The Bosch Yellow Jackets Edition 2001
`
`Technical Instruction
`
`Gasoline-engine management
`
`Automotive Technology
`
`Gasoline-engine
`management
`Basics and components
`
`Æ •
`
`EGAS electronic throttle control
`• Gasoline direct injection
`• NOx accumulator-type catalytic converter
`
`1
`
`PAICE 2018
`BMW v. Paice
`IPR2020-01386
`
`

`

`Robert Bosch GmbH
`
`Reproduction, duplication, and translation of this
`publication, including excerpts therefrom, is only
`to ensue with our previous written consent and
`with particulars of source. Illustrations, descrip-
`tions, schematic diagrams and other data only
`serve for explanatory purposes and for presenta-
`tion of the text. They cannot be used as the
`basis for design, installation, and scope of deliv-
`ery. Robert Bosch GmbH undertakes no liability
`for conformity of the contents with national or
`local regulations.
`All rights reserved.
`We reserve the right to make changes.
`
`Printed in Germany.
`Imprimé en Allemagne.
`
`1st Edition, September 2001.
`English translation of the German edition dated:
`February 2001.
`
`왘 Imprint
`
`Published by:
`© Robert Bosch GmbH, 2001
`Postfach 300220,
`D-70442 Stuttgart.
`Automotive Aftermarket Business Sector,
`Department AA/PDI2
`Product-marketing, software products,
`technical publications.
`
`Editor-in-Chief:
`Dipl.-Ing. (FH) Horst Bauer
`
`Editors:
`Dipl.-Ing. Karl-Heinz Dietsche,
`Dipl.-Ing. (BA) Jürgen Crepin.
`
`Authors:
`Dipl.-Ing. Michael Oder
`(Basics, gasoline-engine management,
`gasoline direct injection),
`Dipl.-Ing. Georg Mallebrein (Systems for
`cylinder-charge control, variable valve timing),
`Dipl.-Ing. Oliver Schlesinger (Exhaust-gas
`recirculation),
`Dipl.-Ing. Michael Bäuerle (Supercharging),
`Dipl.-Ing. (FH) Klaus Joos (Fuel supply,
`manifold injection),
`Dipl.-Ing. Albert Gerhard (Electric fuel pumps,
`pressure regulators, pressure dampers),
`Dipl.-Betriebsw. Michael Ziegler (Fuel filters),
`Dipl.-Ing. (FH) Eckhard Bodenhausen (Fuel rail),
`Dr.-Ing. Dieter Lederer (Evaporative-emissions
`control system),
`Dipl.-Ing. (FH) Annette Wittke (Injectors),
`Dipl.-Ing. (FH) Bernd Kudicke (Types of fuel
`injection),
`Dipl.-Ing. Walter Gollin (Ignition),
`Dipl.-Ing. Eberhard Schnaibel
`(Emissions control),
`in cooperation with the responsible departments
`of Robert Bosch GmbH.
`
`Translation:
`Peter Girling.
`
`Unless otherwise stated, the above are all
`employees of Robert Bosch GmbH, Stuttgart.
`
`2
`
`

`

`Robert Bosch GmbH
`
`Gasoline-engine management
`Basics and components
`
`Bosch
`
`3
`
`

`

`Robert Bosch GmbH
`
`왘 Contents
`
`4 Basics of the gasoline (SI)
`engine
`4 Operating concept
`7 Torque and output power
`8 Engine efficiency
`
`10 Gasoline-engine management
`10 Technical requirements
`12 Cylinder-charge control
`15 A/F-mixture formation
`18 Ignition
`
`20 Systems for cylinder-charge
`control
`20 Air-charge control
`22 Variable valve timing
`25 Exhaust-gas recirculation
`(EGR)
`26 Dynamic supercharging
`29 Mechanical supercharging
`30 Exhaust-gas turbocharging
`33 Intercooling
`
`34 Gasoline fuel injection: An
`overview
`34 External A/F-mixture formation
`35 Internal A/F-mixture formation
`
`36 Fuel supply
`37 Fuel supply for manifold
`injection
`39 Low-pressure circuit for
`gasoline direct injection
`41 Evaporative-emissions control
`system
`42 Electric fuel pump
`44 Fuel filter
`45 Rail, fuel-pressure regulator,
`fuel-pressure damper, fuel tank,
`fuel lines
`
`48 Manifold fuel injection
`49 Operating concept
`50 Electromagnetic fuel injectors
`52 Types of fuel injection
`
`54 Gasoline direct injection
`55 Operating concept
`56 Rail, high-pressure pump
`58 Pressure-control valve
`59 Rail-pressure sensors
`60 High-pressure injector
`62 Combustion process
`63 A/F-mixture formation
`64 Operating modes
`
`66 Ignition: An overview
`66 Survey
`66 Ignition systems development
`
`68 Coil ignition
`68 Ignition driver stage
`69 Ignition coil
`70 High-voltage distribution
`71 Spark plugs
`72 Electrical connection and inter-
`ference-suppressor devices
`73 Ignition voltage, ignition energy
`75 Ignition point
`
`76 Catalytic emissions control
`76 Oxidation-type catalytic converter
`77 Three-way catalytic converter
`80 NOx accumulator-type catalytic
`converter
`82 Lambda control loop
`84 Catalytic-converter heating
`
`85 Index of technical terms
`85 Technical terms
`87 Abbreviations
`
`Volkswagen Technical Site: http://vwts.ru http://vwts.info
`
`4
`
`

