EXPERIMENT AND ANALYSIS OF MOTORCYCLE EXHAUST DESIGN … · and this result can be applied to student formula race. viii ... 2.2 Exhaust Design for Engine Scavenging Performance 5

EXPERIMENT AND ANALYSIS OF MOTORCYCLE EXHAUST DESIGN

ABDUL MUIZ BIN JAAFAR

Report submitted in partial fulfilment of the requirementfor the award of the degree of

Bachelor of Mechanical Engineering with Automotive Engineering

Faculty of Mechanical Engineering

UNIVERSITI MALAYSIA PAHANG

JUNE 2013

vii

ABSTRACT

Internal combustion engine is one of beautiful engineering knowledge in engineeringscope. Internal combustion consists of two type categories which are Spark Ignition (SI)and Compression Ignition (CI). Based on internal combustion engine, a lot of researchcan be done to improve the performance of engine, fuel consumption, and emission.One of the researches is Experiment and Analysis for Motorcycle Exhaust Design. Themain objective is to study the variable design length to increase the performance of theengine. The second is to obtain high power and torque at low speed of engine (rpm)based on the change of exhaust parameter. The experiment is handle by utilize the EddyCurrent Dynamometer 15kW. There are two difference length of exhaust pipeline whichis 570mm and 1140mm. The length that change are from manifold until before thesilencer. Before undergo the experiment, test rig of the engine need to fabricate becausethe engine that use is difference from previous experiment of dynamometer. Tofabricate the test rig, four elements involve which are sketching, designing, analysis,and fabrication. These experiments consist of three different result which is baselinegraph, length of exhaust 570mm and length of exhaust 1140mm. The graphs are plot forpower and torque graph versus speed of engine. When there are changes of the length ofthe exhaust the torque graph will be change according to the difference length. Theshorter the length, the result of torque and power graph will be more improve. But thereare limit to make sure the exhaust pipe length not give bad impact to the engine. Theresult conclude that, the better length of exhaust pipe is the shorter one which is 570mmand this result can be applied to student formula race.

viii

ABSTRAK

Enjin pembakaran dalaman adalah salah satu daripada pengetahuan kejuruteraan yangindah. Pembakaran dalaman terdiri daripada dua kategori salah satunya adalah “SparkIgnition” (SI) dan “Compression Ignition” (CI). Banyak penyelidikan yang bolehdilakukan untuk meningkatkan prestasi enjin, penggunaan bahan api dan pelepasanbahan pembakaran. Salah satu daripada kajian tersebut ialah Eksperimen dan Analisisuntuk rekabentuk ekzos motosikal. Objektif utama projrk ini ialah untuk mengkajipanjang ekzos yang pelbagai untuk meningkatkan prestasi enjin. Yang kedua adalahuntuk mendapatkan kuasa dan tork yang tinggi pada kelajuan enjin (rpm) yang rendahberdasarkan perubahan ekzos parameter. Eksperimen ini menggunakan mesinDynamometer 15kW. Terdapat dua jenis panjang ekzos yang akan di kaji iaitu 570mmdan 1140mm. Panjang ini diukur dari manifold sehingga sebelum penyerap bunyi.Sebelum menjalani eksperimen, tapak enjin untuk di ujikaji perlu dibina kerana enjinyang digunakan adalah perbezaan dari eksperimen sebelumnya. Untuk pembinaan tapakenjin, empat elemen terlibatkan secara langsung ialah lakaran, reka bentuk, analisis, danfabrikasi. Daripada eksperimen yang dibuat terdapat tiga graf yang berbeza mengikutjenis-jenis ekzos pertama ialah graf asas, kedua ialah graf utk panjang ekzos 570mmdan panjang ekzos 1140mm. Graf ini ialah untuk graf kuasa dan graf tork berdasaekankelajuan enjin. Jika terdapat perubahan panjang ekzos,graf tork akan berubah mengikutpanjang perbezaan. Ekzos yang pendek akan menghasil bacaan graf tork dan graf kuasalebih baik jika dibandingkan dengan yang asal. Tetapi ada had untuk memastikanpanjang paip ekzos tidak memberi kesan buruk kepada enjin. Secara konklusi nya,ekzos yang terbaik bagi meningkatkan prestasi enjin GT128 ialah ekzos 570mm dankeputusan ini boleh digunakan untuk perlumbaan formula pelajar.

