Mobility Solutions

How gasoline direct injection works Bosch looks at injection from a systems viewpoint and reduces emissions with techniques such as laser drilling and scavenging

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  • April 07, 2014
  • Mobility Solutions
  • Press releases
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press release

Downsizing: The trend in the global automotive industry is toward small yet powerful engines. Manufacturers from Europe, the U.S., and even China are embracing downsizing concepts to build increasingly compact and economical low displacement engines which continue to offer equivalent levels of performance and driving enjoyment thanks to turbocharging. “Turbocharged three- and four-cylinder engines have taken on a dominant position, especially in the compact class,” says Dr. Rolf Bulander, the member of the board of management of Robert Bosch GmbH responsible for powertrain technology.

Gasoline direct injection

Combustion: Engines with gasoline direct injection prepare the air-fuel mix directly in the combustion chamber. The fuel which the injectors spray into the combustion chamber is so finely atomized that it can be ignited directly without having to mix it in the combustion chamber. This enables higher engine compression, which translates into greater efficiency. The direct injection technology also makes a major contribution to improved cylinder cooling. All that flows through the open intake valve in the intake duct is fresh air. High-pressure injection valves inject the fuel directly into the combustion chamber. This cools the combustion chamber, making basic compression higher thanks to the decreased propensity to knock.

Benefits: The economical consumption and low emissions of Bosch gasoline direct injection are due to the precise metering, preparation, and distribution of air and fuel for each individual combustion cycle. In combination with downsizing and turbocharging, gasoline direct injection offers the potential to reduce consumption and CO2 emissions by some 15 percent.

High-pressure pump and high-performance control unit
Systems idea: Bosch sees gasoline direct injection as far more than just an injection process. Bosch offers a complete system comprising a high-pressure pump, high-pressure rail with injection valve, a large number of sensors, and an engine control unit. If mixture formation is homogeneous, the HDEV5 high-pressure injection valve makes a major contribution to optimum, and thus fuel efficient, combustion. Up to seven individually positioned injection holes enable the spray pattern to be adapted flexibly to different combustion chambers.

Peak performance: The high-pressure injection valve and the high-pressure pump are designed for system pressures up to 200 bar. The demand-controlled HDP5 high-pressure pump is characterized by its compact dimensions and its light weight of 780 grams. Thanks to the use of stainless steel, the current components of the gasoline direct injection system can handle ethanol blends as well as fuels of different qualities, and are thus designed for worldwide use.

Engine management: The Bosch engine control unit performs all the different functions that are required of an efficient engine management system. These include selecting the right injection pressure and the right moment to inject the fuel. To do this, the electronic control unit calculates thousands of times a minute exactly how the injection process should be performed. Bosch systems competence enables optimum networking of all the individual components to ensure they work together at maximum efficiency. The driver's requirement for more or less torque is a key input variable for controlling the mixture formation electronically. The accelerator pedal module provides this mechanical command as a sensor signal. The crankshaft sensor supplies information on the crankshaft's current speed and position. Further input is provided by the knock sensor, temperature sensor, and camshaft speed sensor. Bosch exhaust-gas treatment plays a key role in helping to meet international emissions standards. The planar wide band oxygen sensor and the thimble-type oxygen sensor measure the oxygen content of the exhaust gas and provide the electronic control unit with the basic information required to achieve optimum mixture formation.

