- #1
codyo83
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Does someone know how much torque a 20hp gasoline engine produce at 3500rpm? An equation that I can use to figure this out would be helpful also.
In summary: This is just a general representation though, as different engines will have different pressure-volume curves and therefore different torque curves. In summary, a 20 horsepower gasoline engine will produce approximately 30 lb-ft of torque at 3500 rpm. This can be calculated using the formula HP = T * RPM / 5252, where T is torque in lb-ft. However, keep in mind that this calculation only applies to the specific output point of 20hp at 3500rpm and the actual torque output may vary due to fluctuations in engine performance. Additionally, single cylinder engines may have even more substantial torque fluctuations and may even produce negative torque on certain strokes.
- #2
- #3
SteamKing
Staff Emeritus
Science Advisor
Homework Helper
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codyo83 said:
HP = T * RPM / 5252, where T is torque in lb-ft
For your motor, HP = 20, RPM = 3500, therefore doing a little algebra, T = 20 * 5252 / 3500 = 30 lb-ft of torque produced by the motor at this output condition.
Since 1 HP = 33,000 lb-ft/min, and 1 revolution of the output shaft = 2 pi radians, then the factor 5252 = 33,000 / (2 pi).
The formula works for any motor where the output is in HP and the speed is in RPM.
- #4
cjl
Science Advisor
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Keep in mind though that this only works if the motor is producing 20hp at 3500rpm. What is colloquially called a "20hp" motor is really a motor which, when operated at its peak performance point, outputs 20hp. If peak performance occurs at some other point than 3500rpm, the torque at 3500rpm will be lower than your calculated number.
- #5
Dr.D
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Bear also in mind the fact that the torque produced by any IC engine fluctuates quite substantially. On a single cylinder engine, the instantaneous torque may actually reverse. So, while the power calculation (based on average torque and average speed) can give you an average torque value, instantaneous values will be all over the place.
- #6
Kozy
- 141
- 7
Dr.D said:
Indeed it does. Here's a calculated torque output from a single cylinder engine showing negative torque on compression and exhaust and exhaust strokes.
The peak torque is showing around 430lbft, however this is actually representative of a single cylinder in a four cylinder engine producing an average torque value of a mere 138lbft.
Attachments
- #7
Dr.D
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Kozy, thanks for posting the pressure - crank angle curve. That looks just about right.
It also show how much higher the instantaneous maximum torque is compared to the average torque, as well as showing the torque reversal.
It also show how much higher the instantaneous maximum torque is compared to the average torque, as well as showing the torque reversal.
What is torque?
Torque is a measure of the twisting force that an engine produces, which is responsible for the rotation of the engine's components.
How is torque measured?
Torque is measured in units of force multiplied by distance, such as foot-pounds or Newton-meters.
What factors affect the torque of a small gasoline engine?
The torque of a small gasoline engine is affected by several factors, including the size and design of the engine, the type and quality of fuel used, and the efficiency of the engine's combustion process.
What is the relationship between torque and horsepower?
Torque and horsepower are related, but not the same. Torque is a measure of force, while horsepower is a measure of power, which is the rate at which work is done. In general, an engine with a higher torque output will also have a higher horsepower output.
How can the torque of a small gasoline engine be increased?
The torque of a small gasoline engine can be increased by making design changes to the engine, using higher quality fuel, and optimizing the engine's combustion process. It can also be increased by using a turbocharger or supercharger, which compresses air to increase the amount of fuel and air mixture in the engine, resulting in a higher torque output.
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