Course Work Report ENG 3037M

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SCHOOL OF ENGINEERING DESIGN AND

TECNOLOGY

NAME: Alexandros Alexandrou

U. B. NO: 06025724

COURSE: MSc MECHANICAL ENGINEEERING

SUBMISSION DATE: 18 DECEMBER, 2007

ENGINE AND POWERTRAIN

ENG 3037M

http://www.brad.ac.uk/



University of Bradford Engine and Powertrain (ENG 3037M)

Table of Contents

Page No:

Introduction………………………………………………………………………………………3

Objectives…………………………………………………………………………………………4

1. Engine

Definition…………………………………………………………………….............4

1.1 Specification of the Engine………………………………………………………………4

1.2 Characteristics of the Engine............................................................................................4

1.2.1 Petrol Engine..........................................................................................................4

1.2.2 Port

Injection......................................................................................................4-5

1.2.3 Exhaust Gas

Ignition…………………………………………………………….6

1.2.4 Three Way Catalytic Converter (TWCC)

……………………………………6-7

1.2.5 Activated Carbon

Canister……………………………………………………7-8

1.2.6 Variable Valve

Timing………………………………………………………...8-9

2. Specification of

EMS………………………………………………………………………...9

2.1 Input Sensors…………………………………………………………………………9-11

2.2 Output Actuators……………………………………………………………………11-12

Alexandros Alexandrou Page 2 of 17




3 Calibration of

EMS................................................................................................................12

4 Operation of

EMS……………………………………………………………………….13-14

5 Discussion………………………………………………………………………………..14

-15

6 Conclusion..............................................................................................................................

15

References....................................................................................................................................16

Introduction

“An Engine Control Unit (ECU), also known as Engine Management System (EMS) is an

electronic system, primarily a computer, which controls an internal combustion engine by reading

several sensors in the engine and using the information to control its ignition systems”.

Engine management in general words is an approach to illustrate an electronically controlledengine system (ECU). The most important task of these systems is the continuous process control

in order to assure better fuel economy, emissions control, ignition timing, variable valve timing,

and boost level in turbocharged cars by sensors and actuators in order to have better performance.

Sensors usually give the input signal to the ECU where it is being processed and then it is sent to

the actuator.

The number and type of sensors and actuators that are being used from the engine control unit haveto be compatible with the precise engine that the ECU is controlling and the specific task.





Figure 1: An ECU and its components

Objectives

The main objectives of this coursework are as follows:

To specify an EMS for the engine defined in section (6).

To describe the operation of this EMS.

To evaluate the requirements to calibrate the EMS.

To describe the operation of the EMS for a number of operating regimes of the engine.

1. Engine Definition

1.1 Specification of the Engine





The EMS presented in this report is for a port injection turbocharged petrol engine, which utilises

variable valve timing, an exhaust gas ignition with activated carbon canister and a three way

catalytic converter.

1.2 Characteristics of the Engine

1.2.1 Petrol Engine

Petrol engine is a spark ignition engine (SI) that uses pistons that are moving up and down in

cylinders. A mixture of air and petrol is inserted inside the pistons and are ignited. The pressure

that is produced by the gases from the ignition pushes the pistons down generating power. In a four

stroke engine the piston moves up and down four times in order to make a cycle. This motion of

the pistons rotates a crankshaft that transmits the power to the wheels of the car by the use of

transmission system of clutch, gearbox and final drive.

1.2.2 Port Injection

In a port injection engine the air/fuel mixture is injected inside the intake of the manifold as

opposed to direct injection engine the mixture is injected in the combustion chamber. The fuel is

injected directly into the intake valves simultaneously with the intake air and set up the air/fuel

mixture which is then penetrated in the cylinder each stroke the piston is doing.

The first injection system was introduced by General Motors and it was called central port

injection (CPI). This system came in order to replace the carburetor throughout time because of the

high fuel metering characteristics and as the automobile evolved, carburetors became even more

complicated trying to handle all of the operating requirements. Central port injection sprays in the

cylinder through a nozzle continuously. Thus General Motors redeveloped CPI into a sequential

port injection system (SCPI) that uses the valves in order to measure the fuel going inside the

cylinder during intake and controlling time.

