An overview of the Engine Control Unit (ECU) and its sensors for the Mitsubishi 4G93 Engine D.A. en! A.A. "ainul Abidin Dept. of Electrical Engineering, Universiti Tenaga Nasional, Malaysia #e$words% Engine Control Module; ECM, Engine Control Unit; Mitsubishi 4!" Engine; #uel $n%ector Duty Cycle. Abstra&t% Today&s auto'obile 'anufacturers strive to design auto'obiles that provide the best perfor'ance balanced against good efficiency. Efficiency has beco'e a central issue in the design of ne( engines because of the need to 'eet tighter environ'ental regulations and the de'and for fuel frugal auto'obiles by consu'ers. )t the heart of each auto'obile is the engine, (hich serves as the auto'obile&s po(er plant. Modern engines use soft(are loaded in the engine&s Engine Control Module *ECM+ to opti'i,e perfor'ance and efficiency of the engine. The ECM collects all sensor data, interprets and processes this data, and then sends out control signals necessary for the s'ooth and efficient operation of the engine. This paper (ill investigate ho( the ECM in the Mitsubishi 4!" engine receives infor'ation fro' the various sensors. )n overvie( of the sensors& operations is presented. #inally, this paper loo-s at ho( this infor'ation is used to control the firing of the sparplugs and the a'ount of fuel in%ected by varying the duty cycle of the fuel in%ectors. '.( )ntrodu&tion The auto'obile po(ered by the .tto petrol engine (as invented in er'any by /arl 0en, in 1223. 0en, (as granted a patent dated 4! 5anuary 1226 in Mannhei' for that auto'obile 7 1 8. 0y 1!1", 'ore than a 'illion cars and truc-s (ere racing across )'erica and Europe, and 'ost of the' ran on petrol or diesel 7 4 8. The -ey brea-through that led to the do'inance of the internal co'bustion engine *$CE+ (as that there (as co'pression prior to co'bustion. This not only increased the efficiency, but also yielded a 'uch higher po(er9to9(eight ratio than earlier co'pression9less engines such as the stea' engine. Today, the $CE is by far the 'ost co''on po(er source for the transport sector and (ill re'ain so; at least for the foreseeable future. :hile alternative and rene(able energy technologies are available today, their 'anufacturing costs, deploy'ent issues, and re;uired infrastructure re'ain stu'bling bloc-s to co'peting (ith the $CE. .f the <3= 'illion cars, truc-s, and other vehicles no( roa'ing the planet *and the nu'ber gro(s by 3= 'illion a year+ so'e != percent use oil > not because of so'e vast oil co'pany conspiracy, but because, by conventional 'easures, oil9fueled $CEs generate 'ore po(er, 'ore efficiency, 'ore value for the energy dollar, than any other fuel9technology pair 7 " 8. Nearly a century of continual refine'ent has created a staggeringly efficient
'achine 7 4 8. *.( +a&,ground of the )nternal Co-bustion Engine ()CE) )l'ost all $CEs currently use (hat is called a four9stro-e co'bustion cycle to convert petrol into 'otion. The four9 stro-e approach is also -no(n as the .tto cycle, in honor of Ni-olaus .tto, (ho invented it in 126< 7 3 8. They are? · $nta-e stro-e · Co'pression stro-e · Co'bustion stro-e · E@haust stro-e #igure 1? )n illustration of several -ey co'ponents in a typical four9stro-e engine 7 6 8 #igure 1 illustrates the positions and dyna'ics of the cran-shaft, piston, inta-e valve, e@haust valve, and a D.AC valvetrain configuration. The arro(s indicate the direction of 'ove'ent of these reciprocating co'ponents during the co'pression stro-e. The basic operation of a four9stro-e cycle has re'ained essentially the sa'e for al'ost 13= years. )dvances in 'anufacturing technology, 'etallurgy, 'icroprocessors, and an overall better understanding of the science behind $CE operation, has led to the develop'ent of 'ore co'ple@ designs that continue to refine the $CE. Modern $CEs have 'oved a(ay fro' the ca'9in9bloc- *or .AB+ syste's in favor of overhead ca'shaft *.AC+ valvetrain configurations. The carburetor, (hich is a device (hich 'i@es air and fuel 7 < 8 has been replaced (ith fuel in%ectors and in so'e cases a servo controlled butterfly valve for 'ore precise *and fle@ible+ control. Bariable Balve Ti'ing has been introduced by 'ost 'a%or auto'obile 'anufacturers to i'prove lo(9end tor;ue and high9end po(er. The Engine Control Module *ECM+ has evolved fro' si'ple analogue circuits, to hybrid digital design (ith a loo-9up table, and finally to 'icroprocessor based syste's (hich can process the inputs fro' the engine sensors in real ti'e 7 2 8. 3.( .verview of the Mitsubishi 4G93 Engine The Mitsubishi 4!" engine is a 1.2 liter double overhead ca'shaft *D.AC+ engine used as a po(er plant for cars li-e the Mitsubishi Cancer. ) double overhead ca'shaft *also called double overhead cam, dual overhead cam or twincam+ valvetrain layout is characteri,ed by t(o ca'shafts being located (ithin the cylinder head, (here there are separate ca'shafts for inlet and e@haust valves 7 ! 8. #igure 4? ) cylinder head sliced in half sho(s t(o overhead ca'shaftsDone above each of the t(o valves
