There has been a large amount of discussion lately regarding the competitiveness of Ducati’s 1000cc V-Twin World Superbikes relative to the 1000cc inline-four cylinder machines fielded by various Japanese manufacturers. Ducati is pressing for a rules change to allow them to compete with V-Twins displacing 1200cc (although they may compromise with 1150cc), claiming that they are having trouble matching their power output to that of the Japanese bikes. According to Ducati, in order to reach competitive power they have to tune their motors so aggressively that they need comprehensive rebuilds after nearly every race. They claim that the larger displacement would allow them to produce competitive power with motors that are in a less aggressive, more reliable state of tune.
Although this is sound theory, anyone who believes that the Ducatis are presently down on power in comparison to the Japanese fours should take a look at the trap speeds recorded at Monza a few days ago. As anyone who has experience in drag racing knows, trap speed is a fairly accurate indicator of a machine’s horsepower output – particularly in a class where all machines are of relatively equal weight, as they are in WSB. While aerodynamics do play a role, there is no way that the impressive Ducati trap speeds at Monza could be due to aerodynamics alone.
The fastest trap speed recorded was that of Ruben Xaus, on a Ducati 999. At 192mph, Xaus was 2mph faster than the second-fastest rider, Fonsi Nieto on a Kawasaki ZX-10R.
Series points leader Troy Bayliss clocked the fourth-fastest trap speed at 188mph, while the reputedly high-powered Suzuki of Troy Corser only managed to run 186mph, good for the sixth-fastest spot.
What do these numbers mean? Since the gaps are too big to be explained by aerodynamics alone, the trap speed of the Ducatis tells us that they are, at the very least, on a relatively equal footing with the Japanese fours as far as horsepower and acceleration.
The problem for V-Twins, and the reason Ducati legitimately needs a displacement advantage (or a weight advantage – see discussion below), relates to the inherently lower rev-ceiling of a twin versus a four-cylinder of equal displacement. For some discussion of relevant concepts, take a look at our article on February 21, 2005 titled “An Analysis of MotoGP Engine Configurations”. The bottom line is that the larger and heavier engine components associated with individually larger cylinders (each displacing approximately 500cc in a twin versus ~250cc in a four) make it impossible for a twin to rev as high as a four without running much “closer to the edge” of catastrophic engine failure. When an engine is tuned to take advantage of it, higher revs mean higher horsepower (when an engine moves more air it can make more horsepower).
In the long run, there are two ways to deal with this inherent horsepower deficit, including displacement and weight. Although WSB has traditionally given V-Twins a displacement advantage, the powers that be in MotoGP have instead offered reduced weight as compensation for machines powered by engines with fewer cylinders. In the past, when WSB gave V-Twins as much 33% more displacement (1000cc for twins and 750cc for fours), twins became the dominant force – leading Honda to build a twin and win the championship with Colin Edwards aboard in 2002. 33% was obviously too much, and the proposals this time are for a maximum advantage of 20% (1200cc vs 1000cc).
In the meantime, Ducati is certainly holding its own without any weight or displacement advantage. This legitimizes Ducati’s claim that its v-twins are in a higher state of tune to compensate, and need more frequent maintenance. Ducati has been tuning this basic engine configuration (90 degree V-Twins) for over a decade, and must be close to the limit on developement. As this season progresses, we wouldn’t be surprised to see either one, or both of the following, including (1) increased frequency of engine failures for Ducatis (leading to DNFs) or (2) more highly-tuned four-cylinder machines asserting a clear horsepower advantage over the Ducatis.