Cycle News is a weekly magazine that covers all aspects of motorcycling including Supercross, Motocross and MotoGP as well as new motorcycles
Issue link: https://magazine.cyclenews.com/i/128308
l~~~.------------ Apri/ia RS3 Cube large diameter exhau st, w hich as part of th e smoot hing out of the powe r delivery is actually silenced quite cons iderab ly com pared to 2001' s shr ieking speed king, eas ily the noisiest bike on t he MotoGP grid that year. The Cu be's six-speed tra nsmission w ith dry slipper clutch has a side-loading extractable gear box for ease of changing internal ratio s quickly. This is mated to an AP carbon clutch, whic h is unique on th e grid and ce rtainly addre sses the problems that Honda is ex pe riencing wit h sho rt clutch life on the RC2 11V - the Aprilia's is good for literally hundreds of full-bo re takeoffs from the grid or pit lane, with an infinitesimal wear rate . But the re' s been a problem with the all-or-not hing nat ure of t he lever actio n, says Witteveen, because by definition the carbon plates are not designed to slip, making a clutch start off the line very much an acquired skill, as Edw ards memorably demon strate d in South Africa last April. 'Y\fter two years , we're not far away from having this working just right," says Witteveen . "It' s not 100 percent yet - but both riders got good starts in the final two races, so we 're nearly there. There are two pro blems: Befo re , it was too sensitive, so had a take up like a light sw itch - on or off - but t his is much bett er now, and you can actually slip it properly. The other is temperature - the grip changes accordi ng to the hea t generate d inside the clutch, so you can't predict how it w ill be when you co me to use it. But it's a lot better now than before, and being so strong means we don't ever have to worry about the clutch weari ng." The Cu be's fuel-inject ion system is Aprilia's own - it eve n makes the throttle bodies in-house , says Witteveen, and originally employed a single centrally positioned external injecto r above each intake stack, later changed to a dual-injector format fro m Valencia a year ago, with sequential operation to improve lowdown power, adding around 15 hp this year to the powerband under 10,000 rpm. Aprilia has also de veloped its own electronic engine management package, housed in the ultraco mpact ECU incorporated in the back of the instrument pane l, which it terms a Poker System and co ntro ls not o nly the ignition and fuel injection, but also the F1type ride-by-wire electronic throttle con trol. This dispenses w it h a cable running to the throttle bodies as on ot her MotoGP bikes except for the Suzuki GSV-R, whic h followed Aprilia's lead in adopting ride -byw ire for 2003 . Instead, t he Cube featu res a lead running from the throttle to the sma ll t hrott le position sensor box mounted in front of the ECU, wh ich incorpora te s a spr ing simulating the control pressure of a co nventional mechan ical t hrottle's return spr ing. W hen the rider twists t he wr ist, this move- '---- - - - - -- - - -- - - - - -- - - - -- - ment is measured by a sensor t hat transmits the information to the ECU, which in turn delivers the res ultant th rottl e o pening desired . "We have t he option whether to activate this or not," says Witteveen, "but after a lot of work understanding how to map it, we now have almost a I: I real time operatio n, wh ich gives the ride r a better sense of immediacy and thro ttle response, but also allows us to take out power whe n we wan t to do that." AS IN , TRACTIO N CO N TROL? "Y , we can program that in, also launch es co ntrol off the line if w e want to - t he key to being ab le to do th is was to get the rideby-wire right, and we 're getti ng very close with it, now." In chassis design on ce again Aprilia has o pted to follow a differe nt route from its Japanese co mpetitors' fo ur/five-c ylinder machines, by fitt ing the RS3 engine in a modified vers ion of the RS W500 V-twin tw o-stroke frame that Jeremy McWilliams put o n pole position fo r the bike's last-ever race at the Australian GP in 2000 . Aprilia continue d to test the the n-retired machine during the 200 I season, and the RS3 unveiled at Bologna showed why, having almost the same co mpact physical dimensio ns as the V-twin two-stroke, in spite of an extra cylinder