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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“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 : ………………………………

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Dedicate to my family, my friends and all compatriots.

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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.

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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.

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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.

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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

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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

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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

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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

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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

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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

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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

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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.

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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.

Example car use VVT engine

BMW - Valvetronic

Honda - i-VTEC

Mitsubishi - MIVEC

Proton - Campro CPS

Toyota - VVT-i

Daihatsu - DVVT

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1.1 Project Overview

This project is about to design the new variable valve timing (VVT) system

which wants to applied for internal combustion engine. The design must be suitable for

spark ignition(S.I) engine.

To design this VVT, the mechanisms must be design first. To design this

mechanism, all of aspect must be known to ensure mechanisms can be applied to the

system.

Beside that to design this system, all the calculation for the mechanism must be

calculate to get the theoretical result and the graphs.

1.2 Problem statement

In Malaysia, Proton Wira is the most seller car. It maybe this car is cheap and

comfortable. But according to fuel consumption and power, it left out compare to other

similar car because this car is using more fuel and its power is lower.

The factor of this problem is this car used regular engine with old technology.

Now, almost of new car used the new technology such as turbocharged, VVT, hybrid

and others. This technology will give the car’s engine more energy in performance and

used low fuel consumption.

Now, Proton Wira must use the new engine to walk together with other cars. The

engine must more powerful with low consumption like VVT system. VVT can be

applied at Proton Wira engine because that engine is based on Mitsubishi engine (4G92).

Now Mitsubishi have Mivec which is one of VVT type system.

With VVT in Proton Wira, Proton Berhad which is the manufacturer of this car

can be advance and able to compete with other car manufacturer in worldwide market.

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1.3 Objective of Project

The main objective of this study is:

To design and timing analysis VVT mechanism for Spark Ignition Engine

(SI engine).

1.4 Scope of Project

The scopes of this project generally involve the following:

Analyze the valve timing

Conceptual design for 4 stroke engine passenger car with SI engine.

Drawing VVT mechanism with CAD software.

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CHAPTER 2

LITERATURE REVIEW

2.1 Introduction of VVT

Variable valve timing (VVT) is a generic term for an automobile piston engine

technology. VVT allows the lift or duration or timing of the intake or exhaust valves to

be changed while the engine is in operation. Two-stroke engines use a power valve

system to get similar results to VVT.

Piston engines normally use poppet valves for intake and exhaust. These are

driven by cams on a camshaft. The cams open the valves for a certain amount of time

during each intake and exhaust cycle. The timing of the valve opening and closing is

also important. The camshaft is driven by the crankshaft through timing belts, gears or

chains. The profile, position and shape of the cam lobes on the shaft, is optimized for a

certain engine rpm, and this tradeoff normally limits low-end torque or high-end power.

VVT allows the cam profile to change, which results in greater efficiency and power.

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Figure 2.1: VVT diagram (Source: Ed. M, (2000))

At high engine speeds, an engine requires large amounts of air. However, the

intake valves may close before all the air has been given a chance to flow in, reducing

performance. On the other hand, if the cam keeps the valves open for longer periods of

time, as with a racing cam, problems start to occur at the lower engine speeds. This will

cause unburned fuel to exit the engine since the valves are still open. This leads to lower

engine performance and increased emissions. Pressure to meet environmental goals and

fuel efficiency standards is forcing car manufacturers to turn to VVT as a solution. Most

simple VVT systems advance or retard the timing of the intake or exhaust valves. Others

like Honda's VTEC switch between two sets of cam lobes at a certain engine RPM.

Table 2.1: basic function principle of variable valve timing concept

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TDC

BDC

DC

00

1800

2700 900

160 ATDC

140 BTDC

580 ABDC

520 BBDC

Intake

valve

Intake

valve

2.2 The conventional valve timing

The valve timing for the conventional engine is fixed and not variable. It’s that

means the valve timing is same when the engine run in low RPM and high RPM. For the

4G92 SOCH engine, the valve timing open 140 before top dead center (BTDC) and close

at 580 after bottom dead center (ABDC). For the exhaust valve, it open at 52

0 before

bottom dead center (BBDC) and close at 160 after top dead center (ATDC).

Figure 2.2: Valve timing diagram

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2.3 Categories of VVT

Variable valve timing (VVT) has three main categories. They are variable phase

control (VPC), combined valve lift and phase control (VLPC), and variable event timing

(VET) systems.

2.3.1 Variable phase control (VPC)

Variable phase control, VPC implies varying the overlap so that low speed

torque and, with it, specific fuel consumption is improved over most of the speed range.

Since the duration of opening remains constant, wide-open throttle power is unaffected.

Figure 2.3: The inlet opening point for VPC. (Source: Garrett, T. K. (2001))

The inlet opening point can be retarded to reduce the overlap which, during

idling, ensures stability and low emissions with VPC. For good low-speed torque and

low fuel consumption, the inlet opening should be advanced, to increase the overlap.

2.3.2 Combined valve lift and phase control (VLPC)

VLPC offer further performance enhancement, but is more costly than VPC. It

has axially stepped cams, the variation being effected by shifting the followers from step

to step, but such a mechanism is complex. Tapered cams, such as the Fiat Tittolo system

combining variable lift and event timing, are an alternative but this means virtually point

contact, between cam and follower and, if the duration of opening is kept constant, the

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cam is extremely difficult to manufacture. Moreover, the axial loading introduced is

about 10% of the force between the cam and follower, so a powerful controller is

needed.

Figure 2.4: Stepped cams provide variable lift and timing (VLTC) with rocker actuated

valves. (Source: Garrett, T. K. (2001))

From the figure above, at the lower lifts, friction is reduced, charge swirl

enhanced and fuel consumption improved. The curves represent three steps, though up

to ten are practicable

2.3.3 Variable event timing (VET)

Varying the valve event timing (VET) is the changing of the duration of lift

while keeping the timing and magnitude of maximum lift constant. In other words, only

the opening and closing points are varied. This improves part load emissions and

economy, leaving the wide-open throttle condition unchanged, and has the advantage

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that the ramps on the cam remain effective both as the valve begins to lift and when it

re-seats.

Figure 2.5: Curves of variable event (VET) timing without phase change. (Source:

Garrett, T. K. (2001)).

Valve lift remains constant and the variation is effected continuously. Part-load

emissions and economy are improved, and the wide-open throttle condition is

unimpaired

2.4 Principles of current VVT

After the first patent application for a rotary displacement of a SI engine

camshaft was submitted in 1918 by Haltenberger, hundreds of patents for camshaft

adjustment systems have been issued, but only three construction principles have made

their way to series production. These systems use either mechanical or hydraulic

functional principles.

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2.4.1 Axial movement of a piston with helical gear teeth

The system is obtained from the functional principle of a spur/helical gear sleeve.

When the engine was in idle mode, a return spring keeps the system safely in the first

valve timing position. When engine oil pressure acts on the piston against the load

exerted by the spring, the helical cut gear spline teeth will translate the axial

displacement of the piston into a rotational movement. This causes rotation of the

camshaft relative to the drive sprocket and thus relative to the crankshaft.

Figure 2.6: Helical spline system (Source: Jost, K. (2002))

2.4.2 Camshaft chain adjustment

These systems employ a small chain between the intakes and exhaust camshaft.

The chain tensioner will moving upwards or downwards by oil pressurized piston will

vary the phase angle between the shafts. In this arrangement, the exhaust camshaft is

directly driven by the crankshaft and the intake camshaft can be repositioned by the

adjuster. This system is quite compact and costeffective, but permits only one camshaft

to be adjusted.