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Abstract

The Gasoline Engine Management System electronically controls combustion parameters (amounts of air and fuel and ignition timing) to increase engine output and reduce emissions and fuel consumption.
FUEL SYSTEM
Gasoline Engine
Management System
Prof. Dr. Eng. Medhat A. M. Elkelawy
medhat_abo@yahoo.com
medhatelkelawy@f-eng.tanta.edu.eg
High power
Low fuel
consumption Compact and
light
High reliability Low price
Low pollution Low noise and
vibration
Drivability
High durability
Gasoline Engine Management
Combustion and the Engine Emissions
Knock and the fuel Octan
Number
The following table shows constantly increasing reduction
of pollutants by means of increasingly strict EURO
standards.
Gasoline Engine management
The requirements for safety,
convenience, economy, and environmental
protection have increased continuously,
which required an improvement of the
related technology.
Looking at the engine control system in the
beginning the control was made by
mechanical means, such as the carburetor
and the mechanical distributor.
Gasoline Engine management
With these systems it was very difficult to acquire
optimal engine efficiency with simultaneously
satisfying emission control regulations.
The next development stages were mechanical fuel
injection systems such as so called the K- Jetronic
from Bosch, followed by the first electronically
controlled systems such as the L Jetronic also from
Bosch.
Some systems applied only one centralized
injector, but usually the latest EMS system uses
independent injectors, which can be controlled
individually.
Gasoline Engine management
The systems maintain the optimum conditions for
fuel and air intake rate as well as ignition timing in order to
provide the required torque and power and keeping the
emissions low at the same time.
The EMS systems nowadays consist of various
sensors detecting the operating conditions of the engine,
actuators which are used to influence the operating
conditions accordingly, both processed by an electronic
device, the control unit.
The control unit is processing the data acquired by
the sensors in order to determine the best operating
conditions and then drives the actuators accordingly.
Let’s start with:
the basic engine operation to
understand the control
requirements precisely.
Fuel-air mixture Requirement
rich lean
Engine output
Fuel consumption
100%
99%
98%
Catalyst Efficiency
SI Engine Requirements
Lean limit
Stoichiometric premixed charge SI
engine
- Low part load efficiency
+ Low emissions with 3-way catalyst
Lean burn premixed charge SI engine
+ Reduced pumping work
improved part load efficiency
- Increased HC and NOx
Stratified charge SI engine - GDI
+ Removed pumping work
much improved part load efficiency
- Large problem with NOx and PM
0.8 1.0 1.5
2.0 2.5 5.0
Stoichiometric-ideal
Mixture control
Exhaust Emissions
The engine exhaust consists of products from the combustion of
the air and fuel mixture. Under perfect combustion conditions
the hydrocarbons would combine in a thermal reaction with
oxygen in the air to form carbon dioxide (CO2) and water (H2O).
Unfortunately perfect combustion does not occur and in addition
to CO2 and water, carbon monoxide (CO), oxides of nitrogen
(NOX) and hydrocarbon (HC) occur in the exhaust as a result
of combustion reaction. Additives and impurities in the fuel also
generate minute quantities of pollutants such as lead oxides,
lead halogenides and sulphur oxides. In diesel engines there is
also an appreciable amount of soot created. In Europe and
United States the level of pollution, in terms of HC, CO, NOX
and, for diesel engines, particulates emitted in a vehicle’s
exhaust, is regulated by law.
The control strategies
Fuel consumption
A lot of different factors are working in partnership
to make of central importance fuel economy:
The need of a better and more rational use of
energetic resources to reach a sustainable growth
The fuel price increase and its market
consequence
the legislation requirements both in Europe and
in USA
The electronic engine control system provides the
fuel metering and ignition timing precision
required to minimise fuel consumption.
Driveability
Another requirement of the electronic engine
control system is to provide acceptable
driveability under all operating conditions. No
stalls, hesitations or other objectionable
roughness should occur under vehicle operation.