7 1= 8. $t is a 4 cylinder inline engine that is available (ith either a turbocharger or as a nor'ally aspirated engine. $n order to control the a'ount of air and fuel 'i@ture the 4!" uses an Engine Control Module *ECM+. The engine uses 'ultipoint in%ection in delivering fuel to all the cylinders. This (ould 'ean that each cylinder (ill have one designated in%ector. The engine also uses an electronic distributor9less ignition syste' to provide firing in the co'bustion cha'bers. The sensors connected to the ECM are? · air flo( sensor · air inta-e te'perature sensor · inta-e9'anifold vacuu' or 'anifold absolute pressure *M)E+ sensor · engine coolant te'perature sensor · throttle position sensor · o@ygen sensor · Aall effect cran-shaft sensor · Aall effect ca'shaft sensor $n order to reali,e the decisions of the ECM into 'echanical or co'bustion for', the ECM (ill send its signals to t(o actuators (hich are? · spar- plugs · fuel in%ectors $n order for the engine to have co'plete co'bustion, the air9fuel 'i@ture 'ust be correct. The stoichio'etric ratio for air9fuel in a petrol engine is 14.
'easured. #or e@a'ple, if the te'perature is lo(, the air density (ill be high; therefore, 'ore air (ill enter the inta-e 'anifold. Ao(ever, if the pressure is high, the air density (ill also be high, thus 'ore air (ill enter the inta-e 'anifold. #igure "? The air9fuel 'i@ture ratio F(indo(G, (ithin (hich the air9fuel ratio 'ust re'ain if the three (ay catalytic converter is to (or- efficiently. *General Motors Corporation+ 7 11 8 To collect all this data the Mitsubishi 4!" engine has 'any sensors. These sensors collect data and feed the infor'ation to the ECM. The ECM co'putes in real9ti'e the correct a'ount of fuel to be in%ected into the cylinders and the firing ti'es of the spar- plugs. 4.( Mitsubishi Engine ensors 4.' /he Air 0low ensor $n the case of the Mitsubishi 4!" engine, the air flo( is detected using a hot (ire induction type sensor. The platinu' (ire is -ept hot by current flo(ing through it. )s air enters the 'anifold, this (ire is cooled. The syste' -eeps the (ire hot by increasing *or decreasing+ the a'ount of current flo(ing through the (ire. )s 'ore air flo(s through the 'anifold, 'ore current needs to flo( through the (ire to -eep the te'perature constant. Thus air flo( is 'easured by sensing the a'ount of current flo(ing through the (ire. There are other (ays of 'easuring the a'ount of air entering the inta-e 'anifold. Ao(ever, the 'easuring syste' used (ill depend on the car 'anufacturer. Usually Mitsubishi uses the hot (ire induction 'ethod. .ther 'ethods include the vane syste', the air flo( sensor plate, and the heated fil' 'ethod. 4.* Air )nta,e /e-1erature ensor This te'perature sensor is used to 'easure the te'perature of the air entering the inta-e 'anifold. enerally, this is acco'plished by 'eans of a resistance te'perature detector or HTD. $f the te'perature of the sensor falls then the resistance of the sensor (ill fall, conversely, if the te'perature increases then the resistance (ill also rise. Using a voltage divider circuit, a constant voltage (ill be in%ected into the circuit. The voltage at the HTD, (hich is connected in series (ith a constant resistor, is then 'easured. :hen the te'perature is high, the resistance (ill be high; therefore the voltage across the HTD (ill also be high. This (ill register as a high te'perature in the ECM. 4.3 Manifold Absolute 2ressure Gauge The pressure in the 'anifold is 'easured using a 'anifold absolute pressure gauge *M)E gauge+. The M)E gauge (ill co'pare the pressure in the inta-e 'anifold to the pressure of a specific vacuu'. This provides a 'ore accurate 'easure'ent than the vacuu' gauge because the vacuu' in a M)E gauge is fi@ed, (hereas a vacuu' gauge co'pares inta-e 'anifold pressure to at'ospheric pressure, (hich varies. The vacuu' in a M)E gauge is separated fro' the inta-e 'anifold pressure by a fle@ible diaphrag'. The diaphrag' is connected to a strain gauge (hich (ill
