Cycle News - Archive Issues - 1980's

Fuel injection: T e next G P revolution By Michael Scott The axiom th a t one sh o u ld not look to racing for technical inn ova tion is more reliable than the opposing one, which states: " Racin g improves the breed." Both hav e th eir truths but neither is abso lute. ' O n th e one hand racing . : attracts tech nical bnnkmanship, ta kin g every aspect of design to its ultimate, from metallurgy to g~s-~I ow , from elect ro n ics to internal friction. On th e other . wis e a nd successful pit-lane technicians kn o w very well tha t w hat wins rac es is th e same as what wo n las t year, pl us a few percentage points. And as long as this is true, a nd as lo n g as th e bigmoney ba cking goes to race-win ners rather th an talented mid-field visionaries, th e race tracks are th e last place to . Io o ~ for n ew tr ends i n eng m eermg. This being so , it m ay seem surprising th at th ere is a ny techn ical p rogress. It was on ly th e ride of hi story th at saw four-stro kes give wa y to two- st rokes, a nd even th en th e revol u tion took 10 years or more to work its way up to the 500cc cla ss. against a desperate rearguard action by H onda a nd MV Agusta. T he re is a nother reas on for con ser vat ism in ra cing . .. the rules. Indeed , Ho nda will point o u t th at regu la tio ns limiting 500cc bikes to four cyli n de rs a nd six gears tipped th e bal ance in favor of the hated twostrokes - and co inci de ntally set racing bikes o n a pa th o f devel oprnent th at co nt in ues to di verge from real roa d motorcycles, which in their h i g h es t- p er fo r m a n ce form s are almost invariab ly four-strokes. Raeing improves the br eed. Yes. but what particular br eed ? There I hi ' h . ere IS anot er. revo ~non t at IS lo~ g o verd ue III raci n g - a te~hmque a l.ready com ~on a mong road cars. It IS th e ~dopnor;t f?r t:wo strokes o f electro n ic fu el I.njecnon, a nd .eventl;la lly all-emb racin g electroruc engllle; managem ent systems - .a nd t~e slg!ls .are th a t th e revo Iution WIll begin m 1989. ' Ca gi va has a lready leaked th e n ews th at IlS 1989 500cc class mount for Rand y Mamol a will use integrated electro n ics; while pe rsistent rumors sugges t that Yamaha 's n ew works 250 will b~ a ~ onda-styl e singl ecra nk V-twm (instead o f half th e twin-cra.nk "V - ~ " 500 used until !l~w) ,. hued with elec tro n ic fu el mj ecuon. Th.e ~umor further sug~e~ts tha~ this IS p recursor to an injected sin g le-cran k V4 500. where;. Yamaha goes, can Honda and Suzuki be far behind? Mea ntime, a t least one small-scal e innovator co mes (as they so often do) from Brita in , and in spite of th e usua l ca tch -22 drawback of being unable to secure su fficient financi al backing to assure success u ntil he h as already been su ccessfu l, he hopes to have a fu el -inj ected I25cc British GP racer o n the tracks in th e near future. H e is Mik e Au stin , wh o wa s clos el y in volved with th e desi gn (alth o u gh n ot su bseq ue nt in compl ete development) of th e 250 Exa ct weld, and is now a im ing to mak e hi s mark as a n en gine designer o n h is o w n a Clou.nt, incorporatin g ~".I0n~ other things el~c.tromc fl!e1 m jecuon developed (origi na lly wi th th e Exactweld in mind ) by MicroDyn amics, another British firm. It is Au stin to wh om I am indeb ted for much o f th e following information a bo u t the forthcoming fuel inj ecti on br eakthrough; whil e h e in turn expec ts it to be part of a sea ch a nge in motorcycle raci ng that will create a p lace for gifted and ent h usiastic designers outside th e factory walls, much as is th e case in car ra cing. The design of motorcycles, Au stin beli eves, ha s until now rema ined a so mew ha t in tu i tive a ffa i r . . . a blac k art. T he adven t o f integr at ed electro n ics will mean th e turn of scie nce. Engineers will seek en g ineering so lutions , th e age o f the boffi n is upon u.s. It is not easy to understand wh y it has taken th is Ion!? for electronic fuel inj ection to arrive a t the ra ce tra cks. Inj ecti on for two- strokes has lo n g bee n th e su bject of spe cu la tio n , a nd Dr. j oe Ehrlich is one who expe riern en ted with the