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Development of cost effective smart engine management system for two wheeler application.

ABSTRACT

The air pollution is increasing at an alarming rate now a day mainly due to emissions coming out of automotive vehicles. The exhaust emissions gases are hazardous to human health. The increased number of vehicles on road will make the scenario even worse. In order to control the pollution level, the regulatory bodies are now implementing stringent emission norms. In India, the regulatory authorities has framed the transition of BS IV to BS VI emission norms in 2020 by skipping the BS V emission norms which makes the automotive industries to work on more advanced fuel management technologies. It is more tedious to control the tail pipe emissions beyond BS IV emission norms with the conventional carburetor system since it is operating on open loop system. It is evident that in order to meet the stringent emission norms we need to have a closed loop system which controls the Air Fuel Ratio (AFR) close to stoichiometric to increase the conversion efficiency of the catalytic converter. The vehicle with fuel injection system can able to work on closed loop system, but the fuel injection system is not cost effective.

This paper illustrates the development of a cost effective smart engine management system for two wheeler application to meet the upcoming emission norms with some modification from the conventional carburetor system. Instead of controlling the fuel flow to keep the AFR close to the stoichiometric as in fuel injection system, the smart engine management system has a sophisticated air control mechanism to make the AFR close to stoichiometric. The carburetor was modified to incorporate an air control solenoid which is operated on the pulse width modulation to vary the air flow according to our requirement. The lambda sensor measures the AFR from the exhaust pipe and provides information to the ECU.

Based on the feedback from the lambda sensor, TPS, CPS, etc., the ECU maintains the AFR stoichiometric by controlling the flow through the air control solenoid with varying duty cycles. The vehicle performance test was carried out with vehicle having smart engine management system (Electronic carburetor) and also with fuel injection equipped vehicle on the chassis dynamometer. The test results show that the air fuel ratio of the electronic carburetor vehicle was maintained close to stoichiometric as in fuel injection vehicle which in turn reduce the emission to a considerable extent. Hence the smart engine management system caters a new way for an efficient low cost fuel management system.

Keywords: Engine Management System, Electronic carburetion, Fuel injection comparison, Low cost smart fuel management system, Experimental validation

CITATION: Sakthivel, B., Sridhar, R., Ansh, S., Srinivasan, B. et al., "Development of Cost Effective Smart Engine Management System for Two Wheeler Application," SAE Int. J. Engines 10(1):2017

INTRODUCTION

In countries like India and China, two-wheelers are mainly used for personal transportations not as a recreational tool as used in other advanced countries. Indian two wheeler industry is aligning to current requirements and designed vehicles which are lean burn with high fuel efficiency. This is being supported by the carburetor industry to tune the carburetor for the single cylinder engine to meet the required emission norms without sacrificing the fuel efficiency and driveability To meet upcoming stringent emission norms without sacrificing the customer requirements such as low price, performance, high fuel economy, etc., the automobile manufacturers are now changing the conventional technology from all the parts of two wheeler. One of the most common changes is the fuel management system.

In India, the total domestic two wheeler market last fiscal, is approximately 15 million units. Most of them are running on carburetor-fed engines. The age of old carburetors are slowly getting replaced by the newer fuel injection system.

The functionality of the fuel injection system and carburetor is basically air fuel mixture management. The carburetor is a mechanical device which mixes air and fuel in a predetermined ratio by mechanical parts. On the other hand in a fuel injection system, the ratio of air to fuel that is to be mixed is determined according to the environmental and operating condition, with the help of an electronic control unit and injected at the intake system by a fuel injector [1].

The main disadvantage of the fuel injection technology is the overall cost of the system which in turn increases the cost of the final product. On the other hand, the conventional carburetor is much cheaper than the fuel injection system but they cannot meet the upcoming stringent technical requirements. Hence, this cost and technology trade off trend leads to a development of cost effective smart engine management system which will meet the stringent technical requirement as well as the lower cost requirement.

CURRENT SCENARIO

The conventional mechanical carburetor works on the principle of constant depression at the venturi region to deliver the required amount of air fuel mixture at the upstream of the engine induction system. The air fuel mixture delivered to the engine from the carburetor depends on the loading conditions. i.e., throttle opening and engine RPM. The conventional carburetor is normally tuned with rich air fuel mixture in the idling and low end throttle load to increase the stability of the engine in order to overcome the charge dilution problem. The cruising condition is tuned with leaner mixture to increase fuel economy, since the lean mixture is enough to run the engine optimally. The AFR is tuned richer again at the rated power condition to achieve maximum power [2]. Typical AFR curve for conventional carburetor at various loading conditions is depicted in Fig.1.

