pcd eng abstract may 28infofile.pcd.go.th/air/twostroke_excutiveeng.pdf · pcd 03-083 volume 2/3...

PCD 03-083 Volume 2/3

ISBN 978-974-286-216-9

Executive Summary

The Study on the Possibility of Replacing Two-Stroke Engines with Four-Stroke Engines and Installing Silencers in Tuk Tuk Vehicles

Pollution Control Department King Mongkut’s Institute Ministry of Natural Resources and Environment of Technology Ladkrabang

Air Quality and Noise Management Bureau PCD 03-083 Volume 2/3 Pollution Control Department May 2007 Ministry of Natural Resources and Environment ISBN 978-974-286-216-9 92 ,Phahon Yothin 7, Phahon Yothin Road, Sam Sen Nai, Phayathai District, Bangkok 10400 TEL. 02-298-2349-50 FAX. 02-298-2357 http://www.pcd.go.th Executive Summary Report The study on the Possibility of Replacing Two-Stroke Engines with Four-Stroke Engines and Installing Silencers in Tuk Tuk Vehicles Prepared by : Asst.Prof.Dr. Chinda Charoenphonphanich (Project advisor), Asst.Prof.Dr. Monsak Pimsarn and Asst.Prof. Pongsak Kummul Automotive Technology Laboratory, Department of Mechanical Engineering King Mongkut’s Institute of Technology Ladkrabang, Bangkok 10520 TEL.02-326-4197 FAX. 02-326-4198 E-mail: [email protected]

Copyright : Pollution Control Department.

Ministry of Natural Resources and Environment.

Abstract

The objective of this project is to replace two-stroke engines with four-stroke engines and install silencers in Tuk Tuk vehicles. Five Tuk Tuk vehicles were selected for performance and emissions testing in the automotive emission laboratory of Pollution Control Department and performing urban road test in Bangkok area. New and used four-stroke engines were installed in the sample Tuk Tuk vehicles. Experimentations were conducted to compare emission & performance before and after replacing two-stroke engines by four-stroke engines. Noise measurement at an exhaust pipe was measured to evaluate silencers’ efficiency. In order to install the four-stroke engine into the original frame of two-stroke engine Tuk Tuk vehicle, some of the four-stroke engine components were modified. The test results have shown that the four-stroke engine provides higher performance, lower fuel consumption and lower emissions except NOx. Moreover, according to the cost-benefit studies, it is found that the drivers’ profit can be increased up to 1,539 baht per month if the two-stroke engine is replaced by the four-stroke engine in Tuk Tuk vehicles.

Executive Summary “Study of Possibility of Replacing 2 Stroke Engines by 4 Stroke Engines and Installing Silencers in Tuk Tuk Vehicles”

Pollution Control Department by Asst.Prof.Dr. Chinda Charoenphonphanich (King Mongkut’s Institute of Technology Ladkrabang) i

Contents The study on the Possibility of Replacing Two-Stroke Engines with Four-Stroke

Engines and Installing Silencers in Tuk Tuk Vehicles

Page Contents i

List of Tables ii

List of Figures ii

1. Background of Tuk Tuk vehicles 1

1.1 Tuk Tuk vehicles in Bangkok

1.2 Silencer and sound level

1.3 Tuk Tuk vehicle related regulations

2.. Prototype four-stroke engine Tuk Tuk vehicles and an efficient silencer 2

2.1 Selection of sample Tuk Tuk vehicles

2.2 Selection of four-stroke engine

2.3 Selection of silencer

3. Installation of four-stroke engine and silencer in Tuk Tuk vehicles 4

3.1 Modification and installation of Suzuki engine

3.2 Modification and installation of Monika engine

3.3 Tuk Tuk frame strength analysis

4. Results of laboratory test 7

5. Study of silencers 8

6. Results of road test in Bangkok 9

6.1 Maintenance cost for two-stroke engine

6.2 Maintenance cost for four-stroke engine

6.3 Interview of the driver and owner opinion of using four-stroke engine

7. The cost-benefit studies 10

8. Conclusions 11


Pollution Control Department by Asst.Prof.Dr. Chinda Charoenphonphanich (King Mongkut’s Institute of Technology Ladkrabang) ii

