841 Automated tuning of an engine management unit for an automotive engine CHardie,H Tait,S Craig,J GChase *, B W Smith and G Harris Department of Mechanical Engineering,University of Canterbury, Christchurch, NewZealand Abstract: Modern automotive engines aredigitally controlled using anengine management unit (EMU)that is typicallymanually programmed using anengine dynamometer to obtain desired levels of power, emissions and e ciency.Closed-loop control of anengine dynamometer and EMU, com- bined with anoverall engine tuning algorithm, is used to automate the tuning of the engine map for afour-cylinder engine. The tuning algorithm determines the air-to-fuel ratio necessary for each region of engine speed and throttle position to obtain the desired performance, automaticallymoving to each operating region in the map. Preliminary automated tuning results produce power output curves comparable with those delivered using the originalmanufacturer tuned EMU. At lower engine speeds data ltering is required and results in power outputs slightlylower than the factory-tuned engine. At higher speeds smallimprovements in engine e ciency,for equivalent performance, canbe found. The research presented clearlydemonstrates that engine tuning to averyhigh standard, equivalent to originalequipment manufacturer engine performance, canhe successfully automated, savingtime and adding consistency to the engine tuning process. Keywords: control, automation, engine tuning, dynamometer, engine management, engine map 1INTRODUCTION increased emissions of hydrocarbons and CO.Too little fuel canresult in engine damagesuch asburnt exhaust Enginemanagement units (EMUs) aredigital processors valves.The amount of fuel supplied is controlled bythe that activelycontrol fuel owand ignition timing to EMU, which controls the frequency and pulse width of ensure optimal engine operation and areemployed in the fuel injectors. At steady state, constant engine speed most modern fuel injected engines. Enginetuning plays the pulse width iscalculated from acombination of three avitalpart in ensuring that the EMU is programmed so inputs: ambient airtemperature, the inlet manifold air that the engine performs wellunder avarietyof con- pressure (MAP)and user-dened volumetric e ciency ditions. The manufacturer-developed EMU parameters correction factors (VECFs). aretypically developed to meet design compromises Atypicalengine has atwo-dimensional plane of between performance, market and legislativespeci ca- steady state operating points with engine speed along tions, particularlywith regardto emissions. After- the horizontal axisand throttle position or MAP along market EMUs areavailable to replace adamagedunit, the verticalaxis, as shown in Fig.1. Eachof these points View metadata, citation and similarto papers at core.ac.uk achievespeci cations brought to you by CORE di erent to those used bythe has di ering requirements for fuel and ignition timing. provided by UC Research Repository manufacturer, to enhance the operation of anengine Most EMUs divide this plane up into nite rectangular intended for use both on land and in amarine environ- elements, commonly referred to as‘zones’, that make up ment or to enable the tuning and enhanced performance an‘engine map’and where eachzone has anassociated of amodied engine. user-dened VECF.The engine map acts asa look-up The air–fuel ( A/F)ratio is important in the combus- table for operating parameters used bythe EMU to con- tion and tuning processes. If there is too much fuel, not trol engine operation. allthe fuel is burnt, causinghigh fuel consumption and Currently, engine tuning is typicallyperformed bya skilled technician who manuallyadjusts the operating TheMS wasrecei vedon 3 January2002 and was accepted after re vision parameters for eachzone of the engine map on adyna- forpublication on 6August2002. mometer or whiledriving. The engine is tuned to the *Correspondingauthor: Department of Mechanical Engineering, Universityof Canterbury, Pri vateBag 4800, Christchurch, New Zealand. desired specication for eachzone in which the engine email:[email protected] z is expected to be operated. This process is iterativeand D15501© IMechE 2002 Proc Instn Mech EngrsVol 216Part D:JAutomobile Engineering 842 CHARDIE,H TAIT,S CRAIG,J GCHASE,B WSMITH ANDG HARRIS Fig. 1 Structureof the engine map time consuming, creatingthe potential for signicant mation to enhance engine performance, rather than time savings,additional repeatabilityand more accurate automating EMU controller design. Enginetuning to results viaautomation. meet specic performance criteria istypicallyperformed The primarygoal of this research is the automation largelyby hand viaa combination of experience, science of the engine tuning process viaengine