BMW EfficientDynamics in Detail

Page 1: Overview
Page 2: World first direct gasoline injection
Page 3: EfficientDynamics in a new dimension
Page 4: The highest standard

The world’s first direct gasoline injection with genuine fuel savings under practical driving conditions continues its story of success:
High Precision Injection now also makes BMW’s four-cylinder power units the benchmark for EfficientDynamics.

Introducing second-generation direct gasoline injection and a number of new features around the engine, BMW is now also establishing a new dimension of EfficentDynamics with its four-cylinder power units. The new generation of four-cylinder petrol engines features direct fuel injection appropriately defined by BMW as High Precision Injection, allowing lean burn operation of the engine throughout a wide range of engine speed and therefore helping to significantly reduce fuel consumption in everyday traffic despite the further increase in engine power.

As a result of this new technology, the concept of High Precision Injection already introduced successfully on BMW’s straight-six power units is now available in an even larger number of models. Making this move, BMW is consistently continuing the development strategy of EfficientDynamics, again offering modern technical solutions serving to enhance both sheer driving pleasure and motoring economy at an early point in time throughout the entire model range. In practice, BMW is there-fore focusing on the growing significance of fuel-efficient power units in a particularly attractive and consistent manner.

Direct gasoline injection operating in the lean burn mode meets the latest demands of the European automobile market in terms of dynamic performance, all-round economy and emission management in an ideal manner. BMW’s new four-cylinder power units furthermore combine ultra-precise and therefore uniquely efficient High Precision Injection with numerous other technologies for enhanced fuel efficiency. These include Brake Energy Regeneration, the Auto Start Stop function, a gearshift point indicator, new electrical steering, a pressure-controlled fuel pump, and the option to disconnect the climate compressor from the engine’s belt drive.

Again reflecting the concept and philosophy of EfficientDynamics, this means a perfect combination of greater performance and optimum economy.
The new four-cylinder petrol engine displacing 2.0 litres thus offers an increase in output in its most powerful version by 15 kW or 20 hp over the previous engine. At the same time the new BMW 120i powered by this engine, to take one example, offers a reduction of fuel consumption versus its predecessor by approximately 14 per cent to 6.4 litres/100 kilometres in the EU test cycle, equal to 44.1 mpg Imp. The new BMW 118i, in turn, providing an increase in output by 10 kW or almost 14 hp, comes with a reduction of fuel consumption by approximately 19 per cent to 5.9 litres/100 kilometres, equal to 47.9 mpg Imp. And at the same time this model’s CO2 emissions are down to just 140 grams/kilometre.

Fast-revving performance, superior running smoothness, all-round economy – BMW’s new four cylinder power units excel on all of these points, in all criteria crucial to up-to-date driving pleasure. Through their temperamental development of superior engine power, they ensure sporting performance at all times and under all conditions. And apart from dynamic performance, motoring culture is also enhanced to a level of refinement quite outstanding in this segment: In its most powerful version, the 2.0-litre four-cylinder develops maximum output of 125 kW/170 hp and peak torque of 210 Newton metres/155 lb-ft. The second version of the new drive unit develops maximum power of 105 kW/143 hp, with torque peaking at 190 Nm/140 lb-ft. Yet a further version of the engine following at a later point in time will be a 1.6-litre four-cylinder offering maximum output of 90 kW/122 hp and peak torque of 160 Nm/118 lb-ft.

In both engine classes and in all power stages, High Precision Injection gives the new generation of four-cylinders a standard of all-round efficiency quite unique on a petrol engine.

This progress over the first generation of direct gasoline injection deliberately not used by BMW results from the central position of the piezo-injectors featured for the first time on High Precision Injection between the valves, in the immediate vicinity of the spark plug. This arrangement is indeed the prerequisite for the innovative jet-guided combustion process allowing far more precise dosage of fuel and maintenance of the lean burn mode throughout a wide operating range on the engine control map.

Significant advantages in fuel economy without compromises.

High Precision Injection was presented for the first time in BMW’s 225 kW/306 hp straight-six power unit with Twin Turbo technology featured in the BMW 335i Coupé. Initially, this new fuel injection system was focused on the specific requirements of a particularly powerful engine.

