So to start with I naturally consulted\u00a0Google<\/a>. Most of the top hits for \u201ctorque vs. horsepower\u201d are excellent pieces; they break down the math in a very methodical way, so I won\u2019t repeat that excellent work here. Instead I\u2019ll just summarize the basics that are accepted as fact by everyone:<\/p>\n Horsepower:<\/b><\/p>\n James Watt<\/a>\u00a0came up with the concept of\u00a0horsepower<\/a>\u00a0\u2014 which is a measure of, interestingly enough,\u00a0power<\/em>. 1 HP is the equivalent of 33,000 ft\/lbfs per minute. The reason for the complex unit is that we\u2019re accounting for three things with this number: the amount of weight involved, the distance it\u2019s being moved,\u00a0and<\/em>\u00a0how long it takes to do it (that last one is important).<\/p>\n Torque:<\/b><\/p>\n Torque<\/a>\u00a0is nothing more than a measurement of twisting, or\u00a0rotational<\/em>, force. The easiest way to think of this is to imagine a long shaft \u2014 like a car\u2019s axle \u2014 and imagine it\u2019s in a room suspended in mid air. Hanging on the bottom of one end is a rope with a weight attached \u2014 a very heavy weight.<\/p>\n Now imagine someone trying to, using their hands, twist the shaft so as to lift the weight. Think of them as essentially trying to act like a wench and reel it up. The amount of force they are able to generate to lift the weight in this manner is the\u00a0torque<\/em>\u00a0that they\u2019re able to produce. One unit for measurement of this is the\u00a0foot-pound<\/a>. A foot-pound is the rotational \u2018force\u2019 generated by hanging a one-pound weight at the end of a 1-foot wrench.<\/p>\n The mistake most people make when engaging in this debate is considering horsepower and torque independently. Almost everyone argues as if they are separate, unrelated values. They aren\u2019t.<\/p>\n In fact, there\u2019s not a single machine in existence that measures a car\u2019s horsepower. It\u2019s a man-made number. When a car\u2019s performance is tested, its\u00a0torque<\/em>\u00a0is measured using a\u00a0dynamometer<\/a>. The measure of an engine\u2019s performance is torque. Horsepower is an additional number that\u2019s attained by multiplying the torque by the RPMs.<\/p>\n So now for the\u00a0most<\/em>\u00a0important thing on the page. What determines true acceleration for a vehicle isn\u2019t really debatable \u2014 it\u2019s\u00a0force divided by mass<\/strong>. The formula for acceleration is seen below.<\/p>\n Which means\u2026<\/p>\n The confusion only comes in determining which force we\u2019re actually talking about.<\/p>\n So we are solving for acceleration and we have a constant mass. We\u2019ve already established that torque is the amount of rotational force being generated at the engine, but\u00a0we aren\u2019t concerned with the force at the engine<\/em>. What we\u2019re interested in is the force\u00a0at the wheels<\/strong>. The force at the wheels is the\u00a0THE COMMON MISTAKE<\/h2>\n
Horsepower<\/span>\u00a0=\u00a0<\/span>(Torque x RPMs)<\/span>\u00a0\/\u00a0<\/span>5252<\/span><\/b><\/code><\/center>This equation is the second most important thing on this page, and it\u2019s the reason that anyone telling you that horsepower and torque should be considered equally and separately is significantly off-base. The fact of the matter is that horsepower is the\u00a0product<\/em>\u00a0of torque and another value \u2014 RPMs (divided by 5252). It\u2019s not unrelated, separate, or different.<\/p>\nTHE PHYSICS OF ACCELERATION<\/h2>\n
f<\/span> = m<\/span>a<\/span>\r\n<\/pre>\na<\/span> = f<\/span>\/m<\/span>\r\n<\/pre>\nf<\/span><\/code>\u00a0in\u00a0f = ma<\/span><\/code>\u00a0(actually, it includes the radius of the wheel as well, but we\u2019re simplifying).<\/p>\n