Audi is offering the revamped A4 with many engine options equipped with 12V and 48V mild-hybrid systems (MHEV). This also applies to the Audi S4 TDI (combined fuel consumption 6.3 – 6.2 l/100 km (37.3 - 37.9 US mpg); combined CO₂ emissions 166 – 163 g/km (267.2 – 262.3 g/mi), with a diesel V6 TDI under the hood for the first time, a 48-volt main electrical system and an electric powered compressor (EPC).

Audi S4 Avant TDI

Audi will offer the A4 model line with six turbocharged engines at sales launch in Europe. Their power outputs range from 110 kW (150 PS) to 255 kW (347 PS) – from the Audi A4 35 TFSI (combined fuel consumption 6.0 – 5.5 l/100 km (39.2- 42.8 US mpg); combined CO₂ emissions 138 – 125 g/km (222.1 - 201.2 g/mi) up to the Audi S4 TDI (combined fuel consumption 6.3 – 6.2 l/100 km (37.3 - 37.9 US mpg); combined CO₂ emissions 166 – 163 g/km (267.2 – 262.3 g/mi). All engines—whether the four-cylinder diesel unit, V6 TDI or four-cylinder TFSI—undercut the limits of the Euro 6d-temp emission standard.

For the market launch three engine variants will feature a mild-hybrid system (MHEV) based on 12 volts, which reduces fuel consumption while improving comfort. (Earlier post.) In everyday use, the MHEV system reduces fuel consumption by up to 0.3 liters per 100 kilometers according to individual Audi measurements.

Whether manual transmission, seven-speed S tronic or eight-speed tiptronic, whether front-wheel or quattro drive—each of the six engine variants delivers tailor-made power transmission. All A4 models come off the production line with an automatic transmission as standard.

The sportily balanced suspension ideally harmonizes with the character of the Audi A4. Customers can choose between the standard setup and the sport suspension. There are also two adaptive suspensions. One option is the comfort suspension with damper control, which reduces the ride height by 10 millimeters (0.4 in) and offers superb ride comfort. The other is the sport suspension, either with or without damper control, which is lowered by 23 millimeters (0.9 in). With its even more dynamic basic setup, it underscores the sporty character while maintaining comfort. Both controlled suspensions are integrated into the Audi drive select dynamic handling system. The same applies to the steering, with dynamic steering, the automatic transmission and the throttle valve available for customers as an option. Audi drive select allows the driver to determine which of up to five profiles these systems use.

Diesel and 48V mild hybrid. Both S models of the A4 family—the Audi S4 Sedan TDI (combined fuel consumption 6.3 – 6.2 l/100 km (37.3 - 37.9 US mpg); combined CO₂ emissions 164 – 163 g/km (263.9 - 262.3 g/mi) and the S4 Avant TDI (combined fuel consumption 6.3 l/100 km (37.3 US mpg); combined CO₂ emissions 166 – 165 g/km (267.2 - 265.5 g/mi)—are now equipped with a V6 diesel engine as a power package.

The 3.0 TDI combines hefty torque, smooth running and a long range and provides a power output of up to 255 kW (347PS) and maximum torque of 700 N·m (516.3 lb-ft). It accelerates the S4 Sedan TDI from zero to 100 km/h (62.1 mph) in 4.8 seconds on the way to an electronically governed top speed of 250 km/h (155.3 mph). This combination of power, torque and efficiency makes the Audi S4 TDI unique in the segment.

The electric powered compressor delivers powerful drive-off performance and virtually seamless power buildup when accelerating. As such, it eliminates any turbo lag, providing instant responsiveness in all driving situations. The electric powered compressor is integrated into a new 48-volt main electrical system, which also incorporates the mild-hybrid system.

This provides even more efficiency potential than the MHEV system in the 12-volt electrical system on the A4 models. In the S4 TDI this is the next expansion stage in which the mild-hybrid technology will be rolled out based on 48 volts.

The 12-volt subsidiary electrical system is connected to the 48-volt main electrical system via a powerful DC/DC converter. For the first time a powerful 48-volt belt alternator starter is being used in the S4 TDI as the heart of the mild-hybrid system with a maximum recuperation power of up to 8 kW when braking.

A compact, air-cooled lithium-ion battery with a capacity of 0.5 kWh, which is located under the luggage compartment floor, acts as an energy management center. The mild-hybrid system on the S models has the potential to reduce customer fuel consumption by up to 0.4 liters per 100 kilometers.

An eight-speed tiptronic and the quattro permanent all-wheel drive make up the drivetrain. If desired, an optional sport differential is available to actively distribute power between the rear wheels. In this way, more power can be directed specifically to the wheel on the outside of the bend when cornering at speed, which combats the tendency to understeer early on. The S sport suspension is standard. With its S-specific setup it provides a sporty driving sensation. This can be enhanced even further with the optional S sport suspension with damper control.

The Audi A4 models and the S4 models with a TDI engine and sporty new look can be ordered in Europe from May 2019. The A4 allroad quattro will be available in the early summer and both models will be in the dealerships from fall 2019.

Audi offers the S4 and the S4 Avant with the 3.0 TFSI in markets outside Europe. The turbocharged gasoline direct injection engine has an output of 260 kW (354 PS) and produces torque of 500 N·m (368.8 lb-ft) from 1,370 to 4,500 rpm. The V6 accelerates the S4 Sedan TFSI from zero to 100 km/h (62.1 mph) in 4.7 seconds on the way to an electronically governed top speed of 250 km/h (155.3 mph). The standard sprint takes two tenths of a second longer in the S4 Avant TFSI.