Driveability is influenced by almost every
operation of the control system and, unlike
exhaust emissions or fuel economy, is not easily
measured. Other factors that influence
driveability are the idle speed control, EGR control
and evaporative emissions control.
Evaporative Emissions (Gasoline engine only)
Hydrocarbon (HC) emissions in the form of fuel vapours
escaping from the vehicle are closely regulated. The prime
source of these emissions is the fuel tank. Due to ambient
heating of the fuel and the return of unused hot fuel from the
engine, fuel vapours are generated in the tank. The
evaporative emission control system (EECS) is used to
control the evaporative HC emissions. The fuel vapours are
rotated to the intake manifold via the EECS and they are
burned in the combustion process. The quantity of fuel
vapours delivered to the intake manifold must be metered such
that exhaust emissions and driveability are not adversely
effected. The metering is provide by a purge control whose
function is controlled by the electronic control unit.
.
The control strategies
Evaporative emission control system
A vapour ventilation line exits the fuel tank and
enters the fuel vapour canister. The canister consist of
an active charcoal element which absorbs the vapour
and allows only air to escape to the atmosphere. Only
a certain volume of fuel vapour can be contained by the
canister.
The vapours in the canister must therefore be
purged from and burned by the engine so that the
canister can continue to store vapours as they are
generated. To accomplish these, another line leads
from the charcoal canister to the intake manifold.
Included in this line is the canister purge solenoid valve.
System Diagnostics
The purpose of system diagnostics is to provide a warning to the
driver when the control system determines a malfunction of a
component or a system and to assist the service technician in
identify and correct the failure. To the driver the engine may appear
to be operating correctly, but excessive amounts of pollutants may
be emitted. The ECU determines a malfunction has occurred when
a sensor signal, received during normal engine operation or during
a system test, indicates there is a problem. For critical operations
such as fuel metering and ignition control, if a required sensor input
is faulty, a substitute value may be used by the ECU so that the
engine will continue to operate.
Starting from 2001 (Euro3) the European On Bord Diagnosis
(EOBD) statutes require that, when a failure occur in a system
critical for exhaust emissions, the malfunctioning indicator lamp
(MIL), visible to the driver, must be illumined. Information on the
failure is stored in the ECU. A service technician can retrieve the
information on the failure on the ECU and correct the problem
Cranking - During engine cranking, the goals are
to get the engine started with the minimal amount or delay
and to minimize the exhaust emissions (during crank the
catalyst is cold and its efficiency is very low).
To accomplish a rapid and robust start fuel must be delivered
that meets the requirements for starting for any combinations
of engine coolant and ambient temperatures. For a cold
engine, an increase in the commanded A/F ratio is required due
to poor fuel vaporization and “wall wetting” , which decrease the
amount of usable fuel. Wall wetting is the condensation of some
of the vaporized fuel on the cold metal surfaces in the intake
port and combustion chamber. It is critical that fuel does not wet
the spark plugs, which can reduce the effectiveness of the spark
plug and prevent the plug from firing.
The control strategies
Warm-Up - During the warm-up phase, there are three
conflicting objectives:
keep the engine operating smoothly (i.e. no stalls or
driveability problems),
increase exhaust temperature to quickly achieve
operational temperature for catalyst (light-off) and lambda
sensor so that close-loop control can begin operating,
and keep exhaust emissions and fuel consumption to a
minimum.
The best method for achieving these objectives is very
dependent on the specific application.
If the engine is still cold, fuel enrichment will be required to
keep the engine running smoothly due, again, to poor fuel
vaporization and wall welling effects. The amount of
enrichment is dependent on engine temperature and is a
correction factor to the injector pulse width.
Cut-off
During deceleration, such as coasting or braking, there is no
torque requirement. Therefore, the fuel may be shut off until
either an increase in throttle angle is detected or the engine
speed falls to a speed slightly above idle rpm. During the
development of the fuel cut-off strategy, the advantage of
reduced emission and fuel consumption must be balanced
against driveability requirements.
The use of fuel cut off may change the perceived amount of
engine braking felt by the driver. In addition, care must be
taken to avoid a “bump” feel when entering and when exiting
the fuel cut off mode, due to change in torque.
