Fuel In­jec­tion

We are told that elec­tronic fuel in­jec­tion on the tri­als mo­tor­cy­cle is the fu­ture, but when is this go­ing to hap­pen in tri­als? This tech­nol­ogy is not new in the tri­als world. Who re­mem­bers the Mick An­drews Yamaha YZT 250cc pro­to­type with an early form of

Trial Magazine - - CONTENTS - AR­TI­CLE: YOOMEE

The idea of fuel in­jec­tion in the tri­als world came to light in 1996 when for­ward-think­ing Gas Gas played with the idea and em­ployed Span­ish en­gi­neer Josep Paxau to work on this new project. Work­ing with two young en­gi­neers, Josep Par­res and Toni Gar­rido, they fit­ted an early elec­tronic sys­tem to a tri­als ma­chine. How­ever, when Paxau de­parted from the Span­ish brand in 1997, the idea was put to bed. In a strange turn of events though, the in­for­ma­tion and ex­pe­ri­ence gained in the world of off-road rid­ing would be in­tro­duced to elec­tronic fuel in­jec­tion, or EFI as it is more com­monly known, with Gas Gas on its new 450cc four-stroke en­duro ma­chine in 2002.


The first pro­duc­tion tri­als ma­chine to use EFI was Honda’s four-stroke, sin­gle cylin­der, liq­uid-cooled one with the in­tro­duc­tion of the new Mon­tesa Cota 4RT in 2004. The mo­tor orig­i­nated from HRC in Ja­pan, based around the sin­gle cylin­der, four valve OHC CRF 250cc mo­tocross ma­chine. The fuel sup­ply to the en­gine was by a com­pact sim­ple in­te­grated in­jec­tion sys­tem (PGM-FI) with a lower vol­ume than a con­ven­tional car­bu­ret­tor, aimed at the tri­als ma­chine. The ECU is an in­tel­li­gent high-precision con­trol unit which mar­ried the throt­tle body and its con­trol unit to­gether. Its sen­sors per­form instantaneous cal­cu­la­tions of a wide range of vari­ables such as the en­vi­ron­ment, en­gine tem­per­a­ture and at­mo­spheric pres­sure to give the op­ti­mum per­for­mance of the en­gine. Its suc­cess has been well doc­u­mented, but what about a two-stroke EFI tri­als ma­chine? The HRC de­sign was, and still is a huge suc­cess. Ossa broke new ground with its two-stroke tri­als model at the end of 2010 with its 280cc re­verse-cylin­der tech­nol­ogy and the in­tro­duc­tion of the EFI Koku­san bat­tery-less sys­tem.


Trial Mag­a­zine tested the new Ossa and it was very good, with the en­gine of­fer­ing a very lin­ear per­for­mance with no sud­den power surges re­ported; the chance to stall the mo­tor even on very low throt­tle open­ings had van­ished. The prob­lem was that it was com­pli­cated to ad­just, mean­ing a trip to the dealer or im­porter to make any changes.

Span­ish brand Ver­tigo is the lat­est man­u­fac­turer in tri­als to in­tro­duce EFI on its two-stroke mod­els. The very com­pact en­gines ben­e­fit from a be­spoke elec­tronic sys­tem rep­re­sent­ing the lat­est ad­vances, with the elec­tronic con­trol unit manag­ing and con­trol­ling the per­for­mance of the en­gine in all sit­u­a­tions. With a choice of four dif­fer­ent maps in each of the six gears the rider has ac­cess to 24 maps, al­low­ing an un­equalled level of user re­fine­ment in the world of tri­als. Once again though, as with the Ossa, to make any ad­just­ments is not as easy as on the good-old me­chan­i­cal car­bu­ret­tor and it also re­quires a cer­tain amount of knowl­edge to make changes.


It’s quite un­der­stand­able why the man­u­fac­tur­ers need to look at the elec­tronic fuel in­jec­tion sys­tems with the in­tro­duc­tion of the Euro 4 ho­molo­ga­tion reg­u­la­tions con­cern­ing emis­sions, but will the changes to meet th­ese new rules come from the fuel man­u­fac­turer it­self?

Just over twenty years ago, I was work­ing in Re­search and De­vel­op­ment in the au­to­mo­tive in­dus­try and one of the world-lead­ing car man­u­fac­tur­ers gave us a talk on the fu­ture of diesel en­gines in mo­tor ve­hi­cles. They said that by the year 2020 diesel fuel would be a thing of the past and that a two-stroke car or hy­brid elec­tric/fuel mo­tor ve­hi­cle is where we would be at with emis­sion con­trols. Only time will tell who will be cor­rect, but one thing is for sure is that change is hap­pen­ing whether we like it or not. Or, will we all go elec­tric?

Mon­tesa/Honda was the first man­u­fac­turer to suc­cess­fully use fuel in­jec­tion on its pro­duc­tion four-stroke Cota 4RT tri­als ma­chines.

Jeroni Fa­jardo looks for the cor­rect map as he pro­grammes the elec­tronic fuel in­jec­tion with his me­chanic for the Ja­panese world round.

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