List of Tables

Page Table 1 : Calculated results of frame strength 7 Table 2 : Emissions and fuel consumption of two-stroke and four-stroke

engine Tuk Tuk vehicles 7 Table 3 : Sound level of two-stroke and four-stroke engine Tuk Tuk vehicles 8 Table 4 : Road test data of two-stroke and four-stroke engine Tuk Tuk

vehicles (average) 9 Table 5 : Cost comparison between two-stroke and four-stroke engine

Tuk Tuk vehicles 10

List of Figures

Page Figure 1 : Installation of the two-stroke engine in a Tuk Tuk vehicle 1 Figure 2 : Auto lube oil tank of the two-stroke engine in a Tuk Tuk vehicle 1 Figure 3 : A sample of short-type silencer and modified exhaust pipe 2 Figure 4 : 650 cc two-cylinder engine of Monika Motor Company 3 Figure 5 : Suzuki F6A 660 cc three-cylinders of Suzuki Motor Company 3 Figure 6 :Long straight type silencer of Somchai header 4 Figure 7 : Cross-section picture of the silencer 4 Figure 8 : Suzuki four-stroke engine before and after modification 5 Figure 9 : Installation of Suzuki engine on the conventional frame of

Tuk Tuk vehicle 5 Figure 10 : Monika four-stroke engine before and after modification 6 Figure 11 : Installation of Monika engine on the frame of Tuk Tuk vehicle 6 Figure 12 : Long and short straight silencer 8 Figure 13 : Reverse (upper) and straight silencer 8


Pollution Control Department by Asst.Prof.Dr. Chinda Charoenphonphanich (King Mongkut’s Institute of Technology Ladkrabang) 1

1. Background of Tuk Tuk vehicles 1.1 Tuk Tuk Vehicles in Bangkok

According to the information from Land Transport Department, there are 7,365 Tuk Tuk vehicles in Bangkok in 2006. Most of them (83%) are belonging to the Tuk-Tuk cooperative venture, and the rest of them (17%) is privately owned. Most of Tuk Tuk vehicles (more than 96%) use LPG as a fuel. The two-stroke engines installed in Tuk Tuk vehicles are DAIHATSU 305 and 356 cc, approximately 68%, HINO 300 and 356 cc(12%) and the others(20%). In order to install these engines into the original Tuk Tuk frame, relatively narrow, the engines must be partly modified. The life span of these two-stroke engines is between about 6 months and 2 years depending on the operating conditions. One disadvantage of the two-stroke engine is the need of two-stroke engine oil. This two-stroke engine oil is called “Auto lube” by Thai people. The auto lube is the main expense for two-stroke engines maintenance. Figure 1 shows the installation of the two stroke engine in a Tuk Tuk vehicle. Figure 2 shows an auto lube oil supply tank for feeding auto lube oil into the engine.

Figure 1. Installation of the two-stroke engine in a Tuk Tuk vehicle

Figure 2. Auto lube oil tank of the two-stroke engine in a Tuk Tuk vehicle

2 Stroke Auto Lube Oil Tank



1.2 Silencer and sound level Silencers used in Tuk Tuk vehicles typically either an owner-made silencer or a

commercial silencer. The commercial one is Somchai Header silencer. There are two types of Somchai Header silencers, long and short types. The price of a typical silencer is approximately 300 baht. Some Tuk Tuk drivers modified the exhaust pipe for their favourite sound. Additionally, they always feel that, if the higher sound level, the engine has more power. Figure 3 shows an example of the modified silencer. In fact, most of Tuk Tuk owners or drivers have already known how to reduce the sound level. However, most of them deny to do so because they believe that by using the quiet silencer, the engine power is decreased.