convert the pressure to a voltage signal, (hich is then trans'itted to the ECM as a varying voltage signal. 4.4 Coolant /e-1erature ensor The coolant te'perature sensor functions li-e the air inta-e te'perature sensor. The reading fro' this sensor (ill be used by the ECM to increase the a'ount of supplied fuel (hen the coolant te'perature is lo( > effectively ta-ing the place of the traditional cho-e. )s the engine heats up, the ECM auto'atically reduces the a'ount of fuel in%ected by the fuel in%ectors. This sensor is also used by the ECM to s(itch on an electric fan that is used to cool the radiator (hen the coolant te'perature is too high. The radiator fan&s cut9in and cut9out points are predefined in the ECM to 'aintain opti'al engine te'perature. 4.3 /hrottle 2osition ensor The throttle position sensor is used to control the idle speed of the engine. $t is a rotary type sensor that uses a (iper blade and resistance coil to for' a si'ple voltage divider. This configuration provides a voltage signal to the ECM. $f the throttle is (ide open the sensor (ill send a 3B signal (hile if the valve is co'pletely shut the sensor (ill send a =B signal. The idle speed is controlled by a scre( located on the throttle body. The scre( controls the set point of the throttle position sensor voltage. Air-fuel Mixture Ratio Conversion Efficiency % 100 80 60 40 20 0 13:1 14:1 14!:1 1":1 16:1 #$ x C$ %C &est o'eratin( area for 3-)ay catalyst Ric* +ean 4.4 /he .5$gen ensor The o@ygen sensor (ill be used in order to 'easure the a'ount of o@ygen that is left after the co'bustion process. The o@ygen sensor is about the si,e of a spar- plug and (ill produce a s'all voltage (hen it is e@posed to o@ygen. The voltage that the o@ygen sensor produces is bet(een =.13B to 1."B. This voltage is sent to the ECM to deter'ine (eather the a'ount of fuel is to be increased or decreased. The air9fuel ratio is correct (hen the o@ygen sensor reads =.43B. $f the voltage drops belo( =.43B, there is too 'uch o@ygen and 'ore fuel is needed. Ao(ever, if the voltage rises above =.43B, the o@ygen content is too lo( and the a'ount
of fuel (ill have to be decreased. The o@ygen sensor is also used to deter'ine if the engine is (or-ing in open loop or closed loop because the o@ygen sensor can only operate (ell at a te'perature of bet(een 4==°C and 2==°C. 0elo( 4==°C, the ECM (ill (or- in the open loop 'ode, (ithout feedbac- on the content of o@ygen in the e@haust gases. 4.6 /he 7all Effe&t Cran,shaft ensor The Aall Effect cran-shaft sensor is used in order to calculate the speed of the engine and, at the sa'e ti'e, calculate the position of each cylinder. The transducer (ill send a voltage signal to the ECM via the ignition coil 'odule depending on the 'agnetic field detected. Using a stationary 'agnet, a transducer to detect 'agnetic fields, and three vanes that are connected to the cran-shaft, the Aall Effect cran- sensor can deter'ine the speed of the engine and the piston position. This is done by having the vanes 'ove in bet(een the stationary 'agnet and the transducer. The vanes (ill cause the 'agnetic field *produced by stationary 'agnet+ that is sensed by the transducer to have an interruption thus causing a change in the voltage sent to the ECM. :hen there is an interruption, that is called an off signal and (hen there is no interruption that is called an on signal. Ao( fre;uent the on and off signals happen (ill be used by the ECM to calculate the engine speed. )nother signal fro' the ca'shaft sensor (ill be used (ith the cran- sensor in order for the ECM to calculate the piston position. 4.8 /he 7all Effe&t Ca-shaft ensor Ci-e the cran- shaft sensor the ca'shaft sensor is also Aall Effect in nature. Ao(ever rather than having vanes on the ca'shaft, a per'anent 'agnet is 'ounted on the ca' shaft gear. The ca'shaft is used to open and close valves in the engine. The firing 'ust occur a fe( degrees before Top Dead Center *TDC+ %ust after the co'pression stro-e is over. This sensor (ill be the indicator for the ECM to -no( if the piston has reached that point or not. The ECM (ill use the infor'ation gained fro' the sensors above in order to activate the actuators to generate po(er for the engine. The t(o type of actuators that are connected to the ECM are the fuel in%ectors and the sparplugs. 