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/517599
2015 APRILIA RSV4 RF FIRST RIDE P96 at 5500 revs when the valve is wide open, and accelerates sub- limely hard, but with a very linear delivery, towards the 14,200 rpm redline. I tried to spot the higher transition point at 11,000 rpm where Piero Soatti told me the velocity stacks now lift off the throttle bodies for more oomph up high, but failed—they just do. With the increased power at the crank that allows the Aprilia to join the 200 bhp club—this is just as fearsomely fast, but rideable Superbike with lights as the RSV4 has always been, except now it's even better. Using that gear higher in corners makes the front Pirelli really earn its keep, as it com- bines with the revamped chas- sis geometry to deliver extra turn speed, as well as to cope flawlessly with the hefty weight transfer entailed in stopping hard from high speed with total stability, thanks to the great bite from the super effective Brembo brake package. No weaves, no wobbles, no street-sweeping from the rear tire, it just stops— very, very hard, from very, very fast, with the help of some remaining engine braking left in by the settings chosen for the Aprilia's variable idle speed en- gine braking control working in conjunction with the ramp-style slipper clutch. >>THE TECHNICAL REVOLUTION Six years on after making its debut in the World Superbike arena and having secured a total of seven World Championship titles in that period, Aprilia's unique 65° V4 engine has had its first major upgrade in the new- for-2015 RF/RR duo. It now produces 201 crankshaft bhp at 13,000 rpm, up from 184 bhp at 12,500 rpm previ- ously. This 17 bhp power increase has been obtained at the cost of just a slight 2Nm drop in maximum torque to 115Nm at 10,500 rpm, with the revlim- iter set 500 revs higher than before at 14,200 rpm. While retaining the same radically oversquare 78 x 52.3 mm dimensions as before, the 999.6cc V4 engine has been completely revamped, with most components redesigned in pursuit of the increased performance that according to Aprilia's chief R&D engineer Piero Soatti. It has been obtained primarily via reduced friction, improved combustion efficiency and higher revs, plus less weight, with the motor scaling 5.5 pounds less than before. The upper half of the horizontally- split crankcase comprises a new 3.3 pounds lighter casting, with the water- cooled cylinders containing separate Nikasil-lined aluminum liners cast integrally for greater stiffness, but with an optimized ventilation system aimed at reducing pumping losses caused by air pressure inside the crankcase. The oil system has been completely revamped, and the lower crankcase half now incorporates a redesigned magnesium sump casting to optimize lubrication at full lean and under maxi- mum acceleration or braking, despite the oil level being reduced in order to decrease friction. The RSV4's forged pistons now deliver a high 13.6:1 compression ratio, and sit on new 100 grams lighter Pankl forged steel conrods, running on a redesigned plain-bearing forged one-piece crankshaft that's gone on a one-pound diet, with its crankpins each reduced in diameter to 36mm, making for a crank assembly that's a whole 1.8 pounds lighter than before. The 1-3-2-4 firing order (where 1 is the left rear cylinder and 3 its companion) yields a 0°-180°-425°-605°-0° crank throw, enough of a long-bang format to enhance rear grip, says Aprilia, as well as to prolong tire life. To keep the polished aluminum twin-spar chassis as narrow as pos- sible—an issue essentially dictated by the width of the cylinder heads, where the frame spars wrap around them—Aprilia has retained its modular camdrive arrangement with a lateral chain for each twin-cylinder head casting driven via an idler gear running off the crank, which in turn drives the inlet camshaft for each DOHC cylin- der block. Another pair of idler gears then drives the exhaust camshaft, permitting a narrow 9.8-inch width across the top of the engine, which is actually less than the old RSV1000 V- twin. These camshafts are now forged with new profiles, and are each 1.3 pounds lighter than before, operating valves that are now all titanium—pre- viously only the 1.2 inch inlet ones were, with the 1.1 inch exhaust ones being heavier but less costly nimonic steel items. Those inlet valves have increased in size to 33mm, but the exhausts are unchanged, all sitting at a flat included 22° angle to each other and running in revised higher valve seats intended to improve reliability under heavy loads, and each carrying two new, lighter springs, with lighter tappets and valve caps. The cylinder head porting has also been revised, and the combustion chambers in each head have now been CNC-machined to ensure accuracy, rather than merely cast in at the foundry. The 2015 RSV4 also has a new airbox design - a key component, now that the new Superbike rules require it to be maintained for racing - aimed