The control strategies
Idling - The objectives of the engine control system during
idle are:
Provide a balance between the engine torque
produced and the changing engine loads, thus achieving
a consistent idle speed even with various load changes
due to accessories (i.e. air conditioning, power steering,
and electric loads) being turned on and off and during
engagement of the automatic transmission. In addition, the
idle control must be able to compensate for long-term
changes in engine load, such as the reduction in engine
friction that occurs with engine break-in.
Provide the lowest idle speed that allows smooth
running to achieve the lowest exhaust emissions and
fuel consumption (up to 30 percent of a vehicle fuel
consumption in city driving occurs during idling).
Normal - This mode practically cover the greatest
part of engine operative range. When the engine work
in steady state condition (i.e. without sensible
variation of load and speed) the leaning phase of the
auto-adaptative strategies is activated.
During transition such as acceleration or
deceleration, the objective of the engine control
system is to provide a smooth transition from one
engine operating condition to another (i.e., no
hesitations, stalls, bumps, or other objectionable
driveability concerns), and keep exhaust emissions
and fuel consumption to a minimum.
The control strategies
Acceleration Enrichment:
When an increase in engine load and throttle
angle occurs, a corresponding increase in fuel mixture
richness is required to compensate for increased well
wetting. The sudden increase in air results in a lean
mixture that must be corrected swiftly to obtain
good transitional response. The rate of change of
engine load and throttle angle are used to determine
the quantity of fuel during acceleration enrichment. The
amount of fuel must be enough to provide desired
performance, but not so much as to degrade exhaust
emission and fuel economy. During acceleration
enrichment, the ignition timing is set to the maximum
torque without knocking.
Deceleration Enrichment :
During deceleration the problem with wall
wetting is inverse than in acceleration;
this means that at the end of the
deceleration is possible to have a rich
mixture.
If the deceleration is such that where
is no torque requirement the mode
becomes cut-off.
Engine and vehicle speed limitation
Using the inputs of engine rpm and vehicle
speed to the electronic control unit thresholds
can be establish for limiting these variables with
fuel cut-off. When the maximum speed is
achieved the fuel injectors are shut off. When
the speed decreases below the threshold
fuel injection resumes. These operation must
be done with some caution in order to avoid
poor driveability. The rpm limitation function is
used to protect the engine from overrun. The
rpm limitation is obtained through fuel
modulation
Knock control (Gasoline Engines)
Engine knock occurs when the ignition timing is advanced too far the
operating condition and causes, during the flames propagation,
uncontrolled spontaneously combustion in the end-gas that can lead to
engine damage, depending on the severity and frequency. Unfortunately,
the ignition timing for optimisation of torque, fuel economy and
exhaust emissions is in close proximity to the ignition timing that
results in engine knock. As the ignition timing that results in engine
knock depends from a lot of factors, such as air/fuel ratio, fuel
quality, engine load, and variation in compression ratio, is not possible
to put in the ignition timing table values that are safe with respect to the
knock without penalise the engine performance. To avoid this, knock
sensor (one or more) is installed on the engine block to detect knocking.
Knock sensors are usually acceleration sensors that provide an
electric signal, proportional to the engine vibration, to the electronic
control unit. From this signal, the ECU control algorithm determines which
cylinder or cylinders are knocking. Ignition time is retarded for those
cylinder until the knock is no longer detected. The ignition timing is then
advanced again until knocking is detected
The control strategies
Turbocharger boost pressure control
The exhaust turbocharger consists of a
compressor and an exhaust turbine arranged on a
common shaft. Energy from the exhaust gas is
converted to rotational energy by the exhaust turbine,
which then drives the compressor.
The compressed air leaves the compressor and
passes through the air cooler, throttle valve, intake
manifold, and into the cylinders.
The control strategies
Turbocharger boost pressure control
In order to achieve near constant air charge pressure
over a wide rpm range, the turbocharger uses a circuit that
allows for the bypass of the exhaust gas away from the
exhaust turbine through a valve (wastegate) opening at a
specified air charge pressure.