technique m ~re th a nZll years ago. rejecting it a s impra cti cabl e, . . ~n ~ p roblem , co mpared wI ~h the mj ecu on o f fo~ r-strokes . was Sim p ly th e d ouble-lime frequen cy o f a dem.and?f a two- stroke. Already revvmg hI gher . than .fo u r-strok es, It de ma nded a~ l~j eCllOn pulse o nce every revolu~lOn instead o f o nce.every two revo lutions, Then .there IS th e co n volu ted path o f th e intak e gases ? f a two-stroke - ~here a four-stroke ~n terpose~ only a sm~le po~pet valve in a re latively short induction tract, a two -stroke routes th e inco m ing charge th rough th e cra n kcases , a nd th en via tra nsfe r ports into th e up per cylin der th e ga ses cha n in direction mo;e th an on ce en r~ut!. However , Au st in believes th at technology h as im proved o n both electronic an d m ech anical fronts to the ex ten t th at two- strok e elect ro nic fuel inj ecti on (EFl) has been tech n ically p ossible for five years or m ore. Wh y have the japan ese not adop ted it? One a nswer m us t hark back to th e "racing improves the breed " a xiom, wh ich in th is case must be turned u pon its head. If EFI had started w inn ing o n the race track s. a n in stant two-strokes, su ch as th ey are. By suppressing th e ' technol ogy. th e j apanese factories bough t time for. th eir carb ureto r off-shoots or su bsidiaries, who co u ld th en get five yea rs more uninterrupted manufacture from th eir existing product ion tooling. This implies a tacit agreem ent between th e factori es - but thi s is in no wa y a far-fetched idea. Meantime, it is interesting if not particularly fruitful to wo nd er wha rever happened to Kawasaki's fourstro ke fuel in jecti on, once Iiued to the esti mable GPZl lOO, a nd yielding a co m bina tio n o f civilized beh avior with to weri ng performance. The mode l was qui etl y phased o ut. An o th er reason co u ld be a desi re to postpone th e in evitable esca lation of costs th at a move towards EF I must entail. There are considerations other than purel y budgetary involved .. . th e FIM has in the past blocked technical development when it threatened to send costs skyrocketin g , a n d th e japanese factories ma y have wished to avoid this sort of ,co n fro nta tio n. Speculation aside. it is hard to beli eve that major factories do not have fuel -injected two-strokes at an advanced stage of deve lopment, a nd probably even up and run ning. I su p pose we, shall soon see. , j u st how ca n we ex p ec t fuel inj ection to be arranged? T he single sine q ua non is a type o f si lico ne ch ip named EP ROM erasab le, program mab le read -o n ly mem ory. This is programed with what is ge ne ra lly referred to as a map, ta king into acco u n t th e vari ous measurable paramet ers , including throttle o pe n ing , rpm , cra n ksh a ft positi on, vari ous temperatures su ch as a m b ient . cylinder h ead or exha us t gas, a tm ospheric and in th e case o f a two-stroke th e particu larly crucial ex ha us t pressu res. T h e map determ ines the amount of fue l req uired. a n d tim es th e injector nozzle opening to del iver it. In th e case of a full y integrat ed engin e m anagem ent system , it a lso det erm in es the requ isite spark tim in g. T he firs t two -stok e inj ecti on systems are lik el y to be sep ara te from th e ignit ion, a lt hough sharing certa in sensors. but integration is th e ultimate goal. The o pera tio n o f the exh aust power va lve will a lso eventua lly be included with in th e cent ra l co ntrol box. T he acc uracy of th e map is of co u rse of paramount importan ce, while different states of tunes or s h a pes o f pow er cu rve ca n be obtained from d iffer ent , maps. It is also possible to program a n u m ber o f maps eithe r onto th e same ch ip or on to different ch ips ca rried within the black box, and in th eory th e rid er co u ld select in flight which particul ar type o f power delivery would su it. Th is is not as far-fet ch ed as it mi gh t seem - suc h a facility co u ld be a rea l adva ntage in th e case of a cha nge in track co n di tio n s m id -ra ce - a damp tra ck dryin g-o u t, for in stance, o r vice versa . Given access to a co m purer o f su fficient power , it is possible