Power and Torque
Discussion
Dont worry chaps, its not a "whats the difference" thread! 
My mechanical knowledge would be described as limited at best, so, what attributes of an engine define various characteristics?
For example - the small 4 pot in the CTR produces loads of power but little torque.... the RV8 is a bit of a torque monster, but not that powerful for its size....
Explain!
Ta
My mechanical knowledge would be described as limited at best, so, what attributes of an engine define various characteristics?
For example - the small 4 pot in the CTR produces loads of power but little torque.... the RV8 is a bit of a torque monster, but not that powerful for its size....
Explain!
Ta
Here goes for a gross generalisation that I am sure someone will get pedantic about:
All engines run more or less the same mean piston speed. So a ship engine runs much slower, but because the piston travels so far the mean piston speed is very similar (ball park) to a high-revving motorbike engine. The bike engine runs at maybe 20 times the speed in rpm, but the stroke is shorter and so the mean piston speed ends up the same (more or less).
Power is a function of torque and speed - high speed -> higher power.
Of course, it is more complicated than that, but it is a starting point for someone else to continue...
All engines run more or less the same mean piston speed. So a ship engine runs much slower, but because the piston travels so far the mean piston speed is very similar (ball park) to a high-revving motorbike engine. The bike engine runs at maybe 20 times the speed in rpm, but the stroke is shorter and so the mean piston speed ends up the same (more or less).
Power is a function of torque and speed - high speed -> higher power.
Of course, it is more complicated than that, but it is a starting point for someone else to continue...
Torque * Revs = Power
Keep one of them steady and increase the other, and power increases. So engines with longer strokes tend to run slower but, becase the crank is longer, you get more leverage and thus torque.
Conversely "over square" bore engines with short crank throws tend to be screamers that need to be thrashed to get the same output power.
Keep one of them steady and increase the other, and power increases. So engines with longer strokes tend to run slower but, becase the crank is longer, you get more leverage and thus torque.
Conversely "over square" bore engines with short crank throws tend to be screamers that need to be thrashed to get the same output power.
MrFlibbles said:
Power is a function of torque and speed - high speed -> higher power.
I've heard that before, but cant get my head around why you can have engines with high power, but low torque!
A GSXR 1000 bike engine puts out 170odd BHP and 80 something lb/ft torque. That's 80lb/ft a litre. If you look through the specs of all non-turbo engines, regardless of size, you will find that not many make much more than that.
Look here
www.pumaracing.co.uk/power1.htm
www.pumaracing.co.uk/power2.htm
www.pumaracing.co.uk/power2.htm
Steve
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