Bosch M-Motronic Technical Instruction.pdf

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Gasoline-engine management
M-Motronic
Engine Management
Technical Instruction
Published by:
© Robert Bosch GmbH, 2000
Postfach 30 02 20,
D-70442 Stuttgart.
Automotive Equipment Business Sector,
Department for Automotive Services,
Technical Publications (KH/PDI2).
Editor-in-Chief:
Dipl.-Ing. (FH) Horst Bauer.
Editorial staff:
Dipl.-Ing. (FH) Anton Beer,
Ing. (grad.) Arne Cypra,
Dipl.-Ing. Karl-Heinz Dietsche,
Dipl.-Ing. (BA) Jürgen Crepin,
Dipl.-Holzw. Folkhart Dinkler.
Authors:
Dipl.-Ing. (FH) Ulrich Steinbrenner,
Dipl.-Ing. (FH) Hans Barho,
Dr.-Ing. Klaus Böttcher,
Dipl.-Ing. (FH) Volker Gandert,
Dipl.-Ing. Walter Gollin,
Dipl.-Ing. Werner Häming,
Dipl.-Ing. (FH) Klaus Joos,
Dipl.-Ing. (FH) Manfred Mezger,
Ing. (grad.) Bernd Peter,
Dipl.-Ing. Ernst Wild.
Presentation:
Dipl.-Ing. (FH) Ulrich Adler,
Berthold Gauder, Leinfelden-Echterdingen.
Translation:
Peter Girling.
Technical graphics:
Bauer & Partner, Stuttgart.
Except where otherwise indicated, the above are
employees of the Robert Bosch GmbH, Stuttgart.
Reproduction, copying, or translation of this publi-
cation, wholly or in part, only with our previous writ-
ten permission and with source credit. Illustrations,
descriptions, schematic drawings, and other
particulars only serve to explain and illustrate the
text. They are not to be used as the basis for de-
sign, installation or scope of delivery. We assume
no liability for agreement of the contents with local
laws and regulations. Robert Bosch is exempt from
liability, and reserves the right to make changes at
any time.
Printed in Germany.
Imprimé en Allemagne.
4th Edition, February 2000.
English translation of the German edition dated:
August 1999.
M-Motronic
Engine Management
Modern electronics are opening up
new perspectives in automotive
design. The spark-ignition engine is
being subjected to numerous, some-
times mutually-antagonistic demands.
It is now possible to satisfy these
demands – including high specific out-
put, modest fuel consumption and low
exhaust emissions – by using systems
providing an optimal combination of
operating characteristics.
Separate mixture-formation and igni-
tion systems deal with parts of the
problem: Jetronic controls fuel supply
while the electronic ignition system
provides optimal ignition control.
Motronic combines the two systems.
A computer controls the injection and
ignition systems with reference to
shared optimization criteria.
Digital data processing and micro-
processors make it possible to trans-
late extensive operating information
into program-map-controlled injection
and ignition data.
Installation of a Lambda oxygen sen-
sor and integration of a Lambda con-
trol unit in the CPU allow Motronic
to meet tomorrow's emissions regu-
lations today.
Combustion in the gasoline engine
The spark-ignition or
Otto-cycle engine
2
Gasoline-engine management
Technical requirements
4
Cylinder charge
5
Mixture formation
7
Ignition
Function and requirements
10
Inductive ignition systems
13
Gasoline-injection systems
Overview
16
M-Motronic engine management
M-Motronic: System overview
18
Fuel system
20
Operating-data acquisition
28
Operating-data processing
38
Operating conditions
42
Integrated diagnosis
58
Electronic control unit (ECU)
62
Interfaces to other systems
64
Combustion in
the gasoline
engine
Combustion in
the gasoline engine
The spark-ignition
or Otto-cycle engine
Operating concept
The spark-ignition or Otto-cycle
1
)
powerplant is an internal-combustion (IC)
engine that relies on an externally-
generated ignition spark to transform the
chemical energy contained in fuel into
kinetic energy.
