To the uninitiated, Yamaha’s new YZF-R1 superbike doesn’t appear especially different from its predecessor. Okay, so it looks a little sharper and more aggressive, but the power is much the same and the acceleration… well, it’s still capable of scaring the hell out of any rider careless enough to twist the throttle wide open.
But it’s not quite what it seems. It’s much, much better. For starters, the newly developed 998 cm³ engine, developed from Yamaha’s MotoGP design, features a race-developed crossplane crankshaft that delivers outstandingly pure torque characteristics – think linear and controllable.
It’s a clever concept. An engine produces something called “composite torque”, which is a combination of the torque produced by combustion and the inertial torque resulting from the revolution of the engine’s crankshaft. Although the level of combustion torque is proportionate to the rider’s throttle input, the inertial torque is produced in direct relation to the changes in inertial force caused by the engine’s revolutions – and this element of the composite torque is not under the direct and immediate control of the rider.
This torque level varies throughout the engine’s rev range, regardless of the rider’s throttle input, and its unpredictable nature means that the rider cannot select precisely and immediately the torque level that he desires at any given moment. In order to be able to offer more linear control to the rider, you need to create an engine where the inertial torque can be minimised and the composite torque optimised.
One of the most effective means of achieving optimal composite torque in a 4-cylinder engine is through the adoption of a crossplane crankshaft with the crankpins positioned to give a firing interval of 270º-180º-90º-180º, as opposed to the 180º-180º-180º-180º firing interval of a conventional 4- cylinder engine.
Whereas the conventional engine sees the four pistons and con rods move up and down in the cylinders as two pairs, each piston and con rod in the new crossplane crankshaft has its own individual and separate movement. The result is that the inertial torque created by the reciprocating mass in the new YZF-R1 engine is reduced, while the asymmetric firing sequence achieves a strong pulse at low- to mid-rev range, together with excellent linearity across the whole rev range.
In order to further optimise the combustion forces in the new R1’s asymmetric motor, the electronic mapping for the fuel injection system provides separate fuel injection and ignition timing for each cylinder, resulting in highly linear torque characteristics. For smoother running, the engine is fitted with a primary coupling balancer to reduce the vibration produced by the asymmetric crankpin layout.
What this means is that the new R1 will go around a track considerably faster than its predecessor and probably beat most of its competitors, too. Helping it along is a completely new aluminium Deltabox frame. The engine mount is set 12 mm further forward in relation to the drive axis, making the front wheel feel even more “stuck” to the road. Vroom.
* To watch the video of PM’s editor “testing Yamaha to destruction”, |click here|
* Or does he? Read Alan Duggan’s blog about his ride on Yamaha’s R1 superbike to find out… |click here|