The carburetor system is easy to operate, cheap to replace, quick servicing and finally at a lower cost. The main drawback of the carburetor system is the varying air fuel mixture.

FUTURE TRENDS

Nowadays, all over the world the governments are imposing stringent emission norms which push the OEM to select a fuel management system which will meet emission norms as well as customer requirements. In India, the new emission norms which are expected by 2020 are very stringent than current emission norms. So that the existing power train system in a two wheeler will not be able to meet BS VI emission with open loop system. (without feedback).

Future technology definitely require a closed loop control mechanism in which air fuel ratio fed to the engine can be maintained closer to stoichiometric ratio [3]. Every engine requires air fuel ratio at 14.7:1 for chemically complete combustion to take place. This also enhances the catalytic converter for its best conversion efficiency. Fig.2. shows the catalytic converter conversion efficiency for various AFR range. Maintaining the AFR to stoichiometric ratio is possible only through a closed loop control of air fuel system.

Fig.3. shows the typical AFR trend for the upcoming advanced fuel management system for various throttle load conditions. The closed loop control system to maintain the AFR close to stoichiometric can be possible by two advanced fuel management technologies .i.e., Fuel injection system and Electronic carburettor system, which is described in this paper.

FUEL INJECTION SYSTEM

The fuel injection system consist a number of components which are used to control the air fuel mixture such as ECU, sensors, fuel pump, throttle body and injector. There are multiple sensors available with the fuel injection system to find the engine rpm, engine temperature, intake air temperature, throttle position, manifold pressure and piston position. These inputs are fed into ECU to evaluate engine operating condition. Then the quantity of fuel to be injected is determined by the ECU.

The required amount of the fuel is injected into the induction system of the engine by a fuel injector. The fuel pump delivers a high pressure fuel to fuel injector prior to injection. The throttle body which replaces the carburetor is the only mechanical part in the fuel injection system. Oxygen sensor is also adapted with system to evaluate the engine AFR by measuring the oxygen content of the exhaust gas.

The measured AFR is fed into ECU to apply the correction in the amount of fuel delivery to the engine, which is necessary to maintain the AFR at stoichiometric ratio [4]. Fig.4. shows the Schematic block diagram of Fuel injection system

ELECTRONIC CARBURETOR SYSTEM

The electronic carburetor system consists of an air control solenoid integrated into the constant depression carburetor system instead of variable depression carburetor as in earlier electronic carburetor system [5]. The electronic carburetor system also consists of electronic control unit and various sensors. Electronic carburetor delivers a proper air fuel mixture depending on operating condition such as starting, cruising, acceleration, deceleration and full load. In this electronic carburetor system, sensors, ECU is used to maintain air fuel ratio at stoichiometric by control the secondary air supply through air control solenoid. The oxygen sensor placed at exhaust pipe measures the engine AFR which is fed into ECU. Based on the feedback from the oxygen sensor, ECU controls the flow rate of air through the engine intake system with the help of air control solenoid to maintain stoichiometric air fuel ratio [6]. In electronic carburetor system, in addition to controlling of the air fuel mixture as in earlier electronic carburetor system, the ignition is also controlled based on the varying engine operating conditions to meet future technical requirements in terms of driveability, emission performance, etc., Fig.5. shows the schematic block diagram of current electronic carburetor system.

The number of components i.e., the sensors and actuators used to control the air fuel ratio stoichiometric in both electronic carburetor and fuel injection technology is compared and listed in the Table.1.

VEHICLE TESTING

The vehicle testing with both the fuel systems to evaluate the vehicle performance on various operating conditions such as road load test, wide open throttle test, cold startability, drive cycle, driveability test and idle sweep test. Table. 2 show the engine specification that is used for the vehicle testing.

Before starting the vehicle testing, the necessary precautions must be taken as done for chassis testing.. The engine oil level, tyre pressure, chassis dynamometer friction and coast down values, wiring harness tapping points, battery voltage must be checked prior to the commence of the actual vehicle test. During the test, the engine oil temperature should be monitored to ensure proper testing conditions.

VEHICLE TEST RESULTS AND DISCUSSIONS

The vehicle test setup in chassis dyno is shown in Fig.6. Table.3 show the list of equipments used for the planned tests. After the vehicle performance test, the collected performance data are processed with post processing data analyzing tool (AVL concerto). The various findings from the comparison of electronic carburetor and fuel injection vehicle performance data are described in following sections.