Now High Precision Injection offers an even greater potential for enhanced fuel economy on both a six- and four-cylinder in the lean burn direct injection mode. Applying this combustion concept also referred to as stratified charging, the composition of the fuel/air mixture is masterminded with particular accuracy. This means that unlike a conventional gasoline engine, such an advanced power unit no longer requires a fuel:air ratio of 1 : 14 (lambda = 1). Rather, the share of fuel in the mixture may be reduced significantly throughout a wide operating range (lambda > 1). This is possible because the piezo-injectors positioned directly next to the spark plugs offer controlled combustion in layers (stratified arrangement) over a wide operating range, with the exact composition of the fuel:air mixture varying from one layer to the other.

Significant enhancement of driving dynamics.

Benefiting from this revolutionary injection technology, BMW’s new four-cylinders are entering a new dimension of all-round economy: With High Precision Injection, fuel consumption of the already very efficient engines with variable VALVETRONIC valve management is down once again. And this further optimisation of fuel economy does not in any way detract from the engines’ dynamic performance. On the contrary – the most powerful version of the new engines outperforms the 2.0-litre four-cylinder with VALVETRONIC by a significant 15 kW/20 hp.

Through their supreme engineering performance, BMW’s engine development specialists are able to capitalise more than ever before on the savings potential of a modern petrol engine, BMW’s petrol power units thus offering a standard of fuel economy so far provided only by a diesel.
Not surprisingly, therefore, the new generation of engines ranks clearly at the top in any comparison with the competition.

High Precision Injection – the solution for maximum efficiency in everyday motoring.

The combination of efficiency and dynamics clearly demonstrates that the second generation of direct gasoline injection is far superior to all systems and concepts in the first generation. So far the hopes invested in this technology for a considerable enhancement of fuel economy did not become reality in practice, despite significant technical efforts and far-reaching developments – which is precisely why the BMW Group decided to forego the first generation of direct gasoline injection. The systemic drawback of the first generation was in particular that the economic advantages of running the engine with a large surplus of air were only provided within a very narrow load range at low engine speeds.

With the BMW Group’s engine development specialists recognising this drawback at an early point in time, they started out to develop an alternative solution in order to ensure superior fuel economy also under practical driving conditions, that is an improvement of realistic significance. Precisely this is why BMW introduced throttle-free VALVETRONIC engine load management as early as in 2001, a system now used worldwide throughout BMW’s entire model range, having proven its value in the meantime in more than a million cars.

Innovative piezo-injectors in an optimum position.

The only way to really capitalise on the substantial potential of direct gasoline injection was to develop High Precision Injection, the technology now being introduced by BMW: The BMW Group’s engineers have succeeded in positioning the piezo-injectors between the valves directly next to the spark plug, despite the confined space in the cylinder head. At the same time the injectors are designed and built to resist the high temperature and pressure loads prevailing at this point.

The high-pressure pump on the cylinder head is supplied with fuel by an electric pump in the fuel tank operating on demand, that is exactly as required under all specific conditions. Within the common rail, the high-pressure pump generates pressure of 200 bar for the four injectors delivering fuel to the combustion chambers, with the injector needles responding extremely quickly and consistently to the injection pulses electronically transmitted by a specially developed engine control unit. A further point is that contrary to conventional solenoid valves, piezo-injectors allow up to six injection processes in each operating stroke.

Fuel/air mixture reaching the cylinders with precise and fine dosage.

Opening to the outside, the piezo-injectors form a stable, conical injection jet within the combustion chamber and, as a result, ensure particularly fine dosage of the fuel/air mixture. A further point is that the total amount of fuel injected in each operating stroke may be split up into several “helpings”, thus providing perfect conditions throughout a wide load and speed range for a precise supply of fuel and, accordingly, for a controlled, clean and efficient combustion process.