`

`Robert Bosch GmbH
`
`The call for environmentally compatible and economical vehicles, which nevertheless
`must still satisfy demands for high performance, necessitates immense efforts to de-
`velop innovative engine concepts. The increasingly stringent exhaust-gas legislation
`initially caused the main focus of concentration to be directed at reducing the toxic
`content of the exhaust gas, and the introduction of the 3-way catalytic converter in the
`middle of the eighties was a real milestone in this respect.
`Just lately though, the demand for more economical vehicles has come to the fore-
`front, and direct-injection gasoline engines promise fuel savings of up to 20%.
`This Yellow Jacket technical instruction manual deals with the technical concepts em-
`ployed in complying with the demands made upon a modern-day engine, and explains
`their operation.
`Another Yellow Jacket manual explains the interplay between these concepts and a
`modern closed and open-loop control system in the form of the Motronic. This man-
`ual is at present in the planning stage.
`
`5
`
`

`

`4
`
`Basics of the gasoline (SI) engine
`
`Operating concept
`
`Robert Bosch GmbH
`
`Basics of the gasoline (SI) engine
`
`The gasoline or spark-ignition (SI) internal-
`combustion engine uses the Otto cycle1)
`and externally supplied ignition. It burns an
`air/fuel mixture and in the process converts
`the chemical energy in the fuel into kinetic
`energy.
`
`For many years, the carburetor was respon-
`sible for providing an A/F mixture in the in-
`take manifold which was then drawn into
`the cylinder by the downgoing piston.
`
`The breakthrough of gasoline fuel-injection,
`which permits extremely precise metering of
`the fuel, was the result of the legislation gov-
`erning exhaust-gas emission limits. Similar
`to the carburetor process, with manifold
`fuel-injection the A/F mixture is formed in
`the intake manifold.
`
`Even more advantages resulted from the de-
`velopment of gasoline direct injection, in
`particular with regard to fuel economy and
`increases in power output. Direct injection
`injects the fuel directly into the engine cylin-
`der at exactly the right instant in time.
`
`Operating concept
`
`The combustion of the A/F mixture causes
`the piston (Fig. 1, Pos. 8) to perform a recip-
`rocating movement in the cylinder (9). The
`name reciprocating-piston engine, or better
`still reciprocating engine, stems from this
`principle of functioning.
`The conrod (10) converts the piston’s rec-
`iprocating movement into a crankshaft (11)
`rotational movement which is maintained
`by a flywheel (11) at the end of the crank-
`shaft. Crankshaft speed is also referred to as
`engine speed or engine rpm.
`
`Four-stroke principle
`Today, the majority of the internal-combus-
`tion engines used as vehicle power plants are
`of the four-stroke type.
`
`The four-stroke principle employs gas-ex-
`change valves (5 and 6) to control the ex-
`haust-and-refill cycle. These valves open and
`close the cylinder’s intake and exhaust pas-
`sages, and in the process control the supply
`of fresh A/F mixture and the forcing out of
`the burnt exhaust gases.
`
`1st stroke: Induction
`Referred to top dead center (TDC), the pis-
`ton is moving downwards and increases the
`volume of the combustion chamber (7) so
`that fresh air (gasoline direct injection) or
`fresh A/F mixture (manifold injection) is
`drawn into the combustion chamber past
`the opened intake valve (5).
`
`The combustion chamber reaches maxi-
`mum volume (Vh+Vc) at bottom dead cen-
`ter (BDC).
`
`2nd stroke: Compression
`The gas-exchange valves are closed, and the
`piston is moving upwards in the cylinder. In
`doing so it reduces the combustion-chamber
`volume and compresses the A/F mixture. On
`manifold-injection engines the A/F mixture
`has already entered the combustion cham-
`ber at the end of the induction stroke. With
`a direct-injection engine on the other hand,
`depending upon the operating mode, the
`fuel is first injected towards the end of the
`compression stroke.
`
`At top dead center (TDC) the combustion-
`chamber volume is at minimum (compres-
`sion volume Vc).
`
`1) Named after Nikolaus Otto (1832-1891) who presented
`the first gas engine with compression using the 4-stroke
`principle at the Paris World Fair in 1878.
`
`6
`
`