Road Load Test

Normally road load test is conducted to assess the steady state performance of the vehicle at different speed under road load condition. The road load test has been carried out on both fuel management systems i.e. fuel injection and electronic carburetor. In both the fuel systems, the road load air fuel ratio is maintained at stoichiometric ratio up to 90 kmph. Fig.7. shows road load characteristics - AFR traces for both fuel injection and electronic carburetor system.

The road load points are matched with each other and the CO and C[O.sub.2] of corresponding road load points for both fuel injection and electronic carburetor is shown in Fig.8.

Wide Open Throttle Test (WOT)

The wide open test is to assess the vehicle performance at different speed and full throttle open condition. The wide open points are tuned for best power AFR for both the fuel systems. During full throttle condition, AFR is maintained at rich side to achieve maximum power and to avoid engine temperature rising. Fig.9 shows WOT characteristics - AFR traces for both fuel injection and electronic carburetor system

WOT power curve for both fuel injection and electronic carburettor system is shown Fig.10. From the test result, it is evident that the power curve of electronic carburetor vehicle matches with fuel injector vehicle except at higher engine speed as there is a slight power drop on the electronic carburetor vehicle as compared to fuel injection vehicle

Idle Sweep Test

Idle sweep test is to find out stability of engine speed from low to high temperature of engine oil. Normally in carburetor, the stability of engine speed is poor at low level of engine oil temperature as well as low idle engine speed. At high engine oil temperature, carburetor vehicle engine speed is high and idle fuel consumption is high. In fuel injection system, the vehicle engine speed and AFR are maintained at narrow band throughout engine oil temperature variation. Fig.11 shows idle stability of fuel injection vehicle.

In electronic carburettor system, during idle condition the engine speed as well as the air fuel ratio is also maintained at narrow band with good engine speed stability throughout engine oil temperature variations similar to fuel injection. Fig. 12 shows the idle stability of electronic carburetor vehicle.

Steady State Air Fuel Ratio Characteristics

The steady state air fuel ratio of fuel injection and electronic carburetor system is plotted for different engine speed and throttle opening. The air fuel ratio is maintained in stoichiometric ratio at cruising zone in both fuel injection and electronic carburetor fuel system. Also the air fuel ratio is maintained at richer side in both fuel injection and electronic carburetor system at high load zone to achieve maximum power and reduce engine temperature rising. Fig.13 and Fig.14 shows steady state AFR for fuel injection and electronic carburetor vehicle.

Steady State Engine Speed Characteristics

Figures.15 and 16 shows the standard deviation of engine speed stability for fuel injection and electronic carburettor vehicle at different engine speeds and different throttle position condition. Even though most of the operating regions are maintained with stoichiometric ratio based on the closed loop feedback from ECU, it is observed that the standard deviation of engine speed for Fuel Injection vehicle as well as electronic carburettor vehicle is not more than 20 rpm. Since the standard deviation of engine speed for Fuel Injection vehicle as well as Electronic carburettor vehicle is very low, both engine management systems provides better performance.

Drive Cycle Lambda (1 [+ or -] 0.05) Distribution

Both fuel injection and electronic carburetor system vehicles were driven on World Motorcycle Test Cycle (WMTC), class 2.2 that has part 1, part 2 drive pattern. Each part has 600 seconds cycle time, hence the vehicles were driven under the drive cycle for about 1200 seconds in total. The WMTC class 2.2 drive pattern has 11.33 % of time as idling period, 35 % of time as acceleration period, 31.17 % of time as deceleration period and 22.66 % of time as cruising period.

The fuel injection system has maintained lambda 1 [+ or -] 0.05 for 57 % of the entire drive cycle time, whereas the electronic carburetor system has also maintained 58 % of drive cycle time with in lambda 1 [+ or -] 0.05. Fig.17. and Fig.18. shows drive cycle lambda contribution in Fuel injection and Electronic carburettor vehicle.

Cold Startability Test

The cold startability test is normally carried out to analyze the performance of the vehicle under cold environment. The vehicle is soaked in the cold chamber at 0 [degrees]C for 8 hours. After soaking, the vehicle is connected with all the necessary sensors and instrument to capture performance at cold conditions. Fig.19. and Fig.20. shows the cold startability traces of the both fuel injection and electronic carburetor vehicle respectively. During the test, both fuel injection and electronic carburetor vehicle has taken one kick to start the vehicle with the choke on condition. After 50 seconds, the choke valve is released to measure the idle stability of the vehicle. The both fuel injection and electronic carburetor is having better idle stability.

