Racing has always played a major role in the life of Aprilia. The relatively small factory in Noale started its adventure in the mid-1970s and quickly became a major competitor in motocross. Passionate (and wealthy) founder and owner Ivano Beggio then turned his attention to roadracing, where Aprilia dominated the 125cc and 250cc classes until last year, when the FIM outlawed two-stroke engines.
But the 125 and 250 classes were not enough for Beggio, who extended his challenge into the realm of Superbike, giving life to the RSV1000 built around a 1000cc Rotax 60-degree V-Twin. In the very capable hands of Troy Corser and Noriyuki Haga, the RSV1000 failed to achieve the top laurels only by inches.
The 1000cc four-stroke MotoGP class also looked very attractive to Beggio, who poured bushels of euros into the ill-fated Aprilia Cube project. The bike was powered by a three-cylinder engine designed by Claudio Lombardi, a former Ferrari technician hired to manage all Aprilia four-stroke racing programs. Not only did the 1000cc inline-Three MotoGP racer prove inconsistent, Aprilia’s racing activity was fragmented on too many fronts at the same time money was running low. That combination of negative factors finally led Beggio to sell all of his motorcycling operations—Aprilia and Moto Guzzi—to scooter giant Piaggio.
To replace the no-longer-competitive RSV1000 and give Aprilia a second chance to reach the top of the SBK class, Piaggio launched a new project. After the first round of preliminary evaluations, three engine configurations remained on the table. Surprisingly, despite the Aprilia Cube failure, Claudio Lombardi again came up with an “inline-Three” concept. But he also submitted a narrow-angle V-Four design, along with a more conventional inline-Four.
In the end, the V-Four came out on top by offering the best compromise. It had the potential to be narrower than both the inline-Three and Four, and much more compact, lengthwise, than the 90-degree V-Four that was proposed only as a theoretical comparison but never considered a viable option by Aprilia’s technical team.
In reality, a narrow V-Four would be more balanced than an inline-Three in both primary and secondary order; and though it would be less balanced than an inline-Four in primary order, a very small balancing shaft could cancel any resultant vibrations. A narrow V-Four also is slightly less balanced than an inline-Four in secondary order, but only by a negligible factor; besides, the perceived vibrations would not be any more disturbing than those of an inline-Four.
Another major advantage of the narrow-angle V-Four concept was that it could be harnessed in a frame dimensionally similar to that of the world-championship-winning Aprilia 250 GP racer. This was a very positive point on which to capitalize, since the Aprilia 250 was always regarded as the best-handling bike in its class.
Based on their experience with the RSV1000 V-Twin, the Aprilia technicians started with a 60-degree Vee angle, then enlarged it to 65 degrees for practical accessibility and the best configuration of the intake system’s variable-length velocity stacks. (As a side note, let me point out that all the legendary Ferrari V12s have had their Vee angle set at 65 degrees rather than the customary 60 degrees for such engines. Is there any meaning in that? Hard to say.)
The rest, as the saying goes, is history. Aprilia’s narrow-angle V-Four demonstrated superb performance potential in all forms. The SBK racer delivered in excess of 220 horsepower, as well as absolute rationality in terms of overall dimensions and layout, giving life to a super-compact bike. To ride it, Aprilia hired its never-failing sweetheart, Max Biaggi, who won the SBK title in 2010. He had a less-positive 2011 season but currently is in this year’s championship points lead. And Aprilia’s V-Four now is even trying its hand in MotoGP, powering a couple of CRT racers ridden by Randy dePuniet and Aleix Espargaró.
Apparently, Aprilia’s chief of the Race Department, Luigi Dall’Igna, has got a lot more in reserve. According to credible rumors, there are modifications ready to push the V-Four’s output past 230 horsepower. Further evolution will take advantage of the standard 81mm bore rule established by the FIM, thus bumping the bore from 78mm to 81 and consequently cutting the stroke from 52.3mm down to 48.5 for larger valves and safe higher rpm.
Obviously, this Aprilia narrow-angle V-Four has a few more tricks up its (4) sleeves.
When the men of Aprilia’s R&D Department opted for the narrow-angle V-Four layout, they knew what they were doing. The engine is extremely compact and no taller or longer than an inline-Four, but it is much narrower and shorter than a 90-degree V-Four. At 152 lb. dry, the RSV4 Factory engine does not offer a meaningful advantage over an inline-Four in terms of weight.
This top view shows why the Vee angle had to be stretched from the original 60-degree design to the 65-degree configuration: to make room for properly designed inlet velocity stacks and their variable-length system.