`

`Robert Bosch GmbH
`
`Basics of the gasoline (SI) engine
`
`Operating concept
`
`5
`
`3rd stroke: Power (or combustion)
`Before the piston reaches top dead center
`(TDC), the spark plug (2) initiates the com-
`bustion of the A/F mixture at a given igni-
`tion point (ignition angle). This form of ig-
`nition is known as externally supplied igni-
`tion. The piston has already passed its TDC
`point before the mixture has combusted
`completely.
`The gas-exchange valves remain closed
`and the combustion heat increases the pres-
`sure in the cylinder to such an extent that
`the piston is forced downward.
`
`4th stroke: Exhaust
`The exhaust valve (6) opens shortly before
`bottom dead center (BDC). The hot (ex-
`haust) gases are under high pressure and
`leave the cylinder through the exhaust valve.
`The remaining exhaust gas is forced out by
`the upwards-moving piston.
`
`A new operating cycle starts again with the
`induction stroke after every two revolutions
`of the crankshaft.
`
`Valve timing
`The gas-exchange valves are opened and
`closed by the cams on the intake and ex-
`haust camshafts (3 and 1 respectively). On
`engines with only 1 camshaft, a lever mecha-
`nism transfers the cam lift to the gas-ex-
`change valves.
`The valve timing defines the opening and
`closing times of the gas-exchange valves.
`Since it is referred to the crankshaft posi-
`tion, timing is given in “degrees crankshaft”.
`Gas flow and gas-column vibration effects
`are applied to improve the filling of the
`combustion chamber with A/F mixture and
`to remove the exhaust gases. This is the rea-
`son for the valve opening and closing times
`overlapping in a given crankshaft angular-
`position range.
`The camshaft is driven from the crank-
`shaft through a toothed belt (or a chain or
`gear pair). On 4-stroke engines, a complete
`working cycle takes two rotations of the
`crankshaft. In other words, the camshaft
`only turns at half crankshaft speed.
`
`Figure 1
`a
`Induction stroke
`b Compression stroke
`c Power (combustion)
`stroke
`d Exhaust stroke
`1 Exhaust camshaft
`2 Spark plug
`3
`Intake camshaft
`4
`Injector
`5
`Intake valve
`6 Exhaust valve
`7 Combustion
`chamber
`8 Piston
`9 Cylinder
`10 Conrod
`11 Crankshaft
`M Torque
`α Crankshaft angle
`Piston stroke
`s
`Vh Piston displacement
`Vc Compression
`volume
`
`Complete working cycle of the 4-stroke spark-ignition (SI) gasoline engine (example shows a manifold-injection
`engine with separate intake and exhaust camshafts)
`
`a
`
`b
`
`c
`
`d
`
`OT
`
`Vc
`
`Vh
`
`s
`
`UT
`
`æUMM0011-1E
`
`(cid:95)
`
`M
`
`1
`
`1
`
`23 4 5
`
`6
`
`7
`
`8
`9
`
`10
`11
`
`7
`
`

