MINI Debuts Refreshed Family of Engines

BMW TwinPower Turbo 4-Zylinder Dieselmotor

BMW and MINI have taken the wraps off of a new family of petrol and diesel engines destined by the MINI range. What should we expect? According to BMW more power and torque along with higher levels of efficiency will be on tap across all engines. But beyond that we’ll also see enhanced acoustic properties (i.e. they’ll sound better), smoother operation and (this is key) a reduction in weight.

BMW TwinPower Turbo 4-Zylinder Benzinmotor
BMW TwinPower Turbo 4-Zylinder Benzinmotor

BMW TwinPower Turbo 4-Zylinder Benzinmotor

The turbocharging system, consisting of a turbocharger integrated into the exhaust manifold that enables the flow dynamics of the recirculated exhaust gases to be utilised to particularly positive effect, has undergone further development as part of the engine family’s overhaul. The exhaust manifold and turbocharger are now housed together in the cylinder head. The turbocharger casing for the three- cylinder engines is made from either aluminium or steel depending on the output variant, while the four-cylinder units all feature steel casings.

The more advanced cooling system fitted in the new generation of engines likewise serves to optimise the combustion process with the aim of reducing both CO2 output and other pollutant emissions. The new coolant pump now has separate outlets for the flow of coolant to the cylinder head and engine block, which results in far more effective thermal management.

BMW TwinPower Turbo 3-Zylinder Benzinmotor

BMW TwinPower Turbo 3-Zylinder Benzinmotor

Balancer shafts ensure both the three and four-cylinder petrol engines display the wonderfully smooth operation for which BMW and MINI power units are renowned. These shafts iron out the vibrations that occur when power is transmitted to the crankshaft. Three-cylinder engines will in future benefit from a new balancer shaft complete with a modified drive mechanism that results in a weight saving, improved excitation and further enhanced acoustic properties.

One of the ways that MINI has optimized acoustics is to fit the cars with a single-piece timing chain drive and a new L-shaped belt arrangement driving the alternator, water pump, torsional vibration damper and air conditioning compressor.

For diesel fans BMW has updated the MINI diesel engines to accept a Selective Catalytic Reduction (SCR) system. With this form of emission control, a water-based urea solution known as AdBlue is added to the exhaust flow. This is the system that BMW and Mercedes (and not famously VW) have used for years in the US to meet stringent CO2 requirements. This could also be yet another signal that MINI is serious about bringing diesel to the US in the years ahead.

None of this seems to directly answer our biggest critique of the current Cooper S and JCW engines – a heavy flywheel and an inability to rev quickly. If BMW worked on this aspect of the engine they simply aren’t mentioning it.

Perhaps more importantly to most of you is the question of when. Our guess is that MINI will likely update its range in either March of 2017 (along with a host of other improvements) or in September as part of the model refresh scheduled for the F56 and F55. Given how BMW works these days drivetrain enhancements don’t have to be associated with an LCI but if they can, they will.

Official Gallery

Official Release

The introduction of the latest Efficient Dynamics engine family has seen the BMW Group strike a remarkably impressive balance across all model segments between performance on the one hand and fuel consumption and emissions figures on the other. The BMW Group is now unveiling new versions of the three and four- cylinder petrol and diesel engines, which benefit from rigorous further development and are therefore set to raise the bar all over again.

Like their predecessors, the new power units are based on the modular system that enables the application of consistent design principles, a shared architecture and matching components. The key elements of the standardised concept include the in-line engine’s basic design principle, an aluminium crankcase with uniform positioning of the intake and exhaust sides, a cylinder displacement of around 500 cubic centimetres per combustion chamber, as well as the arrangement of timing chains and ancillary units. In addition to this, the full line-up of petrol and diesel engines feature BMW TwinPower Turbo technology. This generates significant synergies in engine development and manufacture that have a positive impact on both environmental and economical sustainability. The high level of commonality within the engine family ensures that every drive unit – regardless of the number of cylinders, output or combustion method – meets the exacting standards set by the BMW Group for engine efficiency, power delivery and refinement.

The evolution of the Efficient Dynamics engine family has centred around further reducing fuel consumption and emissions at the same time as optimising performance characteristics. A raft of individual measures have been implemented to make the drive units even more efficient, and the resulting drop in consumption is evident on both the EU test cycle and in real-world driving. The improvements that have been incorporated to minimise emissions are furthermore designed to lower levels not just of CO2 emissions but also other exhaust gas components.