Contrary to wall-guided fuel injection as the technology applied so far, the jet-guided process ensures a much faster and, in particular, more efficient fuel/air mixing process in the direct vicinity of the spark plug, without any loss otherwise caused by fuel resting on the walls of the cylinder. This provides exactly the right conditions for a stratified cylinder charge characteristic of lean burn operation, various, intersecting zones of differently composed fuel:air mixtures forming within the combustion chamber. In the process the share of fuel in the mixture decreases consistently with an increasing distance from the spark plug, a rich, ignitable fuel/air mixture being maintained only in the direct vicinity of the spark plug, in the interest of maximum efficiency. As soon as this richer mixture is ignited, the leaner layers further away from the spark plug will also start burning in a clean, smooth and consistent process.

This concept serves to maintain fuel-efficient lean burn operation throughout a very wide range of engine speeds and loads. And this again is a significant reason for the enhanced economy provided by High Precision Injection versus first-generation direct gasoline injection.

Additional innovations for optimum economy.

Both within the car as a whole and on the various ancillary units around the engine, a wide range of innovations serve in addition to High Precision Injection to make the new generation of BMW’s four cylinder petrol engines a new benchmark in technology in terms of both dynamic performance and all-round economy. This wide range of technical innovations comprises Brake Energy Regeneration, the Auto Start Stop function, a gearshift point indicator, an electrical, map-controlled coolant pump, a pressure-controlled high-pressure fuel pump, a climate compressor with a magnetic clutch, lightweight structures on the crankcase and crankshaft as well as EPS Electric Power Steering.

Intelligent lightweight technology also within the engine compartment.

Over and above the enhancement of performance and economy, optimisation of the car’s weight is another development aim in the overall context of EfficientDynamics. Precisely this is why BMW’s engineers pursued a consistent lightweight technology strategy in developing BMW’s new four cylinder petrol engines, neither the additional power nor the enhanced fuel economy coming at the cost of extra weight. So despite the increase in power by 15 kW/20 hp, the new 2.0-litre four-cylinder is approximately 4 kilos lighter than its predecessor with VALVETRONIC – and this ideal weight benefits both the optimisation of fuel economy and the agility of the respective car under practical driving conditions.

This reduction of weight is made possible by a number of lightweight improvements. Two particularly significant components in this process of reducing weight, among others, are the lightweight camshaft made in a hydrofoaming process and the variable intake manifold (DISA) made of a special synthetic material.

The new four-cylinder: proven foundation, detailed innovations.

The all-aluminium power unit with its stable bedplate construction and grey-cast iron cylinder liners cast into the cylinders themselves is based on BMW’s proven four-cylinder with fully variable valve drive. The cylinder bore (84 mm/3.31´´ ), piston stroke (90 mm/3.54´´ ) and, accordingly, engine displacement (1,995 cc) are identical, while the compression ratio has been increased from 10.5 : 1 to 12 : 1 in the interest of enhanced performance.

Two balance shafts rotating in opposite directions eliminate any rotational vibration on the four cylinder and ensure a high standard of smoothness and refinement at all times.

One requirement in implementing lean burn operation with a stratified cylinder charge was to redesign the cylinder from the ground up, the piezo-injectors being positioned between the valves at an optimum point relative to the spark plug, despite the confined space available.

A highly efficient charge cycle within the cylinders is ensured by conventional valve drive with two overhead camshafts and roller-type drag arms optimised for minimum friction. Compared with engine variants featuring VALVETRONIC, this type of valve management allows a significant increase in engine speed by 800 rpm to 7,000 rpm. To maintain a “beefy” torque curve throughout the entire engine speed range, both camshafts come with double-VANOS for infinite adjustment of valve opening times. In order to build up high torque as soon as possible at low engine speeds, in turn, the engine also incorporates a special intake system with variable manifold length (DISA technology).

Clean and efficient: NOX storage catalysts.

The new lean burn engine comes with a main catalyst close to the engine itself and storage catalysts further down the line to avoid NOX emissions. Introducing this wide range of innovations serving to reduce both fuel consumption and emissions from the engine, BMW is once again proving its outstanding skills and competence in the area of engine design.

The progress achieved on the new four-cylinder petrol engines in terms of both efficiency and emission management are also an important step in the further reduction of fleet consumption and emissions with BMW’s new cars.

In this way BMW is clearly expressing its commitment to keep the promise made voluntarily by the Association of European Automobile Manufacturers (ACEA) to reduce the average CO2 emissions of newly registered passenger cars in European car fleets to 140 grams/kilometre by the year 2008.