`

`6
`
`Basics of the gasoline (SI) engine
`
`Operating concept
`
`Robert Bosch GmbH
`
`This is the so-called stoichiometric
`ratio (14.7:1).
`The excess-air factor (or air ratio) λ has
`been chosen to indicate how far the actual
`A/F mixture deviates from the theoretical
`optimum (14.7:1). λ = 1 indicates that the
`engine is running with a stoichiometric
`(in other words, theoretically optimum) A/F
`ratio.
`Enriching the A/F mixture with more fuel
`leads to λ values of less than 1, and if the A/F
`mixture is leaned off (addition of more air)
`λ is more than 1. Above a given limit
`(λ > 1.6) the A/F mixture reaches the
`so-called lean-burn limit and cannot be
`ignited.
`
`Distribution of the A/F mixture in the
`combustion chamber
`Homogeneous distribution
`On manifold-injection engines, the A/F
`mixture is distributed homogeneously in the
`combustion chamber and has the same λ
`number throughout (Fig. 2a). Lean-burn
`engines which operate in certain ranges with
`excess air, also run with homogeneous mix-
`ture distribution.
`
`Stratified-charge
`At the ignition point, there is an ignitable
`A/F-mixture cloud (with λ = 1) in the vicin-
`ity of the spark plug. The remainder of the
`combustion chamber is filled with either a
`very lean A/F mixture, or with a non-com-
`bustible gas containing no gasoline at all.
`The principle in which an ignitable A/F-
`mixture cloud only fills part of the combus-
`tion chamber is referred to as stratified
`charge (Fig. 2b). Referred to the combustion
`chamber as a whole, the A/F mixture is very
`lean (up to λ (cid:53) 10). This form of lean-burn
`operation leads to fuel-consumption savings.
`
`In effect, the stratified-charge principle is
`only applicable with gasoline direct injec-
`tion. The stratified charge is the direct result
`of the fuel being injected directly into the
`combustion chamber only very shortly be-
`fore the ignition point.
`
`Compression
`The compression ratio ε = (Vh+Vc)/Vc is
`calculated from the piston displacement Vh
`and the compression volume Vc.
`
`The engine’s compression ratio has a deci-
`sive effect upon
`
`쐌 The torque generated by the engine,
`쐌 The engine’s power output,
`쐌 The engine’s fuel consumption, and the
`쐌 Toxic emissions.
`
`With the gasoline engine, the compression
`ratio ε = 7...13, depending upon engine type
`and the fuel-injection principle (manifold
`injection or direct injection). The compres-
`sion ratios (ε = 14...24) which are common
`for the diesel engine cannot be used for the
`gasoline engine. Gasoline has only very lim-
`ited antiknock qualities, and the high com-
`pression pressure and the resulting high
`temperatures in the combustion chamber
`would for this reason cause automatic, un-
`controlled ignition of the gasoline. This in
`turn causes knock which can lead to engine
`damage.
`
`Air/fuel (A/F) ratio
`In order for the A/F mixture to burn
`completely 14.7 kg air are needed for 1 kg
`fuel.
`
`A/F mixture distribution in the combustion
`chamber
`
`æUMM0557Y
`
`b
`
`2
`
`a
`
`Figure 2
`a Homogeneous A/F-
`mixture distribution
`b Stratified charge
`
`8
`
`

`

`Robert Bosch GmbH
`
`Basics of the gasoline (SI) engine
`
`Torque and output power
`
`7
`
`Fig. 1 shows the typical torque and power-
`output curve, against engine rpm, for a
`manifold-injection gasoline engine. These
`diagrams are often referred to in the test re-
`ports published in automobile magazines.
`Along with increasing engine speed, torque
`increases to its maximum Mmax. At higher
`engine speeds, torque drops again. Today,
`engine development is aimed at achieving
`maximum torque already at low engine
`speeds around 2000 min-1, since it is in this
`engine-speed range that fuel economy is at
`its highest. Engines with exhaust-gas tur-
`bocharging comply with this demand.
`Engine power increases along with engine
`speed until, at the engine’s nominal speed
`nnom, it reaches a maximum with its nominal
`rating Pnom.
`
`The power and torque curves of the inter-
`nal-combustion (IC) engine make it impera-
`tive that some form of gearbox is installed to
`adapt the engine to the requirements of
`everyday driving.
`
`1
`
`Example of the power and torque curves of a
`manifold-injection gasoline engine
`
`Pnom
`
`P
`
`1000
`
`3000
`Engine rpm n
`
`5000
`
`min-1
`nnom
`
`Mmax
`
`M
`
`Figure 1
`Mmax Maximum
`torque
`Pnenn Nominal power
`nnenn Nominal engine
`speed
`
`æSMM0558E
`
`min-1
`nnom
`
`1000
`
`3000
`Engine rpm n
`
`5000
`
`kW
`80
`
`60
`
`40
`
`20
`
`Power P
`
`N.m
`140
`
`120
`
`100
`
`Torque M
`
`Torque and output power
`
`Via the cranks on the crankshaft, the conrod
`converts the piston’s reciprocal movement
`into crankshaft rotational movement. The
`force with which the expanding A/F mixture
`forces the piston downwards is converted
`into torque.
`
`In addition to the force, the lever arm is the
`decisive quantity for torque. On the inter-
`nal-combustion engine, the lever arm is de-
`fined by the crankshaft throw.
`In general, torque is the product of force
`times lever arm. The lever arm which is ef-
`fective for the torque is the lever component
`vertical to the force. Force and lever arm are
`parallel to each other at TDC, so that the ef-
`fective lever arm is in fact zero. At a crank-
`shaft angle of 90° after TDC, the lever arm is
`vertical to the generated force, and the lever
`arm and with it the torque is at a maximum
`in this setting. It is therefore necessary to se-
`lect the ignition angle so that the ignition of
`the A/F mixture takes place in the crankshaft
`angle which is characterized by increasing
`lever arm. This enables the engine to gener-
`ate the maximum-possible torque.
`The engine’s design (for instance, piston
`displacement, combustion-chamber geome-
`try) determines the maximum possible
`torque M that it can generate. Essentially, the
`torque is adapted to the requirements of ac-
`tual driving by adjusting the quality and
`quantity of the A/F mixture.
`
`The engine’s power output P climbs along
`with increasing torque M and engine
`speed n. The following applies:
`
`P = 2 · π · n · M
`
`9
`
`