Fuel Economy Test

Both fuel injection and electronic carburetor vehicles were driven on the chassis dynamometer under IDC and WMTC class 2.2 drive pattern to find out the fuel economy of the vehicle. The fuel consumption data is logged through the AVL fuel flow meter throughout test. From the results it is evident that the electronic carburetor is having slightly higher fuel economy than fuel injection vehicle. Fig.21. shows the comparison of fuel economy on both fuel injection and electronic carburetor vehicle respectively.

Fuel Economy comparison

                       E.Card  Fl

Drive Cycle  ID C      46.5    46
             WMTC 2-2  38.9    375

Fig.21. Fuel Economy Comparison between Fuel Injection and Electronic
Carburetor Vehicle

Note: Table made from bar graph.


Driveability Test

In addition to meeting the exhaust emission levels, driveability of the vehicle is also the critical factor for evaluating the vehicle performance. Both fuel injection and electronic carburetor vehicle is tested on road by the professional riders and the on road vehicle driveability feedback is recorded. The overall performance rating of the vehicle is depicted in spider web diagram as shown in Fig.22. and Fig.23. for electronic carburetor and fuel injection respectively. The test result shows that driveability performance of electronic carburetor vehicle is comparable with that of fuel injection vehicle. Also the driveability of electronic carburetor at city conditions is better than the fuel injection vehicle.

Mass Emission Test

The mass emission test was carried out on the chassis dynamometer setup as per the EURO IV emission norms and regulations (WMTC Class 2.1) for three different fuel management systems. The vehicle was modified to suit three different fuel system viz., mechanical carburetor, electronic carburetor and electronic fuel injection system for emission measurement. The three way catalytic convertor is used for emission measurement of electronic carburetor fuel system and electronic fuel injection system individually, while the mechanical carburetor fuel system is accompanied by the two way catalytic convertor and air suction valve. The emission values are tabulated against the EURO IV norms considering deterioration factor as shown in Table.4.

CONCLUSION

1. The electronic carburetor vehicle and fuel injection vehicle is taken for comparison of vehicle performance analysis on chassis dynamometer setup.

2. Based on the post processing and data analysis, it is evident that the electronic carburetor vehicle matches with performance of electronic fuel injection vehicle in terms of Road load test, Wide open throttle test, Cold startability, Drive cycle, Driveability test, Idle sweep test and fuel economy.

3. The Mass Emission test results show that both electronic carburetor system and fuel injection system meets the EURO IV emission target values. Also, the emission performance of the electronic carburettor system matches with the Electronic fuel injection system. Hence both fuel management systems meet the future technical requirements.

4. Even though both fuel management technologies cater the technical needs, the over all cost of the technology is a major concern.

5. The cost of the electronic carburetor is comparatively lesser than that of fuel injection system. This is mainly because of number of components in the electronic carburetor system is lower than the fuel injection system. The change over from convention fuel management system to closed loop fuel injection system leads to larger vehicle modification. On the other hand, the electronic carburetor system requires very minimal modifications which in turn reduce the cost of overall vehicle.

6. The serviceability of the electronic carburetor is easier than fuel injection vehicle and also replacement cost of the electronic carburetor system is low.

7. Since the electronic carburetor technology can meet the future technical requirements at a lower cost as compared to the fuel injection technology, the electronic carburetor cater a new way for cost effective smart engine management system for two wheeler applications.

FURTHER WORK TO BE DONE

Based on this encouraging result, in order to work further to meet BS VI regulations, currently we are discussing with OEM's to have a joint program with this concept. In order to make this system capable to meet BS VI emission regulation, certain modifications are necessary in the engine especially to meet HC emissions. Similarly optimization of exhaust and catalyst system is also necessary. In addition to this, work is under progress at various measurement agencies to measure the nmHC emissions. We are co-coordinating with our OEM's to address the above requirements to prepare this low cost system to meet future BS VI emission regulations. Also the Electronic carburettor system has the capability of incorporating the On Board Diagnostics for future requirements.

REFERENCES

[1.] Heywood, J. B., Internal Combustion Engine Fundamentals, International Edition, Pub: McGraw Hill, 1988.

[2.] Arun, G., Ramesh, C., Elayaraja, R., Sureshkumar, J. et al., "Improvement of Part Throttle Performance of Carburetor Used in a Two Wheeler Four Stroke Single Cylinder Engine," SAE Technical Paper 2011-28-0004, 2011, doi:10.4271/2011-28-0004.

[3.] Govindarajan, S., "Technology Options for Control of Emissions in Two Wheelers," SAE Technical Paper 2001-28-0043, 2001, doi:10.4271/2001-28-0043.

[4.] Shankar, R., Udayakumar, G., and Sasikumar, K., "Advanced Port Injection Solution for Motorcycle Application," SAE Technical Paper 2008-28-0031, 2008, doi:10.4271/2008-28-0031.