Despite that the system was still sticky because the valves were sticking all the time. That’s why

another system was developed called Multi-Port fuel injection (MFI) were using one injector in

each cylinder and sprays the pressurized fuel exactly above the intake valves. One very important

factor this system has is that it controls the amount and timing of the fuel injected in each cylinder.





Figure 2: Components of Port injection Engine-control System

1.2.3 Exhaust Gas Ignition

Exhaust Gas systems are controlled by vacuum electronically depending on the application.

Exhaust Gas Recirculation (EGR) intend to reduce the level of NOx in the exhaust gas. This

emission increases by means of combustion temperature or lean burnt mixture.

The EGR system introduces calibrated amounts of exhaust gas into the intake system of the engine.

The unburnt fuel in the exhaust gas is driven in the combustion chamber for the next cycle. As this

proportion of exhaust gas has some usable energy less air/fuel mixture is required for the

combustion. This results to fuel economy and combustion chamber temperature drops as well as

NOx emissions. According to researches been done recently it is shown that engines with EGR, the

torque is increased.





Figure 3: Typical EGR system

1.2.4 Three Way Catalytic Converter (TWCC)

A catalytic converter is used in automobiles in order to reduce the emissions exerted from an

internal combustion engine exhaust and pollutes the environment.

Three Way Catalytic Converter (TWCC) is the most common catalyst that is being used in spark

ignition engines. Is called three way due to the fact that is doing three tasks simultaneously:

• Reduces nitrogen oxides to nitrogen and oxygen.

• Oxidizes carbon monoxide to carbon dioxide.

• Oxidizes sunburn hydrocarbons to carbon dioxide and water.

The catalyst controls the amount of fuel being burnt and assures that the air/fuel ratio is slightly

above the stoichometric point. This ratio is between 14.8-14.9:1 for gasoline. When there is more

air than fuel then the system is said to be running lean and when there is the opposite is said to be

rich.

This stoichometric point can be achieved by operating an engine management system with lambda

sensors. The sensors can detect variations of air /fuel ratio and sends signals to the control unit that

generates the ratio to cycle quickly and bring the system to balance.





Figure 4: Three Way Catalytic Converter

Three Way Catalytic Converter utilizes two types of catalysts. A reduction and an oxidation

catalyst. These are made generally from platinum and have a ceramic formation covered above

them.

1.2.5 Activated Carbon Canister

The operation of activated carbon canister is to absorb harmful hydrocarbons from atmosphere and

supply them back to the engine again when the engine is in operation.





Figure 5: Activated Carbon Canister

1.2.6 Variable Valve Timing

Variable valve timing is an electronic and mechanical system that is being used in some engines

such as Honda VTEC and allows the engine to have multiple camshafts. These engines have an

extra intake cam with rocker that follows the cam. This concept keeps the intake valve open

longer. At low engine speeds the rocker is not connected to the valves although at high speeds the

piston locks the extra rocker to the other two rockers that control the two intake valves.

Some cars use a device that can advance the valve timing. This does not keep the valves open

longer instead; it opens them later and closes them later. This is done by rotating the camshaft

ahead a few degrees.





Figure 6: The VTEC system Honda uses.

2. Specification of EMS

As it is mentioned before an ECU contains sensors and actuators that convert engines temperature,

pressure and other data information into digital or analog signals in order to control different

systems in an automobile engine.

2.1 Input Sensors

Oxygen Sensor (O2): changing voltage signal which allows the ECU to monitor the oxygen

content of the exhaust-gas (known also as Lambda sensor). Also provides information about the

fuel mixture. The ECU uses this to constantly re-adjust and fine tune the air/fuel ratio. This keeps

emissions and fuel consumption to a minimum.

Crankshaft Position (CKP) Sensor: Provides information on crankshaft position and the engine

speed signal to the ECU and helps the computer determine relative position of the crankshaft so the





ECU can control spark timing and fuel delivery in the proper sequence. The ECU also uses the

crank sensor's input to regulate idle speed, or some engines have an additional camshaft position

sensor is used to provide additional input to the ECU about valve timing. Camshaft Position (CMP) Sensor: Produces a signal the ECU to identify the number 1 cylinder and to time sequential fuel injection.

