Yesterday we gave you the overall picture of the next generation MINI's
engine range. Today we'll get down to the details… (From BMW
Joining forces in the joint venture, the BMW Group and PSA Peugeot
Citroen have developed a new family of small petrol engines. These power
units featuring the most advanced engine technologies are intended for
use in Peugeot and Citroen models as well as future versions of MINI
The new engine family is a significant step for both partners in
maintaining the self-commitment assumed by European car makers within
the ACEA Association of Car Manufacturers, promising to reduce fleet
consumption and, as a result, CO2 emissions to 140 g/km by the year
For the first time the project is able to elegantly solve the
conflict of interests between demanding engine technologies, on the one
hand, and the usual cost pressure in the small and compact car segment,
on the other.
Advantageous for both sides.
Both partners have contributed their know-how in technology and their
experience in large-volume production to the project, and now both
parties benefit in the same way. In other words, this is a win-win
situation to which each partner has contributed all its know-how and
expertise. The project proves that fuel-efficient power units with
innovative engine technology may also be built economically in the lower
Each manufacturer has contributed special competences and skills both
in the area of engine development and in using the world's best and most
advanced production methods.
PSA Peugeot Citroen will be building the new engines at its plant in
Douvrin, France. Planned capacity in production is up to 2,500 units a
Curtains Open for a New Engine Family.
Developing the concept for the new engine family, the project team
has opted for two technology variants. The derivatives of these two very
different variants will define a new standard in their class in
technological terms and in terms of their dynamism, economy, and long
The engines are characterised by the exchange of know-how between engine
development specialists on both sides, since, in developing and
implementing the engine concept, the same attention was given to both
BMW's principle of efficient dynamics and the PSA Peugeot Citroen
principle of minimum fuel consumption.
These new engines will offer exceptional power and a muscular torque
curve in their class throughout a very wide useful speed range, at the
same time reducing both fuel consumption and weight to a minimum.
The engines developed in this joint venture incorporate numerous
features carried over from BMW's trendsetting power units, for example
from the latest
generation of straight-six petrol engines.
- Fully variable valve drive
- Flow-controlled oil pump
- Single-belt drive of all
- Individual ignition coils
- Weight-optimised roller-type drag arms
- Cylinder head produced by lost-foam casting
The following new concepts and solutions have also been implemented
in the project:
- Direct gasoline injection for extra power and
- Twin-scroll exhaust gas turbocharger
- On-demand water pump
- Poly-V-belt with built-in tensioner
- Lightweight concept (including an aluminium crankcase,
intake manifold and cylinder head cover made of a special plastic
Optimised fuel economy plus remarkable power.
The first two products in this joint venture will feature a 1.6-litre
petrol engine with fully variable valve drive, maximum output of 85
kW/115 bhp, and maximum torque of 160 Nm/118 lb-ft.
One of the most significant objectives in developing this
normal-aspiration power unit was to achieve a muscular torque curve at
the highest possible level combined with best-in-class fuel economy and
emission management on low weight.
High-performance turbocharged power unit with direct fuel injection.
Direct petrol injection in this engine serves in particular to
combine high specific output with exemplary fuel economy. Further
advantages are a high standard of refinement and outstanding emission
The compact four-cylinder will be featured both in sports-oriented
models as well as PSA Peugeot Citroen cars in the lower segments of the
market, where it will be replacing large-volume normal-aspiration power
units. The reason for this strategy is that small, turbocharged engines
with a high level of power density offer a significant advantage in fuel
economy over normal-aspiration engines of larger capacity.
These two engines are the first members in a complete family of power
units which will ultimately range in output from 55 kW/75 bhp all the
way to 125 kW/170 bhp.
A New Standard Ensured by Successful Implementation of Innovative
From the start, the specifications defined for the project made clear
demands of the new engine family and the standards it was to meet:
Without making any concessions in terms of power, performance, and
motoring refinement, the engines have moved up the benchmark once again
inter alia in terms of specific fuel consumption, their torque curve,
anti-friction smoothness, and in terms of the overall engine package,
thus setting new standards in every respect.
