SpeedyManiac
Member
- Aug 8, 2000
- 2,374
- 0
Hi all,
For the past 4 years I’ve been at the University of Alberta studying Mechanical Engineering. During my studies we’ve covered quite a few topics regarding engines and I thought I’d share some of the stuff I learned and hopefully clear up some misconceptions made by a lot of newbies. Please point out any errors in my descriptions, as I make mistakes too.
Most of you (probably all if you’re part of this site) enjoy the rush twisting the throttle and zooming across the dirt. If you have ever ridden a two-stroke, you’ve felt the ‘hit’ when the powervalve opens, which is basically a sudden increase in power. Many people refer to this as the powerband of a bike. This is wrong. Another misconception is only racing bikes have a powerband. I made this mistake too when I was first introduced to bikes, but have since learned the proper definition.
The powerband of an engine is defined as the range of engine speeds between peak torque and peak power output. Below I’ve shown the torque and power curves for 4 bikes. Thanks to DirtRider for the chart.
Now, to effectively ride a bike, you want to stay in the powerband. Ideally, you should use the clutch and gears to keep the engine just past the peak torque RPM, so that when you hit a hill or something requiring more torque, you will naturally have more torque as you slow down slightly. When you get to an RPM below the peak torque value, you have to downshift or slip the clutch in order to get the engine back to the peak torque value.
The coloured arrows below the chart are representing the powerbands of each bike. As you can see, the four-strokes have longer powerbands than the two-strokes. This makes the four-strokes easier to keep in the meat of the power and results in quicker acceleration.
Hopefully that clears up a little bit of the misconception behind powerbands.
For the past 4 years I’ve been at the University of Alberta studying Mechanical Engineering. During my studies we’ve covered quite a few topics regarding engines and I thought I’d share some of the stuff I learned and hopefully clear up some misconceptions made by a lot of newbies. Please point out any errors in my descriptions, as I make mistakes too.
Most of you (probably all if you’re part of this site) enjoy the rush twisting the throttle and zooming across the dirt. If you have ever ridden a two-stroke, you’ve felt the ‘hit’ when the powervalve opens, which is basically a sudden increase in power. Many people refer to this as the powerband of a bike. This is wrong. Another misconception is only racing bikes have a powerband. I made this mistake too when I was first introduced to bikes, but have since learned the proper definition.
The powerband of an engine is defined as the range of engine speeds between peak torque and peak power output. Below I’ve shown the torque and power curves for 4 bikes. Thanks to DirtRider for the chart.
Now, to effectively ride a bike, you want to stay in the powerband. Ideally, you should use the clutch and gears to keep the engine just past the peak torque RPM, so that when you hit a hill or something requiring more torque, you will naturally have more torque as you slow down slightly. When you get to an RPM below the peak torque value, you have to downshift or slip the clutch in order to get the engine back to the peak torque value.
The coloured arrows below the chart are representing the powerbands of each bike. As you can see, the four-strokes have longer powerbands than the two-strokes. This makes the four-strokes easier to keep in the meat of the power and results in quicker acceleration.
Hopefully that clears up a little bit of the misconception behind powerbands.