Sorry if this is old news, but I've seen threads where people said they asked engineering professors about the difference between torque and horsepower and couldn't get a good answer. Anyway, I was out running the other morning thinking about this and some good imagery came to me that helped me understand it. At least I think so. You all can let me know if I'm wrong. After all, my math isn't the greatest and my physics is limited to a semester of Physics for Poets in college. Some clown on mazda6club.com said I have no idea what I'm talking about, so I thought I try it out here and see what the response is. Here goes.
Engine torque is a measure how much explosive force is being transmitted through however many pistons and rods an engine has in order to turn the crankshaft through one complete engine cycle. In the MS6/3 it's 280 ft/lbs, meaning the force generated by one engine cycle is enough to lob a one pound weight 280 feet or move a 280 pound weight one foot. Peak torque comes when the engine is running at maximum efficiency for each cycle. You can increase torque by adding more cylinders, or by boosting air pressure and/or compression to get more force from each explosion.
Horsepower is the measure of an engine's ability to do work when an engine is running at a given number of cycles per minute (rpms). By adding this time dimension, you get a measurement of the power that adds together the force of x number of cycles. Maximum horsepower is reached at the point where the positive effect of adding any additional cycles per minute is overcome by the negative effect of decreases in the efficiency of each individual cycle. You increase horsepower by doing things that allow the engine to add more cycles per minute while maintaining at least a minimum level of efficiency for each individual cycle.
Now for the visualization. Tommy gun vs. M-15. An engine that has high torque relative to it's horsepower is like a tommy gun. It delivers a heavy load of lead in each shot, but it cannot fire off as many shots per minute. An engine that has high horsepower relative to its torque is like an M-15. Each shot carries a smaller load of lead, but it can fire off a lot more shots per minute than the tommy gun. When you add up the total amount of lead that's been fired, the higher horsepower engine wins every time. But, to me the rhythm is a lot less pleasant. I'll take the tommy gun any day.
Engine torque is a measure how much explosive force is being transmitted through however many pistons and rods an engine has in order to turn the crankshaft through one complete engine cycle. In the MS6/3 it's 280 ft/lbs, meaning the force generated by one engine cycle is enough to lob a one pound weight 280 feet or move a 280 pound weight one foot. Peak torque comes when the engine is running at maximum efficiency for each cycle. You can increase torque by adding more cylinders, or by boosting air pressure and/or compression to get more force from each explosion.
Horsepower is the measure of an engine's ability to do work when an engine is running at a given number of cycles per minute (rpms). By adding this time dimension, you get a measurement of the power that adds together the force of x number of cycles. Maximum horsepower is reached at the point where the positive effect of adding any additional cycles per minute is overcome by the negative effect of decreases in the efficiency of each individual cycle. You increase horsepower by doing things that allow the engine to add more cycles per minute while maintaining at least a minimum level of efficiency for each individual cycle.
Now for the visualization. Tommy gun vs. M-15. An engine that has high torque relative to it's horsepower is like a tommy gun. It delivers a heavy load of lead in each shot, but it cannot fire off as many shots per minute. An engine that has high horsepower relative to its torque is like an M-15. Each shot carries a smaller load of lead, but it can fire off a lot more shots per minute than the tommy gun. When you add up the total amount of lead that's been fired, the higher horsepower engine wins every time. But, to me the rhythm is a lot less pleasant. I'll take the tommy gun any day.
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