Figure 3. A sample of short-type silencer and modified exhaust pipe

1.3 Tuk Tuk vehicle related regulations The Tuk Tuk regulation declared by Department of Land Transport on January 6th, 2006 states that “Public Tuk Tuk vehicles must have one or two row of passenger seat with roof cover. Outside dimensions of Tuk Tuk vehicle must not be larger than 1.5 x 4 x 2 m. (Width x Length x Height) and internal height must be higher than 1.2 m. The engine total capacity must not be exceeding 660 cc.” 2. Prototype four-stroke engine Tuk Tuk vehicles and an efficient silencer 2.1 Selection of sample Tuk Tuk vehicles

In this project, five Tuk Tuk vehicles were selected for testing. Two of them were bought by Pollution Control Department and the rest were rented. The sample Tuk Tuk vehicles must be a good representation of the real Tuk Tuk vehicles in the market. 2.2 Selection of four-stroke engine

The four-stroke engines used in this project are composed of one new engine and three used engines. The selected engines are based on possibility of practical use, ease of installation with the original Tuk Tuk frame, having less



effect to drivers, reasonable price and low emissions. In this study, the engines were selected as follows.

1) New engine: 650 cc two-cylinder engine with water cooling, Monika Motor Company.

Reason to select: A new four-stroke engine will most likely be the engine imported from China. Because Japanese engine maker companies do not usually sell only the engine. Presently, there are only two suppliers of new engine. Those are Monika Motor Company and Tiger Motor Sales Company. There are only two choices, 150 cc engine by Tiger motor sales company and 650 cc engine by Monika motor company. The 150 cc engine has been installed in the Tuk Tuk vehicle but its power is not adequate. The 650 cc engine by Monika provides more than 8 kW which is higher than the 2 stroke engine in conventional Tuk Tuk vehicles. The price of this engine is 40,000-45,000 baht. This engine is shown in Figure 4.

Figure 4. 650 cc two-cylinder engine of Monika Motor Company

2) Used engine : Suzuki F6A 660 cc three-cylinder engine with water

cooling, Suzuki Motor Company. Reson to select: Plenty of these engines are available on the market. Engine power is about 16 kW which is enough for Tuk Tuk vehicles. The engine’s dimension is not large. Therefore, this engine can easily be installed in Tuk Tuk vehicles with little chassis modification. The price of this engine is between 8,000 to 10,000 baht. This kind of engine is shown in figure 5.

Figure 5. Suzuki F6A 660 cc three-cylinders of Suzuki Motor Company



2.3 Selection of silencer There are not many types of Tuk Tuk silencer available in the market. All of

them are from one maker, Somchai Header. From the test results, the long straight type of Somchai Header silencer efficiently reduces the noise from exhaust pipe. It can reduce the sound level of one sample Tuk Tuk vehicle from 100 dBA to 86 dBA. Figure 6 shows the picture of this silencer. The material used for this silencer is steel pipe filled up with fiber glass. The inside of steel pipe has many small holes to allow the sound to be absorbed by fiber glass. The cross-section picture of the silencer is shown in Figure 7. However, there are short and long types of silencer that are popularly used. The length of the silencer of long type and short type is 40 cm. and 17.5 cm., respectively.

Figure 6. Long straight type silencer of Somchai header

Figure 7. Cross-section picture of the silencer

3. Installation of four-stroke engine and silencer in Tuk Tuk vehicles In this study, the frame of conventional Tuk Tuk vehicle was not altered. Instead, the engine was modified. This is due to that any modification of the Tuk Tuk frame is much more difficult and expensive. The original engine is too big to be installed in the original frame, quite narrow. The engine modification is done to make the engine small enough to put into the original Tuk Tuk frame.



3.1 Modification and installation of Suzuki engine The used Suzuki engine was modified as follow.

1. Modifying intake port 2. Modifying exhaust port 3. Repositioning the alternator 4. Resizing of engine oil pan 5. Rotating the transmission

Figure 8 shows the engine before and after modification. After the modification, the engine was mounted into the original frame as shown in Figure 9.