tuning software and art. No references werefound specically addressing that communicates with both the dynamometer control- automation of the engine tuning process, although there ler and the EMU to create aclosed-loop engine tuning is some prior research that generallyreferences the system. The engine tuning algorithm that governs the possibility of performing this task [ 5]. process is designed to optimize automaticallythe engine The following sections address the test system and control parameters for eachoperating zone, to achieve software developed to enable the automated tuning of performance in accordance with user-dened specica- an EMU using anengine dynamometer and the basic tions. In addition, the software ensures that potentially tuning algorithms developed. Subsequent sections test damagingsituations aredetected and responds byplac- one of these tuning methods, compare the performance ingthe engine in anon-damaging state, sounding an obtained with that provided bythe manufacturer’s EMU alarmand pausing the process until the problem canbe and summarize the results and conclusions. corrected. This second requirement ensures that the pro- cess canbe run largelyunsupervised. Finally,the auto- mation process, and the specic software developed, 2AUTOMATEDENGINE TUNING TEST adds both speed and consistency to the engine tuning SYSTEMAND SOFTWARE process. The after-market EMU employed is developed byThe experimental automated engine tuning system is Link Electro-Systems of Christchurch, NewZealand. tested on a1992Toyota 3S-GE engine from aToyota This EMU alongwith the PCLink control and communi- MR2. This four-cylinder engine has two overhead cam- cation software is used to control the engine. Aservo- shafts, displaces 1998cm 3 and generates manufacturer- controlled Froude-Consine hydraulic dynamometer is listed peak outputs of 121kW at6800 r /min and employed for the tuning process. The automated tuning 191N mat4800r /min. Loadis applied to the engine via algorithm comprises software designed to interface with, aservo-controlled Froude-Consine hydraulic dyna- and control, these two units for the end purpose of mometer that is controlled bya Test Automation tuning the Link EMU parameters for everyusable zone TA2000controller interfaced with aPC-based data of engine map. acquisition system utilizing anAdvantech PCL-818ana- Enginetuning is awell-known art documented in alogue-to-digital converter (ADC )card. The test bed is varietyof texts on the topic of internal combustion set up so that either the originalToyota EMU or the engine performance [ 1].Prior research in the areaof Link EMU cancontrol the engine. The dynamometer automated engine tuning is scarce with most research in and Link EMU areindependently controlled viaa PC the areaof automated engine tuning focusing on mod- program to close the loop on the engine tuning process. ifyingspeci c engine functions, such asspark ignition, Specically, the engine dynamometer and controller to enhance performance whilethe vehicleis in operation set and delivervalues for engine speed, torque and [2, 3].Other works focus on systems to adaptivelyelim- throttle position. The Link EMU candeliver valuesfor inate undesirable operating conditions or e ects such asengine speed, throttle position, engine temperature, air knock [4].All of these e orts focus on applyingauto- temperature, the injector duty cycle,ignition advance, Proc Instn Mech EngrsVol 216Part D: JAutomobile Engineering D15501© IMechE 2002 AUTOMATEDTUNING OF ANENGINEMANAGEMENT UNIT 843 the oxygensensor and the entire engine map. Where map. Once atuning algorithm is run on the engine, per- there isoverlap,such asengine speed, the control algor- formance dataare extracted for analysisand compari- ithm uses these valuesto determine when transients haveson. The power output, fuel consumption and e ciency stabilized, asboth units willreport the same value. curves arecompared to evaluatethe performance of the The automation of the engine tuning process is tested tuning algorithm. achievedvia speci c software written to communicate with and control independently both the engine dyna- mometer and the Link EMU. An overalltuning algor- 3ENGINE TUNING ALGORITHMS ithm steps through each zone in the engine map and tunes the EMU parameters for eachzone according to Optimum engine performance is typicallyobtained ata user specications. User specications that set the tar- constant air–fuel ratio ( l)and the most desirable settings get(s) for the tuning process in each zone areset prior for emissions areobtained when l is valuedaround 1.0 to tuning using agraphicaluser interface (GUI). A [1, 6 ].Smallreductions of l canoptimize power output di erent GUI is used to provide the user with real-time but maylead to sizeable