ix

TABLE OF CONTENTS

Page

SUPERVISOR’S DECLARATION ii

STUDENT’S DECLARATION iii

DEDICATION iv

ACKNOWLEDGEMENTS v

ABSTARCT vi

TABLE OF CONTENTS ix

LIST OF TABLES xii

LIST OF FIGURES xiii

LIST OF SYSTEM xv

LIST OF ABBREVIATION xvi

CHAPTER 1 INTRODUCTION

1.1 Project Background 1

1.2 Problem Statement 2

1.3 Project Objective 3

1.4 Scope of Project 3

CHAPTER 2 LITERATURE REVIEW

2.1 Introduction 4

2.2 Exhaust Design for Engine Scavenging Performance 5

2.3 Exhaust Pipe Length 8

2.4 Intake and Exhaust Tuning 9

2.5 Exhaust Megaphone 11

2.6 Noise and Silencer 13

x

CHAPTER 3 METHODOLOGY

3.1 Introduction 15

3.2 Designing the Test Rig for Four Stroke Engine 17

3.2.1 Analysis of Test Rig by FEA 22

3.2.2 Fabrication of Test Rig GT128 26

3.3 Engine Specification 28

3.4 Exhaust Design 29

3.5 Experimental Study of Dynamometer 31

3.5.1 Test Rig Preparation 31

3.5.2 Experiment Procedure of Dynamometer 34

CHAPTER 4 RESULT AND DISCUSSION

4.1 Experiment Result 38

4.1.1 Baseline Result of Engine GT128 with Standard Exhaust 38

4.1.2 Result for Exhaust Length of 570mm 39

4.1.3 Result for Exhaust Length of 1140mm 40

4.1.4 Result Comparison of Baseline Graph with Difference

Length of Exhaust 41

4.2 Discussions 42

4.2.1 Backpressure 42

CHAPTER 5 CONCLUSION

5.1 Conclusion 44

5.2 Recommendation 45

REFERENCES 46

xi

APPENDIX 48

A1 Engineering Drawing of Test Rig 48

A2 Raw Data of Experiment 51

xii

LIST OF TABLE

Table No. Title Page

1.1 Population of Motorcycle in January 2012 1

2.1 Intake and Exhaust Configuration 9

3.1 List of material to fabricate Test Rig 19

3.2 Material Properties of AISI 1005 Steel 22

3.3 Tool used for Fabrication 26

3.4 Engine Specification 28

3.5 Engine Transmission 28

3.6 Example data recorded 37

xiii

LIST OF FIGURE

Figure Title Page

2.1 Valve timing event showing valve overlap Valve Guide 5

2.2 Tuned engine ingest exhaust gas into the cylinder

during the overlap 5

2.3 Reflection of rarefaction wave at exhaust pipe end which

returns to the exhaust valve 6

2.4 Variation of volumetric efficiency with intake and

exhaust length 7

2.5 Measured and calculated power and torque when

change exhaust length 8

2.6 Torque Curve for Intake and Exhaust Tuning 10

2.7 Power Curve for Intake and Exhaust Tuning 10

2.8 Exhaust Diffuser/Megaphone 11

2.9 Horsepower for Exhaust Megaphone 12

2.10 Torque for Exhaust Megaphone 12

2.11 Power curve for silencer 13

2.12 Noise level for silencer 14

3.1 Flow Chart of Methodology 16

3.2 Previous test Rig for FZ150 17

3.3 Flow Chart of Designing New Test Rig 18

3.4 Isometric View of GT128 Test Rig 20

3.5 Drawing of the Test Rig 21

3.6 Boundary Condition and Force Applied to the Test Rid 23

3.7 Result of Stress von Mises 24

3.8 Result of Strain von Mises 24

3.9 Displacement of Y Component 25

3.10 Test Rig that Finish 27

3.11 Left view of Test Rig 27

3.12 Exhaust Pipe Length of 570mm 30

3.13 Exhaust Pipe Length of 1140mm 30

3.14 Test Rig of FZ150 31

xiv

3.15 Test Rig of GT128 32

3.16 Connector of Input and Output Shaft 32

3.17 Cooling Tank for Dynamometer 34

3.18 Indicator of Dynamometer is Ready to Use 35

3.19 Control Panel of Speed, Torque and Button type of Experiment 35

3.20 Throttle Lever Controller 36

3.21 Engine Speed Reader 36

3.22 Torque Reading on the Main Control Panel 37

4.1 Graph of Torque and Power versus Speed 38



4.4 Graph comparison between baseline parameter and difference

length of pipe length 41

xv

LIST OF SYMBOLS

D Diameter of exhaust pipe

ET Exhaust valve duration

Li Intake length

Le Exhaust length

kW Kilowatt

L Length

mm milimeter

rpm Rotational per minute

xvi

LIST OF ABBREVIATIONS

1D One Dimensional

CC Centimeter Cubic

CI Compression Ignition

CO2 Carbon Dioxide

FEA Finite Element Analysis

MAI Malaysia Automotive Institute

NOx Nitrogen Oxide

SAE Society Automotive Engineering

SI Spark Ignition

SOHC Single Overhead Camp

CHAPTER 1

INTRODUCTION

1.1 INTRODUCTION

Motorcycles are two-wheel vehicle that powered by internal combustion engine

either two-stroke or four-stroke. According to the latest statistics in Table 1.1,