(a) Conventional engine (b) Modified engine Figure 8. Suzuki four-stroke engine before and after modification

Figure 9. Installation of Suzuki engine on the conventional frame of Tuk Tuk

vehicle



3.2 Modification and installation of Monika engine The Monika engine was modified in the same way as done in the Suzuki

engine. Figure 10 shows engine before and after modification. Figure 11 shows how the engine is mounted on the Tuk Tuk frame.

(a) Conventional engine (b) Modified engine Figure 10. Monika four-stroke engine before and after modification

Figure 11. Installation of Monika engine on the frame of Tuk Tuk vehicle

3.3 Tuk Tuk frame strength analysis

To confirm the safety of four-stroke engine Tuk Tuk vehicles, the strength analysis of Tuk Tuk frame is needed. In the analysis, finite element method is employed to investigate stress distribution in the Tuk Tuk frame. In this study, the commercial finite element program, Unigraphics NX2, is adopted for the analysis. Three cases of analysis are performed.

1. Original frame 2. Original frame with some part cut ( 2 x 8 cm.) 3. Frame with 10 cm. extension in the width direction



Strength analysis by finite element method The analysis was done based on assumption of 1000 kg loading on the Tuk Tuk frame. The frame is under bending moment which is incurred by the weight of the engine and the passengers.

Results of the analysis

The Von-Misses stress of the Tuk Tuk frame must not exceed the material yield stress to avoid plastic deformation inside the frame. The obtained results indicate that the Von-Misses stresses of three cases are lower than the yield strength of the material (338 MPa) as shown in Table 1. That means that the four- stroke engines can be installed in the Tuk Tuk frame without any damage.

Table 1. Calculated results of frame strength

Cases Max. Von-Mises Stress (MPa)

Original frame 88.95 Frame with small cut for engine installation 175.09 Modified frame with 10 cm. expansion 88.55 * Calculated yield stress of the Tuk Tuk frame material is 338 MPa 4. Results of laboratory test

Five Tuk Tuk vehicles were tested in the Automotive Emission laboratory of Pollution Control Department. Table 2 shows the comparison of emissions and fuel consumption of two-stroke and four-stroke engine. The results show that CO and HC emissions of four-stroke engine are lower in overall, especially, at constant speed 40 and 60 km/h. On the other hand, NOx emission of four-stroke engine is higher due to more complete combustion and higher temperature of combustion.

Fuel consumption of four-stroke engine is approximately the same as two-stroke engine in overall. But at constant speed of 40 and 60 km/h, the four-stroke engine provides lower fuel consumption. This may caused by the larger capacity of four-stroke engine. In case of using smaller engine, such as 250-350 cc of four-stroke engine, the fuel consumption should be better.

Table 2. Emissions and fuel consumption of two-stroke and four-stroke engine Tuk Tuk vehicles

Emissions/Fuel Consumption

Bkk driving cycle (average

19 km/h)

Overall driving cycle (average 34.55

km/h)

Constant speed 40

km/h

Constant speed 60

km/h

Engine type 2 stroke

4 stroke

2 stroke

4 stroke

2 stroke

4 stroke

2 stroke

4 stroke

THC (g/km) 10.88 3.47 5.51 1.28 4.42 0.56 3.66 0.41 NOx (g/km) 0.14 1.68 0.08 1.30 0.04 0.35 0.07 1.70 CO (g/km) 5.93 8.42 4.58 4.31 2.50 1.33 5.14 3.75 CO2 (g/km) 92.21 126.90 68.59 84.81 52.39 62.54 64.73 73.51 Fuel Consumption (km/l) 12.20 10.86 17.54 17.11 23.56 24.53 19.56 20.33



5. Study of silencer In this study, three types of silencers were examined to investigate its effect

on sound level and engine performance. Figure 12 and 13 show the sample of silencers consisting of long straight type, short straight type and reverse type.

Figure 12. Long and short straight silencer Figure 13. Reverse (upper) and

straight silencer Table 3. shows the sound level results. The sound level was reduced to 90

dBA for both two-stroke and four-stroke engine when using long straight type of silencer. The return type is also available for four-stroke engine without the need of fiber glass replacement.

