says fuel consumption is reduced by up to 0.7 liters (0.2 gallons) / 62 miles (100 km).
The fourth-generation A8 will be unveiled on July 11 at the Audi Summit event in Barcelona.
Looking ahead to the new Audi A8: More voltage for enhanced efficiency
Luxury sedan available for first time with standard electrified powertrain
48-volt primary electrical system opens up fresh scope
Flagship model making world debut at the Audi Summit in Barcelona on July 11
The new Audi A8 is advancing electrification on a broad front. In the next model generation, the flagship will for the first time feature an electrified powertrain as standard. To that end, the combustion engines will be equipped with mild hybrid technology. What this means for the customer is refined running and enhanced performance, coupled with greater efficiency. The basis is the 48-volt electrical system, which features for the first time in the new Audi A8 as the primary electrical system.
The mild hybrid drive comprises two main components: first, the watercooled 48-volt belt alternator starter (BAS), which complements the conventional pinion starter. The latter is only required for cold starts in the new Audi A8. Then there is the lithium-ion battery in the luggage compartment to act as the energy accumulator for the MHEV (mild hybrid electric vehicle) with a 10 Ah charge carrier capacity and a 48-volt system.
The advantage of the BAS becomes particularly clear when the driver approaches a red traffic signal or a roundabout. If the traffic signal turns green during braking while the vehicle is coasting to a stop or if a gap appears for the driver to weave into, and the driver releases the brake, the combustion engine is started immediately. The car accelerates without any delay. This is all thanks to the belt alternator starter, which is permanently connected to the combustion engine.
The new drive combines efficiency with comfort in a very special way: The fourth-generation A8 can enter the noiseless coasting mode within the speed range of 55 to 160 km/h (34.2 to 99.4 mph). The automobile can then coast with zero emissions for up to 40 seconds with the engine off altogether. As soon as the driver steps on the gas again, the BAS prompts a swift, very smooth restart. In addition, start/stop operation is actually active from 22 km/h (13.7 mph).
The convenient start/stop function in the new Audi A8 differs markedly from previous systems. The high-connectivity luxury sedan can distinguish between different traffic situations. When the road ahead is clear, the BAS starts the combustion engine conveniently and promptly, letting the Audi A8 drive off swiftly. After long standstill phases and if the customer wants to turn up the air conditioning, the combustion engine is started extra-smoothly and quietly. There is the new feature of predictive convenient starting: As soon as the vehicle in front of the Audi A8 moves, the engine starts even if the brake is still pressed. In this scenario the control strategy concludes that the driver will spontaneously fall in with the flow of traffic.
To achieve the high standard of efficiency, the new Audi A8 comes with sophisticated powertrain management: It processes both route data and information from its highly networked set of sensors, which include the front camera. The powertrain management uses this equipment to decide whether the A8 is in coasting or recuperation mode. It recovers energy not just from brake applications or when coasting; the Audi A8 also does so if it is in danger of getting too close to a preceding vehicle while coasting. All these measures are beneficial not just to comfort, but also at the gas station: In the A8, the mild hybrid drive reduces fuel consumption during customer operation by up to 0.7 liters (0.2 US gal) per 100 kilometers (62.1 miles).