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/126848
(Above) The GSXR11 00 engine weighs far less than the GS 1150 engine, and it's more compact as well. Four-into-one exhaust system is heavy. (A bove) GSXR11 00 clutch basket is made of stamped steel instead of more usual aluminum cast ing or forging. It shouldn 't break or distort. (A bov e) GSXR 11 0 0 pistons measure 76mm and have moderate domes; they ' re cooled on the underside by oil jets. (Be low) A drawing of a frame t ube in cross sectio n . Note extra material at corners . 12 coo ling medium. ' T he Suzuki Advanced Cooling System (SACS) uses o il to carry away combustion heat; in th e system. th e o il velocity is twice as fast as it is in a water-cooling system (so me of that velocity advantage is' effectivel y lost because oil is a lessefficient cooling medium ), and the cooling oi l contacts th ree times more a rea than a typical water-cooling system . Using oi l instead of wa ter makes the en gine simpler and ligh ter, avoiding th e useof a wat er pump, radiator, fan , water jackets , a nd water; no separate systems are needed to separate cooling water from lubricating oil, a nd maintenance is sim p lified. At th e same time, the oil cooling system keeps parts coo ler than in even water-cooled engines, the Suzuki en gineers say, and low er temperatures reduce the strain on engine parts such as connecting rods and pistons, (less meta l is needed to handle a given load as temperature drops) and those parts can in turn be made lighter . The GSX R l lOO's pistons, for example , are cooled by oil jets blasting up inside the piston domes; even though they're larger in diameter than GSl150 pistons (76m m vs. 74mm ), the y weigh 13% (a bo u t one ounce) less. Lighter pistons and rods reduce crankshaft loading, a nd where th e GSXRllOO really saves weight com- pared to the GS 1150 is in the crankshaft; 21.8 pounds, to be exact. The GSXR IIOO has a one-piece, forged , plain-bearing crank vs. the GSI150's multi-piece, built-up, roller-bearing crank, and the GSXRIIOO crank is a lightweighiexarnple of a plain-bearing crank to boot. It weighs about as much as the plain-bearing crank out of a 1985 GS750E. and has similar ma in bearing journal sizes, being 36mm in diameter and 70mm wide. The GSX RllOO 's connecting rods are made of chrome-moly steel (vs. carbon steel) and are shot-peened; shot-peeni ng increases strength by 30%. The cooling system uses a separate oil pump to send o il from the sump into the cylinder head, where eigh t jet nozzles blast it against the floor of the camshaft case, directly over the tops of the combustion chambers. At peak rpm , the system floods oil from the 5.3-quart-capacity sump to the cylinder head at a rate of 22.2 quarts per minute; because the oi l is jetblasted against the casting surface, there's lots of turbulence and good heat transfer fro m the surface to the oil. Bo lt-in plates keep the tu rbulent coo ling oil fro m flo wing over the cam chain and valve gear a nd causing friction losses and oil foaming; the oil flows from the cylinder head to the sump via two large tubes in front of th e cylinders and through cyl inder head stud passageways. In the sump, the oil is picked up by the lubricating oil pump and sent through a thermostat-controlled line to a la rge, 12-pass, 8000-kilocalories· per-hour aluminum o il coo ler, where it typically lo ses 100° F. From the cooler, the oil is routed through the crankshaft, to the piston-cooling jet spray nozzles, and into the transmission, eventually returning to the sump. Other efforts to reduce weight are simpler, including a cast magnesium cam cover. Just as straightforward are the efforts Suzuki made to maximize power output. T he GSXR II 00 has the latest version of Suzu ki's four-valves-percyli nder Twin Swirl Combustio n Chamber; it st ill features two halfdomes wit h a slight ridge bet ween them, eac h half-dome carryi ng on e intake and one exhaust valve , the configuration promoting intake swir l for more complete cylinder charging a nd more efftcient combustion. Bu t now the entire combustion chamber fits inside the circumference of the cylinder bore, without the original TSCC's over-lapping, odd-shaped corner pockets. The larger bore of the GSXRIIOO(compared to the GS 1150) helps, a nd the GSX R I IOO has larger valves than the GSI 150, 28.5m m intakes a nd 25mm exhausts vs. 28mm in takes and 24mm ex ha us ts. T he GSX R IIOO a lso ha s more valve lift. 8.8mm intake and 8.2mm exhaust. vs. the GS 1150's 8.0mm intake and 7.5mm exhaust. Valve timi ng is more radical as well. being 42-70° intake and 65-39° exhaust instead of 34·66° intake and 62-32° exhaust, (measured at 0.5mm lift ). To control the cam chain better at higher rpm, there's an