Table 3. Sound level of two-stroke and four-stroke engine Tuk Tuk vehicles

Tuk Tuk vehicle data

Stroke

Sound level (dB A) No. Engine

(Maker) Capacity

(cc) 2 4 License Plate

Number 1 2 Silencer

1 DAIHATSU 356 สก–951 Samutprakan 86 87 Long Straight 2 DAIHATSU 356 สก-6022 Bangkok 87 88 Long Straight 3 DAIHATSU 356 สก-5527 Bangkok 96.3 96.6 Short Straight

100.4 100.6 Short Straight 4 DAIHATSU 356 สก-12 Bangkok

86 86.1 Long Straight 94 93 Short Straight 89 88 Long Straight 5 DAIHATSU 356 สก-3850 Bangkok 96 97 Reverse

6 SUZUKI 660 ย-0661 Samutprakan 85.2 85.4 Long Straight 7 SUZUKI 660 สก-5316 Bangkok 82.2 81.3 Long Straight 8 SUZUKI 660 สก-5320 Bangkok 78 79 Double Silencer

83.7 83.4 Return 9 SUZUKI 660 สก-31 Bangkok

79.9 80.8 Long Straight 10 MONIKA 650 สก–951 Samutprakan 86 86 Long Straight



From the engine performance and emissions test results, the engine power, fuel consumption and emissions, in case of using the long straight type of silencer, are not significantly changed. These results are opposite to general perception of Tuk Tuk drivers. The results are identical for both two-stroke and four-stroke engines. 6. Results of road test in Bangkok

Before and after installation of four-stroke engine, the Tuk Tuk vehicles were tested on the road in Bangkok for at least 7 days. The collected data are the driving distance, hours, route, fuel consumption and cost of maintenance. The summary of road test results is shown in Table 4.

Table 4. Road test data of two-stroke and four-stroke engine Tuk Tuk vehicles

(average) Fuel consumption (km/l) Fuel cost (baht/km)

Two-stroke engine

Four-stroke engine

Two-stroke engine

Four-stroke engine

9.14 10.26 1.12 1.00 * Note* Caculation is based on price of LPG 9.75 baht per litre on March 8, 2007

As the results, the fuel consumption of four-stroke engine is about 12% lower than that of two-stroke engine. However, this factor is highly depended on the condition of Tuk Tuk vehicles. These results are slightly different to the laboratory test results. The difference may come from the neglecting of effect of auto lube oil (two-stroke engine oil) on the calculation of fuel consumption. 6.1 Maintenance cost for two-stroke engine

The major cost of maintenance for two-stroke engine is from auto lube oil. The auto lube oil burns with the fuel in the engine. Thus, the consumption of auto lube oil is higher than that of the four-stroke engine oil. The cost of normal auto lube oil is about 8,500 baht per 200 liter. The low smoke auto lube costs 11,000 baht per 200 liter. The auto lube oil consumption is 382 cc per 100 km. The Tuk Tuk vehicle owner has to pay 16.24 baht per 100 kilometer. The costs of spare part are 3,000-4,000 baht for a crank shaft set and 1,000 baht for a piston set. The overhaul cost is 5,000-6,000 baht. The lifespan of the engine is between 6 months to 2 years. 6.2 Maintenance cost for four-stroke engine

The four-stroke engine does not need to use auto lube oil. The engine oil costs 260 baht per 5,000 kilometer. Compared with the two-stroke engine, the cost of auto lube oil for 5,000 kilometer is 812 baht. A Tuk Tuk owner can save 812-260= 552 baht per 5,000 kilometer The costs of spare parts for the four-stroke are 3,000 baht for a crankshaft set, 1,000 baht for a piston set and 1,000 baht for a gasket set. Even though the overhaul process is more difficult, the four-stroke engine can be overhauled as done so in the two-stroke engine.



6.3 Interview of the driver and owner opinion of using four-stroke engine The interview was done by four drivers and one owner. The results were summarized as follow.