This success is attributable in part to numerous innovations and
solutions adding up to make the new engine family a new benchmark in its
- Fully variable valve drive.
Without requiring a throttle butterfly, fully variable valve drive
controls engine output by infinite adjustment of valve stroke and intake
valve opening times. This loss-free load management reduces fuel
consumption, cuts back emissions, and ensures better engine response
with an enhanced standard of motoring refinement.
- Twin-scroll turbocharger.
On the twin-scroll turbocharger the ducts of each set of two
cylinders are separated from one another in the exhaust gas manifold and
the turbocharger. This serves to build up a charge effect from just
about 1,400 rpm, with torque being generated just as quickly as on a
- Direct gasoline injection.
High-pressure gasoline injection (120 bar), together with advanced
turbocharger technology, is the main reason of the high level of
specific output, low fuel consumption and the exemplary emission
management ensured by the turbocharged engine.
- Fully controlled oil pump.
On-demand oil supply delivers only as much oil as is actually
required. Depending on operating conditions, the volume flow-controlled
oil pump requires up to 1.25 kW less drive energy and reduces fuel
consumption by up to 1 per cent.
- On-demand water pump.
Driven by a friction gear, the water pump is not activated until the
engine has reached its normal operating temperature, thus enabling the
engine to warm up more quickly. This serves both to reduce fuel
consumption and improve emissions at the same time.
- Aluminium crankcase in bedplate design.
Offering best-in-class stiffness, excellent noise management, and
the integration of numerous functions and ancillary units, the
aluminium crankcase is quite unique in every respect.
Optimum friction management on both the crankdrive and valve drive.
Optimum configuration of the bearings and the conversion of all
mechanical transmission elements in the valve drive to roll friction
serves to minimise friction losses to the lowest level in this engine
Optimum package dimensions.
Integration of numerous functions and ancillary units into the
cylinder head and crankcase avoids the use of conventional add-on
systems, improves the engine's noise management, and reduces both weight
and dimensions. Single-belt drive of engine components and modules also
makes a significant contribution to the compact design and dimensions of
The Engine Block: Setting the Foundation for Two Very Different
Variants in Technology.
A strong foundation is obviously the basic prerequisite for a
successful engine concept. Hence, the engine block is conceived and
designed to meet the requirements of both technology variants in every
respect and without the slightest concession.
For production reasons, the geometrical dimensions of the new engine
family are to a large extent identical in all derivatives of the engine.
Inter alia, this includes the distance between cylinders of 84 mm
(3.31″), the bore of 77 mm (3.03″), and the height of the crankcase.
The two 1.6-litre power units also share the same stroke of 85.5 mm
(3.36″) and a capacity of 1,598 cc.
Innovative crankcase with outstanding qualities.
The two-piece bedplate construction of the aluminium crankcase made
up of the cylinder block and the bearing housing is an elaborate
achievement in technology carried over from motorsport. Together with
its reinforcement ribs, this strong structure gives the engine an
extremely high level of stiffness and sets new standards in this class
This special structure is also the reason for the engine's excellent
acoustics and noise control quite comparable to the features of a much
heavier grey-cast iron engine block and indeed marking the very best
among engines with an aluminium block. The aluminium bedplate housing
the crankshaft is fitted to and bolted on the cylinder block. In the
turbocharged engine the bedplate incorporates sintered steel inserts for
the crankshaft bearing taking the higher forces acting on the engine
into account. A further sign of distinction is that the cast-in
grey-cast iron liners end flush at the top with the cylinder head gasket
(open liner design).
The crankcase has open cross-sections at the top reducing any pump
losses caused by the movement of the crankdrive.
Integrated functions for enhanced quality.
The chain housing integrated in the engine block offers the advantage
of not requiring any additional seals, with the complete chain drive
entering the assembly process as a partly pre-assembled module.
The mounts cast into the engine block for ancillaries such as the
alternator and a/c compressor also reduce the complexity of the entire
unit, at the same time cutting back weight and shortening the period
required for assembly. And last but certainly not least, this kind of
integration improves sound management and provides even stiffer, firmer
fastening points for the ancillary units.
