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Why Did Honda Choose a V-4 Configuration for Their 800cc MotoGP Machine?

Journalists and MotoGP fans alike got their first look at Honda’s prototype 800cc MotoGP racer a few days ago, with the machine being tested at the Motegi Circuit in Japan in the aftermath of the MotoGP held there. Ever since the 800cc regulations were announced (going into effect next year), speculation has been rife as to what engine configuration Honda might choose for their next-generation MotoGP machine; speculation ranged from a V-3 to a V-6.

Why go with a V-4? For an in-depth analysis of the factors involved and the advantages of the different configurations, refer back to the article I wrote last year entitled An Analysis of MotoGP Engine Configurations. However, there’s a little more to it than that, especially considering that the weight limit is the same for both four-cylinder and five-cylinder machines.

No, we suspect that a big part of Honda’s decision revolved around the fact that if you take a 990cc five-cylinder (like their current RC211V) and basically lop off one of the cylinders, you’ll be left with a 792cc four-cylinder. Although developing their new 800cc motor was obviously more complicated than the procedure described above, the benefit for Honda is that they can keep the same or very similar piston diameter (and thus bore size). This means that all their complicated research into areas like piston dome shape, combustion chamber shape, compression ratio, and even their knowledge or computer simulations of the combustion event itself, will all carry over from the old V-5 to the new V-4.

Don’t be surprised if this puts Honda a step ahead of its competitors as far as power output, especially early in the 2007 season.