The advances made in the new-generation Efficient Dynamics engine family also herald further improvements to the engines’ smoothness and acoustic comfort while reducing weight. The new petrol and diesel units are suitable for both longitudinal and transverse installation, meaning that they can be fitted in a wide variety of BMW and MINI models.

New generation of petrol engines: greater output, torque and efficiency.

For the petrol engines, the BMW TwinPower Turbo technology comprises a turbocharging system, direct petrol injection, variable control of intake valve lift (VALVETRONIC) and continuously variable opening times for the intake and exhaust valves (Double-VANOS). This combination is the ideal set-up for instantaneous power delivery, free-revving performance, efficient fuel metering and clean combustion. These trademark qualities stand out even more clearly in the new generation of engines, thanks to a further cut in fuel consumption and emissions of up to 5 per cent, and an increase in the power units’ output and maximum torque of 5 kW/7 hp and 20 Newton metres (15 lb-ft) respectively.

The turbocharging system, consisting of a turbocharger integrated into the exhaust manifold that enables the flow dynamics of the recirculated exhaust gases to be utilised to particularly positive effect, has undergone further development as part of the engine family’s overhaul. The exhaust manifold and turbocharger are now housed together in the cylinder head. The turbocharger casing for the three- cylinder engines is made from either aluminium or steel depending on the output variant, while the four-cylinder units all feature steel casings.

A reworked version of the direct injection system provides for added efficiency in the new petrol engines. The injectors positioned centrally between the valves are fed from a new fuel pump via a modified system of fuel lines, and will in future operate at an increased maximum pressure of 350 bar. The higher injection pressure enables even more precise metering of the fuel and has the additional effect of helping to improve emissions quality over wide load ranges.

The more advanced cooling system fitted in the new generation of engines likewise serves to optimise the combustion process with the aim of reducing both CO2 output and other pollutant emissions. The new coolant pump now has separate outlets for the flow of coolant to the cylinder head and engine block, which results in far more effective thermal management.

Balancer shafts ensure both the three and four-cylinder petrol engines display the wonderfully smooth operation for which BMW and MINI power units are renowned. These shafts iron out the vibrations that occur when power is transmitted to the crankshaft. Three-cylinder engines will in future benefit from a new balancer shaft complete with a modified drive mechanism that results in a weight saving, improved excitation and further enhanced acoustic properties.

Other modifications that have a positive impact on engine efficiency include the use of a single-piece timing chain drive, which has the additional effect of optimizing acoustics. Plus, the revised engines are fitted with a new belt drive that is now the same on all variants. An L-shaped belt arrangement is used for driving the alternator, water pump, torsional vibration damper and air conditioning compressor.

Next-generation diesel engines: fuel consumption and CO2 emissions lowered by up to 5 per cent.

When it comes to the diesel power units, the BMW Group has again already set the standard for economy, power delivery and refined performance with the current Efficient Dynamics engine family. The BMW TwinPower Turbo technology for diesel engines consists of a turbocharging system with one or more turbochargers and common-rail direct injection. These two key elements have undergone substantial development for the modified engines, while enhancements to the basic engine’s construction have also been implemented along with numerous other detail refinements. Again, these serve to both boost engine efficiency and minimise emissions. The newly enhanced versions of the diesel units in the Efficient Dynamics engine family burn up to 5 per cent less fuel on average, which in turn means they also emit up to 5 per cent less CO2. Internal engine modifications and improved exhaust gas aftertreatment result in a considerable reduction in other emissions too.

To ensure even sharper throttle response while also increasing engine efficiency, all four-cylinder diesel units will in future benefit from the multi-stage turbocharging system that was previously only found on the most powerful four-cylinder engines of this type. This principle involves using two turbochargers of different sizes whose precision interaction is designed to put pulling power on tap early and keep it constant over a broad rev range. The multi-stage turbocharging on the new four- cylinder units features a low-pressure stage with variable inlet geometry and a high- pressure stage. To further enhance responsiveness and acoustics, both turbochargers are equipped with the latest slide bearing technology. The new turbocharging system’s high-pressure stage is fully integrated into the exhaust manifold.