Laser drilling: Bosch is also helping to drive forward the development of specific aspects of gasoline direct injection. The exceptionally high quality of the drilled holes in the HDEV5 injector helps ensure particularly good combustion of the fuel and helps reduce emissions at the same time. The gasoline is injected directly into the cylinder at high pressure (200 bar) through five tiny laser-drilled holes. The sharp edges and smooth inner walls of the holes ensure that the fuel is atomized into extremely small droplets. This is exactly the effect desired. The finer the spray achieved, the greater its surface area. This leads to particularly good contact with the oxygen in the air so that virtually all the gasoline is burned on ignition. For efficient, clean combustion, it is important to prevent droplets of injected fuel from being deposited on the walls of the cylinder or the surface of the piston. Such deposits result in poor-quality combustion. By drilling the five holes in the injection nozzle with different diameters, Bosch achieves the best possible control over fuel distribution in the combustion chamber. The diameters range from 0.25 millimeters down to 0.1 millimeters. The smallest openings allow less gasoline though, the larger ones slightly more. This creates a specific spray pattern in the cylinder, enabling the fuel to be used to maximum effect. Bosch, Trumpf, and the University of Jena were awarded the 2013 German Future Prize by the German Federal President for developing the innovative process for producing the holes with ultrashort pulse lasers.

Using scavenging to eliminate turbo lag: Turbochargers achieve their standard boost pressure only from a certain engine speed. Low engine power output produces a phenomenon known as “turbo lag.” Scavenging, an innovative system approach developed by Bosch, eliminates this turbo lag by briefly opening the intake and exhaust valves simultaneously, creating a dynamic head between the intake and exhaust sides of the engine and increasing the supply of fresh air in the combustion chamber. This fresh air purges the exhaust gas contained in the cylinder by forcing it through the open exhaust valve in the direction of the exhaust manifold. The increased exhaust gas mass flow generates up to 50 percent higher torque at low engine speeds, which counteracts the turbo lag.


Controlled valve operation: Future legislation aimed at reducing particulates places new challenges on internal combustion engines. With its innovative and unrivalled controlled valve operation (CVO) system solution for direct gasoline injection engines, Bosch has successfully adopted a mechatronic approach that contributes substantially to meeting future emissions limits, such as EU6 and SULEV. The key components of CVO are the Bosch electronic control unit and the Bosch high-pressure injector which – unlike conventional precontrolled injection – form a closed loop. In a CVO system, the electronic control unit records the triggering signal during the injection and determines the optimum timing for opening and closing the valve needles. This enables the electronic control unit to calculate the actual injection quantities of each individual injector and adjust this as required. This regulated control system allows even the tiniest quantities of fuel to be injected with minimal tolerances.


Online-Dossier gasoline direct injection

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Mobility Solutions is the largest Bosch Group business sector. In 2015, its sales came to 41.7 billion euros, or 59 percent of total group sales. This makes the Bosch Group one of the leading automotive suppliers. The Mobility Solutions business sector combines the group’s expertise in three mobility domains – automation, electrification, and connectivity – and offers its customers integrated mobility solutions. Its main areas of activity are injection technology and powertrain peripherals for internal-combustion engines, diverse solutions for powertrain electrification, vehicle safety systems, driver-assistance and automated functions, technology for user-friendly infotainment as well as vehicle-to-vehicle and vehicle-to-infrastructure communication, repair-shop concepts, and technology and services for the automotive aftermarket. Bosch is synonymous with important automotive innovations, such as electronic engine management, the ESP anti-skid system, and common-rail diesel technology.

The Bosch Group is a leading global supplier of technology and services. It employs roughly 375,000 associates worldwide (as of December 31, 2015). The company generated sales of 70.6 billion euros in 2015. Its operations are divided into four business sectors: Mobility Solutions, Industrial Technology, Consumer Goods, and Energy and Building Technology. The Bosch Group comprises Robert Bosch GmbH and its roughly 440 subsidiaries and regional companies in some 60 countries. Including sales and service partners, Bosch’s global manufacturing and sales network covers some 150 countries. The basis for the company’s future growth is its innovative strength. Bosch employs 55,800 associates in research and development at 118 locations across the globe. The Bosch Group’s strategic objective is to deliver innovations for a connected life. Bosch improves quality of life worldwide with products and services that are innovative and spark enthusiasm. In short, Bosch creates technology that is “Invented for life.”

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PI8515 - April 07, 2014

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