In Imitating Its MotoGP Championship-Winning YZR-M1 By Fitting The '09 R1 With The "Crossplane" Crankshaft, Yamaha Has Altered The Literbike Playing Field
By Kent Kunitsugu
Photography by Courtesy Of Yamaha Motor Europe
There's no doubting that sportbike performance just keeps getting better year after year. Engines gain more power, machines get lighter, handling becomes more agile, suspension is better controlled. As every new bike season unfolds, we're continually amazed at the annual increase in speed. How can they keep getting better?
2009 Yamaha YZF R1 Right Lean Front View
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2009 Yamaha YZF R1 Right Lean Front View
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And yet there was beginning to be a subtle, creeping boredom to it all. The marketing hyperbole was starting to get a little old--"The new bike is more powerful, lighter, better handling than before..." Yawn. The conventional approach to better performance is a road that's beginning to get pretty worn down. And while some have ventured off the beaten path, they might receive some accolades for innovation--but the end result was usually more an exercise in engineering soap-boxing than in increased performance.Until now.
Born In MotoGP
Yes, the buzzwords "developed in MotoGP" are starting to get a bit overused in marketing press materials, but in the '09 Yamaha YZF-R1's case, it's far more than just adspeak describing some overall design brief or fancy exhaust.
SR's OG ("Original Geek") Trevitt explained some of the intricacies of the crossplane crankshaft in our December '08 issue ("New Bikes '09 - 2009 Yamahas"). Descended from the same design used by the YZR-M1 MotoGP racebike, the crossplane crankshaft utilizes 90-degree (instead of 180-degree) cylinder phasing and an uneven firing order to radically change the behavior of a typical inline-four engine. The main goal was to provide a more linear power response to throttle movements, allowing the rider to better sense traction and thus allow earlier and stronger drives off the corners.
An engine primarily produces torque by combustion. However, there is also a secondary torque produced by the spinning crankshaft due to the counterweights used to balance out each cylinder's inertia, and this is aptly named inertial torque. In a conventional 180-degree inline-four crankshaft, the inertial torque actually causes the crankshaft to spin faster at top dead center and bottom dead center (12 o'clock and 6 o'clock positions) than it does at the 90-degree and 270-degree (3 o'clock and 9 o'clock) positions. Because of this variance, the inertial torque rapidly influences the combustion torque as rpms rise, and this results in a spikey torque curve that can often be out of step with throttle movements.
The crossplane crankshaft changes the cylinder phasing from 180-degree to 90-degree intervals. As a result, instead of combustion occurring every 180 degrees of crankshaft revolution, the crossplane crank's first two power pulses are separated by a long 270 degrees of rotation, followed by one firing 180 degrees later and the next taking place only 90 degrees after that, with the same firing pattern beginning again 180 degrees later. By spreading out the engine's power pulses at 90-degree intervals, the inertial torque is smoothed out to the point that crankshaft rotational speed is nearly even throughout each revolution. By having combustion and inertial torque working together, the result is not only a more linear torque response to throttle movements, but the uneven firing intervals also produce the low-rpm torque of a V-twin with the usual high-rpm horsepower of a four-cyinder.
2009 Yamaha YZF R1 Left Lean Side View
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2009 Yamaha YZF R1 Left Lean Side View
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The Right Venue
To introduce the new R1, Yamaha chose the famous Eastern Creek International Racing Circuit just outside of Sydney, Australia, and they didn't select it just for the great weather. Eastern Creek has an abundance of corners that place an emphasis on lower gear acceleration, perfect to showcase the Yamaha's newfound power characteristics.
Immediately noticeable when climbing aboard the new R1 are the revised ergos. The clip-on bars are now positioned 10mm farther rearward, while the shorter fuel tank moves the rider forward another 7.6mm; the footpegs are also moved forward 10mm (the footpeg bracket is also adjustable in two positions, with a more track-oriented setup that positions the pegs 15mm higher and 3mm rearward). This makes the new Yamaha feel shorter and smaller, with less of the "perched atop the front of a rocket" sensation that the older model had.
Blipping the throttle produces a unique feel and sound that is unlike any other motorcycle--with the exception of Rossi's M1, of course. The exhaust note is an exact copy of the M1, with the usual inline-four shriek almost canceled out by a deeper, almost V-four-ish growl; we can't wait to hear it with a set of slip-ons. Just as interesting, though, is how the engine revs. It responds instantly to the throttle and revs super-quick like any well-tuned sportbike engine should, but at the same time its character is softer and less frenetic than your typical inline-four.
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