Cycle News - Archive Issues - 2000's

(Left) The 990cc V4 is as compact as the RGV500 It supplants. Rev ceiling is about 14,300 rpm, some 700 rpm less than a GSX·R750 streetbike. Oh yeah, It is also claimed to make 210 horsepower, about 67 more than a GSX-R1000. (Above) The GSV·R's clutch Is part of an electronically managed system that allows for full-tilt, multi-gear downshifts without causing wheel chatter. (Right) The carbon 320mm Brembo brakes are strong enough to 11ft the rear wheel even under casual braking. engineers devoted to the GSV-R project, alongside Team Suzuki's 20man race squad - had opted to build a GSX-R990 Evo and rationalized the costs of going racing with the result as being a sort of rolling R&D testbed for its next generation of streetbikes. Only they didn't. Instead, the GSV-R (otherwise known in-house as project XR-EO "E" as in experimental, "a" as in first of a series) is a purebred 60-degree V4 four-stroke racer completely unlike anything else Suzuki has ever built before. "We wanted to use the existing RGV500 Gamma chassis, which in winning the 500cc World Championship, Kenny Roberts proved to have excellent handling characteristics, as the basis for the new fourstroke machine," says Suzuki's GP technical guru Yasuo Kamomiya, leader of the youthful group of engineers charged with producing the RGV-R as part of the company's policy of focusing new minds on a new generation of racebike. "This meant that the engine must be very compact, to occupy the same space as the old twin-crankshaft 500cc twostroke V4, and so we opted for a narrow-angie single-crankshaft 60degree V4 engine of full 990cc capacity permitted under the new rules. This format also has fewer mechanical losses than an in-line four, with two less main bearings, so that was another reason to choose this layout, which helped us reduce weight, as well." (t also had the added bonus of producing a slim bike with improved ground clearance and reduced fronta I area compared to an in-line fourcylinder design, as well as delivering another crucial advantage. "Additionally, we wanted a new challenge," says Kamomiya-san. "Suzuki already has much experience in working with in-line four-stroke engine designs, so in order to gain added benefit from competing in MotoGP, we decided to investigate V4 technology in building the RGV-R." The result is a motorcycle hardly any bigger physically than the RGV500 with which Kenny Roberts earned Suzuki GP history's penultimate 500cc world title in 2000, powered by a four-camshaft 16-valve 60degree V4 four-stroke engine which is only 10 percent heavier than the twostroke it replaces. It has a single gear-driven balance shaft to minimize vibration from the narrow-angle motor, a single plain-bearing crankshaft with paired crankpins, gear camshaft drive, titanium rods, valves with very flat included angles, and forged aluminum pistons - probably with just two rings each, to minimize friction without creating oil blow-by problems - which help deliver a very high compression ratio of around 14.5: I, surely a factor in the bike's sparkling acceleration. Suzuki prefers not to disclose the exact dimensions of the engine which, given that it produces the claimed maximum power of "over 210 bhp" at 14,000 rpm and is rev limited to just 14,300 rpm (compared to the 15,000 rpm of its only slightly smaller capacity GSXR750 in-line counterpart) may not yet? - be as radically oversquare as some observers have conjectured. Certainly, the GSV-R has more of a muscular, even gruff exhaust note when you ride it compared to its Superbike kid sister, but it also sounds much throatier from the side of the track than Yamaha's Ml or Kawasaki's ZX-RR MotoGP in-line fours, and that's after taking into account the lazier-sounding nature of a V4 compared to an in-liner. What it doesn't have, though, is the flat drone of the last lBO-degree RC45 Honda Superbike, indicating that Suzuki presently has the engine set up with the cylinders firing evenly in a 360degree format - but Tamomiya admits they're currently experimenting with various big-bang options which could be adopted in the future, possibly as an aid to extending the life and enhancing the performance of the rear tire. The GSV-R is fitted with Suzuki's own fuel-injection system, which employs a Mitsubishi ECU matched to four separate Keihin throttle bodies of undisclosed bore positioned centrally in the middle of the vee, and two injectors per cylinder, one mounted below the throttle butterfly and the other above it, but located to the side, almost parallel to the lower injector rather than directly above the intake trumpet, as on some other F1derived systems. This is partly to avoid making the engine package any taller, and also because Suzuki employs a so-called "dual funnel" intake system, whereby a secondary air trumpet is sleeved into the primary one to optimize torque characteristics and enhance intake flow. The team has also experimented with different length trumpets - longer is better for torque, shorter better for outright power and thus top speed while the 3-2-1 exhaust system has a very slim silencer whose diameter is enough to ensure it meets MotoGP's thankfully non-PC 125dB noise limit. The choice of a 60-degree V4 is understandable for packaging reasons - but it brings the risk of compromising intake flow, as Aprilia RSV Mille engine designer Claus Holweg admitted when he broadened that engine's 60-degree included cylinder angle for his second attempt at designing a benchmark V-twin Superbike engine, in the form of KTM's new 75-degree LCB motor. "If we had done this, by choosing 72-degree or 75-degree V4 cylinder angle, the distance from front to rear of the engine would have been too great for our needs, making the engine too long," says Kamomiya. "We wanted to keep this short, so we .. U ... e n could use a longer swingarm for better traction and less whee lies - but I admit that in designing this first bike, our main priority was for chassis layout." Read into that what you will - but it could be that the GSV-R's apparent lack of breath at the top end and its restricted appetite for revs could be partly down to a less-than-optimum intake flow from the massive carbon air duct at the front of the fairing feeding the relatively small-volume pressurized airbox because of the lack of space to permit a straighter hit at the paired inlet valves. Maybe the new Mark II GSV-R which Kamomiya confirms his team is working on for next year, using the lessons learned this past season with . the prototype machine - and which he says will have a new engine with a different configuration compared to the existing one and a new chassis to match - will have a wider cylinder angle, aimed at redressing this factor? In spite of the limited time they allowed themselves to develop the engine before going racing with it, Suzuki's achievement in making it strong and reliable as well as competitive from the very first race is underlined by the fact that the team didn't suffer any major engine problems in GP races. Its fleet of power units was rotated every 1000km for servicing back at the factory, unlike the old two-stroke motors which were rebuilt during the season by the Team Suzuki race mechanics in the back of the truck or at the team's British base. "All the engine maintenance is carried out in Japan, where they freshen them up with new rings and a set of crankshaft bearings and check them over," says Team Suzuki's chief mechanic Bob Toomey. "Crankshafts and main engine parts all last for 2000km before they're replaced as a matter of course. It's a well-engineered and reliable package that's e _ S • DECEMBER 1 1 ,2002 19

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