Honda CBR650 launch
Is the new ‘CBR’ worthy of such a title? Frodo went to find out.
More revs, more power
So, to truly put things in perspective, how does the Panigale V4R redline compare with its peers nowadays? Well, it’s fair to say it makes them all look a bit donkey-like. The other new litre superbikes for this year are the BMW S1000RR and the revamped Kawasaki ZX-10R range. The Beemer makes peak power at 13,500rpm, with a redline marked on the tacho at 14k. Pfft. In the green corner meanwhile, the new RR version of the ZX-10 Ninja has a special new valvetrain design aimed to raise revs by 600rpm, and now makes its peak power at 13,500rpm and the rev limiter calls time at 14,800rpm. That’s good, but it’s still a hefty 1,700 revs shy of the V4R. So, the Panigale is the rev boss. But why are high revs such a good thing? Well, broadly speaking, revs means power. Literally. The power output from an internal combustion engine is calculated by the force applied at the crank (we call this torque), multiplied by the rpm (the equation is pretty simple: power = torque x rpm / 5,252, using ft lbs for torque and bhp for power). That’s why, when you look at a dyno chart, the power curve kinda follows the shape of the torque curve. If the torque stays steady, the power increases gradually as the revs increase, but if there’s a sudden spike in the torque curve, then you get a corresponding peak in the power curve. Increasing the torque you get from an engine can get you so far. In crude terms, the torque is a measure of the force created at the piston top by the combusting fuel/air mix. A bigger bang will, all things being equal, give a bigger shove to the piston. Imagine a Tour de France cyclist – give him a bigger pair of thighs (say, by injecting him with elephant steroids), and he’ll be able to shove harder on the pedals, pull a higher gear, get up a steeper hill faster – make more power, in other words.
Performance at a price
If you’re limited by the amount of fuel and air you can burn in each cylinder, then there comes a point where you hit the limits of the force produced on each combustion stroke. Improving efficiency is one route to making a bigger bang – making sure all the fuel burns efficiently, increasing compression ratio, having a strong ignition system, ensuring the fuel/air mixture is exactly right. If you can fit a turbocharger, or increase the cylinder bore, you can force more in fuel and air in, and make a bigger bang that way.
If you can’t do this (as with a WSBK homologated 999cc motor), then the only way to make more power is to make the same size of bang, but at higher revs. Our massively thighed cyclist could go even faster if he manages to pump his giant legs up and down faster on the pedals. More revs – or pedal pushes – per minute, with the same force makes you go faster, because you’re producing more power.
There are a few enemies of revs in an engine. As the rpm increases, there is less and less time to get fuel/air into the cylinder, burn it, and get the exhaust gasses out again. Even at a lowly 5,000rpm, a four-stroke engine is firing nearly 42 times a second, and the piston moves up and down the bore four times as often - about 170 times a second. So, if the inlet valve opens for the whole of the piston inlet stroke, there’s just 1/170th of a second to get the whole fuel/air charge into the cylinder before the valve closes. At the redline of the new Panigale V4R – 16,500rpm in top gear remember – there are 137.5