In the most modern turbocharged engines, by controlling
the wastegate with a pulse-wide modulated solenoid valve,
different wastegate opening pressure can be specified,
depending on the engine operative conditions. Therefore,
only the level of air charged pressure required is developed.
The control strategies
(1) Knock sensor
(2) APC control unit
(3) Pressure transducer
(4) Solenoid valve
(5) RPM signal from ignition distributor
APC (Automatic Performance Control) is an
electronic turbo boost control system that
adjusts maximum boost pressure as a function
of engine knock (detonation) and RPM
The electronic control unit uses information on
engine load from either manifold pressure or the air meter
and rpm and throttle position. From these information, a
data table is referenced and the proper boost pressure
(actually a duty cycle of the control valve) is determined.
On systems using manifold pressure sensor, a close-
loop control system can be developed to compare the
specified value with the measured value.
The boost pressure control system is usually used in
combination with the knock control for turbocharged
engines. When the ignition timing is retarded due to knock,
an increase in already high exhaust temperatures of
turbocharged engines occurs. To counteract the
temperature increase, the boost pressure is reduced when
the ignition timing is retarded past a predetermined
threshold.
The torque of common S.I. engines is primarily influenced
by the throttle, controlling the mass airflow and therefore
also the amount of fresh air flowing into the combustion
chamber. In addition to this, other variables are influencing the
relative variation of the engine torque: ignition timing, air/fuel
ratio, deactivation of injection of certain cylinders, boost
pressure control for turbocharged engines, EGR, variable
valve timing/lift and variable manifold.
But there are other torque-influencing control
functions that affect engine torque as idle speed control,
cruise control, traction control, transmission control, etc.: all
these additional functions drastically increased the complexity
of the complete system over the past years.
Torque based control
Since many “torque” interactions occur
simultaneously, priorities must be established.
However, since the interactions take place in the
individual functions, it’s not easy to observe the
effects on the overall system. If torque-relevant
control values are directly called up by one of the
systems or subsystems, the various interactions
influence each other.
This requires a complex data calibration of
the various ECU’s installed in the vehicle.
Between the subsystems themselves there are also
strong interdependencies of the parameters to be
calibrated.
Torque based control
The most new strategy that
introduced the clutch torque as central
intermediate value became the
decisive step for solving this situation.
Based on these physical values, all
demands can be coordinated, before the optimal
conversion to the respective engine control
values takes place (criteria such as emissions,
fuel economy and protection of components).
Torque based control
With the torque based approach to a
system architecture of an engine control
system, all demands which can be
formulated as torque or efficiency are
defined, based on these physical values.
This means that interfaces within
single functions as well as between (sub)
systems, are defined as torques or
efficiencies, enabling a transparent and
simplified system architecture.
Torque based control
Torque Guided Engine Management Systems
Torque Based System Structure for PFI Systems
Ind. fuel
cut-off
Torque
demand
coordinator
Idle speed
actuator
Ignition timing
Injection time
Waste gate
control
Coordination
of torque and
efficiency
demands
Realization
of desired
torque
Torque
conversion
Torque
Torque
External Torque
Demands
Vehicle dynamic
control
Driveability
Internal Torque
Demands
Engine start-up
Idle speed control
Engine speed limitation
Engine protection
Efficiency Demands
Engine start-up
Catalyst heating
Idle speed control
Efficiency
Engine
Driver
Throttle angle
Calculation of
driver‘s request
Current cylinder charge & engine speed Current cylinder charge & engine speed
Calculation of
driver‘s request
Current cylinder charge & engine speed
Calculation of
driver‘s request
Current cylinder charge & engine speed
Calculation of
driver‘s request
Current cylinder charge & engine speed
Calculation of
driver‘s request
Subsections of the engine control system
Air Induction System
Electronic
Control
System
Fuel delivery system Ignition system
Control unit
INPUT CONTROL UNIT OUTPUT
Sensors to detect
the engine operating
conditions, such as
engine speed,
coolant temperature etc
Actuators
to influence
the engine
operating conditions,
such as engine speed,
coolant temperature etc
ECM
signal
processing
actuator control
Control unit Input signal and
output signals
Fuel delivery overview
Fuel tank
Fuel gauge Fuel pump
Rollover valve
Fuel pump connector
Control unit
Fuel pressure regulator
Fuel rail
Injectors
Charcoal
canister
Fuel filter
Optimizing an Engine's Diet
Optimizing an Engine's Diet
The engine is run at some fixed throttle opening, and the load is
adjusted to keep the RPM constant. Starting with a very rich air :
fuel ratio, the mixture is adjusted leaner in small steps, and the fuel
flow is measured at each setting.
