solo racer
RC Newbie
- Messages
- 12
- Reaction score
- 0
- Points
- 0
- RC Driving Style
Nitronewbie, what I was trying to get at was that torque is NOT the only determining factor in how fast something will accelerate and when it comes down to it the RPM and Horsepower ( think of it as the ability to maintain torque) of the engine along with the gears are what determines acceleration.
A lot of the Honda's and Acura's with 170hp and only 120lb/ft of torque versus other cars with largers motors that have 170hp and 170lb/ft torque yet still go the same speed and accelerate similarly. Because the Honda/Acura motor revs so high, the gears can be used to compensate for the lack of torque the motor makes so the car can perform much better. THAT is what I was trying to get at. In essence torque is not as relevant when there are many other variables.
Both engine torque and power is measured at the engine flywheel. The power is proportional to the torque times the engine speed. If an engine has 200 Nm at 4000 RPM, it has 114 HP at the same engine speed. One european HP equals 736 Watts, as opposed to the american HP, which is 746 Watts.
(formula: 736*HP=Nm*2*PI*RPM/60)
The gearbox has the ability to amplify torque. Most engines are too weak to get a car going with a 1:1 ratio. Because of this, most cars have more than 10:1 reduction through the gearbox and differential in the first gear. This amplifies the torque at the wheels to more than ten times the torque at the flywheel. In the top gear the ratio is typically 3:1.
Power, on the other hand, is unchanged on either side of the transmission, at least if you ignore the mechanical loss, which might be about 10 percent.
Power is the amount of energy the engine can produce every second. This energy is used to increase or maintain the kinetic energy of the car. The higher the power, the more acceleration you get.
Power can also be expressed as force times speed. If the car goes faster, the force (and acceleration) is reduced, even though the power is unchanged. If there is more power available in another gear, the car will accelerate better if you change to that gear. Always.
Since the torque curves on modern cars are very flat, the power curves usually rise all the way to the maximum allowed engine speed. To obtain the best possible acceleration, you should not change gears before right at the rev limiter.
Within one specific gear, the best acceleration will take place at the point of maximum torque. Still, it would be even more effective to use a lower gear, since the torque at the wheels is greater than in the current gear.
If you take air drag into consideration, the maximum acceleration will of course occur slightly before you reach maximum torque, since drag increases with speed.
The conclusion is that the torque is important, but it is just as important at what engine speed the torque is produced. 200 Nm at 5000 RPM is twice as useful as 200 Nm at 2500 RPM. The reason for this is that a twice as low gear can be used, and this doubles the torque at the wheels.
The power takes engine speed into consideration, and says a lot more. The power at the wheels is the same, no matter what gear you are using.
As for the bicycle crank, I belive you are forgetting that you are not simply standing on the crank but also using your muscles to push it down creating more force than simply your weight at the end of the crank.
A lot of the Honda's and Acura's with 170hp and only 120lb/ft of torque versus other cars with largers motors that have 170hp and 170lb/ft torque yet still go the same speed and accelerate similarly. Because the Honda/Acura motor revs so high, the gears can be used to compensate for the lack of torque the motor makes so the car can perform much better. THAT is what I was trying to get at. In essence torque is not as relevant when there are many other variables.
Both engine torque and power is measured at the engine flywheel. The power is proportional to the torque times the engine speed. If an engine has 200 Nm at 4000 RPM, it has 114 HP at the same engine speed. One european HP equals 736 Watts, as opposed to the american HP, which is 746 Watts.
(formula: 736*HP=Nm*2*PI*RPM/60)
The gearbox has the ability to amplify torque. Most engines are too weak to get a car going with a 1:1 ratio. Because of this, most cars have more than 10:1 reduction through the gearbox and differential in the first gear. This amplifies the torque at the wheels to more than ten times the torque at the flywheel. In the top gear the ratio is typically 3:1.
Power, on the other hand, is unchanged on either side of the transmission, at least if you ignore the mechanical loss, which might be about 10 percent.
Power is the amount of energy the engine can produce every second. This energy is used to increase or maintain the kinetic energy of the car. The higher the power, the more acceleration you get.
Power can also be expressed as force times speed. If the car goes faster, the force (and acceleration) is reduced, even though the power is unchanged. If there is more power available in another gear, the car will accelerate better if you change to that gear. Always.
Since the torque curves on modern cars are very flat, the power curves usually rise all the way to the maximum allowed engine speed. To obtain the best possible acceleration, you should not change gears before right at the rev limiter.
Within one specific gear, the best acceleration will take place at the point of maximum torque. Still, it would be even more effective to use a lower gear, since the torque at the wheels is greater than in the current gear.
If you take air drag into consideration, the maximum acceleration will of course occur slightly before you reach maximum torque, since drag increases with speed.
The conclusion is that the torque is important, but it is just as important at what engine speed the torque is produced. 200 Nm at 5000 RPM is twice as useful as 200 Nm at 2500 RPM. The reason for this is that a twice as low gear can be used, and this doubles the torque at the wheels.
The power takes engine speed into consideration, and says a lot more. The power at the wheels is the same, no matter what gear you are using.
As for the bicycle crank, I belive you are forgetting that you are not simply standing on the crank but also using your muscles to push it down creating more force than simply your weight at the end of the crank.
Last edited:
