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Twin Turbo and EfficientDynamics for 4cyl Petrol and Diesel - 4-cyl Gasoline: High Precision Injection

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Article Index
Twin Turbo and EfficientDynamics for 4cyl Petrol and Diesel
4-cyl Gasoline: Introduction
4-cyl Gasoline: High Precision Injection
4-cyl Gasoline: Clean and Efficient
4-cyl Gasoline: Specifications
4-cyl Diesel: Introduction
4-cyl Diesel: Fuel Economy and Variable Twin Turbo
4-cyl Diesel: Specifications
All Pages
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.

Last Updated on Monday, 09 April 2007 13:58  

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