Today’s standard spark-ignition engines
employ manifold injection for mixture
formation outside the combustion
chamber. The mixture formation system
produces an air/fuel mixture (based on
gasoline or a gaseous fuel), which is
then drawn into the engine by the suction
generated as the pistons descend. The
future will see increasing application of
systems that inject the fuel directly into the
combustion chamber as an alternate
concept. As the piston rises, it compresses
the mixture in preparation for the timed
ignition process, in which externally-
generated energy initiates combustion via
the spark plug. The heat released in the
Fig. 1
Reciprocating piston-engine design concept
OT = TDC (Top Dead Center); UT = BDC (Bottom
Dead Center),
V
h
Swept volume,
V
C
Compressed
volume,
s
Piston stroke.
V
C
OT
s
V
h
UT
combustion process pressurizes the
cylinder, propelling the piston back down,
exerting force against the crankshaft and
performing work. After each combustion
stroke the spent gases are expelled from
the cylinder in preparation for ingestion of
a fresh charge of air/fuel mixture. The
primary design concept used to govern
this gas transfer in powerplants for
automotive applications is the four-stroke
principle, with two crankshaft revolutions
being required for each complete cycle.
The four-stroke principle
The four-stroke engine employs flow-
control valves to govern gas transfer
(charge control). These valves open and
close the intake and exhaust tracts
leading to and from the cylinder:
1st stroke:
2nd stroke:
3rd stroke:
4th stroke:
Induction,
Compression and ignition,
Combustion and work,
Exhaust.
Induction stroke
Intake valve: open,
Exhaust valve: closed,
Piston travel: downward,
Combustion: none.
The piston’s downward motion increases
the cylinder’s effective volume to draw
fresh air/fuel mixture through the passage
exposed by the open intake valve.
Compression stroke
Intake valve: closed,
Exhaust valve: closed,
Piston travel: upward,
Combustion: initial ignition phase.
1
)
OT
UMM0001E
UT
2
After Nikolaus August Otto (1832 –1891), who
unveiled the first four-stroke gas-compression engine
at the Paris World Exhibition in 1876.
As the piston travels upward it reduces
the cylinder’s effective volume to
compress the air/fuel mixture. Just before
the piston reaches top dead center (TDC)
the spark plug ignites the concentrated
air/fuel mixture to initiate combustion.
Stroke volume
V
h
and compression volume
V
C
provide the basis for calculating the
compression ratio
ε
= (V
h
+V
C
)/V
C
.
Compression ratios
ε
range from 7...13,
depending upon specific engine design.
Raising an IC engine’s compression ratio
increases its thermal efficiency, allowing
more efficient use of the fuel. As an
example, increasing the compression ratio
from 6:1 to 8:1 enhances thermal
efficiency by a factor of 12 %. The latitude
for increasing compression ratio is
restricted by knock. This term refers to
uncontrolled mixture inflammation charac-
terized by radical pressure peaks.
Combustion knock leads to engine
damage. Suitable fuels and favorable
combustion-chamber configurations can
be applied to shift the knock threshold into
higher compression ranges.
Power stroke
Intake valve: closed,
Exhaust valve: closed,
Piston travel: upward,
Combustion: combustion/post-combus-
tion phase.
Fig. 2
The ignition spark at the spark plug
ignites the compressed air/fuel mixture,
thus initiating combustion and the
attendant temperature rise.
This raises pressure levels within the
cylinder to propel the piston downward.
The piston, in turn, exerts force against
the crankshaft to perform work; this
process is the source of the engine’s
power.
Power rises as a function of engine speed
and torque (P =
M⋅ω).
A transmission incorporating various
conversion ratios is required to adapt the
combustion engine’s power and torque
curves to the demands of automotive
operation under real-world conditions.
Exhaust stroke
Intake valve: closed,
Exhaust valve: open,
Piston travel: upward,
Combustion: none.
As the piston travels upward it forces the
spent gases (exhaust) out through the
passage exposed by the open exhaust
valve. The entire cycle then recommences
with a new intake stroke. The intake and
exhaust valves are open simultaneously
during part of the cycle. This overlap
exploits gas-flow and resonance patterns
to promote cylinder charging and
scavenging.
Otto cycle
Operating cycle of the 4-stroke spark-ignition engine
Stroke 1: Induction
Stroke 2: Compression
Stroke 3: Combustion
Stroke 4: Exhaust
UMM0011E
3

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