The first point to be made is that a MotoGP bike is a prototype, and as such there is no required minimum quantity that must be built and no ceiling price on the machine. But for World Superbike, the homologation procedure begins with 125 machines and by the end of the first year of participation, 500 must have been built, and by the end of the second year, 1,000. A price ceiling for the homologated model is set at 40,000 euros (approximately $45,500). Ducati’s Panigale V4 R gets its Superbike-legal reduced 998cc displacement from a shorter stroke.
Production methods that are economical for building 500 bikes are different from those for building a prototype. Yamaha’s MotoGP bike engine crankcases are machined from solid in a 70-hour process. Honda’s RC213V cases are sand-cast. But for quantity production in the hundreds or thousands, it makes better sense to die-cast the crankcases, cylinder heads, etc. As a result, parts produced in larger quantities tend to be both heavier and weaker.
MotoGP engines are required by tech rules to last through three-plus events each (each rider has six engines with which to complete the 19-race series). To achieve this, component quality must be the highest possible. So, for example, crankshafts will be forged from a low-defects vacuum-remelted aerospace steel alloy similar to 4340M and the job will be done by a specialist supplier. A production bike, by contrast, is expected to last through a normal road-vehicle lifetime at a street-legal stress level.
Performance levels also differ. While it is known that Ducati’s MotoGP V-4 can operate safely to 18,000 rpm, where it may produce as much as 275 hp, the one-liter production V4 R homologated for World Superbike, even though having the same bore and stroke of 81.0mm x 48.4mm, is rated at 221 hp at 15,250 rpm. Redline in sixth gear is 16,500 rpm, which says, “Eat your heart out, Kawasaki” to its most obvious World Superbike rivals, whose 13 percent longer piston stroke makes such high revs harder to attain reliably.
Ducati points out in its V4 R press materials that the relatively broad torque and docile power production of the 1,103cc Panigale V4 are achieved with modest-sized intake ports (which boost midrange by creating higher intake velocity there) and limited valve timing. The result is 214 hp at 13,000 rpm while meeting European sound and emissions levels. To achieve greater power from only 90 percent of the displacement, the 998cc V4 R must turn faster and generate higher stroke-averaged net combustion pressure. It is able to do this only by sacrificing some the V4’s drivability (which former Ducati rider Marco Melandri praised highly in a conversation at Laguna Seca this past season). Much of that change comes from longer cam timings, which move the point of best cylinder filling up the rpm scale.
In the V4 R, lightweight titanium connecting rods replace the steel rods of the V4. The pistons are described as “molded” (i.e., cast) of “box-in-box shape” and as having the pure racing fit of a single compression ring plus an oil scraper. The lighter the reciprocating parts can be, the lower become stresses and bearing loads, allowing reliable operation at higher rpm. The V4 R’s crankshaft, like that of the V4, has Ducati’s MotoGP-originated 70-degree-offset crankpins but is almost 2-1/2 pounds lighter. It turns on three of what are cryptically called “brass bushings.” Hard brass bushings of the kind common on railroad axles of 1900 would be strange indeed for a 15,250-rpm internal-combustion-engine crankshaft.
What this may mean is that, as in the case of Honda Formula 1 engines, the old heavy-duty form of bearing called “copper lead” has been revised upward in strength. A copper-lead bearing derives its fatigue strength from a matrix of copper, which is impregnated with lead to provide essential “embedibility.” That is the softness that allows the hard crank journal to drive potentially destructive wear or contaminant particles into the bearing surface, rendering them harmless. Therefore the “brass bushing” probably means a bearing whose endurance comes from brass being stronger than copper and whose embedibility is provided by infused softer metal. It is almost illegal even to utter the word “lead” in today’s heavy-metals-free world, so other soft metals such as tin, zinc, etc. provide the necessary softness.
In the MotoGP engine, a train of steel spur gears drives the camshafts, but the production V4 and V4 R are given less noisy and cheaper cam drive by silent chains. Why the difference? With gears it is easy to maintain accurate valve timing through hard racing use, a task that is harder with a chain that has perhaps 100 links and pivots.
The purpose of a homologation special is to make legal for racing those elements essential to the highest performance but which would in mass production add needless cost, being superfluous to the requirements of even the most spirited of everyday riders. Therefore, in a sense, such bikes are designed by the rule book. I expect most V4 Rs will go to actual race teams.