Low-friction crankdrive reducing fuel consumption. Since, given the
right configuration, the combination of a four-cylinder power unit and
front-wheel drive will not cause any noise problems, the project team
has chosen a design concept without balance shafts, which would only
have meant unnecessary weight.
In the development process the reduction of frictional forces to a level
never seen before in this class was given very high priority for reasons
of fuel economy alone. With the crankshaft contributing significantly to
frictional forces, the decision was taken to use relatively small
bearing journals measuring just 45 mm or 1.77″ in diameter. To minimise
oil consumption and, as a result, frictional losses, the bearing shells
on all engines have been split up into five categories in order to limit
bearing play in the main crankshaft bearing.
A further highlight of the engine's lightweight concept is the
optimisation of crankshaft weight. As a result, crankshaft stiffness
decreases from rear to front, which also offers benefits in terms of
The forged crankshaft on the turbocharged engine comes additionally
with four smaller balance weights over and above the four
Weight-optimised trapezoidal connecting rods for even greater running
smoothness. Seen from the side, the upper conrod opening in the
trapezoidal connecting rods is trapezoidal in shape. The connecting rod
opening is thus tapered at the top in the interest of lower weight at
this decisive point. Given a mean operating speed of 18.5 m/sec, that is
the speed at which the connecting rods move up and down, every gram of
oscillating masses saved in this way serves to improve engine vibration.
The trapezoidal connecting rods are made in cracked technology,
meaning that the lower connecting rod opening is broken at a
predetermined point in the machining process.
The pistons on the turbocharged direct-injection power unit come with
four valve pockets and the combustion chamber trough right in the middle
in order to stratify the cylinder charge. And to reduce thermal loads,
the pistons are cooled by splash oil. On the normal-aspiration power
unit the pistons feature valve pockets without any further modifications
On-demand oil supply without any loss of oil.
Equipped with a volume flow-controlled oil pump, the new power units
rank unique in their class also in terms of their oil supply.
Operating as a function of oil pressure, the external gear pump
driven by a chain delivers precisely the amount of oil required under
all operating conditions. In other words, there is no need for a bypass
feeding back excess oil or extra volume not needed. Benefitting from
this optimised on-demand management without any unnecessary energy or
forces, the volume flow-controlled oil pump consumes up to 160 W less
drive energy than a conventional pump, reducing fuel consumption in the
European driving cycle by approximately 1 per cent. And under normal
driving conditions with the car in the hands of a customer, the
reduction in fuel consumption is far greater, with a power saving of
1.25 kW or 1.7 bhp at 6,000 rpm.
Looking at the oil filter, the development engineers have opted in
favour of a solution highly beneficial to the environment. As a result,
the oil filter is not a metal cartridge difficult to recycle as special
waste, but rather a paper filter insert easy to dispose of from its
usual position in an easily accessible aluminium case with a plastic
cover on top.
With turbocharged engines being subject to significant thermal loads
and forces, an oil/water heat exchanger integrated in the oil filter
housing keeps the engine oil temperature at a safe level even when
running under full load. A further point is that the heat exchanger, by
heating up the coolant more quickly, shortens the warming-up period and
reduces both fuel consumption and exhaust emissions in the process.
The engines are filled initially with 4.2 litres of light running
oil, with 3.7 litres being required when changing oil.
The cylinder head – the main sign of distinction.
The two engine variants differ primarily through the concept of the
cylinder head and the fuel supply system. This explains why they share
only a few common features in this area, to be specific the two
camshafts, four valves per cylinder with a shaft diameter of 5 mm or
0.20″, one valve spring on each engine and the spark plug fitted
vertically in position.
The large valve angle allows optimum design of the combustion
chambers combined with low overall engine height. And converting all
mechanical transmission elements to anti-friction rollers (roller-type
drag arms), the engineers have significantly reduced friction forces.
Integration of numerous functions and components such as the oil
dipstick, the vacuum pump, the high-pressure pump, thermostat housing
and intake silencer serves additionally to meet the great demands made
of the engine package.