1. Engine power is better than conventional two-stroke engine. The disadvantage is only initial slow acceleration rate.

2. In term of fuel economy, the fuel consumption rate is seemed to be lower than two-stroke engine.

3. The noise of four-stroke engine is noticeably lower than that of the two-stroke engine.

4. The Tuk Tuk owner can save for auto lube oil cost. However, the differential gear and front shock absorber should be changed to match with the four-stroke engine. Because the four-stroke engine is heavier and it effects the drivability.

7. The cost-benefit studies

The assumptions for the cost-benefit study are 24 working hours or 200 km of driving per day, engine life is 1 year for two-stroke engine and two years for four- stroke engine and fuel consumption is based on the road test data that four-stroke engine consumed fuel 12% less than two-stroke engine. Table 5 shows cost comparison between two-stroke and four-stroke engine Tuk Tuk vehicles

Table 5. Cost comparison between two-stroke and four-stroke engine Tuk Tuk

vehicles

Two-stroke engine Four-stroke engine Items

Unit Cost (baht) Unit Cost (baht)

Used engine 1 unit 8,000 Engine 1 unit 12,000

New engine 1 unit 40,000

Installation expense 1 unit 2,000

Engine Modification

included differential

8,000

Engine oil (per day, 200 km)

380 cc per 100 km 32.50 3 litre per 5,000 km

and oil filter 5.2

Fuel 22.97 litre 224 20.51 litre 200

Case of replacing the expired engine with the used four-stroke engine

Initial cost is higher than installing the two-stroke engine but the break even will come on 39 days after the installation. After that the profit income increases 51.3 baht per day or 1,539 baht per month.



Case of replacing the expired engine with the new four- stroke engine In case of the new engine, the break even will come on 1 year and 23 days

and after that the owner will get more profit 1,539 baht per month. 8. Conclusions

Five Tuk Tuk vehicles were tested in the automotive emission laboratory of Pollution Control Department and on the roads. The four-stroke engines and efficient silencer were selected and installed in the Tuk Tuk vehicles. From the test results, it can be summarized as follow.

1. The new and used four-stroke engines can be installed into the conventional

Tuk Tuk vehicles without the need of extension of the frame. Therefore, the cost of Tuk Tuk frame reconstruction is not necessary.

2. Performance of four-stroke engine is good enough for conventional Tuk Tuk vehicle.

3. The CO and HC emissions of four-stroke engine Tuk Tuk vehicle is lower than the conventional one but NOx emissions is higher due to a more complete combustion.

4. The fuel consumption of four-stroke engine Tuk Tuk vehicle is lower at constant speed of 40 and 60 km/h but higher for city cycle. The road test results show 12% lower fuel consumption for 4 stroke engine.

5. The long straight type of silencer can efficiently reduce noise from exhaust pipe without any significant effects to the engine performance, fuel consumption and emissions.

6. From the cost-benefit studies, replacing a two stroke engine with a four-stroke engine is recommended, especially, for used engines. Although the initial cost of four-stroke engine is higher but the break even will take place in short period of time. After that, the owner is expected to get more profit, 1,539 baht per month.

Recommendations

The four-stroke engines selected for this study have relatively larger capacity (660 cc) compared to the two-stroke engine (356cc). Therefore, the engine power is more than that of the two-stroke engine. However, the fuel consumption of these four- stroke engines is approximately the same as the two-stroke engine, even bigger capacity. This is due to higher efficiency. In case of the lower fuel consumption, if necessary, the lower capacity of the four-stroke engine is recommended. The 250-350 cc of four-stroke engine is expected to provide enough engine power with much lower fuel consumption. If high engine power is not needed, 200 cc of engine is also a good choice. The fuel consumption and emissions are lower when using smaller capacity of an engine.

Due to more complete combustion, NOx emission from four-stroke engine is higher than that from the four-stroke engine. However, this emission can be reduced by using a catalytic converter.

pcd eng abstract may 28infofile.pcd.go.th/air/twostroke_excutiveeng.pdf · pcd 03-083 volume 2/3...

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