motorcycles population has increase about 11.6% from 54,619 units in January 2011 to

60,956 units in January 2012.

Table 1.1: Population of Motorcycle in January 2012

Engine Capacity (cc) Units

50 cc or under 7076

51 – 125 1817

126 – 250 8086

Over 250 43977

Source: Malaysia Automotive Institute (MAI), 2012

These populations show that many people in Malaysia usually use motorcycle as

their transportation. A power source for motorcycle is internal combustion engine.

Internal combustion engine is combustion that occur in the combustion chamber by

ignite the mixture of compress of air and fuel. The combustion produce power can move

the motorcycle from one place to another.

2

Other than produce power as a power source to move the motorcycle, it is also

produce emission of NOx and CO2 gas that dangerous to humankind and environment.

All manufacture of engine especially automotive engineer in this world doing research

on improvement of internal combustion engine for both CI and SI engine. Their

researches focus on the improvement power of the engine, decrease emission of NOx

and CO2 gas and fuel consumptions.

There are many parameters that can increase the power of the engine such as

change the size of the bore of the cylinder block and change the cylinder head to

performance standard. Nowadays, researcher want to increase the performance the

engine without change the bore size, but change other parameter that have relation

before the combustion chamber and after it. The important variables that can increase

the performance of the engine are gas flow through the four-stroke engine, and

discharge coefficients of flow within four stroke engine (Blair, 1999).

Gas flow through four-stroke engine is process of into, through, and out of an

engine. The gas involve is unsteady which the pressure, temperature, and gas particle

velocity in a duct are variable with time. In the case of exhaust flow, the unsteady gas

flow behavior is produced because the cylinder pressure falls with the rapid opening of

the exhaust valve or valves. This gives an exhaust pipe pressure that change with time.

In the case of induction flow into the cylinder through an intake valve whose area

change with time, the intake pipe pressure alters because the cylinder pressure is

affected by the piston motion causing volumetric change within that space.

1.2 PROBLEM STATEMENT

In performance of racing engine, each parameter is very important to get the best

engine performance. Investigations of the engine performance characteristics, especially

for power and torque need to considered. The characteristic are gas flow through and

discharge coefficient of flow in four-stroke engine. There are two parameters that

usually involve in the gas flow thought engine, intake and exhaust valve.

3

1.3 PROJECT OBJECTIVE

a) To study the effect of the variable exhaust design length to the performance of

the engine.

b) To obtain high power and torque at low speed of engine (rpm) based on the

change of exhaust parameter.

1.4 SCOPE OF PROJECT

a) Literature review on the performance of 200cc engine and below based on the

exhaust parameter change.

b) Design and fabricate variable exhaust length for engine Modenas GT128.

c) Test the engine performance by utilizing engine dynamometer.

d) Plot graph of the engine performance.

CHAPTER 2

LITERATURE REVIEW

2.1 INTRODUCTION

Quality design of an exhaust system requires an understanding of its contribution

to both the overall power output of an engine and to noise attenuation (Blair, 2009).

Good design of exhaust is to increase the performance of engine without unharmed to

human kind and environment. A well designed exhaust system is one of the cheapest

ways of increasing engine efficiency, and then increasing engine power. In a four stroke

cycle engine, only one stroke out of the four does useful work which is the power

stroke. The other three strokes which are intake, compression and exhaust will absorb

some of the power that was produced during the power stroke. If the amount of power

that is lost by these idle strokes can be minimized, more power will be available to drive

the wheels, which is what the engine is supposed to be doing (Mohideen, 2008).

It is also important to understand the mechanisms that enable these contributions

as well as their significance. A wide variety of sources were studied to determine

current exhaust theories, design and analysis methods as well as to better understand the

restrictions imposed by SAE noise regulations.

