New entry-level diesel 5-series is a great car in the right specification but it faces stiff competition from the excellent Audi A6 Ultra BMW's 5-series with a new generation of four-cylinder diesel engine, offering reduced emissions and reputedly improved consumption.Pleasingly, the new 'B47' 2.0-litre diesel, which replaces the 'N47', is also more powerful – albeit marginally – than the engine it supersedes. BMW has thusly acquired some cake, and consumed it.The all-new 'TwinPower' turbocharged diesel, which features a single variable-geometry turbocharger – despite what its name suggests – utilises BMW's latest 'modular' design, entailing a 500cc displacement per cylinder.Other changes compared to the previous 518d version of the N47 include a higher-pressure common rail injection system, which now operates at 2000 bar as opposed to 1600 bar, and new injectors. These upgrades grant more precise fuel metering and better atomisation, resulting in a more efficient combustion cycle.There are also myriad other tweaks. At low engine speeds and loads the pump's flow can be throttled back, for example, cutting the power required to drive it and improving overall efficiency.The net result of all these upgrades is a hike of 7bhp to 148bhp. The claimed average economy rises from 62mpg to 64.2mpg, while CO2 emissions drop from 119g/km to 115g/km. Torque remains unchanged however, at 266lb ft.Fractional gains at best, admittedly, but as VED and company car tax costs become increasingly prominent concerns, and consumers are oft considering downsizing into a smaller car, every little helps in order to maintain the competitiveness of the larger saloons.Some may be somewhat disappointed to see the new engine retain the rear-mounted and often-problematic timing chain assembly of its predecessor, however; alas the company has had to retain it in order to grant the required bonnet clearance to meet pedestrian crash regulations – which was also the original reason for that design choice. Hopefully, by now, any potential issues have long been engineered out.
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