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
the high revs we are using we've had quite few technical failures . "The n a third reason is that from a prod uction point of view, a three -cylinder engine is the cheapest to rep roduce when we co me to develop a street-legal re plica or eve n a Superbi ke, later on . It's less expensive to build than a V-tw in, because there is o nly one cylinder head casting, one cylinder block, one camsha ft drive , one of everything - in fact, I'm sure that it's t he least-costly e ngine to manufacture in all of MotoG P. Th is is a strong advantage when we bring this concept to production, as Mr. Beggio has said from the beginning was always his intention. "Finally, anot her point is the weight-sav ing benefits fro m using a trip le , w hich has a I 35kg minimum weight limit [297 pou nds], 10 kilos [22 pounds] less t han the fours or We haven't been able to meet this yet, but instead of being 15kg [33 pounds] overweight, as we we re last year, we've now got it down to 14 Ikg [3 10 pounds , from 334 poun ds in 2002]. So now it' s lighter than the fours, and there are still savings to co me , even before we bring out our new engine next year, which will be lighter and more compact than the existing one, as well as benefit ing from the technical lesso ns we've learned over the past two seasons . However, the re 's also the question of fuel co nsumption, which will become very impo rtant when the fuel tank capacity dro ps to 22 liters [5.72 gallons] for 2005, from the present 24 liter s [6.24 gallo ns]." This wo uld have bee n intro duced for 2004 but was de layed one year by the FIM in spite of Aprilia's protests, thank s to con certed pressure from t he Japanese ma nufacturers, led by Honda, which has the biggest fuel co nsumption pro blem of anyone, with its thirsty five-cylinder bike . "I believe a three-cylinder engine is the most efficient in terms of consumption: ' insists Witteveen , "so we look forward to the red uced fuel capac ity becau se it will not affect the perfor mance of our bike , as it will the others. Toget he r, I be lieve all these points speak in favor of having a three-cylinder, and I'm still as convinced abou t that now as when we started the pro ject over th ree years ago, so no regrets - eve n though the fewer cylinders you use , the more high-tech the engineering solutions you must adopt to get competitive performance, just as the more cylinders you use , the lower-tech e ngineeri ng yo u can employ." Ah, yes - as in the V-five Ho nda. The first dyno runs of Aprilia's threecylinder e ngine too k place in O ctobe r, 200 I, since w hen Witt eveen declares the essentia l architecture of t he motor has remained unchanged, mean ing it's still a dry sump design Oust as Aprilia's RSVI000 Superbike and all Formula I e ngines are) , though the reason is for improved engine performance via reduced oil drag, insists Witteveen, rather than superior installation , as in F I. Whatever, there's still the ens uing weight pe nalty of three different oil pum ps to over co me , w hich together with the compressed air tan k for the pneu matic valves, the coun terbalancer and t he quite big-looking engine , all can't have helped in meet ing that e lusive 297-poun d minimum weight . The fabricated oil tank is located on the right of the engine , in front of the clutch, and it curves down aro und the cra nkcase partly to position the lubricant pretty much where it wou ld be in a wet sump motor like all the others in MotoGP. The Cube's engine sees the upper half of the ho rizo ntally split crankcase cast in unit w it h the cylinder block, for added rigidity, and gear drive to the twin ove rhead cam shafts is car ried up the left side of the engine, which has t he cylinder block canted forw ard aro und 20 degrees for improved chassis packaging. Valve operatio n is pne umatically co ntrolled, as o n all current Formu la I cars, including Coswo rt h's own V- IO Jaguar motor, which allows the height of the very compact engine to be reduced compared to a valve-spr ing design, as we llas target ing improved to p-e nd pe rformance by permitting safe revs in excess of 15,000 rpm , w ith the larger-diameter pistons, which allow bigger valves (four t itanium ones per cylinder) on the three-cylinder engine compared to fours of the same capacity. "We didn't need pneumatic valves to begin with, " admits Witteveen, "but I wanted to have the system in place fo r when it did beco me necessary, as we raised the rev ceiling in searc h of mo re po w er. That's now happened, with a 16,5 00 rpm revlimiter at pre se nt and power peaking at 15,000 rpm , wh ich gives a nice overrev - but we can go to 17,000 , even 17,500 without problems." It's worth not ing that the Cube's cylinders are on ly slightly larger tha n those of Cosw o rth 's current F I e ngine design, tra pped third fastest at 327.5 kph (203 mph) in th e Italian GP this year w ith Haga aboard - thr ee mph down o n the Desmo sed ici, but 2 1/ 2 up on the best of the Hondas and Yamahas. That's 240 hpplus top-speed territory - t hough for tighter circuits Aprilia is likely to have backed the power off to aro und 225-230 hp this season to improve ridability. Th is significant power de livery originally req uired huge radiato rs to disperse all the heat generated , but this had an adverse effect on both handling and, especially, weight . So for 2003 it was replaced by a much smaller and thus lighter one, easily the dinkiest o n the Moto GP grid, mea ning tha t wit h all that powe r and thus heat, it would have to be pressurized w hen ambient cond itions demanded , probably by the installatio n of a bicycle-type Schrader valve in o ne of the waterhoses. But t he threecylinder e ngine runs very hot as a matter of course , says Witteveen - 95-100 degrees C is its normal operating range, indicating t hat Coswo rt h's experience in coo ling powerful pe rformance motors, like its w hich already revs even higher to over 18,000 rpm and has a specific power output of aroun d 280 hp per liter. An eventual figure of 270 hp fo r the Aprilia engine in 990 cc for m w ould therefo re be qu ite feasible - "but reliability at those engine speeds will become an issue, which it isn't at pres- 1000 hp Indycar turbo engine, has bee n bro ught to bear on the RS3. There's a small, beautifully made catchtank on the left of the engine , match ing the corresponding oil tank o n the o ther side. The Cube's I20-degree crankshaft w ith evenly spaced throws - no 180-degree two-up Big Bang effect, like on the last Laverda triples - features a balance shaft moun te d betw een it and the clutch to remove vibration, which means the crank runs backward on the Aprilia, as on the Yamaha MI . "It rotates in the opposite direction to the w hee ls of the bike , which gives an improved gyroscopic effect, resu lting in more stability in high-speed corners, and doesn't affect it too badly in low -speed o nes ," ex plains Wittevee n. "The inert ia of the balance shaft is much less than the crankshaft, so it's an ove rall ben efit." The 6-3-1 Akrapovic exha ust system feat ures twin -port head ers exiting eac h of the three cylinders, all merging into a single ent," warns Witteveen. "H owever, we have lots of pote ntial locked up in the engine, and it now pulls fro m very low, between 7000 to I 1,000 rpm, so it's quite ridable now - a big improvement over last year! We had good top speed from the very beginning, but there was a problem with bott o m-end power, which this year we fixed. But now we need more top end again, which we 'llget with our new engine coming next season. II Official powe r figure for the Apr ilia in its end-of-'03 guise is a coy "over 220 hp'' at the gearbox, according to Witt eveen - but how much ove r? Well, after becoming the first European race bike to break t he 200 mph barrier at Mugello in 2002 in the hands of Regis Laco ni, the R5 Cub e was . . .. a... ,_ •• ,.I,enc\A'c:. ,..nlTl