Powerbands: What Gear And What Rpm Range - Riding Skill Series
Honda's CBR600RR has a surprisingly strong midrange, illustrated by the torque curve's steep climb near 8500 rpm. The horsepower peaks at 105.1 at 13,650 rpm, yielding a wide powerband with a generous overrun to its 15,000-rpm redline. Even though it produces little more than half the torque of the Ducati and about two-thirds the horsepower of the Suzuki, the Honda spreads a very usable amount of power over a relatively broad 6000-rpm range, making it supremely user-friendly and requiring less shifting than you'd think possible on a middleweight
One of the most frequent questions heard among riders centers around which gear to be in for a given corner. Often you're torn between high revs in a low gear or pulling a taller gear at lower rpm. Naturally, different engine sizes and configurations behave differently, and occasionally you'll find the perfect gear that pulls smoothly and strongly off a particular corner.
A motorcycle's final gearing is always a compromise in some way for every rider, however; there will inevitably be situations where a corner or series of bends puts you outside the optimum gear and rpm. Varying engine configurations only make selecting what gear to be in that much more confusing.
The '07 SR Bike of the Year test was a good cross section of the popular sportbike segments represented by the middleweight Honda CBR600RR, the literbike Suzuki GSX-R1000 and the big-twin Ducati 1098S. All have decidedly different powerbands that require some adaptation and skill to get the most out of.
Common belief has always been that twins are torquey and therefore require less shifting than higher-revving inline-fours, because you don't have to keep the engine spinning at high rpm to get enough power to enable a good drive off the turn. But as engine technology progresses and rev ceilings continue to rise for both twins and fours, there are many exceptions to the rule due to the overrev capability and improved powerbands of the multicylinder machines.
A good example is the GSX-R1000's powerband. Looking at the dyno charts, the Ducati 1098S may begin generating good steam as low as 4000 rpm on up to 9500 rpm, but the Suzuki begins its charge at 5000 rpm and carries it all the way to just past 12,000 rpm. The telling point is how much overrev each bike has. While the 1098S quickly bumps into the rev limiter at 10,200 rpm, the GSX-R continues pulling an additional 1000 rpm past its power peak. This means that while the Ducati's 6200-rpm power spread initially sounds like a lot, it pales in comparison to the Suzuki's 8000-rpm band.
The flip side to that coin is that while the GSX-R has a wider power spread, the four-cylinder's more responsive and quicker-revving character makes throttle control much more crucial than on the Ducati. The Suzuki rises to its torque peak more aggressively and thus is more apt to break the rear tire loose while accelerating off a corner. The Ducati's comparatively lazy power characteristics not only help maintain traction while leaned over, but also enable you to begin your drive earlier off the corner because the engine isn't always threatening to spin the rear tire out from under you.
Although the CBR has similarly aggressive four-cylinder torque characteristics to the Suzuki, they're tempered drastically by its lower power output. This results in easier throttle control and allows acceleration to begin even earlier than on the Ducati. Coupled with its more agile handling and superb brakes, the Honda can give the literbikes fits on a tighter road or track. The downside is that faster roads require more gearshifts to maintain speed and generate good drives off the corners, and taking advantage of the CBR's better corner entrance speed requires skill.
Twist the throttle at any reasonable rpm and Ducati's mighty 1098S lunges forward with more torque and immediacy than any true sportbike available (which rules out musclebikes like Hayabusas, ZX-14s and such). Between 6000 and 9000 rpm its torque curve towers over even the GSX-R1000, squirting the bike between corners with almost shocking suddenness. Lacking the high rev ceiling of the fours, the big twin's peak horsepower is 142.3 at 9650 rpm. But contrary to common wisdom, the 1098S offers a narrower rev range than the fours and less peak speed than the CBR600RR in first through fourth gears.
Horsepower curves peak later in the rev range (often 80 percent to 95 percent of redline in most sportbikes) and signify the point at which power begins to drop off. This in turn indicates the point at which to upshift the engine as long as the rpm doesn't drop much below the torque peak after the shift. The spacing between gears gets ever narrower as we upshift to higher gears, making this less of a worry. In theory, the optimum shift point is different in each gear, based on the gap between transmission ratios; in real- world terms, shift up when you feel the acceleration go flat up top. Don't be fooled by a screaming engine that higher rpm always equals more power. Find the rpm at which the engine makes its peak power on the dyno chart and then factor in that most tachometers (like speedometers) tend to be very optimistic. When you feel the push diminish in the seat of your pants and see the tach needle slow its climb, it's time to shift up.
Perhaps more significantly than sheer thrust, throttle response and rideability play a large factor in determining which gear works best in a particular corner. While more horsepower is available in a shorter gear, throttle response tends to be less sensitive in the middle rpm range than buzzing near the ceiling. The smoother power delivery in the taller gear may let you roll through the corner faster and carry more speed down the straight even without a killer drive.
In some cases the overrev capacity of a four-cylinder can allow you to carry a lower gear farther down the following straight without danger of bumping into the rev limiter and upsetting the chassis. Even if you're past the engine's power peak it can be quicker and certainly easier to rev out the gear you're in rather than grab an upshift, only to have to downshift an extra time at the next corner. This is one situation where fours, with their wider rev ranges, can require less shifting than twins.
Suzuki's GSX-R1000 produces all the power you can use and more. Only when you ride it side by side with a five-year-old version is it apparent that the midrange has softened some in its quest for nearly 160 horsepower. The torque curve climbs sharply between 7000 and 8000 rpm, leaving the rear tire begging for mercy from there to past 13,000 rpm. You nearly always have a choice of two gears with Big Blue; do you want it arm-straighteningly hard or impossibly harder? First gear alone takes you to nearly 100 mph.
Twins often have the advantage of more torque at low rpm, which can make them more forgiving of coming off the corner a gear taller. Just as you can use a four-cylinder's overrev capability to shift less, the twin's torquey bottom end can let you carry a higher gear through a corner without having to shift on the following straight. A twin's relaxing, pulsing power delivery is also more pleasant on street rides, where the higher-strung middleweight fours are often a downshift or two away from meaningful acceleration.
Take advantage of your engine's strong points to reduce the number of shifts you make as much as possible while still maximizing its power output. Even at race pace, the fewer shifts you have to make-and the smoother and simpler those shifts are-the better and quicker you'll go. Most riders have the tendency to shift more than is needed rather than less. When in doubt try rolling through the corner in a taller gear and see if eliminating the extra downshift and corresponding upshift isn't less work and more fun.
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