`

`8
`
`Basics of the gasoline (SI) engine
`
`Engine efficiency
`
`Robert Bosch GmbH
`
`Engine efficiency
`Thermal efficiency
`The internal-combustion does not convert
`all the energy which is chemically available
`in the fuel into mechanical work, and some
`of the added energy is lost. This means that
`an engine’s efficiency is less than 100%
`(Fig. 1). Thermal efficiency is one of the im-
`portant links in the engine’s efficiency chain.
`
`Pressure-volume diagram (p-V diagram)
`The p-V diagram is used to display the pres-
`sure and volume conditions during a com-
`plete working cycle of the 4-stroke IC en-
`gine.
`
`The ideal constant-volume cycle
`Fig. 2 (curve A) shows the compression and
`power strokes of an ideal process as defined
`by the laws of Boyle/Mariotte and Gay-Lus-
`sac. The piston travels from BDC to TDC
`(point 1 to point 2), and the A/F mixture is
`compressed without the addition of heat
`(Boyle/Mariotte). Subsequently, the mixture
`burns accompanied by a pressure rise (point
`2 to point 3) while volume remains constant
`(Gay-Lussac).
`From TDC (point 3), the piston travels
`towards BDC (point 4), and the combus-
`tion-chamber volume increases. The pres-
`sure of the burnt gases drops whereby no
`heat is released (Boyle/Mariotte). Finally, the
`burnt mixture cools off again with the
`volume remaining constant (Gay-Lusac)
`until the initial status (point 1) is reached
`again.
`
`The area inside the points 1 – 2 – 3 – 4
`shows the work gained during a complete
`working cycle. The exhaust valve opens at
`point 4 and the gas, which is still under pres-
`sure, escapes from the cylinder. If it were
`possible for the gas to expand completely by
`the time point 5 is reached, the area de-
`scribed by 1 – 4 – 5 would represent usable
`energy. On an exhaust-gas turbocharged
`engine, the part above the line (1 bar) can
`to some extent be utilized (1 – 4 – 5⬘).
`
`Real p-V diagram
`Since it is impossible during normal engine
`operation to maintain the basic conditions
`for the ideal constant-volume cycle, the ac-
`tual p-V diagram (Fig. 2, curve B) differs
`from the ideal p-V diagram.
`
`Measures for increasing thermal efficiency
`The thermal efficiency rises along with in-
`creasing A/F-mixture compression. The
`higher the compression, the higher the pres-
`sure in the cylinder at the end of the com-
`pression phase, and the larger is the enclosed
`area in the p-V diagram. This area is an indi-
`cation of the energy generated during the
`combustion process. When selecting the
`compression ratio, the fuel’s antiknock qual-
`ities must be taken into account.
`Manifold-injection engines inject the fuel
`into the intake manifold onto the closed in-
`take valve, where it is stored until drawn into
`the cylinder. During the formation of the
`A/F mixture, the fine fuel droplets vaporise.
`The energy needed for this process is in the
`form of heat and is taken from the air and
`the intake-manifold walls. On direct-injec-
`tion engines the fuel is injected into the
`combustion chamber, and the energy
`needed for fuel-droplet vaporization is taken
`from the air trapped in the cylinder which
`cools off as a result. This means that the
`compressed A/F mixture is at a lower tem-
`perature than is the case with a manifold-in-
`jection engine, so that a higher compression
`ratio can be chosen.
`
`Thermal losses
`The heat generated during combustion heats
`up the cylinder walls. Part of this thermal
`energy is radiated and lost. In the case of
`gasoline direct injection, the stratified-
`charge A/F mixture cloud is surrounded by a
`jacket of gases which do not participate in
`the combustion process. This gas jacket hin-
`ders the transfer of heat to the cylinder walls
`and therefore reduces the thermal losses.
`
`10
`
`

