Four turbos for diesel-powered BMW M550d

BMW has revealed the most potent diesel-powered vehicle in its entire range with the M550d xDrive, which packs an inline six-cylinder engine with four turbochargers for greater engine response and power output.

Manufactured in both sedan and wagon guise, Australian fans will be unable to get their hands on the quad-turbo diesel as BMW is only producing the M550d in left-hand-drive guise.

The 3.0-litre engine produces 294kW at 4400prm and a massive 760Nm from 2000-3000rpm, sending power to all four wheels via an eight-speed Steptronic automatic transmission.

All-paw traction comes from BMW’s rear-biased xDrive set-up which will also be featured in some form on the forthcoming M5 – although it is still unknown if the M550d will share its heavily rear-biased 20:80 front-rear torque split or if the flagship 5 Series will opt for a more even split.

For the powerplant, BMW has replaced the triple-turbo diesel unit from the previous-generation M550d with a new engine that adds an additional turbocharger to boost power by 14kW/20Nm.

Two low-pressure chargers replace the old larger third turbocharger for more direct engine response, while only one of the larger turbochargers is permanently activated, with the second large turbo only kicking in when engine speed is above 2500rpm.

The multitude of turbochargers means that the engine is able to build boost pressure more quickly and earlier in the rev range, allowing 450 of the 760Nm to be available from 1000rpm.

Emissions and fuel efficiency is improved with the introduction of exhaust-gas recirculation, which allows the turbochargers to operate more efficiently, returning fuel efficiency figures of 5.9 litres per 100km for the sedan (6.2L/100km for the wagon) – down 0.4L/100km on the old model – and CO2 emissions of 154g/km (163g/km).

Sprinting from zero to 100km/h takes just 4.4 seconds in the sedan, while the wagon takes 0.2s longer. Top speed is electronically capped at 250km/h.

M sports suspension gives the M550d a 10mm lower stance, while stopping power comes courtesy of M sports brakes with callipers finished in a blue metallic colour.

19-inch alloy wheels finished in Cerium Grey comes as standard, while two different 20-inch designs can be optioned.

Visually, the M550d adds an M aerodynamic package that features an enlarged air inlet, Cerium Grey trim on the radiator grille edges, lower side intakes and side mirrors, and a rear spoiler for sedan variants.

Inside, buyers get contoured sports seats with electrical adjustment and memory function, fabric/Alcantara seat covers, aluminium trim strips and a number of M additions including pedals, footrest, leather steering wheel and instrument display.

It also gets the suite of active safety features seen on the 5 Series range, including active lane change warning, lane departure warning, active cruise control with intelligent speed limit assist and remote parking.

The M550d will be on sale overseas this year, with the sedan set for an arrival in July, while the wagon will follow by the end of the year.