Audi is launching the A8 L with five engines: three gasoline and two TDI engines. The lineup covers a wide range, including six, eight and twelve-cylinder engines displacing from 3.0 to 6.3 liters and producing between 184 kW (250 hp) to 368 kW (500 hp). Three of the engines are either turbocharged or supercharged; all five receive their fuel via direct injection. They consume up to 22 percent less fuel than their predecessors thanks to the use of numerous Audi efficiency technologies. The 3.0 TDI offers the greatest efficiency, emitting CO2 emissions of only 176 g/km (283.24 g/mile).
Topping the lineup is the powerful 6.3 FSI, a normally aspirated, twelve-cylinder gasoline engine. Audi first offered this type of engine in the first generation of the A8 beginning in 2001, with an updated version used in the following model series beginning in 2004. The engineers revised the engine from top to bottom for use in the third generation of the A8 L, enlarging the bore by 2 millimeters (0.08 in) and adding direct fuel injection.
The 6.3-liter (6,299 cc) W12 produces 368 kW (500 hp). 600 Nm (442.54 lb-ft) of torque are available from 1,800 rpm; peak torque is 625 Nm (460.98 lb-ft) at 4,750 rpm. It accelerates the Audi A8 L like a supercar: The sprint from zero to 100 km/h (62.14 mph) takes 4.7 seconds. As with all of the engines, the electronically limited top speed of 250 km/h (155.34 mph) is just a formality.
The long-stroke engine (bore x stroke 86.0 x 90.4 millimeters (3.39 x 3.56 in) dazzles with its effortless power delivery – and with its fuel economy. In the EU cycle it consumes only 12.4 liters per 100 km (18.97 US mpg), corresponding to 290 grams of CO2 per km (466.71 g/mile), much less than it competitors with V12 engines.
This represents an improvement of 1.2 liters/100 km, or 9 percent, over the engine it replaces, which produced 331 kW (450 hp) from 6.0 liters of displacement and consumed 13.6 liters/100 km (17.30 US mpg).
Behind this increase in efficiency are technologies from the Audi modular efficiency platform, which can be found in similar form in all of the engines used in the new A8 L. Crank and chain drives have been optimized for minimal friction. During deceleration, a recuperation system converts the kinetic energy to electricity, which is buffered in the battery. The innovative thermal management ensures the ideal distribution of the flows of heat between the engine, transmission and the cabin in every situation. After a cold start, the cooling loop is configured such that optimal use is made of the thermal energy of the coolant to heat the entire engine. This greatly shortens the warmup phase with its elevated friction losses.
The W12: three cylinders in each of four rows
The “W12” abbreviation alludes to the engine’s unusual configuration: four rows consisting of three cylinders each. Two rows face each other in a mutually offset configuration at 15-degree angles, respectively, and collectively form a single broad bank. Both cylinder banks thus form a 72-degree V configuration. This layout makes the W12 engine extremely compact. It is less than 50 centimeters (19.69 in) long – much shorter than a V8 – and roughly 70 centimeters (27.56 in) in width and height.
The 6.3 FSI weights just 247 kilograms (544.54 lb), a top value in which the crankcase plays a major role. It is cast from a high-strength, lightweight aluminum-silicon alloy, with a traverse with embedded cast iron bearing seats forming the bottom. The pistons are cast of a high-strength light alloy and have beveled surfaces due to the V-position within the cylinder banks.
The forged crankshaft has a crankpin offset of twelve degrees so that the twelve cylinders ignite in the ideal interval of 60 degrees. The engine is extremely cultivated. Only under higher loads and engine speeds do the passengers hear a pleasant technical music, the expression of superior performance.
Rotating inside the aluminum cylinder heads are four camshafts, which can be moved hydraulically through up to 52 degrees of crankshaft rotation. They actuate the 48 valves via low-friction roller cam followers and are chain-driven via an intermediate shaft.
The conversion of the W12 engine to FSI gasoline direct injection lead to multiple changes to the cylinder heads. The fuel enters the combustion chambers at up to 130 bar of pressure through injection valves on the sides. The special shape of the inlet channel induces a rolling type of movement in the incoming air. Together with the high compression ratio of 11.8:1, this “tumble” also increases efficiency.
