DESIGN AND TIMING ANALYSIS OF VARIABLE VALVE TIMING (VVT) FOR INTERNAL COMBUSTION ENGINE MOHD EFENDI BIN HUSIN This report are submitted to the Faculty of Mechanical Engineering As a partial to fulfill the requirement of Bachelor of Mechanical Engineering (Automotive) Faculty of Mechanical Engineering Universiti Teknikal Malaysia Melaka April 2008
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DESIGN AND TIMING ANALYSIS OF VARIABLE VALVE TIMING (VVT)
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DESIGN AND TIMING ANALYSIS OF VARIABLE VALVE TIMING (VVT)
FOR INTERNAL COMBUSTION ENGINE
MOHD EFENDI BIN HUSIN
This report are submitted to the Faculty of Mechanical Engineering
As a partial to fulfill the requirement of
Bachelor of Mechanical Engineering (Automotive)
Faculty of Mechanical Engineering
Universiti Teknikal Malaysia Melaka
April 2008
ii
“I hereby to declare that the work is my own except for summaries and quotations which
have been duly acknowledged “
Signature : ………………………………
Author : MOHD EFENDI BIN HUSIN
Date : ………………………………
iii
Dedicate to my family, my friends and all compatriots.
iv
ACKNOLEDGEMENT
Alhamdulillah, thanks to God because with His blessing, I can finish this project
with successful. I would like to express my gratitude and appreciate to my PSM
supervisor, Mr. Herdy Rusnandi because he gives many valuable suggestion and advice
throughout the project. He also help in obtaining the reference and read through the
manuscript of this report.
Thanks should also to be forwarded to UTeM for their cooperation especially to
staff and librarian because give support and provide facilities and references in
completing this research.
Also to take this opportunity to thanks my family and friends who have been my
sides throughout this time for their moral support and loyalty. Thanks to you all.
v
ABSTRACT
This project is focusing about design and analysis variable valve timing (VVT)
mechanism for spark ignition engine. This VVT mechanism will be applied to Proton
Wira 1.6 L with 4G92 SOCH engine as a car model to develop which does not have
VVT system yet. VVT is a system which that allows for more varying time at which
valve open, duration and valve overlap period. Design of this VVT system is based on
three parameters which are the configuration, dimension and complexity of the engine.
The timing analysis wil be done to get the suitable mechanism for this system.
vi
ABSTRAK
Projek ini memfokuskan tentang rekabentuk dan analisis mekanisma VVT untuk
enjin S.I. Mekanisma VVT ini akan di masukkan pada Proton Wira 1.6 L yang
menggunakan enjin 4G92 SOHC sebagai model kerata yang ingin dibangunkan. Sistem
VVT ini membenarkan masa untuk bukaan dan tutupan injap masukan berubah-ubah
mengikut kesesuaian kelajuan enjin. Rekabentuk system VVT ini adalah dengan
mengambil kira konfigurasi, dimensi dan kerumitan sesuatu enjin. Analisis masa akan
dilakukan untuk menentukan masa dan tempoh yang sesuai dengan mekanisma VVT.
vii
TABLE OF CONTENT
CHAPTER CONTENT PAGE
DECLARATION ii
DEDICATION iii
ACKNOWLEDGEMENT iv
ABSTRAK v
ABSTRACK vi
TABLE OF CONTENT vii
LIST OF TABLE xi
LIST OF FIGURE xii
CHAPTER I INTRODUCTION
1.1 Project overview 3
1.2 Problem statement 3
1.3 Objective 4
1.4 Project scope 4
CHAPTER II LITERATURE REVIEW
2.1 Introduction of VVT 5
2.2 The conventional valve timing 7
2.3 Categories of VVT 8
2.3.1 Variable phase control (VPC) 8
viii
CHAPTER CONTENT PAGE
2.3.2 Combined valve lift and phase
control (VLPC) 8
2.3.3 Variable event timing (VET) 9
2.4 Principles of current VVT 10
2.4.1 Axial movement of a piston with
helical gear teeth 11
2.4.2 Camshaft chain adjustment 11
2.4.3 Vane Type Systems 12
2.5 Advantages of VVT 13
2.6 Application of VVT 13
2.6.1 MIVEC by Mitsubishi 13
2.6.2 Valvetronic by BMW 15
2.6.3 VTEC by Honda 16
2.6.4 VVTL-i by Toyota 16
2.7 Mechanism of VVT 18
2.7.1 Rocker Arm 18
2.7.2 Camshaft 19
2.7.3 Poppet Valve 20
CHAPTER III METHODOLOGY
3.1 Introduction 21
3.2 Research on the problem involving
4G92 engine. 21
3.3 Analysis of engine system 23
3.3.1 Car specification 23
3.3.2 Engine Specification 24
ix
CHAPTER CONTENT PAGE
3.4 Research on the problem involving
conventional 4G92 SOCH engine. 25
3.5 Research for VVT system 25
3.6 Research the potential VVT system 25
for existing engine
3.7 Design cam profile 25
3.7.1 Prescribed rocker arm motion 27
3.8 Conceptual Design 29