to rewrite th e ma p a t the tra ck . More co mmon ly in car rac ing (where th ese electroni c engi ne managem ent systems h a ve been de rige u r for several years ) th e u su al nuts -and -b olts m ech an ics are a u gme nted by teams o f electro n ics engineers, who ca rry with th em gr eat .bo xes full of a lte rnative chips. Pull into th e pits, slot in a n ot he r ch ip . a nd out you go to see if a different em p h asis to th e power cu rve, perhaps a boost to midrange power at the inevitable cost o f top-end, can improve yo ur lap time. Su ch is a layman's overview of th e software. Ev en wh e n you onl y scratch th e su r face, it becomes obvio us that we a re on the threshold o f a wh ol e n ew era o f engine tuning refinement. The co m p lexities are staggering , and include th e opportunities for variable engine geome try elsew here th an th e si m p le exha us tport pow er valves of tod a y. H ow about electronicall y tim ed cran kcase reeds? Meanwhile. the sca le of the task of racing must be redrawn. What one man could once do with a good car for exhaust note and an intuitive feel for gas flow willi now require a team of com p u ter experts. The hardware is easier to understand. The first thing to decide is where to inject the mixture. Diesel en gin es, whe re fuel in jection was p ioneered, squirt directly into th e co m bustio n chamber, but th is route has not p ro ved popular with hotterru nni ng a nd much more efficient high-performance petrol engines . In th e four-stroke car world, injection ge nerally ta kes p lace in the in duction tract, upstream of the throttle . butterfly as well. With a two-stroke, there a re five possible inj ecti on po ints: I. U pstream of th e throttle valve. 2, Between the throttle valve an d th e cra n kcase reed valv e (or rotary in let valv e). 3. Into th e cra n kcase . 4. In to . th e transfer ports. 5. Into the upper cylin de r/comb us tio n cha m ber. Aus tin , workin g wi th a si nglecylinder engi ne, favo rs th e fi rst o p rio n - choosi ng the plenum chamber from whi ch the in let tra ct bell-m outh d raws its gases. T h is g ives th e longest poss ible mi xing n rne, a n d a lso a llows the crankshaft a nd cylinder lu bricatio n p roblem to be so lved in th e us ual way by use of a pe tro l m ixture. H e reject s th e o ther o p tio ns for a variety o f reasons: downst ream of th e throttl e val ve because it clu tters th e o the rwise pristine inlet tra ct; th e cra n kcase because th e positio n ing of th e nozzle is ver y sens it ive, a nd it must also be placed so me w he re where it is not vulnerable to accident damage, ruling o u t th e cra n kca se sides ; the transfer ports because these a rc already subject to deli cate flo w patterns, a nd a lso because th ere is no existing inj ecti on technol ogy ca pa ble o f delivering suffici ent fuel in th e very sh o rt space of tim e wh en th e transfer p orts a rc o pen ; a nd th e u p per cylinder pressu re. Keeping th e inj ecti on hardware a way from th e eng ine itself a lso a llows th e best usc of wha t h e terms "arch itectural" .benefits o ffered bv th e fact th a t bulky ca rb uretors close to the eng ine ha ve been d iscarded. Pu t sim p ly, this co ns idera bly frees up overa ll engine des ig n. In th e cas e o f a 500cc V4, it wo u ld a llow a much narro wer included a ngle between th e cylinders, and much m ore co m pan engi ne . T h is br in gs a w hole raft o f associa ted ben efits, fro m a lo wer cen ter of gravity 10 improved airflo w within th e fairin g. This is mo re im porta n t th an it ma y a t first seem . .. if you improve th e exi t path behind th e radiator, yo u ca n use a smaller ra d ia tor, g iving sign ificam ly low er d ra g. But the most obvious ben efits of fu el injection a n d associa ted electronic en g ine managem ent systems co m e in engine effi ciency - whi ch . in raci ng terms, means horsep ower. Wit h small er en g i nes. th is will improve th e ultimat e power o u tp u t; in th e case o f the 500s. al ready endowed with a su per-ab un da nce of Iull-throule top en d pow er, it will p robably be used to boost mid-range, (Contin ued to page 25) 13

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