and up to twice the engine capacity. But, from the first track tests conducted by factory teste r Marcellino Lucchi at Jerez in January, 2002, the Cu be has put on weight and girth, and since then there 's been constant revision to the chassis design, w ith the engine location move d up and down, back and forth, or tilted at an angle, in a series of experi ments aimed at redressing handling co mplaints underl ined by the fact that Edwards ste pped off the Aprilia o n the fourt h lap of his first-eve r test of the bike at Jerez, 12 months to the day before my ow n te st of the bike. "I don't think we have a chassis problem," says Witteveen. "Eve n though it looks like we do , the prob lem is something else , and next year we fix it." He won 't elaborate, but Edwards isn't so tight-lipped , especially now that he's riding a Honda next season. "When I got o n the thing fi rst, it was a light switc h," says Edwards, "and at that first test I to ld 'em the re were five things I needed, and top of the list was a heavier crank . Throughout t he year there were improvem ents kept showing up, but none of those five things I asked for until the very last race of t he year and what turned out to be t he last time I rode the bike, and - guess w hat, it had a heavier crank! It helped a lot, impro ved things right away but while I can't fault the Aprilia guys and they 've bee n a straight -up company to deal with , it was kinda dishearten ing they had such a poor reac tion time - we ll, none xist- ent, really. Iwas so gung-ho about the project, really wanted to make it work, but it's got so many things tha t ne ed fixi ng - like yesterday." The beefy re inforced sw ingarm (w hich may in future be made out of carbon fiber if the RS3 st ill needs further help to reach the weig ht limit with the new, lighter engine com ing midway th roug h next season) is linked to an O hlins shock via a rising rate link, which inco rporates a ride height adjuster to allow the rear of t he bike to be raised or lowered without affecting the shock preload . Ohlins' 45mm fo rks are employed, along with 320mm Brembo carbon brakes, matched with radial-mounted Brem bo four-po t calipers, w ith what was originally a 14 10mm wheelbase which has now grown 30mm longer to counter its eagerness to wheelie, as well as to load up the fro nt w hee l bet ter weightwise in pursuit of better feel and grip. With its inclined cylinders , the rather tubby-look ing Aprilia is however quite low, even with provision for a 6,42-gallon fuel load in the rear section of the tank rather than below the seat , as is com mon place with ot he r bikes. However, the incred ibly swoopy-looking streamlining used by the Aprilia in its deb ut seaso n, with its svelte lines and pointed nose that helped propel it to that impressive top speed in its debut seaso n - on a par with the works V-fIVe Ho ndas - has since been rep laced by a more co nventional design, w hich is now pointedchinned , instead , and is designed to achieve .AOth Ann iv.:rC;::llrll down force at speed in a straight line. The fo rward part of the fuel tan k is occupied by t he airbox, fed by the twin ducts in the nose of the RS3 's bodywork, through holes in the chassis spars , as on the Kawasak i ZX-RR. "When I we nt to the race department to check on progress and I saw the bike looking so beautiful, I asked them who had designed it," says lvano Beggio at the bike's Bologna lanch. "They told me, 'The wind!'" "We worked in the wind tunnel to find a high-speed fairing, which worked well at first, but this year not, " says Jan Witteve en. "The problem was , it penalized the handlingso mewhat, so we changed to t he present des ign, wh ich is okay but can be much better. Fo r 2004 we'll be taking several different fairings to o ur preseason tests, looking for a goo d com promise in this vital area," Aprilia's MotoGP trip le hasn't covered itself in glory in its two years of competition , but neither has it disgrace d itself. Instead , it's unde rgone two seasons of on track racing development, as a resu lt of wh ich Witteveen and his team believe they have a handle on w hat's needed to w in races with the ir unique three-cylinder contender. It' ll be interest ing to see if that's what they succeed in doing with the new tr iple schedu led to de but at the Ita lian GP at Mugello in June . eN