Max. Power
SI Engine Special Diets
Cold Starting
Typical cold start fuel-to-air ratios are
between 2-to-l and I-to-l.
Idle Enrichment
Acceleration
One special circumstance that requires a
much richer than stoichiometric mixture
Engine Management Systems
Fuel Injection Concepts for S.I. Engines
Port Fuel Injection Gasoline Direct Injection
Mixture transport over the
intake stroke Mixture transport by charge
motion and piston geometry
Dual Fuel Technology
Diagram of Bosch Dual Fuel system: 1 gas pressure regulator, 2 air pressure and temperature sensor, 3 throttle, 4
turbocharger’s release valve, 5 oxygen sensor, 6 CNG controller, 7 diesel oil controller, 8 CNG tanks, 9 engine
speed sensor, 10 gas pedal, 11 CNG injector, 12 knock sensor, 13 engine temperature sensor, 14 diesel oil
injector, 15 engine phase sensor, 16 high-pressure pump, 17 diesel common rail, 18 fuel filter, 19 oxidation
catalyst, 20 diesel oil tank, 21 gas pressure and temperature sensor, 22 CNG fuel rail
Multiple Injection System
UNIJET 2000 ECU
Electronic Control Unit with
Advanced Injector Drivers
From Pilot Injection...
TDC +60° -60°
PILOT MAIN
COMBUSTIO
N
RATE
FUELLING
… to Sequential Multiple Injections
TDC +60° -60°
PILOT PRE MAIN AFTER
COMBUSTION
RATE
FUELLING
POST
Different types of fuel
injection
Single-point or throttle body injection (TBI)
Port or multi-point fuel injection (MPFI)
Sequential fuel injection (SFI)
Direct injection Intermittent Injection
Single-point or throttle body injection (TBI)
Mono-Jetronic
1 Fuel tank, 2 Electric fuel pump, 3 Fuel filter, 4 Fuel-pressure regulator, 5 Solenoid-operated fuel injector, 6 Air-temperature
sensor, 7 ECU, 8 Throttle-valve actuator, 9 Throttle-valve potentiometer, 10 Canister-purge valve, 11 Carbon canister, 12
Lambda oxygen sensor, 13 Engine-temperature sensor, 14 Ignition distributor, 15 Battery, 16 Ignition-start switch, 17 Relay, 18
Diagnosis connection, 19 Central injection unit.
Mono-Jetronic schematic diagram
Port or multi-point fuel injection (MPFI)
Port or multi-point fuel injection (MPFI)
The "K" in K-Jetronic stands for kontinuierlich,
the German word for continuous.
Port or multi-point fuel injection (MPFI)
K-Lambda System
Port or multi-point fuel injection (MPFI)
KE-Jetronic Mechanical Electronic Fuel injection
KE3-Jetronic& KE-Motronic systems
KE3-Jetronic and KE-Motronic systems
also integrate control over ignition
timing.
A fundamental difference between these
two is that the ignition "brain on KE3
systems is a separate package from the
fuel "brain"; on the KE-Motronic both
functions are integrated into the same
ECU.