3.( Mitsubishi Engine A&tuators 3.' /he 1ar, 2lug The 4!" is a four cylinder engine. Each cylinder has one spar- plug to ignite the air9fuel 'i@ture. The ECM (ill first obtain the piston position fro' the ca'shaft and the cran-shaft position sensors. These readings (ill be sent to the ECM through the ignition 'odule. ) decision of (hich cylinder has reached TDC (ill be 'ade by the ECM using the readings obtained fro' the ignition 'odule. The cylinder that has reached TDC (ill then be given a signal through an ignition circuit. $n our case the 4!" has 4 ignition coils. The ignition coil has 4 (indings? a pri'ary and a secondary (inding. The signal fro' the ignition 'odule (ill go into the pri'ary (inding and induce a voltage in the secondary (inding, (hich steps the voltage up to 43-B. This (ill cause the spar- plug connected to the secondary (inding to ignite. 3.* /he 0uel )n9e&tors
The 4!" uses solenoid operated fuel in%ectors. :hen the ignition -ey is turned on, there (ill be a voltage present at the solenoid. The fuel pu'p in the gas tan- (ill also start pressuri,ing the fuel lines at this ti'e. ) 'echanical fuel regulator (ill allo( so'e of the fuel to enter the fuel rail and so'e to return bacto the fuel tan-. During operation, the ECM (ill provide a ground signal (hen it (ants the solenoid to open. :hen the solenoid is open, the pressuri,ed fuel fro' the fuel rails (ill spray out the fuel in%ector no,,le and enter the co'bustion cha'ber. The driver of the car (ill press the accelerator that (ill open a butterfly valve (hich allo(s air to enter the inta-e 'anifold via the air cleaner or air filter. This air (ill then enter the inta-e 'anifold. The ECM (ill use the readings fro' the follo(ing sensors to deter'ine the duty cycle of the fuel in%ectors? · The air flo( sensor · )ir inta-e te'perature sensor · Manifold absolute pressure gauge · Coolant te'perature sensor · Throttle position sensor · The o@ygen sensor #igure 4 illustrates the various different fuel in%ector firing profiles. These profiles are built into the ECM to allo( the ECM to cater for the different driving condition. Transition bet(een any t(o profiles is fully transparent to the driver and occurs (hen the ECM deter'ines that a specific profile is invalid. ) ne( profile is then selected based on the input fro' the sensors at the ti'e. )ll this is calculated by the ECM in real ti'e. #igure 4? The (ider the pulse (idth, the longer the in%ector is open and the greater the a'ount of fuel that sprays out *Ford Motor Company+ 7 14 8. 4.( Con&lusion The Mitsubishi 4!" engine is indeed a co'ple@ and (ell tuned po(er plant that is able to deliver the best perfor'ance in an econo'ical 'anner. $t is able to use both open loop and closed loop control depending on driving conditions. The develop'ent and integration of the ECM into the auto'obile has greatly enhanced the reliability, perfor'ance, and efficiency of the $CE. Together (ith better aerodyna'ics and lo( rolling9 resistance tire technology, the ECM has contributed to raising the average 'ileage of vehicles fro' 13'pg in 1!<3 to 41'pg in 4==4 7 1" 8. :eferen&es 1 78 http?IIen.(i-ipedia.orgI(i-iI)uto'obile, 1! 5une 4==6. 2 78 J.A. Jchurr, Energy in the American Economy, The 5ohns Aop-ins Eress. 0alti'o re, MD., 1!6=, pg 116. 3 78 E. Hoberts, The End of Oil, 0loo'sbury Eublishing, Condon, 4==3, pg 62. 4 78 E. Hoberts, The End of Oil, 0loo'sbury Eublishing, Condon, 4==3, pg 2!. "
78 http?IIen.(i-ipedia.orgI(i-iI$nternalKco'bustion Kengine, 1! 5une 4==6. 6 78 http?IIen.(i-ipedia.orgI(i-iI$'age?#ourKstro-eK cycleKco'pression.%pg, 4= 5un e 4==6. ! 78 http?IIen.(i-ipedia.orgI(i-iICarburetors, 4= 5une 4==6. 8 78 http?IIen.(i-ipedia.orgI(i-iIEngineKControl KUnit, 14 5une 4==6. , 78 http?IIen.(i-ipedia.orgI(i-iIDohc, 13 5une 4==6 10 78 http?IIen.(i-ipedia.orgI(i-iI$'age?D.AC9Lylinder-opf9Jchnitt.%pg, 13 5une 4== 6. 11 78 :.A. Crouse M D.C. )nglin, Automotive Mechanics 1 th Edition, Mcra(9Aill, 1!!", pg 446. 12 78 :.A. Crouse M D.C. )nglin, Automotive Mechanics 1 th Edition, Mcra(9Aill, 1!!", pg 44<. 13 78 C. Cave, A !ew CAF", University of California > 0er-eley, 4==1, pg 4.
