PAT SYMONDS TECH

ENGINE MAPPING

F1 Racing - - CONTENTS - Pat Symonds ex­plains

Let’s start at the be­gin­ning: what is engine mapping and how does it work? In their most sim­ple form, the maps are an ar­ray of num­bers – in ef­fect a big ta­ble of rows and col­umns, such as you might see on a Mi­crosoft Ex­cel spread­sheet. These ta­bles give val­ues of var­i­ous pa­ram­e­ters, which de­ter­mine how those pa­ram­e­ters may vary as a func­tion of the engine op­er­at­ing con­di­tions.

To give an ex­am­ple, the amount of fuel that is in­jected into an engine will de­pend on both the engine speed and the torque that the driver is de­mand­ing by means of the po­si­tion of the throt­tle pedal. For each dis­crete value of both these in­puts to the map, there will be a spe­cific amount of time for which the fuel in­jec­tors need to be open in or­der to pro­vide just the right amount of fuel that the engine needs.

If you imag­ine look­ing at a train timetable, you look along the col­umns un­til you see the sta­tion you are in­ter­ested in. You then look down the rows un­til you nd the time of the next train. The engine maps work in a sim­i­lar way in that the Engine Con­trol Unit (ECU) will mea­sure the engine speed and in­dex along the ta­ble to the cor­rect rpm, while si­mul­ta­ne­ously mea­sur­ing the throt­tle-pedal po­si­tion and in­dex­ing down the ta­ble to the rel­e­vant po­si­tion to nd a value that will tell it how long to hold the in­jec­tors open.

Of course there are many more maps than this. As well as the amount of fuel in­jected, you need to de­ter­mine ex­actly when in the com­pres­sion stroke it needs to be in­jected as well as de­ter­min­ing when the spark needs to be ig­nited. Sim­i­larly, the turbo boost re­quired will be de­ter­mined by yet another map.

Why are they called maps?

If you imag­ine that in the case above we looked at it in three di­men­sions, with engine speed rep­re­sent­ing North/South and throt­tle po­si­tion East/West, then the val­ues of in­jec­tion du­ra­tion would rep­re­sent val­ues in the ver­ti­cal di­men­sion. The ef­fect would be that the data would look like a three-di­men­sional map of the earth, hence they are called ‘maps’. Are these maps fixed? The base maps are fixed but they may be mod­i­fied by other in­puts. For ex­am­ple, the cur­rent For­mula 1 en­gines run close to the point of det­o­na­tion, or ‘knock’ as it also some­times known. This is a pre­ma­ture fir­ing of the fuel and air mix­ture, which can be very de­struc­tive and can cause rapid engine fail­ure. The en­gines are tted with knock sen­sors which, if they de­tect any cylin­der knock­ing, can ap­ply an off­set from the base-map ig­ni­tion tim­ing, thereby re­duc­ing the propen­sity to knock. Has it al­ways been like this? No, the tech­nol­ogy was not avail­able in the time of the ubiq­ui­tous Cos­worth DFV F1 engine for ex­am­ple. Even some of the rst-gen­er­a­tion tur­bocharged en­gines re­lied on purely me­chan­i­cal means to con­trol the fuel, ig­ni­tion and boost. As mi­cro-elec­tron­ics be­came more read­ily avail­able in the early 1980s, so engine con­trol was able to in­crease in so­phis­ti­ca­tion.

Where are the maps stored?

They are held in the ECU. In the early days they were held in a spe­cific sort of chip called an EEPROM. These were read-only mem­o­ries, whose con­tents could be erased and re­pro­grammed us­ing a pulsed volt­age. This was done by re­mov­ing the chip from the ECU and putting it in a pro­gram­ming de­vice.

In 1986 when I was work­ing for Benet­ton, we used the BMW turbo engine, which utilised these de­vices. I bought a pro­gram­mer and learnt how to re-pro­gramme the chips, which were pro­grammed in hexa­dec­i­mal – a com­plex num­ber sys­tem us­ing base 16 rather than the nor­mal dec­i­mal sys­tem, which uses base 10.

The late Paul Rosche, who ran the works en­gines in the Brab­ham cars, could never un­der­stand why we had such good per­for­mance and of­ten asked if he could check our chips. I was ex­tremely adept at the sleight of hand needed to re­move a chip and sub­sti­tute it with an ‘ap­proved’ one – which I would then hand to him for check­ing.

These days the maps are loaded into the car re­motely be­cause the ECU is part of the net­work. This is done by the engine en­gi­neers at the cir­cuit who will hold the maps on their com­put­ers and down­load them to the ECU us­ing a spe­cific piece of soft­ware. How ex­actly do the engine maps af­fect the per­for­mance of the engine? The power-unit man­u­fac­turer will de­ter­mine the base map (or cal­i­bra­tion as it is of­ten known) by ex­per­i­men­ta­tion on a dy­namome­ter, bal­anc­ing peak per­for­mance with the re­li­a­bil­ity needed for ac­cept­able life. Un­der the cur­rent F1 reg­u­la­tions, they also have to check that the fuel ow does not ex­ceed the reg­u­la­tory limit. This base cal­i­bra­tion will then be used at the cir­cuit, al­though the en­gi­neers work­ing at the track will also be able to make mi­nor changes in re­sponse to spe­cific prob­lems or driver re­quests.

Do you need to use dif­fer­ent engine maps for dif­fer­ent cir­cuits?

Not re­ally, since the so­phis­ti­ca­tion of the cur­rent elec­tron­ics is such that the maps are suit­able for all nor­mal con­di­tions. There may be a few ex­cep­tions, for ex­am­ple in Mex­ico where the

ex­treme al­ti­tude means in­creased work­load for the turbo-com­pres­sor, a dif­fer­ent turbo speed map may be used.

Can the driver al­ter the engine maps?

To some ex­tent he can. While there is a base engine map on which the engine may op­er­ate, he can also se­lect al­ter­na­tive maps for cer­tain con­di­tions. If we as­sume that the base map is one that is suit­able to use for the en­tire race then there may be maps loaded that are less ag­gres­sive and hence will en­hance engine life for use dur­ing prac­tice. Equally there will be a special map that he can se­lect just for the hot laps in qual­i­fy­ing, which will push both the engine and the elec­tri­cal power de­ploy­ment to the max­i­mum.

Is the power unit the only sys­tem that is mapped in this way?

The chas­sis en­gi­neer also has a sim­i­lar mapping sys­tem avail­able to him. These days there are not many maps avail­able, but brake bal­ance and the dif­fer­en­tial lock­ing are used ex­ten­sively to op­ti­mise han­dling. The dif­fer­en­tial mapping is par­tic­u­larly use­ful as it can recog­nise cor­ner en­try from mid-cor­ner and ap­ply dif­fer­ent lock­ing in dif­fer­ent parts of the cor­ner. This is par­tic­u­larly use­ful since the driver can then ad­just base maps in re­sponse to tyre degra­da­tion to keep the car bal­anced through a stint.

Engine maps de­ter­mine the amount of fuel that is in­jected into an engine, de­pend­ing on the engine speed and torque re­quested by the driver via the throt­tle. These maps are up­dated by en­gi­neers on ar­rival at the cir­cuit

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