Mini Open New Driving Dynamics Workshop

Press Release

Page 1: Short Version
Page 2: Innovative Drive Technology
Page 3: Chassis & Suspension
Page 4: Safety Equipment

Innovative Drive Technology for Enhanced Driving Pleasure and Efficiency.

More power, greater economy, more driving pleasure, less emissions – the introduction of innovative petrol engines brand-new from the ground up is not only the key to enhanced driving dynamics in the MINI, but also an important step in the process of implementing the pledge made by the European automotive industry to cut CO₂ emissions to a fleet average of 140 g/km by the year 2008. “Introducing the new range of engines, we have succeeded in carrying over the most demanding and technically sophisticated engine technology to the segment of small and compact carsâ€ÂÂÂ�, states Erich Sonntag, the Drivetrain Project Manager in the development of the new MINI. “Our fundamental philosophy is that of Efficient Dynamics. In other words: enhanced performance on less fuel.â€ÂÂÂ�

The first representatives of the new engine family are a normal-aspiration and a turbocharged power unit each with four cylinders and built at the BMW Group Engine Plant in Hams Hall, Great Britain. Compared with the previous power units, both of the new engines have been turned around
by 180°, with the exhaust side now facing to the front.

The engine block as such is highly similar on both the normal-aspiration and turbocharged petrol engines: Both power units share the same distance between cylinders of 84 millimetres or 3.31´´, the same bore of 77 millimetres or 3.03´´, stroke of 85.5 millimetres or 3.37´´, and, accordingly, engine displacement of 1,598 cubic centimetres.

The two-piece bedplate structure of the crankcase is a technology carried over from motorsport, with the cylinder block and bearing cast out of an aluminium alloy. Integration of the chainbox into the crankcase helps to save weight, improve engine acoustics, and reduce the number of components and design features required.

Yet a further innovation in the MINI segment is the introduction of a volume flow-controlled oil pump on the engines. Driven by a chain, the pump delivers only as much oil at any time as is actually required by the engine, thus reducing the drive power required by the ancillary units by approximately 160 Watt, saving approximately 1.25 kW at 6,000 rpm, and reducing fuel consumption by roughly 1 per cent.

The on-demand water pump featured in the coolant circuit offers a similar effect, only being switched on when the engine has reached its regular operating temperature. This helps to save fuel in the warming-up phase, with the catalyst reaching the temperature required for optimum efficiency more quickly and efficiently than before.

Both engines come with composite-structure camshafts. And contrary to conventional castings, the cam rings are made of high-strength stainless steel and are shrunk-fit on to the camshaft as such, after which the cams are fine-polished down to an accuracy of ¹?1,000 ^th millimetre. The eccentric shaft for phase adjustment is also made in this process, helping once again to save weight.

The lightweight concept consistently applied in developing the new MINI’s power units also serves to reduce frictional losses. The crankshafts on both drive units, for example, are weight-optimised in their construction and come with special bearing shells as well as relatively small bearing journals measuring just 45 millimetres or 1.77´´ in diameter.

The alternator and air conditioning compressor, in turn, are each driven by one single poly-V-belt, while the water pump is driven by a friction wheel. Both of these features help to make the power units featured in the new MINI particularly compact, the new engines thus ranking among the shortest four-cylinders in their class.

Normal-aspiration power unit with fully variable valve control.

Notwithstanding all their similarities and, indeed, common features in their overall design and configuration, the two power units in the new MINI differ significantly in terms of their cylinder heads: The 1.6-litre normal-aspiration engine featured in the MINI Cooper comes with fully variable valve control developed on the basis of the BMW Group’s VALVETRONIC technology.
The particular forte of this valve management concept is that valve lift and the intake valve opening periods are modified within fractions of a second to current power and performance requirements. To provide this effect the camshaft does not act directly on the valves via a rocker arm, but rather incorporates a further lever in between, where the pivot point is adjusted by an eccentric shaft driven by an electric motor.
So depending on the position of the pivot lever, intake valve lift is varied infinitely between 0.2 and 9.5 millimetres (0.008 – 0.374.´´). And the entire process of switching over from minimum to maximum valve lift takes just about 300 milliseconds.

This technology provides the same effect that otherwise requires adjustment of a throttle butterfly within the intake manifold of a conventional engine. Variable valve management thus renders throttle butterfly control superfluous and avoids the disadvantages of undesired air swirl in the intake manifold particularly when running under half-load. And while the new normal-aspiration power unit of the MINI Cooper still incorporates a throttle butterfly, the throttle butterfly in this case serves only emergency and diagnostic functions and otherwise remains fully open under normal operating conditions for a smooth and dynamic flow of the fuel/air mixture. The underpressure required by the brake servo, finally, is generated by a vacuum pump driven by the outlet camshaft.

In addition to variable management of valve lift on the intake side, valve timing on the intake and outlet side are spread apart individually as a function of engine speed. Valve timing is therefore also infinitely controlled, with a spread range of 70° on the intake and 60° on the exhaust camshaft.