2.2 EXHAUST DESIGN FOR ENGINE SCAVENGING PERFORMANCE

Performance considerations of exhaust design are a result of the nature of the

gas exchange process in a four stroke engine (Blair, 2009). This process includes a

period of valve overlap where both the intake and exhaust valves are open

simultaneously as seen in Figure 2.1. Without due regard by the designer this period

could see the induction of exhaust gases into the cylinder as shown in Figure 2.2 ,

effectively reducing the amount of fresh combustibles ingested and therefore overall

power.

Figure 2.1: Valve timing event showing valve overlap

Source: Blair, 1999

Figure 2.2: Tuned engine ingest exhaust gas into the cylinder during the overlap

Source: Blair, 1999

Exhaust Valve

TDC

Ovelap Period

Intake Valve

Valv

e Li

ft

⁰Crank

EVO IVO EVC IVC

Power Stroke Exhaust Stroke Intake Stroke Compression Stroke

TDC BDC TDC BDC

Closing exhaust Valve

Opening Intake valve

Piston Descending at Start of induction stroke

5

Performance aspects of exhaust design are concerned with minimizing residual

quantities or otherwise maximizing scavenging efficiency of the engine. To achieve the

maximum efficiency, the pressure of exhaust valve must reduce during valve overlap

such as to bias this exchange process to achieve this scavenge. Exhaust scavenging is

achieved via two methods. Firstly, scavenging is achieved through techniques wave

tuning and inertial scavenging depending on which of these mechanisms that utilize.

The aim of wave tuning is to tuned exhaust pipe harnesses the pressure wave

motion of the exhaust process to extract a greater mass of exhaust gas from the cylinder

during the exhaust stroke and initiate the induction process during the valve overlap

period. This scavenging effect is possible if a pressure wave originating from the

exhaust valve travel at the local acoustic velocity, over a tuned length such that it is

reflected back to the valve face as a rarefaction wave, as seen in Figure 2.3, in time to

assist the gas exchange process during valve overlap.

Figure 2.3: Reflection of rarefaction wave at exhaust pipe end which returns to the

exhaust valve

Source: Morrison, 2009

Another perspective of the priorities of exhaust system design is provided by a

parameter (Sammut and Alkidas, 2007). This study utilizes the engine simulation

software Ricardo WAVE to quantify the effects of and interactions between exhaust,

intake and valve timing parameters. For a constant valve timing and engine speed,

6

shows a comparison of the scavenging effect of the intake and exhaust measured in

volumetric efficiency.

Figure 2.4: Variation of volumetric efficiency with intake and exhaust length

Sources: Sammut and Alkidas, 2007

The data presented firstly shows that the individual contributions of the intake

and exhaust are independent as the contribution made by the exhaust is relatively

constant for any intake length. All data presented here in illustrating variation in

scavenging as a function of tuned length is obtained for constant valve timing. Variation

in valve timing would inevitably change the characteristics of the overlap period and

therefore the action of exhaust scavenging. Secondly, data presented in Figure 2.4 also

concludes that the effect of exhaust tuning is relatively small compared to the benefits

of intake tuning.

As a consequence of the diminishing significance of exhaust scavenging

benefits, minimizing the losses conceded to increased pumping losses whilst achieving

sufficient noise attenuation becomes of relatively high importance if a maximum

amount of power is to be derived from the engine.

7

2.3 EXHAUST PIPE LENGTH

According to 1D-Simulation method, the output power and pressure in the

intake-exhaust system can be calculated. Engine that use for dynamometer are 150cc

with air-cooled system. The parameters for tested are refer to pipe length exhaust. The

parameter that changes is pipe length before the catalyst (Horikawa et al., 2010).

Figure 2.5 show the measured and calculated output power for this type of

engine that tested using dynamometer. Those graphs indicate that when the length of the

piping system is change the performance of the engine for torque and speed also

change. The measured result indicates that output power increases at low engine speeds

and decreases at high engine speeds when the exhaust pipe becomes longer, and the

opposite when the exhaust pipe becomes shorter. A similar trend is found in calculation,

and the rate of output power change is also close to the measurement (Horikawa et al,

2010).

Figure 2.5: Measured and calculated power and torque when change exhaustlength

Sources: Horikawa et al., 2010

7













2010).



7













2010).



8

2.4 INTAKE AND EXHAUST TUNING

It is important to understand that the resonant length of the intake and exhaust

systems should be tuned separately. It is suggested that the intake system be tuned for

the desired speed range and then the exhaust system should be adjusted to compliment

the intake system (Blair, 1999).

