The Yamaha YZF-R1 Crossplane Explained more Clearly
Anybody interested in buying a Yamaha YZF-R1 knows about the new 'crossplane' crankshaft setup, and most people have the idea that the Yamaha 'crossplane' or 'big bang' produces more power. Therefor we would like to explain the benefits of the new 'crossplane' crankshaft setup more clearly.First, the Yamaha YZF-R1 'crossplane' engine isn't faster than the 2008 model (no crossplane), at least not in pure straight-line acceleration and top speed. The difference brought about by the YZF-R1's 'crossplane' crankshaft design is not in the amount of power the engine produces but instead is in the way it produces it. A traditional inline-four's crankshaft is flat, with its outside pair of throws located 180 degrees from the inner pair, giving it evenly spaced firing intervals (180-180-180-180). And its single-plane construction requires all four pistons to come to a complete stop every 180 degree, at both TDC and BDC, creating a considerable inertial loss.
On the Yamaha YZF-R1 crossplane crankshaft, however, the throws are spaced at 90-degree intervals, resulting in a 270-180-90-180 firing sequence. This unevenness helps rear-tire traction by giving the tire one larger interval during each set of four firing pulses to better maintain grip; it also reduces inertial losses by requiring only two pistons to come to a stop during any TDC or BDC event. The end result is a marginally more efficient engine that provides improved off-corner acceleration as a result of better rear-tire grip under power. So, while the 0-to-100 times and 400-meters numbers of the new Yamaha YZF-R1 Crossplane might not be appreciably different than those of the YZF-R1 without Crossplane, the newer Yamaha YZF-R1's lap times on a road-race course-as well as its point-to-point E.T.s on a twisty backroad - are likely to be better in the hands of a capable rider.
By the way, though the term 'Big Bang' is often used by people to describe the new crossplane Yamaha YZF-R1, that is not a correct representation. The term dates back to the two-stroke GP race motorcycles of the late '80s and early '90s when four-cylinder two-stroke race motorcycles would fire two cylinders simultaneously, hence the 'big bang' moniker. I believe it started with inline-fours, such as the Yamaha TZ750, later versions of which fired its cylinders in pairs at 180-degree intervals instead of separately every 90 degrees. The concept ultimately evolved to V-four that fired in pairs at anywhere between 67- and 90-degree intervals, depending upon their Vee spread. This meant there was between 293 and 270 degrees of freewheeling, respectively, before the next firing sequence to help the rear tire maintain grip off of corners. Since no two cylinders fire simultaneously on the new Yamaha YZF-R1 Crossplane, calling it a big-bang engine is incorrect.
Furthermore, the crossplane crankshaft is far from a new concept. If I'm not mistaken, all current American automotive V-eight engines have crossplane crankshafts, which date back to the early '20s when they were first used by Cadillac. The name derives from the fact that the throws are positioned 90 degrees apart, putting them in two 'planes' that 'cross' one another. In effect, the Yamaha YZF-R1's crankshaft is simply half of a V-eight crankshaft.