The system is controlled by means of the low-pressure stage’s electrically adjustable charger vanes as well as the wastegate valve for the high-pressure stage and a compressor bypass, both of which are actuated pneumatically. This allows the supply of compacted air to the combustion chambers to be precisely adjusted at all times to suit the load requirements and the driving situation. In future, switchable cooling for the low-pressure stage housing will further improve the most powerful four-cylinder diesel engine’s efficiency.

A redesigned system of exhaust gas recirculation (EGR) also helps to both reduce fuel consumption and minimise emissions. A single-stage version of this system is fitted on the new four-cylinder diesel engines and a two-stage version on the three- cylinder units, ensuring particularly effective reduction of nitrogen oxide emissions (NOX). The EGR high-pressure module employed in all next-generation engines diverts the exhaust gases straight out of the manifold via an infinitely adjustable valve before directing them to the intake system, either in a cooled or a non-cooled state, as required. The new three-cylinder diesel units are additionally equipped with a low-pressure EGR module that likewise includes a cooling facility. This captures exhaust gas that has already flowed through the diesel particulate filter (where it is stripped of its soot particles) and reroutes it to the clean air line. The low-pressure exhaust gas recirculation can also be used in engine running conditions where the pressure difference in the turbocharging system is insufficient to activate the high-pressure EGR.

The common-rail direct injection system for the new three and four-cylinder diesel engines has also undergone further improvement and now operates at a higher pressure and with greater precision. Its revised injectors feature an upgraded system of sensors that enables extremely exact metering of the injected fuel. In multiple injections within a stroke sequence, the intervals between the individual injections can also be shortened as a result. The finer atomisation of the fuel brought about by the further increase in maximum injection pressure leads to exceptionally clean combustion with reduced residue in the exhaust gas. The injection systems on the three-cylinder engines will in future work with up to 2,200 bar of pressure, while the maximum pressure for the four-cylinder diesel units will increase to 2,500 bar or 2,700 bar in the most powerful variant.

Manufacture of both the three and four-cylinder diesel engines will in future rely on a process known as “form honing” for machining the cylinder bores in the aluminium crankcase, with their twin-wire arc-sprayed coating. The standard procedure used to date involves giving the cylinder bores a perfectly cylindrical shape, meaning they have an identical diameter from top to bottom. The influence of thermal and dynamic forces causes expansion in the top section of the cylinder bores, which starts during assembly of the cylinder head but is particularly noticeable during engine operation. Depending on the piston design, this either causes play at the top of the cylinder bores that has a negative effect on the engine acoustics or increased friction low down that is detrimental to efficiency. The new manufacturing technique being used for the first time for production engines makes allowance for these subsequent alterations. In order to compensate for them, the cylinder bores are now flared slightly towards the bottom. The desired geometry is obtained by means of an axial lifting motion with overlapping rotation. When the engine is operating, the expansion in the top section therefore creates a largely uniform diameter throughout the cylinder bores, allowing the pistons’ friction losses to be reduced without any negative impact on the engine’s acoustics.

A newly improved oil circuit with switchable piston cooling for on-demand operation and a modified belt drive for the ancillary units are two more innovations that help to increase efficiency, while a new tensioning technique for the balancer shafts serves to further enhance the acoustic properties of the four-cylinder diesel engines.

The internal engine measures will be complemented by a remarkably effective system of exhaust gas aftertreatment in the future three- and four-cylinder diesel units. Besides the close-coupled diesel particulate filter and NOX trap, all next- generation diesel engines can also be equipped with a Selective Catalytic Reduction (SCR) system. With this form of emission control, a water-based urea solution known as AdBlue is added to the exhaust flow. A water-cooled dispensing module injects precise quantities of the solution, which transforms into ammonia in the exhaust pipe before reacting with the nitrogen oxides inside the SCR catalytic converter to produce nitrogen and water. The effectiveness of this exhaust gas aftertreatment is permanently monitored by another sensor positioned downstream from the SCR unit.

The AdBlue solution – carried in a separate reservoir – is injected into the exhaust pipe in precisely calculated doses without the driver noticing. Together with the optimised combustion process and all the other emission control measures, this ensures that all drive unit variants worldwide from the upcoming generation of the Efficient Dynamics engine family will again comply with both current and future legislation governing emissions reduction.