Air/Fuel Sensor: works like Oxygen Sensors and is mounted to upstream of the catalytic

converter. It controls from the ECU the air-fuel ratio, in order to do this it needs a constant flow of

information about the amount of air flowing into the engine. The ECU will send out a signal to the

injectors to provide the correct amount of fuel.

Engine Coolant Temperature (ECT) Sensor: monitors engine coolant temperature and sends the

ECU a voltage signal that affects ECU control of the fuel mixture, ignition timing and EGR

operation. The ECU uses this information to regulate a wide variety of ignition, fuel and emission

control functions. When the engine is cold, for example, the fuel mixture needs to be richer to

improve drivability. Once the engine reaches a certain temperature, the ECU starts using the signal

from the O2 sensor to vary the fuel mixture. This is called "closed loop" operation, and it is

necessary to keep emissions to a minimum.

Intake Air Temperature (IAT) Sensor: provides the ECU with intake air temperature

information, in order to control fuel flow, ignition timing, and EGR system operation.

Throttle Position Sensor (TPS): senses throttle movement and position, and then transmit a

voltage signal to the ECU to determine when the throttle is closed, in a cruise position, or wide

open. The ECU uses this input to change spark timing and the fuel mixture as engine load changes.

A problem here can cause a flat spot during acceleration as well as other drivability complaints.

Mass airflow (MAF) Sensor: measures the mass of the intake air by detecting volume and weight

of the air from samples passing over a hot wire element. Problems with the airflow sensor can

upset the fuel mixture and various drivability problems (hard starting, hesitation, stalling, rough

idle, etc.) There are several types of airflow sensors including hot wire mass airflow sensors and

the older flap-style vane airflow sensors. All are very expensive to replace.





Vehicle Speed Sensor (VSS): provides information to the ECU to indicate the vehicle’s speed.

This is needed to control other functions such as torque converter lockup. EGR Valve Position Sensor: monitors the position of the Exhaust Gas Recirculation pintle in

relation to the operating conditions of the EGR system. This allows the ECU to detect problems

with the EGR system that would increase pollution.

Vapour Pressure Sensor: the fuel tank is part of the evaporative emission control system and it is

used to monitor vapour pressure in the fuel tank. The ECU uses this information to turn on and off

the vacuum switching valves (VCV) of the evaporative emission system.

Power Steering Pressure (PSP) Switch: is used to increase engine idle speed during low speed

vehicle manoeuvres.

Knock sensors: are used to detect vibrations produced by detonation. When the ECU receives a

signal from the knock sensor, it momentarily retards timing while the engine is under load to

protect the engine against spark knock.

The manifold absolute pressure (MAP) sensor: measures intake vacuum, which the ECU also

uses to determine engine load. The MAP sensor's input affects ignition timing primarily, but also

fuel delivery

Transmission Sensors: the ECU on models with automatic transmission receive input signals

from a direct clutch (or input shaft) speed sensor.

2.2 Output Actuators

EFI Main Relay: activates power to the fuel pump relay, it is activated by the ignition switch andsupplies battery power to the ECU and the EFI system when the switch is in the Start Position.

Fuel Injectors: the ECU opens the fuel injectors individually. The ECU also controls the time the

injector is open (pulse width).





Igniter: triggers the ignition coil and determines the proper spark based on inputs from the ECU.

Idle Air Control (IAC) Valve: controls the amount of air to bypass the throttle plate when the

throttle valve is closed or at idle position. The IAC valve opening and the airflow is controlled by

the ECU.

EVAP Vacuum Switching Valve (VSV): is a solenoid valve operated by the ECU to purge the

fuel vapour canister and route fuel vapour to the intake manifold for combustion.

Vapour Pressure Sensor Vacuum Switching Valve (VSV): is used by the ECU as part of the on-

board diagnostic check and during an emission test of the evaporative system.

3 Calibration of EMS

Calibration is the most important thing in an engine in order to run smoothly and effectively.

Calibration, also known as engine mapping is a procedure which sensors signals are processed by

the ECU and give the most appropriate result. These results are stored in the EMS and are used in

other processes to reduce time response.