[5.] Mudgal, R., Marathe, M., Karle, U., Babu, K. et al., "Development of Electronic Feedback Carburettor to Meet Year 2000 Indian Emission Norms," SAE Technical Paper 990034, 1999, doi:10.4271/990034.

[6.] Sundar, D., VenuMadhav, S., Srinivasan, B., Govindarajan, S. et al., "Electronic Control of Air/Fuel Ratios in a carburettor for 2-Wheeler Application," SAE Technical Paper 2008-28-0057, 2008, doi:10.4271/2008-28-0057.

CONTACT INFORMATION

B.Sakthivel

Engineer - Research and Development

M/S Ucal Fuel Systems Ltd

Tel: +91 044 665 44 746

sakthivelprasath@gmail.com

W.Subin Ansh

Engineer - Research and Development

M/S Ucal Fuel Systems Ltd

Tel: +91 044 665 44 718

gr8cl@ucalfuel.co.in

R.Sridhar

D.G.M - Research and Development

M/S Ucal Fuel Systems Ltd

Tel: +91 044 665 44 724

sridhar@ucalfuel.co.in

Dr. J.Suresh Kumar

D.G.M - Research and Development

M/S Ucal Fuel Systems Ltd

Tel: +91 044 665 44 707

jskumar@ucalfuel.co.in

B.Srinivasan

G.M - Research and Development

M/S Ucal Fuel Systems Ltd

Tel: +91 044 665 44 705

bsrini@ucalfuel.co.in

ACKNOWLEDGMENTS

The authors would like to thank the management of M/S UCAL Fuel Systems Ltd., for granting permission to carrying out the experiments and publish this paper.

DEFINITIONS / ABBREVIATIONS

AFR - Air Fuel Ratio

ECU - Electronic Control Unit

WMTC - World Motorcycle Test Cycle

IDC - Indian Driving Cycle

OEM - Original Equipment Manufacturer

CPS - Crank Position Sensor

TPS - Throttle Position Sensor

EOT - Engine Oil Temperature

IAT - Intake Air Temperature

MAP - Manifold Absolute Pressure

CO - Carbon monoxide

C[O.sub.2] - Carbon dioxide

ECARB - Electronic Carburetor

EFI - Electronic Fuel injection

B Sakthivel, R Sridhar, Subin Ansh, B Srinivasan, and J Suresh Kumar

UCAL Fuel Systems, Ltd.

Table 1. Comparison of components for Electronic Carburetor versus Fuel
injection system

DESCRIPTION  ELECTRONIC CARBURETOR  FUEL INJECTION

             CPS                    CPS
Sensors      TPS                    TPS
             EOT                    EOT
             Lambda Sensor          Lambda
                                    Sensor
                                    IAT
                                    MAP
             Ignition Coil          Ignition Coil
Actuators    Solenoid               Fuel Injector
                                    Fuel Pump
                                    Throttle Body
             Carburetor             Intake
Others       ECU                    Manifold
                                    ECU

Table 2. Engine specifications

Displacement        346 [cm.sup.3]
Stroke              90 mm
Bore                70 mm
Compression ratio   8.5:1
Number of Cylinder   1
Number of valves     2
Engine Stroke       Four Stroke
Spark Plug           2
Maximum Power       14.5 KW @ 5250 rpm
Maximum Torque      28Nm @ 4000 rpm
No. of Gears         5
Cooling             Air Cooling
Lubrication         Wet Sump

Table 3. List of equipments

S.NO  EQUIPMENTS

 1    Chassis Dynamometer
 2    Engine Dynamometer
 3    ETAS Lambda meter
 4    Horiba Portable Raw Emission Analyzer
 5    Onosoki RPM Indicator
 6    Scopecorder
 7    AVL Fuel meter
 8    Cold Chamber
 9    Thermocouple Temperature Sensors
10    CAN module

Table 4. Mass Emission Values

Description                                       CO,    HC,    NOx,
                                                  g/km   g/km   g/km

EURO IV Norms                                     1.14   0.38   0.07
Limit with Deterioration factor                   0.876  0.316  0.058
Mechanical carburetor system emission values      2.576  0.500  0.027
Electronic carburetor system emission values      0.582  0.198  0.038
Electronic Fuel Injection system emission values  0.516  0.147  0.034
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Author:Sakthivel, B.; Sridhar, R.; Ansh, Subin; Srinivasan, B.; Kumar, J. Suresh
Publication:SAE International Journal of Engines
Article Type:Report
Date:Feb 1, 2017
Words:3995
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