`

`Robert Bosch GmbH
`
`Basics of the gasoline (SI) engine
`
`Engine efficiency
`
`9
`
`Further losses stem from the incomplete
`combustion of the fuel which has condensed
`onto the cylinder walls. Thanks to the
`insulating effects of the gas jacket, these
`losses are reduced in stratified-charge opera-
`tion. Further thermal losses result from the
`residual heat of the exhaust gases.
`
`Frictional losses
`The frictional losses are the total of all the
`friction between moving parts in the engine
`itself and in its auxiliary equipment. For in-
`stance, due to the piston-ring friction at the
`cylinder walls, the bearing friction, and the
`friction of the alternator drive.
`
`1
`
`Efficiency chain of an SI engine at λ = 1
`
`10%
`
`10%
`
`7%
`
`15%
`
`13%
`
`Useful work,
`drive
`
`Frictional losses,
`auxiliary equipment
`
`Pumping
`losses
`
`Losses due to (cid:104) =1
`
`Thermal losses in the cylinder,
`inefficient combustion,
`and exhaust-gas heat
`
`æSMM0560E
`
`Thermodynamic losses during
`the ideal process
`(thermal efficiency)
`
`45%
`
`2
`
`Sequence of the motive working process in the
`p-V diagram
`
`Figure 2
`A
`Ideal constant-
`volume cycle
`B Real p-V diagram
`a
`Induction
`b Compression
`c Work (combustion)
`d Exhaust
`ZZ Ignition point
`AÖ Exhaust valve opens
`
`5
`
`æUMM0559E
`
`5
`
`4 1
`
`AÖ
`
`B
`
`b
`d
`
`c
`
`a
`
`Vh
`
`3
`
`A
`
`2
`
`ZZ
`
`Cylinder pressure p
`
`1 bar
`
`Vc
`
`Volume V
`
`Losses at λ =1
`The efficiency of the constant-volume cycle
`climbs along with increasing excess-air fac-
`tor (λ). Due to the reduced flame-propaga-
`tion velocity common to lean A/F mixtures,
`at λ > 1.1 combustion is increasingly slug-
`gish, a fact which has a negative effect upon
`the SI engine’s efficiency curve. In the final
`analysis, efficiency is the highest in the range
`λ = 1.1...1.3. Efficiency is therefore less for a
`homogeneous A/F-mixture formation with
`λ = 1 than it is for an A/F mixture featuring
`excess air. When a 3-way catalytic converter
`is used for efficient emissions control, an
`A/F mixture with λ = 1 is absolutely impera-
`tive.
`
`Pumping losses
`During the exhaust and refill cycle, the en-
`gine draws in fresh gas during the 1st (in-
`duction) stroke. The desired quantity of gas
`is controlled by the throttle-valve opening.
`A vacuum is generated in the intake mani-
`fold which opposes engine operation
`(throttling losses). Since with a gasoline
`direct-injection engine the throttle valve is
`wide open at idle and part load, and the
`torque is determined by the injected fuel
`mass, the pumping losses (throttling losses)
`are lower.
`In the 4th stroke, work is also involved in
`forcing the remaining exhaust gases out of
`the cylinder.
`
`11
`
`