Different types of fuel
injection
Single-point or throttle body injection (TBI)
Port or multi-point fuel injection (MPFI)
Sequential fuel injection (SFI)
Direct injection Intermittent Injection
Sequential fuel injection (SFI)
Sequential fuel injection, also called sequential port fuel injection
(SPFI) or timed injection, is a type of multi-port injection.
Electronically Controlled Gasoline
Injection (ECGI)
"D" stands for druck-German for pressure
the calculation of the
quantity of fuel to be
injected was based on
manifold pressure.
Sequential fuel injection (SFI)
“L" stands for luft, the German word for air
L-Jetronic (Mechanical Air Flow Sensor)
L-Jetronic established the principle of calculating the fuel quantity required-
and thus the pulse time of the injectors the basis of airflow
Sequential fuel injection (SFI)
“H" stands for heiss, the German word for hot.
LH-Jetronic (Air Flow Sensor by using
Hot Wire Sensors)
Motronic MP
Sequential fuel injection (SFI)
Motronic M5
Sequential fuel injection (SFI)
Motronic ME 7
Sequential fuel injection (SFI)
GDI -Direct injection
Early Injection and Late Injection strategies
Wall-Guided combustion system:
The fuel is transported to the
spark plug by using a specially
shaped piston surface. As the fuel
is injected on the piston surface, it
cannot completely evaporate and, in
turn, HC and CO emissions, and fuel
consumption increase. To use this
system alone is not efficient.
Air-Guided combustion system:
The fuel is injected into air flow, which moves the fuel spray near
the spark plug. The air flow is obtained by inlet ports with special shape
and air speed is controlled with air baffles in the manifold. In this
technique, fuel does not wet the piston and cylinder. Most of stratified-charge
GDI engines use a large-scale air motion (swirl or tumble) as well as specially
shaped piston a surface in order to keep the fuel spray compact and to
move it to the spark plug.
In the air-guided and wall-guided combustion systems the injector is
placed remote to the spark plug.
Volkswagen (VW) direct injection combustion
system is a combination of two systems: Wall guided
and air guided by tumble flow. This system is less sensitive against the
cyclic variations of airflow. This combustion system shows advantages as
well in the stratified and in the homogenous mode.
Injector is intake-side placed, Fig. The fuel is injected to the
piston under given angle. The piston has two bowls. The fuel bowl is on the
intake-side; the air bowl is on exhaust-side. Tumble flow is obtained by
special shaped intake port. The fuel is guided simultaneously via air and
fuel bowl to the spark plug.
Fig. Volkswagen FSI engine air-wall
guided combustion system (Anon,
2002).
Spray-Guided combustion system:
In the spray-guided technique fuel is injected near spark plug where it also
evaporates. The spray-guided technique theoretically has the highest
efficiency. The spray guided combustion process requires advanced injector
systems such as piezo injection. This technique has some advantages:
reduced wall wetting, increased stratified operation region, less sensitive to
in-cylinder air flow, less sensitive to cylinder to cylinder variation and
reduced raw HC emissions. Reported disadvantages are spark plug
reliability (fouling) and poor robustness (high sensitivity to variation in
ignition &injection timing). Mercedes-Benz developed a new spray-guided
combustion system. This system has the Stratified-Charged Gasoline
Injection (CGI) engine with Piezo injection technology. The spray-guided
injection achieves better fuel efficiency than conventional wall-guided direct
injection systems. The main advantage of the CGI engine is obtained at the
stratified operating mode. During this mode the engine is run with high
excess air and thus excellent fuel efficiency is provided. Multiple injections
extend this lean-burn operating mode to higher rpm and load ranges, too.
During each compression stroke, a series of injections is made spaced just
fractions of a second apart. This allows the better mixture formation and
combustion, and lower fuel consumption.
Spray-guided Gasoline Direct Injection
A stable, misfire free lean operating spray-guided Gasoline Direct Injection combustion
system have an estimated fuel consumption reduction potential of about 20% in the new European driving
cycle (NEDC) which means 20% reduction in CO2 emissions. In fact for typical highway driving (low load)
the fuel consumption reduction in (lean) mode can be up to 40% higher than the same engine operating in
homogeneous mode.
