FOUR FOR MORE
Compared to four cylinder engines, triples still lose out on outright power and if you want to win at motorcycle Top Trumps, you’re going to need four-cylinder bikes in your deck. Fair enough, transverse, inline four-cylinder engines pose a slight width problem. But they can be made very compact lengthways by stacking the gearbox up behind the cylinders. This can give a transverse, inline four-cylinder powered bike excellent weight distribution, even with a short wheelbase. Inline-fours also balance out their piston forces quite nicely, so they don’t need additional balance shafts to keep them smooth even at high rpms.
The big ‘H’ has long insisted that the V-four engine configuration was the optimum for a performance motorcycle. Fair enough, their range-topper sports bike is a V4, but at £137,000 the RC213V-S makes more of a statement about the owner’s bank balance, than the bike’s chassis balance. By comparison, not only was Ducati’s £40,000 MotoGP replica Desmosedici RR something of a bargain back in 2007, but a more honest demonstration of the potential of the V4. For all the fuss and pomp that surrounds these two willy-waving collector’s bikes, neither pose a serious alternative to the dominance of inline-four sports bikes.
As with a 90º V-twin, a 90º V4 also balances its primary piston vibration forces. Unsurprisingly, the majority of V4 powered bikes have taken advantage of this, but just like they did with their V-twin, Aprilia decided weight distribution was the prime focus of the 2009 RSV4 and they settled upon a 65º angle for the RSV-twin replacement. Judging by the way the 2017 RSV4 carved up the competition at Portimao during this year’s SBOTY, I’d say they’ve done their homework. In fact, Aprilia are the only ones to have made a serious
attempt at proving a V4 sports bike can compete on equal financial terms with an inline-four and win. I wonder how Honda feel about that.
The V4 engine isn’t perfect though. Compared to an inline-four, it’s more expensive to manufacture and their cooling systems need to allow for the uneven airflow between front and rear cylinders. Exhaust routing is also complicated on a V4 and space in the engine’s V is tight for an effective intake system. Nonetheless, both Ducati and Aprilia have successfully made Honda’s point about this configuration: from a pure performance point of view, the V4 is hard to beat.