`

`10
`
`Gasoline-engine management
`
`Technical requirements
`
`Robert Bosch GmbH
`
`Gasoline-engine management
`
`without at the same time having a detrimen-
`tal effect upon the normal engine’s favorable
`efficiency in the upper load ranges. Gasoline
`direct injection is the solution to this prob-
`lem.
`
`A further demand made on the engine is
`that it develops high torque even at very low
`rotational speeds so that the driver has good
`acceleration at his disposal. This makes
`torque the most important quantity in the
`management of the SI engine.
`
`SI-engine torque
`The power P delivered by an SI engine is de-
`fined by the available clutch torque M and
`the engine rpm n. The clutch torque is the
`torque developed by the combustion process
`less friction torque (frictional torque in the
`engine), pumping losses, and the torque
`needed to drive the auxiliary equipment
`(Fig. 1).
`
`In modern-day vehicles, closed and open-
`loop electronic control systems are becom-
`ing more and more important. Slowly but
`surely, they have superseded the purely me-
`chanical systems (for instance, the ignition
`system). Without electronics it would be
`impossible to comply with the increasingly
`severe emissions-control legislation.
`
`Technical requirements
`
`One of the major objectives in the develop-
`ment of the automotive engine is to generate
`as high a power output as possible, while at
`the same time keeping fuel consumption
`and exhaust emissions down to a minimum
`in order to comply with the legal require-
`ments of emissions-control legislation.
`Fuel consumption can only be reduced by
`improving the engine’s efficiency. Particu-
`larly in the idle and part-load ranges, in
`which the engine operates the majority of
`the time, the conventional manifold-injec-
`tion SI engine is very inefficient. This is the
`reason for it being so necessary to improve
`the engine’s efficiency at idle and part load
`
`1
`
`Torque at the drivetrain
`
`1
`
`1
`
`2
`
`3
`
`4
`
`Air mass (fresh-gas charge)
`Fuel mass
`Ignition angle (ignition point)
`
`Combustion
`torque
`
`Engine
`
`Engine
`torque
`–
`
`Clutch
`torque
`–
`
`Drive
`torque
`
` Clutch
`–
`–
`
`Gearbox
`–
`–
`
`æUMM0545-1E
`
`Exhaust and refill cycle, and friction
`Auxiliary equipment
`Clutch losses
`Gearbox losses and transmission ratio
`
`Figure 1
`1 Auxiliary equipment
`(alternator, A/C
`compressor etc.)
`2 Engine
`3 Clutch
`4 Gearbox
`
`12
`
`

`

`Robert Bosch GmbH
`
`Gasoline-engine management
`
`Technical requirements
`
`11
`
`The combustion torque is generated during
`the power stroke. In manifold-injection en-
`gines, which represent the majority of to-
`day’s engines, it is determined by the follow-
`ing quantities:
`
`쐌 The air mass which is available for com-
`bustion when the intake valves close,
`쐌 The fuel mass which is available at the
`same moment, and
`쐌 The moment in time when the ignition
`spark initiates the combustion of the A/F
`mixture.
`
`The proportion of direct-injection SI en-
`gines will increase in the future. These en-
`gines run with excess air at certain operating
`points (lean-burn operation) which means
`that there is air in the cylinder which has no
`effect upon the generated torque. Here, it is
`the fuel mass which has the most effect.
`
`Engine-management assignments
`One of the engine management’s jobs is to
`set the torque that is to be generated by the
`engine. To do so, in the various subsystems
`(ETC, A/F-mixture formation, ignition) all
`quantities that influence torque are con-
`trolled. It is the objective of this form of
`control to provide the torque demanded by
`the driver while at the same time complying
`with the severe demands regarding exhaust
`emissions, fuel consumption, power output,
`comfort and safety. It is impossible to satisfy
`all these requirements without the use of
`electronics.
`In order that all these stipulations are
`maintained in long-term operation, the en-
`gine management continuously runs
`through a diagnosis program and indicates
`to the driver when a fault has been detected.
`This is one of the most important assign-
`ments of the engine management, and it
`also makes a valuable contribution to sim-
`plifying vehicle servicing in the workshop.
`
`Subsystem: Cylinder-charge control
`On conventional injection systems, the dri-
`ver directly controls the throttle-valve open-
`ing through the accelerator pedal. In doing
`so, he/she defines the amount of fresh air
`drawn in by the engine.
`
`Basically speaking, on engine-management
`systems with electronic accelerator pedal for
`cylinder-charge control (also known as
`EGAS or ETC/Electronic Throttle Control),
`the driver inputs a torque requirement
`through the position of the accelerator
`pedal, for instance when he/she wants to ac-
`celerate. Here, the accelerator-pedal sensor
`measures the pedal’s setting, and the “ETC”
`subsystem uses the sensor signal to define
`the correct cylinder air charge correspond-
`ing to the driver’s torque input, and opens
`the electronically controlled throttle valve
`accordingly.
`
`Subsystem: A/F-mixture formation
`During homogeneous operation and at a de-
`fined A/F ratio λ, the appropriate fuel mass
`for the air charge is calculated by the A/F-
`mixture subsystem, and from it the appro-
`priate duration of injection and the best in-
`jection point. During lean-burn operation,
`and essentially stratified-charge operation
`can be classified as such, other conditions
`apply in the case of gasoline direct injection.
`Here, the torque-requirement input from
`the driver determines the injected fuel quan-
`tity, and not the air mass drawn in by the
`engine.
`
`Subsystem: Ignition
`The crankshaft angle at which the ignition
`spark is to ignite the A/F mixture is calcu-
`lated in the “ignition” subsystem.
`
`13
`
`

