For the first time ever, the Audi S5 (Combined fuel consumption for Coupé/Sportback in l/100 km: 6.2 (37.9 US mpg)*; Combined CO2 emissions in g/km: 163 – 161 g/km (262.3 – 259.1 g/mi)*) has a V6 diesel under the hood. The 3.0 TDI engine in the S5 Coupé and the S5 Sportback produces 255 kW (347 hp) and delivers up to 700 Nm (516.3 lb-ft) of torque to the crankshaft. An electric powered compressor provides for strong off-the-line performance; a mild hybrid system enhances efficiency. This combination of power, torque and efficiency makes the S5 unique in its segment.
The 3.0 TDI engine: brawny torque
The 3.0 TDI in the S5 models is the most powerful version in the Audi V6 diesel engine lineup. Its combination of performance and efficiency sets it apart in this segment. Output is 255 kW (347 hp), and 700 Nm (516.3 lb-ft) of torque is available between 2,500 and 3,100 rpm. Despite significantly greater performance, NEDC consumption derived from the WLTP values for the S5 Coupé TDI and the S5 Sportback TDI is just 6.2 liters of diesel per 100 kilometers (37.9 US mpg), a CO2 equivalent of 161 grams per kilometer (259.1 g/mi). The new S models consume on average 19 percent less fuel than their predecessors with gasoline engines despite producing significantly more torque.
The six-cylinder diesel engine accelerates the S5 Coupé in 4.8 seconds and the S5 Sportback in 4.9 seconds from 0 to 100 km/h. The electronically limited top speed is 250 km/h (155.3 mph). With these characteristics, the V6 diesel engine is the ideal power plant for agility, spontaneity, low fuel consumption and long range. It also has a sporty sound and is very smooth.
The engine in the S TDI models features the electric powered compressor (EPC) and mild hybrid technology (MHEV). Both systems are embedded in the standard 48-volt main electrical system. For the first time in the S5 TDI, a powerful 48–volt belt alternator starter is the heart of the mild hybrid system with maximum recuperation power of up to 8 kW. A DC/DC converter steps this voltage down for components in the 12–volt electrical system. A compact, air-cooled lithium-ion battery with a capacity of 0.5 kWh installed under the luggage compartment floor serves as the energy center.
The EPC: fast support for the turbocharger
The electric powered compressor in the Audi S5 TDI is new to this segment. It is located in a bypass downstream of the intercooler and thus close to the engine. From the outside, the compressor looks similar to a conventional turbocharger. A compact electric motor replaces the turbine wheel, however. With an output of up to 7 kW, it accelerates the compressor wheel to 65,000 rpm in approximately 300 milliseconds. It is activated whenever the power demand from the driver is high but the energy available in the exhaust flow for driving the compressor wheel is low. If this is the case, the bypass valve closes and directs the intake air to the EPC. The compressed air flows directly into the combustion chamber. This enables the driver to tap the full power of the 3.0 TDI instantly even at low engine speeds, whether passing another vehicle or accelerating out of a curve. Because the technology increases torque at the lower end of the rpm range, it provides for lower engine speeds and less frequent downshifts during relaxed driving. From a standing start, the new S models quickly move several meters ahead of comparable vehicles without an EPC.
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