Torque vs. Horsepower: The Science Behind Car Performance
People tend to flip out when they see power numbers on a car. Seven-hundred horsepower this, 450 foot pounds of torque that, people claiming that “There ain’t no replacement for displacement!” It isn’t just car buyers that are hopped-up over the whole power figure craze — it seems like every time we turn on the tube there’s some automaker boasting about how their latest offering sports a gazillion stampeding horses and that to have a real truck it has to have the torque to haul a concrete cesspool. But everyone should probably calm down, since 90% of the people who end up buying these cars are not going to be able to utilize this raw strength regularly as they are likely to be stuck in traffic more times than naught.
As car buyers, we need to understand that power does not always constitute enjoyment. Sure, the rush of hammering the throttle on the 467 horsepower Lexus RC F was an undeniable adrenaline trip, but the driving experience cannot merely be summed up by this one simple slice of the pie.
There have been quite a few cars in history that have proven that a car doesn’t have to have ridiculous numbers to put a smile on someone’s face. The Subaru BRZ rules at carving corners with its rear-wheel drive configuration and simple-yet-functional gearbox, and the 201 horsepower Honda Civic Si is a budget blast with its sporty suspension and helical limited-slip differential. And let’s not forget the 1.6 liter pipsqueak of an engine found in the Ford Fiesta ST, which doesn’t even crack 200 horsepower and yet somehow has won over almost every critic who has mashed gears in the damn thing.
We’re are not saying that we hate horsepower or have contempt for torque. We love unrefined power just as much as the next guy. But buyers need to know that having a 707 horsepower Dodge Hellcat might feel a little unwieldy since it weighs about as much as a small rhinoceros. Power can easily be negated by weight, and in the case of some of the smaller cars listed in a piece we did on performance recently, it is quite obvious that American car buyers are finally beginning to grasp this fact. But for those of you who need a bit of a crash course this cheat sheet is for you, as it highlights the strengths and weaknesses of both torque and horsepower, along with how they are measured.
Before you even can consider horsepower you have to work your way through torque. Literally. Edmunds did a great write-up on the importance of torques a few years back, and an excerpt from these writings sums-up this power source perfectly: “The measurement of torque is stated as pound-feet and represents how much twisting force is at work. If you can imagine a plumber’s pipe wrench attached to a rusty drainpipe, torque is the force required to twist that pipe. If the wrench is two feet long, and the plumber pushes with 50 pounds of pressure, he is applying 100 pound-feet of torque (50 pounds x 2 feet) to turn the pipe.”
Torque is also is what moves you at lower speeds, so a car’s ability to jump off the line from a complete standstill all depends on how much torque it has, and to quote auto enthusiast extraordinaire Jay Leno, “Horsepower sells cars, torque wins races.” However, once you get moving it is important to have less torque and more horsepower to maintain a high speed, which is why there is a huge differentiation between bottom-end and top-end power.
On the high-end of the spectrum is horsepower, which is typically what people think of when they hear the phrase “performance vehicle.” Images of horses galloping across windswept plains, and a Ferrari stallion rearing its legs in defiance of all things commuter car-related come to mind, but when in reality this is nothing more than one giant marketing ploy. Horsepower is just as mathematical in nature as torque when you break it down to its fundamental design and execution, and horsepower basically picks up where torque leaves off.
At its very simplest, one horsepower equals the amount of power it takes to perform 33,000 foot-pounds of work in one minute. According to an article in Hot Rod Magazine, this measurement of force was first discovered by an engineer in the 18th century by the name of James Watt, who observed that the amount of work performed by a horse that was operating a gear-driven mine pump could indeed be measured. Centuries later, we still use this same equation to measure an engine’s ability to create power at higher speeds, and is the surge in power we feel under throttle at increased velocity.
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