UNDER THE CURVE!!!
Much as I dislike "buzzwords", this phrase is an excellent one to know. Read on, and know what the "area under the curve" is all about. Savvy and experienced tuners know, and the vast multitude of "Internet Expert" advice slingers have obviously never heard of it.
Granted, this is a much more complicated way of determining the level of performance expectations from a paper dyno graph, when compared to my previous points about "averaging" the peak Torque figures at every 500 RPM <5252 RPM, then the peak HP Figures at 500 RPM intervals > 5252 RPM. Both will provide the same end result, but this one is more scientific and mathematical.
When you hear someone loudly spouting off about his "Peak" horsepower fiqures all the time, you can be 100% assured he's a novice at best.
A good read...
Tech: Area Under The Curve
After having ridden these bikes for a few days it's no secret to any of us that the GSX-R1000 is the class leader in power. After one ride, anyone's seat-of-the-pants power gauge can tell you that, and we confirmed this on our DynoJet model 250 Dyno. But what, exactly, is the proper way to know which bike is truly the most powerful? Peak horsepower? No. Peak torque? No. In both cases, a narrow-band spike of power can sway the numbers. What you want to look at is the area under the curve (one can use a plotter, MS Excel, or the thinking man's way is via a simple integral, although it can be profusely argued that the real thinking man's way is to have graduate students do it). Look at those nice lines drawn across the dyno charts, it's the total area under that curve that is meaningful -- basically, it's the total volume of power produced.
When you look at a dyno chart, horsepower and torque always cross at 5,250*, because horsepower is just a calculation of torque at a given rpm divided by the constant 5,250 (5252.1 if you use generally accepted 3.14159265 for pi). So it's accurate to say that high-revving, high-horsepower bikes just make decent amounts of torque at a high rpm.
Torque, in a nutshell, can be thought of as big lever -- the longer the bar, the more leverage. Here, the GSX-R clearly reigns supreme, besting the R1 by 12.7 percent, the Honda by 13.9 percent and the Kawasaki by 13.9 percent. That's it, that is the outright difference in power measurements for these engines. But this is somewhat misleading in the real world, and here's why: Transmissions are just torque reducers. The "taller" a bike is geared, the more the torque applied to the ground is being reduced -- you've got a shorter lever (more so with each upshift).
For instance, to go a mile a minute, a 1,500 rpm Cummings diesel truck needs significantly "taller" gearing than a Kawasaki Ninja 250 screaming along at 12,000 rpm. Think of the truck's transmission as a shorter lever and you've got the right idea: the amount of torque being applied to the ground at any given instant that's going to determine how rapidly you can accelerate. It's all down to those torque-reducing transmission again (technically for you sticklers, multiplying less, except in Harley-Davidson Sporter Transmissions' fifth gear, which is 1:1 and is why they make more power in fifth -- 1:1 gear ratio means less frictional gear loss -- this is why we insisted our 90 bhp spec racebikes were always dyno'd in fourth gear, but we digress). Every time you upshift, you're reducing the effective torque that can be put on the ground. Torque is either multiplied or divided. If you have a 10:1 final drive gear ratio, torque is multiplied by a factor of 10. If the engine produces seven ft-lbs of torque at the crankshaft, the transmission will output 70 ft-lbs to the rear wheel. If you have a lower-revving engine that only turns half as fast, it'll need a 5:1 ratio to go the same speed, so it will only output 35 ft-lbs to the rear wheel.
'Son, I say son, let me tell you how it's done...'
So why is torque so important? Want move big heavy things really slowly up long hills? Get an engine with a ton of torque and give it a long lever -- a really short transmission like the 13-speed ones in big diesel trucks. It's not going to go fast, but it has the outright power to move the weight. Ultimately, the power a little Ninja 250 can put out is very limited so even with the shortest of reasonable gearing you just can't lift tons of load -- at least not with any expectation of getting over the top in this lifetime, let alone with angry SUV drivers behind you!
So why is horsepower so important? Because
motorcycles are relatively light, and since we want to move them quickly over a period of time we need a way to measure torque with relation to time. This is where horsepower comes in -- it's a mathematical representation of torque and time divided by a constant. So a motorcycle should, theoretically, make the same amount of horsepower in any gear. Since we want to get places quickly on our bikes, measuring the area under the horsepower curve is a good indicator of that. Here, the GSX-R still shines, besting the R1 by 12.6 percent, the ZX-10R by 11.6% and the Honda by a whopping 18.7 percent.
Comparing area under the curves of the torque vs. horsepower graphs is very enlightening and much insight can be gained about the bike's real-world characteristics. Look at the Honda, in area under the torque curve, it's only 13.9 percent behind the class-leading Suzuki. But it lags by 18.7 percent in the horsepower arena -- this means the Honda makes more of it's power down low. Conversely, the Kawasaki trails the Suzuki in torque area by 13.9 percent but gains more than two percent horsepower (11.6 percent down) versus torque as compared to the Honda, which loses 4.8% -- and you can tell that the Kawasaki makes more power at higher rpm and will have more of a top-end "rush", while the Honda would be classified as "more tractable." It's no surprise that the Honda was the least-frightening engine on the track, this and its stable front end gave it the outright track
victory. The real speed freaks like Sean will want the Suzuki but will also get a kick out of the Kawasaki's lunge. For the newbie, a flatter torque curve will have an easier learning curve.
Copious amounts of power do you little good when you've got ham for a fist.
Let's look at this a little more, and consider more generalizations of low-horsepower versus high-horsepower bikes of the same displacement. Torque shreds things. Remember that horsepower is a function of rpm, so in order to make more bhp with the lightest possible parts, you want to rev the engine higher. Indeed, to rev the engine higher, you need lighter parts. One compliments the other. You can see why spinning things higher and higher is so important: 75 ft-lbs of torque at 5,250 is 75 horsepower, but 75 ft-lbs of torque at 10,500 rpm is 150 bhp. A lot can be gained by simply shifting the torque peak higher. Put another way, think of horsepower as that long torque lever spinning. Think of a higher-horsepower engine as that long lever spinning much faster and -- given the same length of that lever -- you're going to make more horsepower in the later, faster-spinning scenario. In many cases, it is more advantageous to spin that lever faster than it is to make it longer -- because it's got to be stronger to be longer, you have to make everything else stronger to support it, thus things tend to get heavier.
Another example: Start out with a lower-revving bike and you need taller gearing to go the same speed, thus your basic design has you starting out with less available torque on the ground. Take any motorcycle, put it in first gear and measure the acceleration vs. the acceleration it produces in sixth gear and first gear wins out every time. Think of it like this: drag race two of the same bikes from 0-60 mph, one bike using first through fourth gears, the other using third through sixth gears. The former -- the higher-revving bike in our analogy -- is going to win every time because it's putting more real power to the ground by not reducing it so much via the transmission. In closing, if you really want to know which bike is fastest -- outside factors such as weight, wind drag and friction being equal -- we want to look at the area under the curve of the all-gear dyno runs, using the X-axis to mph instead of rpm. This will tell you the theoretical winner of any zero-to-whatever-mph race you want to run. Look for MO to be doing the math in future features. --Martin
ALL TORQUE
ALL POWER
Respectfully copied from Motorcyle.Com
Thanks,
Ride Safe (and in the curve!)!
Bob
Dynamometer results analysis thread 
Re: Dynamometer results analysis thread 