3.8.1 Example drawings with
Catia software 29
CHAPTER IV RESULT AND DISCUSSION 31
4.1 Introduction 31
4.2 Concept of VVT design 31
4.3 Timing analysis 32
4.3.1 Timing of opening and closing
exhaust valve 32
4.3.2 Timing of opening and closing
intake valve 34
4.3.2.1 Intake valve for
conventional timing 34
4.3.2.2 Engine speed at low RPM 38
4.3.2.3 Engine speed at high RPM 41
4.3.3 Comparison of conventional,
low speed and high speed RPM 44
4.4 Cam profile design 45
4.4.1 The low RPM camshaft profile 47
4.4.2 The high RPM camshaft profile 48
x
CHAPTER CONTENT PAGE
4.5 Full design 49
CHAPTER V CONCLUSION AND RECOMMENDATION 51
5.1 Conclusion 51
5.2 Recommendation 52
5.2.1 Fully variable valve timing
without camshaft 52
5.2.2 Variable Valve Event and Lift (VVEL) 53
REFERENCES
BIBLIOGRAPHY
APPENDICES
xi
LIST OF TABLE
NUMBER TITLE PAGE
2.1 Basic function principle of variable valve 7
timing concept
3.1 Proton Wira Specification 23
3.2 4G92 SOCH Engine Specification 23
4.1 Exhaust valve displacement for conventional 32
4.2 Valve timing for conventional 34
4.3 Intake valve displacement for conventional engine 35
4.4 Valve timing at low engine speed 38
4.5 Intake valve displacement for low engine speed 39
4.6 Valve timing at high speed engine 41
4.7 Intake valve displacement for high engine speed 42
xii
LIST OF FIGURES
NUMBER TITLE PAGE
2.1 VVT diagram 6
(Source: Ed. M, (2000))
2.2 Valve timing diagram 7
2.3 The inlet opening point for VPC 8
(Source: Garrett, T. K. (2001))
2.4 Stepped cams provide variable lift and 9
timing (VLTC) with rocker actuated valve
(Source: Garrett, T. K. (2001))
2.5 Curves of variable event (VET) timing 10
without phase change
(Source: Garrett, T. K. (2001))
2.6 Helical spline system 11
(Source: Jost, K. (2002))
2.7 Camshaft chain adjuster 12
(Source: Jost, K. (2002))
2.8 Vane Type system 12
(Source: Jost, K. (2002))
2.9 Mivec mechanism 14
2.10 Vanos VVT mechanism 15
2.11 Toyota VVTL-i cover engine 17
xiii
2.12 Rocker arm 18
2.13 Camshaft 19
2.14 Poppet valve 20
3.1 Flow chart project 22
3.2 Cam profile design – flat face follower. 29
3.3 Poppet valve 29
3.4 Rocker arm 30
3.5 Camshaft 30
4.1 Valve timing diagram for conventional engine 35
4.2 Timing diagram for conventional engine 37
4.3 Timing diagram at low engine speed 38
4.4 Timing diagram for low engine speed 40
4.5 Timing diagram at high engine speed 41
4.6 Timing diagram for high engine speed 44
4.7 Comparison between conventional,
low speed and high speed engine 45
4.8 Cam profile for low engine speed 47
4.9 Cam profile for high engine speed 48
4.10 The full mechanism of VVT 49
4.11 The variable camshaft 50
1
CHAPTER 1
INTRODUCTION
Nowadays, technology in automotive was blooming. Many automotive
manufacturer produce may invention to conquer the market. These inventions are
including producing the engine. Many consumer want cars with low capacity engine but
have high performance and low fuel consumptions. As example, VVT (Variable Valve
Timing) can give the small engine the high performance.
Variable valve timing is a system that allows for more efficient engine operation
by varying the time at which valves opens, duration of opening, and valve overlap
period. Some manufacturer called this mechanism in various name such as VVT-i, i-
Vtec, Mivec, VTC, CVVT and others. Common camshaft was designed with the
tolerance between low RPM for better fuel economy and high RPM for better
performance.
When we increase the rpm, this configuration for the camshaft does not work
well. If the engine is running at 4,000 rpm, the valves are opening and closing 2,000
times every minute. When the intake valve opens right at the top of the intake stroke, it
turns out that the piston has a lot of trouble getting the air moving into the cylinder in the
short time. Therefore, at higher rpm ranges we want the intake valve to open prior to the
intake stroke, so that by the time the piston starts moving downward in the intake stroke,
the valve is open and air moves freely into the cylinder during the entire intake stroke.
2
For maximum engine performance at low engine speeds, the valves need to open longer
and close differently than they do at higher engine speeds.
So, VVT engine have an ability to vary the valve timing and opening duration in
both low and high speed operation. New technology such as i-Vtec mechanism allow
camshaft to operate at best performance on any speed.