But the most impressive aspect of the RSV4 is the performance of that wonderful engine offering the best of both worlds between a four and a twin. To design the new motor, Aprilia hired one of Italy's greatest living engine progettisti, Ing. Claudio Lombardi, 67, creator of the fabulous Lancia Delta Integrale racecar that won four World Rally titles between 1987 and 1992, before he moved to Ferrari. After a stint as its Formula 1 race team manager, he then served as Technical Director until ‘94, where he moved to Ferrari's GT and sports car engine department, becoming responsible for creating the V8 engines powering many Ferrari automobiles today. The RSV4 is his first motorcycle engine design, created entirely in Aprilia's Noale base where he works full time.
The RSV4 engine features a...
The RSV4 engine features a very flat 22-degree included valve angle, specified by designer Claudio Lombardi from his days at Ferrari as the optimum setup. Forged pistons force a high 13:1 compression ratio, with titanium intake and nimonic steel exhaust valves.
As usual on an Aprilia Factory...
As usual on an Aprilia Factory model, the latest Öhlins 43mm inverted fork is used up front, with radial-mount monoblock Brembo calipers biting on 320mm discs for superb stopping power. New design forged aluminum wheels are lighter than previous models.
The extreme chassis adjustability...
The extreme chassis adjustability of the Aprilia includes adjustable steering rake angle via eccentric inserts (top), adjustable swingarm pivot height inserts (middle), and even engine mounting adjustability using frame inserts (bottom).
The result of Lombardi's efforts is a unique 65-degree V4 engine, with horizontally-split crankcases and the Nikasil cylinders cast integrally with the upper crankcase half for greater stiffness. "When we started work on the project in September 2005, the intention was to design a 60-degree V4," says Lombardi. "But it soon became clear that the intake tract was flawed. By opening the cylinder angle out slightly to 65 degrees, we had the straighter run that was needed to obtain our design target of 180 horsepower in street form." A single gear-driven counterbalancer in front of the cylinders consumes an estimated three horsepower in canceling out the vibration caused by the narrow cylinder angle. "It's slightly better balanced now than a 90-degree V4 engine," declares Lombardi with satisfaction, although he admits, "I don't pretend it's ideal, but it isn't an unduly tall engine package, either," referring to the fact that the bank of four 48mm Dell'Orto throttle bodies can't be sunk any lower between the cylinders owing to the narrow angle. "It's perfectly satisfactory in terms of height, and allows us to produce the narrow, compact motorcycle we were seeking."
Utilizing a setup similar...
Utilizing a setup similar to the Yamaha R1/R6, the RSV4 engine features a variable length intake tract system controlled by the Magneti Marelli ECM. At 10,000 rpm, the top 35mm sections separate to create a shorter intake trumpet for optimum high rpm performance. Note the shower style secondary injectors.
The RSV4’s cockpit is a beautifully...
The RSV4’s cockpit is a beautifully clean, no-frills design, with ergos that aren’t cramped for those over six feet tall. The top of the fuel tank is flared out to give the rider's knees added leverage in turns.
This CAD illustration shows...
This CAD illustration shows the various pressed sheet and cast aluminum pieces that make up the construction of the frame and swingarm. The frame weighs just a bit over 22 pounds, while the swingarm scales in at 11.2 pounds.
Despite the 999.6cc engine's seemingly radical oversquare 78 x 52.3mm bore/stroke dimensions, Lombardi says he'd have preferred an even shorter stroke, but was forced to settle on this configuration by the World Superbike rules then in effect. "At the time we were designing the engine, the FIM had imposed a 1.5:1 bore-to-stroke limitation on four-cylinder machines, to protect the 1000cc twins," he says. "By the time this restriction was removed from the SBK rulebook for ‘08, to allow 1200cc twins, it was too late for us to change. I would have preferred to have a shorter stroke, for more power at higher revs, while still retaining valve springs. I had experience at Ferrari with high-revving non-pneumatic valve engines, and it would have been good to adapt this technology to the RSV4."
The RSV4's forged pistons deliver a high 13:1 compression ratio, with twin oil pumps ensuring adequate lubricant pressure at all rpm. To make the chassis as narrow as possible, Lombardi has adopted a modular cam-drive arrangement, with a chain driving the intake camshaft for each cylinder block, which in turn drives the exhaust camshaft through an idler gear, permitting a narrow 250mm cylinder head width across the top—less than the RSV1000 V-twin, according to Aprilia. The pairs of 32mm titanium inlet and 28mm nimonic steel exhaust valves for each cylinder sit at a very flat 22-degree included angle, and here once again Lombardi's F1 experience came to the fore. "At Ferrari, we experimented with an included angle of everywhere from 16 to 28 degrees," he says. "We found this was the best angle. I used titanium intake valves because you aren't allowed to change the valve material for superbike racing, and for 15,000-rpm engine speeds, you need titanium. Retaining steel exhaust valves was for economic reasons." Two springs are fitted per valve, and it's worth noting that the RSV4's water radiator is very small, indicating that Lombardi has achieved a high degree of thermodynamic efficiency for such a compact engine design. "I'm quite proud of that," he admits. "It was also an important issue in keeping the bike as narrow as possible. For a 180-horsepower engine, it runs very cool." He also reveals that Aprilia is already working on a bored-out 1200cc version of the engine. "Another advantage of the V4 layout is that you can easily change to a bigger bore," said Lombardi.
The Aprilia engine lulls you into thinking it's not revving very hard, until you look at the analog tach and discover that it is revving higher than you thought, thanks to that gruff exhaust note. It'll pull cleanly from as low as 3000 rpm on part throttle, helped no doubt by the Magneti Marelli engine management system that controls the throttle valves, the variable-length intake trumpets, and an exhaust powervalve. Similar to the Yamaha system, the Aprilia intakes use a 265mm-long intake trumpet for low rpm, with a servo motor separating the upper 35mm half at 10,000 rpm for better top-end performance.