Two engine variants cast in different processes.
Two different casting processes are used in production of the
cylinder head: While the cylinder head on the direct-injection power
unit is manufactured in a low-pressure die-casting process, the
normal-aspiration engine is made in the innovative lost-foam casting
process developed for the first time to production level in a
six-cylinder power unit in the light-alloy foundry at BMW's Landshut
Since the cylinder heads are made by PSA Peugeot Citroen, the BMW
Group has supported PSA Peugeot Citroen in introducing this process for
large-volume production by providing appropriate know-how in production
technology. Both processes are particularly well-suited for perfectly
rendering the elaborate internal contours together with their hollow
cavities for the air ducts as well as the oil and coolant circuits.
Contrary to conventional casting technologies, lost-foam casting is a
positive process helping to further reduce the weight of the engine. In
this case, an identical cylinder head model made of polystyrene is
covered by a ceramic layer, shaken into a bed of sand and completely
surrounded by casting sand with the exception of one duct cast into the
cylinder head. The fluid aluminium then runs into the casting duct
during the automated casting process, completely replacing the
polystyrene model and taking on the shape of the cylinder head itself.
Given the very high precision of this casting process, even filigree
features such as oil ducts, reflow pipes and blow-by channels can be
properly integrated within the overall module. This, in turn, helps to
avoid numerous production processes formerly required in the machining
Ideal package dimensions thanks to single-belt drive.
For package reasons one of the objectives in the development process
was to make the engine as short and compact as possible. Hence, both the
alternator and the a/c compressor are driven by only one poly-V-belt
tightened by means of a single-arm torsion-spring tensioner. With the
coolant pump being driven via a friction gearing, there is no need for a
second belt level, which makes the engine one of the shortest
four-cylinders in its class.
Intelligent thermal management with an on-demand water pump.
On-demand management of the coolant volume delivered is one of the
numerous measures taken to reduce fuel consumption. A friction gear
mounted on a bearing arm is positioned between the water pump gear and
the pulley on the crankshaft. An electrically operated eccentric gear
serves to change the position of the gear wheel, and the water pump may
be switched off when starting the engine cold in order to warm up the
engine more quickly.
To save drive power and expedite the warming-up process, coolant is
not circulated until the engine has reached its normal operating
temperature. Then, when it has reached the appropriate temperature, the
engine is held steady at that point by a thermostat masterminded by the
engine's electronic “brain”, ensuring the most fuel-efficient coolant
temperature at each respective operating point.
Service-friendly range of engines.
Ease of service and an appropriate maintenance concept were essential
features in determining the engines' specifications. Depending on
running conditions and the driver's style of motoring, oil service
intervals will be approximately 30,000 km or 20,000 miles. The spark
plugs and air filter, in turn, only have to be exchanged approximately
every 60,000 km or 40,000 miles. The timing chain driving the camshafts
is not only very precise and reliable, but also remains maintenance-free
throughout the full running life of the engine. And automatic hydraulic
valve play compensation serves last but not least to rule out any
service or maintenance on the valve drive.
Naturally Aspirated Power Unit with Fully Variable Valve Drive:
Best-in-Class in Every Respect.
With its compression ratio of 11:1, the naturally aspirated power
unit develops maximum output of 85 kW/115 bhp at 5,700 rpm and revs up
to a maximum speed of 6,500 rpm. Engine displacement of this
four-cylinder is 1.6 litres, with torque reaching 140 Nm or 103 lb-ft at
just 2,000 rpm and peaking at 160 Nm/118 lb-ft at 4,250 rpm. The wide
useful engine speed range provided in this way offers an optimum
combination of driving pleasure and fuel economy from this compact power
Fully variable valve management as well as a wide range of features
extending from the fully controlled oil and water pumps all the way to
the optimisation of friction losses make this normal-aspiration power
unit one of the most efficient engines throughout its entire segment,
even including engines with direct gasoline injection.
Fully variable valve drive for enhanced fuel economy and even more
Fully variable valve management applies the principle of
throttle-free load control, masterminding engine power through the
infinite adjustment of valve lift and the intake valve opening times.