Again, this entire adjustment process requires a mere 300 milliseconds when needed, such an extremely high reaction speed being ensured by way of a high-performance 32-bit computer networked with the engine management system as a whole. Interacting with one another, variable valve lift and engine speed-related camshaft management serve to optimise the torque and power curves.

Even at low engine speeds, therefore, the power unit of the new MINI Cooper develops high torque, while at high engine speeds it delivers a lot more power than conventional engines.

A further advantage is that both technologies help to significantly reduce fuel consumption: Depending on the route, fuel consumption is down by up to 20 per cent and in the EU test cycle the car’s fuel consumption has been reduced by approximately 12.5 per cent.

Yet a further advantage is the ability of the engines to run smoothly and reliably on any grade of fuel quality. This is indeed an essential criterion for a global player like MINI. This versatility is also ensured by the single ignition coils masterminded by the engine’s electronic control unit for optimum ignition voltage on the spark plugs in each cylinder. Anti-knock control, finally, enables the engine to run on various fuel grades between 91 and 98 octane.

The 1.6-litre normal-aspiration engine develops maximum output of 88 kW/120 hp at 6,000 rpm and has a top engine speed of 6,500 rpm. Torque is a significant 140 Nm or 103 lb-ft at just 2,000 rpm, with the engine reaching its peak torque of 160 Nm or 118 lb-ft at 4,250 rpm. With its wide useful range of engine speed, the compact power unit therefore combines optimum driving pleasure with superior fuel economy at all times.

Turbocharged power unit with twin-scroll turbocharger and direct petrol injection.

The turbocharged version of the new 1.6-litre four-cylinder featured in the MINI Cooper S offers even more impressive performance data: Maximum output is 128 kW/175 hp, a figure which certainly sets the standard for an engine of this size reaching its maximum power at 5,500 rpm.

The engine’s peak torque of 240 Nm or 177 lb-ft is maintained consistently between 1,600 and 5,000 rpm. When accelerating, torque is even boosted briefly to 260 Nm or 192 lb-ft by a short increase in turbocharger pressure. Referred to as “Overboost�, this function gives the MINI Cooper S even more dynamic acceleration, acting exclusively on the engine’s torque, not on maximum output.

The four valves per cylinder are controlled by two overhead camshafts, friction-optimised roller arms, and hydraulic valve clearance compensation units. The exhaust valves are filled with sodium in order to meet the greater cooling requirements of a turbocharged power unit. The intake camshaft comes with infinite phase adjustment setting the valve timing to the driver’s current power and performance requirements. On the road, this means optimum power and torque combined with superior fuel economy and emission management.

Fuel is injected into the turbocharged four-cylinder by means of common-rail direct gasoline injection: The stainless-steel common rail delivering fuel to all cylinders is filled with fuel under high pressure by a high-pressure pump at the rear end of the intake camshaft. Injection valves positioned at the side on the cylinder head deliver fuel from the common rail directly to the combustion chambers with exact dosage within fractions of a second. Four valve pockets and the combustion chamber trough in the middle of each piston ensure optimum stratification of the homogeneous fuel/air mixture, consistently maintaining a lambda factor of 1.0. Running in cast-iron bushes and subjected to high thermal loads also on account of the compression ratio of 10.5 : 1 relatively high for a turbocharged power unit, the pistons themselves are cooled by splash oil lubrication.

Featuring a twin-scroll turbocharger, the new MINI Cooper S is introducing a new technology in its segment in the interest of particularly dynamic and spontaneous power and performance: “Twin-scroll� means that the ducts in the exhaust manifold and the turbocharger are separated from one another in each case for two cylinders. Reducing exhaust gas counterpressure at low speeds, this enables the engine to capitalise on the dynamic action of the gas columns pulsating within the manifold. The result is even better response by the turbocharger, with its blades building up optimum momentum right from the start at lower engine speeds.

Charge pressure limited by a wastegate to 0.8 bar starts to build up from an engine speed of just 1,400 rpm, virtually eliminating the “turbo gap� so typical of a conventional turbocharged engine but hardly to be felt at all when accelerating in the new MINI Cooper S. Indeed, the 1.6-litre turbocharged power unit shows the kind of response you would normally only expect in a much larger normally aspirated engine: “The principle to get the same kind of power and performance out of a smaller and more efficient engine, enjoying all the advantages of a large engine, is referred to as ‘downsizing’�, states Drivetrain Project Manager Erich Sonntag. “And developing output per litre of approximately 110 horsepower, the turbocharged power unit of the new MINI is a particularly good example of this principle.�

The flow of exhaust gas rushing by accelerates the turbine wheel to a speed of up to 220,000 rpm. The compressor wheel running on the same shaft, in turn, compresses intake air at the same time. To increase the supply of fresh air to the cylinders – cold air contains a larger share of oxygen – the intake air compressed by the turbocharger flows through intercoolers before reaching the combustion chamber.

The technology for cooling the turbocharger is equally sophisticated in technical terms, with the twin scroll turbocharger in the new MINI being maintained within the optimum temperature range by a combination of oil and water cooling. An electrical auxiliary pump maintains the coolant circulation process for some time after the engine itself has been switched off in order to avoid the risk of excessive heat building up in the turbocharger subject to extremely high thermal loads.