BMW’s B-series of modular petrol and diesel engines have been finding their way under the bonnets of nearly every model they, and subsidiary MINI, produce. And now the Munich automaker have improved it further.
The B-series is modular as it can be made to suit the many size, power, packaging and displacement needs of the car, being able to be mounted transversely or longitudinally with each cylinder adding or subtracting its 500cc volume, and power ultimately being easily tuned with turbocharger calibration.
The three, four, or six cylinder versions of the engine share many other similarities as well such peripheral component arrangement and timing chain placement to ensure that progress with each iteration is made available to all version as well as making sure parts and repairs can be easily understood and carried out.
In this newest evolution, BMW has optimised their TwinPower technology, tuning the turbocharging system, direct fuel injection, variable valve lift and timing, to yield better power and efficiency figures.
The turbocharger and exhaust manifold are now more tightly integrated with the engine block while the new injectors are more centrally positioned that receive fuel via a new pump that is able to deliver petrol pressure at up to 350 bar – which in turn allows for more accurate fuel metering and reduced consumption.
Such a tightly packaged motor means that the cooling system also had to undergone some improvement. The coolant pump now has separate outlets to disperse heat. Through optimised thermal management, these new engines can improve the combustion process and generate less carbon output than its predecessor.
All these improvements also translate to an improved diesel version of the B-series engine, but focused more on reducing pollutants and raise engine responsiveness. As before, the twin-scroll turbocharger used in the petrol engines are replaced with two separate turbines in the oil burners. However, this multi-stage forced induction approach has been further optimised to provide quick reflexes to throttle input through a revised low-pressure calibration and variable inlet geometry.
This new arrangement allows the low-pressure, first-stage turbocharger to provide a supply of compressed air to the cylinders at all times depending on the engine’s load requirements. A redesigned exhaust gas recirculation system (EGR) has been fitted to both 2.0-litre four-cylinder or 1.5-litre 3-cylinder versions of the diesel engine, further reducing nitrogen oxide (NOX) emissions.