`

`12
`
`Gasoline-engine management
`
`Cylinder-charge control
`
`Robert Bosch GmbH
`
`The majority of the fresh air enters the
`cylinder with the air-mass flow (6, 7) via the
`throttle valve (13) and the intake valve (11).
`Additional fresh gas, comprising fresh air
`and fuel vapor, can be directed to the cylin-
`der via the evaporative-emissions control
`system (3).
`
`For homogeneous operation at λ (cid:41) 1, the air
`in the cylinder after the intake valve (11) has
`closed is the decisive quantity for the work
`at the piston during the combustion stroke
`and therefore for the engine’s output torque.
`In this case, the air charge corresponds to
`the torque and the engine load. During lean-
`burn operation (stratified charge) though,
`the torque (engine load) is a direct product
`of the injected fuel mass.
`
`During lean-burn operation, the air mass
`can differ for the same torque. Almost al-
`ways, measures aimed at increasing the en-
`gine’s maximum torque and maximum out-
`put power necessitate an increase in the
`maximum possible charge. The theoretical
`maximum charge is defined by the displace-
`ment.
`
`Residual gas
`The residual-gas share of the cylinder charge
`comprises that portion of the cylinder
`charge which has already taken part in the
`combustion process. In principle, one differ-
`entiates between internal and external resid-
`ual gas. The internal residual gas is that gas
`which remains in the cylinder’s upper clear-
`ance volume following combustion, or that
`gas which is drawn out of the exhaust pas-
`sage and back into the intake manifold when
`the intake and exhaust valves open together
`(that is, during valve overlap).
`External residual gas are the exhaust gases
`which enter the intake manifold through the
`EGR valve.
`
`Cylinder-charge control
`
`It is the job of the cylinder-charge control to
`coordinate all the systems that influence the
`proportion of gas in the cylinder.
`
`Components of the cylinder charge
`The gas mixture trapped in the combustion
`chamber when the intake valve closes is re-
`ferred to as the cylinder charge. This is com-
`prised of the fresh gas and the residual gas.
`The term “relative air charge rl” has been
`introduced in order to have a quantity
`which is independent of the engine’s dis-
`placement. It is defined as the ratio of the
`actual air charge to the air charge under
`standard conditions (p0 = 1013 hPa,
`T0 = 273 K).
`
`Fresh gas
`The freshly introduced gas mixture in the
`cylinder is comprised of the fresh air drawn
`in and the fuel entrained with it (Fig. 1). On
`a manifold-injection engine, all the fuel has
`already been mixed with the fresh air up-
`stream of the intake valve. On direct-injec-
`tion systems, on the other hand, the fuel is in-
`jected directly into the combustion chamber.
`
`1
`
`Cylinder charge in the gasoline engine
`
`3
`
`12
`
`10
`
`2
`
`5
`
`8
`9
`
`æUMM0544-3Y
`
`1
`
`(cid:95)
`
`4
`
`11
`
`6
`
`13
`
`7
`
`Figure 1
`1 Air and fuel vapor
`(from the evapora-
`tive-emissions con-
`trol system)
`2 Canister-purge valve
`with variable valve-
`opening cross-
`section
`3 Connection to the
`evaporative-emis-
`sions control system
`4 Returned exhaust
`gas
`5 EGR valve with vari-
`able valve-opening
`cross-section
`6 Air-mass flow (ambi-
`ent pressure pu)
`7 Air-mass flow (mani-
`fold pressure ps)
`Fresh A/F-mixture
`charge (combustion-
`chamber pressure
`pB)
`9 Residual exhaust-
`gas charge (com-
`bustion-chamber
`pressure pB)
`10 Exhaust gas (ex-
`haust-gas back
`pressure pA)
`11 Intake valve
`12 Exhaust valve
`13 Throttle valve
`α Throttle valve-
`angle
`
`8
`
`14
`
`

`

`Robert Bosch GmbH
`
`Gasoline-engine management
`
`Cylinder-charge control
`
`13
`
`2
`
`Throttle characteristic-curve map for an SI engine
`– – – Intermediate throttle-valve settings
`
`WOT
`
`Fresh-gas charge
`
`æUMM0543-2E
`
`Throttle fully closed
`
`min.
`Idle
`
`max.
`
` rpm
`
`Direct injection
`On direct-injection (DI) gasoline engines
`during homogeneous operation at λ (cid:41) 1
`(that is, not lean-burn operation), the same
`conditions apply as with manifold injection.
`
`To reduce the throttling losses, the throttle
`valve is also opened wide in the part-load
`range. In the ideal case, there are no throt-
`tling losses wit