An experiments were executed with the variables intake primary length (Li) and

exhaust length (Le) using 450cc by 1-Dimensional Simulation (Correia, 2009). Results

from three of the most outstanding instances are presented. The three configurations of

intake and exhaust system settings are indicated in table 2.1.

Table 2.1: Intake and Exhaust Configuration

Li(mm) Le(mm)

Config 1 198 660

Config 2 254 1194

Config 3 198 381

Source: Correia, 2009

Figure 2.6 and 2.7 shows that the configuration 2 has the longest intake and

exhaust lengths and exhibits a wider spread of torque from 4500rpm onwards.

Configurations 1 and 3 both have the same intake primary length to highlight the effect

of exhaust tuning on performance.

9

Figure 2.6: Torque Curve for Intake and Exhaust Tuning


Figure 2.7: Power Curve for Intake and Exhaust Tuning


0

5

10

15

20

25

30

35

40

2000

2500

3000

3500

4000

4500

5000

5500

6000

6500

7000

7500

8000

8500

9000

9500

1000

0

Configuration1Configuration2Configuration3

Engine Speed(rpm)

Torq

ue(N

.m)

0

10

20

30

40

50

60

70

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

Series1

Series2

Series3

Engine Speed(rpm)

Pow

er(k

W)

10

2.5 EXHAUST MEGAPHONE

Exhaust diffusers (also referred to as megaphones) are sometimes used on highly

tuned four stroke engines (Blair, 1999). There are analogy between the wave

phenomenon active with an exhaust megaphone and the behavior of ocean waves as

they approach the beach. As ocean waves approach the beach and water depth becomes

shallow, the conservation of wave energy forces the waves to increase in amplitude. In a

similar fashion, as reflected exhaust pulses travel back along the megaphone the

amplitude of these pressure waves increase as the cross section of the duct decreases

progressively.

The advantage of an exhaust megaphone is evaluated by modeling it to the

optimize horsepower from 6,000 to 10,000rpm. According to the Figure 2.8 the factors

that adjusted were the secondary length Le2, and the secondary diameter De2 of the

exhaust megaphone in addition to the exhaust primary length Le1. The final values

chosen were Le1 = 510mm, Le2 = 770mm and De2 = 150mm.

Figure 2.8: Exhaust Diffuser/Megaphone


198mm Ø41mm

Le1

3.5L

Ø36mm

Le2

11

The Figure 2.9 and 2.10 show the resulting performance trends offered from an

exhaust diffuser. Configuration 3 has length of exhaust 381mm. According to the graph

both systems offer high peak horsepower numbers compared to configurations 1 and 2.

However the exhaust diffuser delivers about 3% more power between 7,500 and

8,500rpm, whilst output remains virtually comparable onwards (Correia, 2009).

Figure 2.9: Horsepower for Exhaust Megaphone


Figure 2.10: Torque for Exhaust Megaphone


0

10

20

30

40

50

60

70

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17Exhaust megaphone Configuration 3

Engine Speed (rpm)

Pow

er(k

W)

05

10152025303540

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17Exhaust megaphone Configuration 3

Engine Speed(rpm)

Torq

ue(N

.m)

12

2.6 NOISE AND SILENCER

Noise can be describe as unwanted sound, but in producing exhaust noise cannot

be remove but can only reducing the noise from the exhaust. When tuning race engines,

silencer design or selection is often not considered a priority, though it is an integral

part of tuning the exhaust system (Blair, 1999).

Formula SAE requires cars to be tested for noise at an angle of 45 degrees and

0.5m away from the silencer outlet. The noise level must not exceed 110dB (A scale) at

any time during the noise test. A car will not be allowed to compete unless it passes the

noise test. A simulated version of the Formula SAE noise test was setup in WAVE and

two silencer designs were compared along with the scenario of not fitting a silencer to

the exhaust. The simulation was conducted from 5500rpm upwards as it is time

intensive and it was expected that the greatest noise intensity would occur at the higher

speeds (Correia, 2009).

Figure 2.11 and 2.12 compares the engine performance change from fitting of

the silencers. The two silencers have similar output with the absorption model

outperforming the two-box design marginally from about 7,000 to 8,000rpm. The un-

silenced power curve is different in nature likely due to fact that the silencers affect

exhaust tuning.

Figure 2.11: Power curve for silencer


0

10

20

30

40

50

60

Two box

Absorbtion

Engine Speed(rpm)

Pow

er(k

W)

Documents

EXPERIMENT AND ANALYSIS OF MOTORCYCLE EXHAUST DESIGN … · and this result can be applied to student formula race. viii ... 2.2 Exhaust Design for Engine Scavenging Performance 5