Elegant power: the 4.2 FSI and the 3.0 TFSI
Audi offers the new A8 L with two other gasoline engines in addition to the 6.3 FSI. The 4.2 FSI draws 273 kW (372 hp) of power from 4,163 cc displacement and 445 Nm (328.22 lb-ft) of torque at 3,500 rpm. The highly cultivated V8 accelerates the large sedan from zero to 100 km/h (62.14 mph) in 5.8 seconds. In the EU cycle it consumes just 9.7 liters/100 km (24.25 US mpg) and emits 224 grams of CO2/km (360.49 g/mile), a reduction of 1.2 liters or eleven percent over the predecessor while power increased by 19 kW (26 hp).
The six-cylinder, the 3.0 TFSI, embodies Audi’s philosophy of downsizing strategy: it substitutes forced induction for engine displacement. Located in the V of the cylinder banks is a crankshaft-driven supercharger that compresses the induction air. Two intercoolers keep the air temperature low so that more oxygen gets into the cylinders. With its powerful thrust, spontaneous throttle response and sonorous sound make the 3.0 TFSI a sporty powerplant for the A8 L.
Displacing 2,995 cc, the supercharged V6 produces 213 kW (265 hp) and 420 Nm (309.78 lb-ft) of torque, the latter between 2,500 and 4,850 rpm. It uses this power to bring the sedan from a standstill to 100 km/h (62.14 mph) in 6.2 seconds. It consumes just 9.3 liters of fuel per 100 km (25.29 US mpg) on average, which corresponds to only 217 grams of CO2/km (349.23 g/mile). Compared to the previous engine, the 3.2 FSI, fuel consumption has decreased by 1.6 liters per 100 km, or 15 percent, while power has increased by 22 kW (30 hp). Audi also offers a second version of the 3.0 TFSI producing 245 kW (333 hp) in certain markets.
Hefty torque: the 4.2 TDI and the 3.0 TDI
The 4.2 TDI is the top engine among the two TDI units. Displacing 4,134 cc, it generates 258 kW (350 hp) and a hefty 800 Nm (590.05 lb-ft) of torque, which is available between 1,750 and 2,750 rpm. The power V8 delivers impressive performance, with the sprint from rest to 100 km/h (62.14 mph) taking just 5.6 seconds. Its standard fuel consumption has been reduced by 1.7 liters/100 km, an improvement of 18 percent. The new A8 L 4.2 TDI gets by on only 7.7 liters/100 km (30.55 US mpg), corresponding to CO2 emissions of 204 g/km (328.31 g/mile).
The output of the V8 diesel, however, has increased by 18 kW (24 hp) and a full 150 Nm (110.63 lb-ft). This is due primarily to the increased pressure of the common rail system, which now injects at 2,000 bar. Other focal points of the development work were improvements to the turbochargers and the exhaust recirculation system and the reduction of internal friction.
The second TDI in the lineup, the 2,967 cc V6, has been completely redesigned. It weighs just 194 kilograms (427.70 lb). Six kilograms (13.23 lb) of weight were saved by the crankcase alone, which is made of high-strength vermicular graphite cast iron, just like in the V8 TDI. This engine’s innovative thermal management is particularly sophisticated: The crankcase and the cylinder heads have separate cooling water loops and the coolant is not circulated through the block during the warmup phase.
The 3.0 TDI works with a start-stop system that switches off the engine when the A8 L comes to a stop, and restarts the engine as soon as the driver’s foot leaves the brake. The driver can deactivate the system, which works together with a particularly powerful battery, at any time. It reduces fuel consumption in the standard cycle by approximately 0.4 liters per 100 km.
The 3.0 TDI produces 184 kW (250 hp) and delivers 550 Nm (405.66 lb-ft) to the crankshaft between 1,500 and 3,000 rpm – increases of 17 kW (23 hp) and 100 Nm (73.76 lb-ft) over the predecessor.
Consumption, on the other hand, decreased by 1.9 liters, or 22 percent, to 6.6 liters/100 km (35.64 US mpg). The V6 TDI diesel emits only has 174 grams of CO2 per km (280.03 g/mile) – easily best in the segment. It accelerates the new A8 L from zero to 100 km/h (62.14 mph) in 6.2 seconds.
The equipment and data specified in this document refer to the model range offered in Germany. Subject to change without notice; errors and omissions excepted.