Cold start emissions is a well known problem in the automotive industry. However, by
utilizing stratified cold starts the engine out emissions of unburned fuel prior to catalyst light-off can be
dramatically reduced. Stratified cold starts give us a bonus thanks to the improved vaporization rate; it also
enables cold starts on alternative fuels such as alcohols. This is good since alcohol fuels need much more
energy to vaporize than gasoline.
Why does this combustion system give a fuel
consumption reduction?
The fuel consumption reduction is obtained in stratified
(late injection combustion mode) and is due to:
Much lower heat losses
No pump losses
Higher thermodynamic efficiency due to:
Higher compression ratio
Lean burn (lambda > 1)
Higher volumetric efficiency
Fast burn
The challenge:
Why is it difficult to design a spray-guided stratified
combustion system which runs stable and without
misfires? The challenge lies in how to create a suitable
stratified fuel cloud which must meet the following
requirements:
Good stratification
Fuel/air ratio within ignitibility limits at spark
Not too small and not too steep fuel gradients
Good mixing ability
Low cycle-to-cycle variations
Low sensibility to in-cylinder motion
Low sensibility to back pressure
Not too high cross-flow velocities at the spark
Not too low and not to high turbulence levels at the
spark
Not too sensitive to flash-boiling
Fuel distribution with laser spectroscopy
(LIF) in optical engine. Spray formation from a fuel injector.
Photograph from a spray chamber.
Late Direct Injection System
BASIC TECHNICAL FEATURES OF GDI ENGINE
The Upright Straight Intake Port.
The Curved-top Piston.
The High Pressure Fuel Pump.
The High Pressure Swirl Injector.
MAJOR CHARACTERISTICS OF THE GDI ENGINE
Lower fuel consumption and higher output
Ultra-lean Combustion Mode
Superior Output Mode
In-cylinder
Airflow
Fuel Spray
Optimized Configuration of the Combustion Chamber
REALIZATION OF LOWER FUEL CONSUMPTION
Basic Concept
Combustion of
Ultra-lean Mixture
Vehicle Fuel Consumption
Fuel
Consumption
During Idling
Fuel Consumption
during Cruising Drive
Emission Control
REALIZATION OF SUPERIOR OUTPUT
Improved
Volumetric
Efficiency
Increased
Compression
Ratio
Notice that there are conditions when the port fuel-injector located in the intake
manifold, and the gasoline direct injector, located in the cylinder both operate to
provide the proper airfuel mixture.
SUMMARY of GDI System
1. A gasoline direct-injection system uses a fuel injector that
delivers a short squirt of fuel directly into the combustion
chamber rather than in the intake manifold, near the intake
valve on a port fuel-injection system.
2. The advantages of using gasoline direct injection instead of
port fuel-injection include:
Improved fuel economy
Reduced exhaust emissions
Greater engine power
3. Some of the disadvantages of gasoline direct-injection
systems compared with a port fuel-injection system include:
Higher cost
The need for NOX storage catalyst in some applications
More components
4. The operating pressure can vary from as low as 500 PSI during
some low-demand conditions to as high as 2,900 PSI.
SUMMARY of GDI System
5. The fuel injectors are open for a very short period of
time and are pulsed using a 50 to 90 V pulse from a
capacitor circuit.
6. GDI systems can operate in many modes, which are
separated into the two basic modes:
Stratified mode
Homogeneous mode
7. GDI can be used to start an engine without the use
of a starter motor for idle-stop functions.
8. GDI does create a louder clicking noise from the
fuel injectors than port fuel-injection injectors.
9. Carbon deposits on the injector and the backside of
the intake valve are a common problem with
engines equipped with gasoline direct-injection
systems.
REVIEW QUESTIONS about GDI
1. What are two advantages of gasoline
direct injection compared with port fuel-
injection?
2. What are two disadvantages of gasoline
direct injection compared with port fuel-
injection?
3. How is the fuel delivery system different
from a port fuel-injection system?
4. What are the basic modes of operation of
a GDI system?
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