This technology based on the BMW Group's VALVETRONIC concept allows
truly outstanding driving dynamics and performance on low fuel
In a conventional internal combustion engine output is controlled by
means of the throttle butterfly. The engine is required to draw in fresh
air particularly at part load against the resistance of the butterfly
closed entirely or in part, which means a certain loss of power and
efficiency as well as unnecessary fuel consumption.
The innovative valve management system used in this case controls
both valve lift as well as the valve opening period and timing without
requiring a throttle butterfly as a function of the gas pedal position.
Almost free of losses, this control concept reduces fuel consumption,
cuts back exhaust emissions, and ensures a far better engine response
with greater refinement.
How this innovative valve management works.
This revolutionary engine technology is based on BMW's variable
camshaft adjustment: Turning the two camshafts relative to one another,
valve opening times can be infinitely adjusted for their beginning and
end, but engine output can only be controlled within certain limits.
Such individual, highly efficient control is now allowed by variable
valve lift for infinite adjustment of both the opening cross-section and
the intake valve opening periods.
In this case the camshaft no longer acts directly on the follower
lever operating the valve, but rather on an intermediate lever placed in
the middle of a roller forming the surface contour followed by the cam.
The lower end of the lever rests on the roller running on the follower
lever, while in the middle the lever rests on an eccentric shaft via a
When turning, the camshaft now moves the intermediate lever to and
fro. Exactly when and where the lever exerts its effect is determined by
the swivel point on the pivot lever itself. Driven by an electric motor,
the eccentric shaft modifies this rotating point, thus varying valve
lift infinitely from 0.2-9.5 millimetres (0.008-0.374″) as a function
of the rise or “hump” on the intake cam.
The electric motor fitted directly on the cylinder head and adjusting
the eccentric shaft by means of a worm gearing moves the lever in just
300 milliseconds from minimum to maximum lift. During the same period
the intake camshaft is turned by up to 70, the outlet camshaft by up to
60. To achieve this enormous adjustment speed, valve management is
controlled by an extremely fast, high-performance 32-bit engine
management computer directly networked to the engine control unit.
Potential reduction of fuel consumption by up to 20 per cent.
Depending on the route taken and traffic conditions, variable valve
drive may reduce average fuel consumption by up to 20 per cent, with a
saving in the EU test cycle of approximately 9 per cent. This innovative
technology now making its debut in the small and compact car segment
with this new naturally aspirated engine operates independently of fuel
quality and the oil grade and does not require sulphur-free fuel,
meaning that it is fully suited for all markets worldwide. Both the BMW
Group and PSA Peugeot Citroen nevertheless advocate the ongoing
improvement of fuel quality, in particular the de-sulphurisation of
Mechanical production technology of the highest standard.
This highly advanced valve management system demands the utmost in
terms of production technology. The contours of the intermediate lever
determining valve lift, for example, are ground down to an accuracy of
8/1,000ths of a millimetre. The camshafts on both engines are composite
structures, meaning that cam rings made of high-strength stainless steel
are shrunk on to a cast shaft and subsequently machined. In the final
fine-polishing process the cams are then 1 machined to an accuracy of 1
micron (?1,000 mm). For reasons of weight the eccentric shaft is also
made in this process for the first time, likewise with tolerance levels
in the micron range.
Optimised combustion process for exemplary emission management.
An electric pump delivers fuel into the plastic injection rail
housing the four injection valves. The optimum injection volume is
calculated by the engine control unit taking numerous parameters into
account, fuel being injected into the intake duct at a pressure of
approximately 5 bar.
Individual coils on each spark plug provide exactly the right
ignition voltage again controlled individually by the electronic
management system. An anti-knocking sensor monitors the combustion
process within the combustion chambers, retarding the ignition angle
where necessary. Benefitting from this highly efficient knock control,
the engine is able to run on fuel grades between 91 and 98 octane.
The emission management system incorporating a ceramic catalyst and
two oxygen sensors is connected directly to the exhaust manifold.
Ancillaries: everything in place.
