[Date of writing: nov 28, 2006]

Earlier this year Leo Francesco Mercanti, Aprilia brand manager, told us about Aprilia's intention to re-enter World Superbikes in 2008 with a v4, and at the Milan Motorcycle show today, we saw the remarkable engine of the new bike, bristling with innovation.

Developed entirely in-house, the Aprilia engineers have used a slightly wider configuration of 65° between the cylinders (compared to the current RSV twin's 60°), maintaining excellent fluid dynamics in the inlet ports whilst still allowing a short and narrow engine that'll give the chassis engineers a lot of flexibility over placement.

The primary vibration inherent in a 65° angle between the pairs of cylinders is negated through use of a balance shaft.

Space is further saved by a very unusual design for driving the dual overhead cams. Only the inner (inlet) cams are driven by chains which in turn, drive the outer cams through a series of gears between each pair of cylinders. The importance of a highly compact v configuration was learnt from the hugely successful SXV v-twin engine which achieved it's compactness through a different route, via a single overhead cam per cylinder.

Aprilia have been so successful that the RSV 4 v-four engine is even more compact than the venerable Rotax V60 v-twin with which Aprilia first entered WSB in 1999, and which drives the current RSVR Factory, this year crowned the fastest production motorcycle in the world in the objective and prestigious Masterbike competition.

In WSB racing trim the engine revs to 13,500rpm and already produces 207bhp (at the crank obviously) with plenty of development work to do before the 2008 season.

The throttle linkage is fly-by-wire with the throttle butterflies on each pair of cylinders operated by two stepper motors controlled directly by the Magneti Marelli ECU, which also controls two injectors per cylinder, one either side of the throttle butterfly.

WSB entry also means that Aprilia will be producing RSV4 homologation specials for the road, much like the RSV SP, which should also mean a range of full production bikes, hopefully also for 2008. The power on these production models will have to be a fair bit lower for cost and longevity reasons, but it's abit early to speculate on what exactly to expect, suffice it to say that it'll be more than competitive. The price will obviously be in excess of the current RSVR Factory, but not as much as you might think, and certainly less than the 999R.

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