Under the hood of the 518d. Click to enlarge.

The new entry-level diesel models—the BMW 518d Sedan and BMW 518d Touring—now offer output of 110 kW/150 hp and peak torque of 360 N·m (266 lb-ft). The 140 kW/190 hp variant of the new four-cylinder power unit, meanwhile, boosts peak torque by 20 N·m (15 lb-ft) to 400 N·m (295 lb-ft). Compression ratio on both versions is 16.5.

This version of the engine is fitted in the BMW 520d Sedan and BMW 520d Touring as well as the BMW 520d xDrive Sedan and BMW 520d xDrive Touring models with intelligent all-wheel drive. The likewise updated eight-speed Steptronic transmission is available for the rear-wheel-drive models as an option in place of the standard six-speed manual gearbox, and included as standard on the all-wheel-drive models.

Both diesels are members of the BMW Group’s new modular engine family. They feature an aluminium crankcase with thermally joined cylinder liners (to reduce internal friction) and integrated balancer shafts, turbochargers with variable intake geometry and optimized efficiency, and further developed common rail direct injection systems.

The extra output, more instantaneous power delivery and high-revving character that these measures provide go hand in hand with not only greater fuel economy but also a reduction in weight of around two kilograms (4.4 lbs) over the outgoing engines. In addition, fresh advances have been made in the area of acoustic comfort.

The effectiveness of the turbochargers has been enhanced by a new roller bearing and effective and need-based exhaust gas recirculation. The newly designed heat exchangers for the exhaust gas flow have a compact construction and optimized cooling performance, which leads to an effective reduction in maximum combustion temperatures. Another special feature is the vacuum-operated bypass valve, which allows a higher proportion of uncooled exhaust gas to be fed into the engine while it is warming up, for example.

The common rail direct injection system’s new solenoid valve injectors ensure the engine uses even more precise quantities of fuel. They now allow increased injection pressure of up to 2,000 bar, which paves the way for extremely economical and, at the same time, clean combustion.

Furthermore, the thermodynamic efficiency around the core engine has been optimized, as have the starting characteristics of the diesel engines with the Auto Start Stop function.

The new four-cylinder diesel engines are also equipped with map-controlled oil pumps. The new fully variable vane-type pumps enable continuously adjustable control of the volume flow and therefore the oil pressure in response to the operating status of the engine at any given time. The result is a significant reduction in the energy required by the oil pumps which—as with all the need-based ancillary components—means a greater proportion of the engine’s output is available to drive the vehicle.

The new four-cylinder diesel engines generate their respective maximum outputs of 110 kW/150 hp and 140 kW/190 hp at 4,000 rpm, and their peak torque of 360 / 400 N·m (266 / 295 lb-ft) is on tap between 1,750 and 2,500 rpm. The increase in output and torque has a noticeable effect on the sporty driving characteristics of the BMW 518d, BMW 520d and BMW 520d xDrive.

All the model variants—in both Sedan and Touring guise—accelerate from 0 to 100 km/h (62 mph) 0.2 seconds more quickly than their respective predecessors. With the standard six-speed manual gearbox fitted, the new figures are 9.5 seconds for the BMW 518d Sedan (BMW 518d Touring: 9.9 seconds), 7.9 seconds for the BMW 520d Sedan (BMW 520d Touring: 8.1 seconds) and 7.9 seconds for the BMW 520d xDrive Sedan (BMW 520d xDrive Touring: 8.2 seconds).

Steptronic. The latest update of the automatic transmission has been tuned precisely to the performance characteristics of the new-generation power units. Further improvements to internal efficiency and longer gear ratios open up additional efficiency potential.

An rpm-linked vibration damper with engine-specific tuning allows economical driving at low revs to be combined with increased driving and acoustic comfort. In addition, converter slip during gear changes has been further reduced.

The updated eight-speed Steptronic transmission also offers a predictive shift strategy, which works in conjunction with the car’s navigation system—even when the route guidance is not active—to ensure that gear changes are timed precisely according to the driving situation at hand.

Based on navigation data, the gearbox identifies and takes into account an approaching corner, intersection, roundabout or highway slip road. If the vehicle is approaching an intersection or a bend, for example, it changes down early to the most appropriate gear, making optimum use of the engine braking effect. The gearbox then shifts to the optimal gear to accelerate dynamically out of the bend. Furthermore, interaction with the navigation system allows unnecessary gear changes between two successive bends to be avoided.

BMW said that the new gains in fuel economy represent further evidence of the effectiveness of the ongoing development work focused on optimizing combustion engines and other components under the BMW EfficientDynamics banner.

The current (sixth) generation of the BMW 5 Series makes extensive use of BMW EfficientDynamics innovations, such as BMW TwinPower Turbo technology, the eight-speed Steptronic transmission, Electric Power Steering, Brake Energy Regeneration and other measures. Driver assistance systems from BMW ConnectedDrive and chassis technology as well as additional innovations such as ECO PRO mode and the Auto Start Stop function (also available with the automatic transmission) also contribute.