While the engine with fully variable valve drive still has a throttle
butterfly, its only purpose is to provide a failsafe and diagnostic
function. Under normal running conditions, therefore, the butterfly is
always open. An additional vacuum pump at the rear end of the outlet
camshaft generates the underpressure required for the brake servo.
For reasons of safety the ancillaries and peripheral components in
all areas exposed to impact energy in a collision are designed to
absorb and destroy energy in a well-defined process in the event of an
impact, before penetrating the interior of the car under any such
The High-Performance Power Unit: A Turbocharged Engine with Direct
The turbocharged fuel injection power unit combines the torque curve
of a diesel with the benefits of a modern reciprocating-piston engine.
Maximum torque of 240 Nm or 177 lb-ft comes at just 1,400 rpm, remaining
virtually unchanged all the way to 4,000 rpm. This ensures significant
thrust and muscle from low engine speeds, powerful acceleration, a
perfect response, and maximum driving pleasure. Together with its
maximum output of 105 kW/143 bhp at 5,500 rpm, this engine guarantees
sporting performance wherever you go.
Cylinder head with conventional valve drive.
Contrary to the normal-aspiration engine, the cylinder head on the
turbocharged four-cylinder with conventional valve drive features two
overhead, composite camshafts, friction-optimised roller-type follower
levers, and hydraulic lash adjusters. Valve drive has also been
optimised for weight, reflecting the engine's fast-revving performance.
Precisely this is why the valve shafts measure only 5 mm or 0.20″ in
diameter, with the hollow shaft outlet valves being filled with sodium.
The closing function is ensured by a valve spring building up the
Fully variable adjustment of the intake camshaft guarantees maximum
power and torque on very good fuel economy and emission management.
Direct gasoline injection for even more power.
Mounted at the rear end of the intake camshaft, the mechanically
driven two-piston high-pressure pump delivers fuel to the injection
valves via a stainless-steel distributor rail. These high-pressure
valves inject fuel directly into the combustion chambers from the side
at a pressure of up to 120 bar, in the process maintaining a homogeneous
distribution of the fuel/air mixture in the combustion chambers.
At a compression ratio of 10.5:1, the turbocharged engine is
compressed to a relatively high level for an internal combustion engine
of this type. Precisely this is why the combustion process is monitored
also in this case by anti-knock control correcting the ignition angles
and charge pressure whenever required.
Elaborate twin-scroll turbocharger technology avoiding the usual
For the first time in this class, the direct injection
engine in the new family comes with a twin-scroll turbocharger.
Featuring this technology, the ducts of each two cylinders in the
exhaust manifolds and turbochargers are different from one another in
their design. Reducing exhaust gas counterpressure at low engine speeds,
twin-scroll charger technology capitalises on the dynamic effect of the
pulsing gas columns in the exhaust manifolds. The result is additional
power and thrust on even less fuel, enabling the turbocharger to boost
engine output from an earlier point. This effect is clearly noticeable,
with the charger building up extra power from roughly 1,400 rpm, almost
completely avoiding the “turbo lag” often criticised on turbocharged
engines, and generating torque almost as fast as in a compressor engine.
The flow of exhaust gas accelerates the turbine wheel to a speed of
up to 220,000 rpm. And at the same time the compressor running on the
same shaft compresses the fresh air fed into the system. A wastegate
complete with a check valve monitors the maximum turbocharger pressure
of 0.8 bar. In addition, overpressure in the system is controlled by a
dump valve activated when coasting with the intake manifold closed. To
increase the charge level, the pre-compressed fresh air is cooled down
in an intercooler before flowing into the combustion chamber. The
intercooler itself is fitted in the car at a predetermined point meeting
all the requirements of this particular configuration.
Maximum exhaust gas temperature is monitored by the electronic engine
“brain” and is limited to 950 C (1,742 F). To prevent excessive
build-up of heat in the oil- and water-cooled turbocharger after the
engine has been stopped, an additional electrical water pump starts
automatically as soon as the car comes to a standstill, dissipating any
excess thermal energy from the system
You can download this press release as PDF (including power graphs and detailed engine specs) here.