BMW details updated EfficientDynamics engines

At the recent BMW Group Innovation Days 2016 in Munich, the company announced first details of its updated EfficientDynamics engines. The new three- and four-cylinder mills will replace the current B38 and B48 petrol units and B37 and B47 diesels, delivering increased performance, improved fuel economy and reduced fuel consumption, along with lower weight and better smoothness and acoustics.

Like the current petrol engines, the new ones feature turbocharging, direct injection, variable intake valve lift
(Valvetronic) and continuously variable intake and exhaust valve timing (Double Vanos). However, the turbocharger has now been integrated to the exhaust manifold in the cylinder head, with the casing made of either aluminium or steel on the three-pot engines (depending on engine output), or steel on all four-pot mills.

The direct injection system has also been revamped with a new fuel pump, modified fuel lines and an increased maximum pressure of 350 bar – enabling more precise fuel metering and improved emissions quality over wide load ranges.

Meanwhile, the cooling pump gains separate outlets for coolant to the cylinder head and engine block for more effective thermal management. Refinement has also been improved with the use of a new balancer shaft on three-cylinder engines, fitted with a modified drive mechanism that is lighter and improves excitation and acoustic properties.

There’s also a more efficient single-piece timing chain that also optimises acoustics, while a new belt drive – now identical across all variants – uses an L-shaped belt arrangement. The result of all these upgrades is a bump in outputs of seven hp and 20 Nm, along with an up to five percent reduction in fuel consumption and emissions.

On the diesel side, the new Euro 6-compliant turbocharged engines with common-rail direct injection have also been enhanced, with all four-cylinder engines gaining multi-stage turbocharging (with twin turbos) for increased throttle response and efficiency – something that was previously reserved for the most powerful engines.

Power outputs range from 94 hp and 220 Nm to 114 hp and 270 Nm for the three-cylinder units, while the outputs for the four-cylinder units will start from 147 hp and 350 Nm, right up to 228 hp and 450 Nm.

Revisions include a low-pressure turbo with variable inlet geometry and a high-pressure turbo that is now fully integrated in the exhaust manifold; both feature the latest slide-bearing technology for improved response and acoustics. Switchable cooling for the low-pressure turbocharger housing on the most powerful engines will further aid efficiency.

Elsewhere, a redesigned exhaust gas recirculation (EGR) system (single-stage on four-cylinder engines, twin-stage on three-cylinder units) reduces fuel consumption and emissions, while the direct injection has also been revised, working at a higher pressure (2,200 bar on three-pot mills, 2,500 or 2,700 bar on the four-pots) and an upgraded system of sensors that enables extremely exact fuel metering.

Also fitted is a newly-improved oil circuit with switchable piston cooling and a modified ancillary belt drive for improved efficiency, as well as a new tensioning technique for the four-cylinder engines’ balancer shafts to enhance acoustics. There will also be a new Selective Catalytic Reduction (SCR) exhaust aftertreatment system using AdBlue urea injection on all three- and four-cylinder diesel engines.

Lastly, the diesel engines will be manufactured using a new “form honing” for machining cylinder bores, with slightly flared bottoms to counteract expansion at the top section due to thermal and dynamic forces – this reduces friction losses at the bottom end without impacting acoustics at the top end. All-in-all, fuel consumption and emissions are claimed to be reduced by up to 5%.

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