The most important factor for an engine to run smoothly and effectively is the calibration. This

occurs through a procedure that signals from sensors of the engine are processed by the ECU and

accordingly give the ideal result every time. These results are stored in the EMS as tables and may

be used in next processes to reduce time respond. Once the data required is chosen then the output

signals are deployed. These signals are used by components that are going to make the adjustments

to the engine.

4 Operation of EMS





Start from cold

Primary control throughout engine cracking

Fuel pump is filled with fuel to control pressure and when the pressure reaches the required fuel

line it switches off for safety reasons.

The speed of the engine at cracking is above 1500 rpm but below idle speed.

The engine coolant temperature is low; the air/fuel ratio is below stoichometric. Also the

microprocessors use calibration tables to run the engine taking measurements from temperature

sensors on the manifold.

The pressure inside the combustion chamber is equal to the atmospheric pressure.

Throughout this phase the turbocharger is not rotating and returns pressure to the system.

Idling

ECU controls the spark timing. Generally the lowest spark angle value is selected and that depends

according the data received.

The engine coolant temperature is still low but rising. As the temperature is still low the ECUkeeps the air/fuel mixture rich and when the temperature starts to rise keeps the mixture close to

stoichometric.

Rapid acceleration

Sensors time respond to the ECU creates a delay among the opening of the throttle and the

response of the system

Accelerator clamp occurs when the ECU adds extra fuel over short periods

Open loop is used by the ECU in order to adjust the control of fuel flow rate, ignition time and

spark angle in the engine





W.O.T (Wide open throttle)

Spark timing is retarded

Zero losses from the pump

The pressure from the manifold is achieved by the turbocharger and depends according to the

specifications each manufacturer gives.

Engine Switched Off

Ignition and fuel pump switches off by the ECU when the engine is turned off

The cooling system works for a few minutes after the engine is turned off in order to cool down the

engine

5 Discussion

Engine Management System was developed in order to control and make sure the polluting

emissions created by the engine were reduced. Also improves the performance and provides fuel

economy.

These can be achieved by the use of different systems such as the three way catalyst, the most

common device used in a spark ignition engine, which controls the emissions in a gasoline engine

by reducing the polluting emissions.

The ECU can control the Ignition Timing, Variable Valve Timing and other regimes like start from

cold, idle speed, WOT, engine switched off. For each case the ECU is taking signals from

different sensors in order to control these operations.





The power produced is regulated by the use of engine control. The driver controls engine power

via the accelerator pedal, which determines the setting of the throttle via a mechanical linkage

system. The throttle plate is situated in the air intake.

The power produced by the engine is proportional to the mass flow rate of air into the engine. Thedriver can control the engine power by controlling air mass flow rate going into the engine using

the throttle plate.

The power produced by the engine is also dependent on the fuel being presented in the correct

proportions. The fuel introduced to the air in the fuel-metering device.

The control of the spark timing is carried out by the ECU and is dependent on the data such as

load and rotational speed.

6 Conclusion

A turbocharged spark ignition engine can achieve high performance characteristics if is using a

good and complicated engine management system. This is not a turnover because it can maintain

fuel economy and exhaust gas emissions relatively to high speeds. New technologies applied to the

ECU and calibration process can achieve the tasks mentioned above.

Also consumer demands have forced the industry to rapidly develop engine management systems

in order to control the engine and exhaust emissions for better efficiency, performance, durability

and noise levels. Most modern systems use sophisticated control and monitor several engines

variables so the ECU can take the appropriate action.





References

1. Catalytic converters: http://www.madabout-kitcars.com/kitcar/kb.php?aid=381

2. Emissions Control: http://www.carcare.org/Emission_Control/egr.shtml

3. Dr. Seale, Engine and Powertrain (ENG3037M), lecture notes

4. Robert Bosch, (2004), Gasoline-Engine Management, 2nd edition

5. Engine Definition: http://www.autospeed.com/


http://www.carcare.org/Emission_Control/egr.shtml

http://www.carcare.org/Emission_Control/egr.shtml

Course Work Report ENG 3037M

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