A wide range of improvements in the area of drive technology, aerodynamics and lightweight construction already introduced by the BMW Group already ensures a significant reduction of fuel consumption and CO2 emissions by BMW cars. Hence, the BMW Group has already made its contribution to the voluntary commitment assumed by the Association of the German Automobile Industry (VDA) to reduce fuel consumption by 25 per cent in the period between 1990 and 2005, even outperforming the commitment made by achieving a reduction of approximately 29 per cent. The introduction of VALVETRONIC technology alone in all new petrol engines has reduced fuel consumption in the EU test cycle and, accordingly, CO2 emissions by approximately 10 per cent.

The significant effect of this progress in technology also comes out clearly in a more long-term comparison: Fuel consumption of the entry-level model in the BMW 3 Series with its four-cylinder petrol engine was reduced by 22 per cent from 1983–2003, while at the same time the cars involved gained 32 per cent more weight on account of greater safety and comfort requirements. In the process the emissions relevant to the determination of exhaust standards have been reduced by an even more significant – and quite remarkable – 95 per cent.

The new family of BMW four-cylinder petrol engines is being introduced initially only in the European markets, since a complete supply of sulphur-free fuel over the entire area is guaranteed only here – and this is essential for the NOX storage catalysts on the engines. European customers will nevertheless be able to use their cars also in other countries where sulphur-free fuel is not yet available everywhere, the only drawback being that there the engines will not be able to fully capitalise on their particular economy benefits and technologies, since the storage catalyst, running under such conditions with sulphur in the fuel used, will require a regeneration cycle more often than is otherwise the case.

High Precision Injection operating in the lean burn mode can therefore only be introduced step-by-step also in other markets when such environmentally-friendly fuel is also available in those countries. Precisely this is why VALVETRONIC will continue to play an important role in BMW four-cylinder engines also in future, offering excellent conditions for extremely economic operation of the engine in the same way as before.

Indeed, emission management by the latest generation of BMW’s four-cylinder power units with VALVETRONIC has now been optimised once again, with modifications, inter alia, of the engine management, the cylinder head cover, exhaust technology, and the injection valves. And last but not least, the optimisation of weight ensured by consistent lightweight engineering also helps to further improve the efficiency of BMW’s four-cylinder power units with VALVETRONIC.

Specifications of BMW’s new four-cylinder gasoline engines with High Precision Injection.

Feature/entity	Unit	Normal aspirated 4 cylinder engine with lean-burn second-generation direct gasoline injection (High Precision Injection)	For comparision: Normal aspirated 6 cylinder engine with lean-burn second-generation direct gasoline injection (High Precision Injection)
Fuel		Gasoline ( RON 91–100)	Gasoline ( RON 91–100)
Max output	kW/hp	125	200/272
at	rpm	6,700	6,750
Max torque	Nm	210	315
at	rpm	2,250	2,750
Max engine speed	rpm	7,000	7,000
Stroke	mm	90.0	88.0
Bore	Mm	84.0	85.0
Displacement	cc	1,995	2,996
Distance between cyls	mm	91	91
Cylinder arrangement		Four-cylinder inline	Six-cylinder inline
Valve plate diameter, intake	mm/in	31.4	32.4
Valve plate diameter, outlet	mm/in	28.0	29.0
Compression ratio		12.0 : 1	12.0 : 1
Fuel injection		Second-generation direct injection (High Precision Injection); piezo-injectors; ? >>1	Second-generation direct injection (High Precision Injection); piezo-injectors; ? >>1
Fuel injection pressure	bar	200	200
Engine weight to BMW standard	kg	135	168
Output per litre	kW/L	62.7	66.8
Engine power-to-weight ratio	kg/kW	1.08	0.84
Crankcase		Aluminum with cast liners	Composite magnesium/aluminium
Waterpump		electrical	electrical
Camshaft		Composite, hydroformed	Composite, hydroformed
Inlet manifold		2 stage	3 stage
Valvetrain		Infinite camshaft adjustment for intake and outlet (double-VANOS); roller rocker arms	Infinite camshaft adjustment for intake and outlet (double-VANOS); roller rocker arms