You often see them listed as one spec — X horsepower and X pound-feet of torque. But what does that mean, really? Is one more important when it comes to MPH? How do they relate?
If you’re a car aficionado, you’re probably laughing by now, but the truth is that many average car buyers don’t fully understand the differences between HP and torque. Sure, they see that the bigger number is usually better, but that’s not always the case!
So, for the benefit of all our non-motorhead readers, here’s what these terms are really telling you about a particular car’s performance.
What is Horsepower?
Usually synonymous with speed, “horsepower” actually refers to the amount of power needed to move a certain amount of weight a certain distance over a certain period of time. In strict mathematical terms, one horsepower is the amount of effort that’s needed for a vehicle to move 33,000 pounds just one foot in one minute.
What is Torque?
Torque is the rotating force that’s produced by an engine’s crankshaft. That twisting force is applied to the transmissions gears and sent to the tires. Because torque is a vector — a force that operates in a certain direction — it’s measured by the foot and in pounds (commonly pounds-feet or lb.-ft.). A higher torque is usually an indicator that the vehicle has a higher towing capacity.
How is Horsepower Calculated?
An engine’s horsepower is measured on a machine known as a dynamometer. It works by placing a load — usually braced by brakes to prevent the vehicle’s wheels from spinning — on the engine and measuring the twisting force the crankshaft places against the load. Easy enough, right?
Here’s where it can get a little confusing: the dynamometer is actually measuring the “torque” output of the engine (see next section). That’s because torque and rpm must be calculated first to determine the vehicle’s horsepower. Here’s the formula in its simplest form:
Horsepower = (Torque x RPM)
Are Horsepower and Torque Related?
Just as Campbells’ Soup extolled the relationship between soup and sandwich in that corny old commercial ditty, so too can be said about the hp-torque relationship. Both are necessary ingredients in measuring a vehicle’s speed and engine power.
Is One More Important Than the Other?
Well, according to John M. Vincent for U.S. News/Cars, the answer to that question depends on what you’re looking for in terms of performance.
Torque is really important if you’re going to be towing a big boat or a trailer around. Diesels have the most torque at low RPMs of any engine, which is why semis and some full-size pickup trucks are powered by diesel engines — so they can haul those long trailers loaded to the gills with goods for stores and businesses.
On the other hand, if you’re more concerned with zipping down the highway and passing easily when it’s called for, you’ll probably be happier with a high-revving, high-horsepower car that can weave in and out of traffic without too much trouble.
Remember the Formula?
Once automakers have measured an engine’s torque on a dynamometer at different speeds, they use the formula to create graphs showing horsepower and torque as the engine goes from idle to its maximum speed — also known as its “redline.” The published horsepower-torque numbers are usually the maximum points on the graph and the engine speeds where they occur. Thus, you’ll typically see something like “185 horsepower at 6,400 rpm” and “181 pound-feet of torque at 3,900 rpm” in a vehicle’s description.
So, there you have it. In the simplest possible terms, torque refers to the amount of work an engine can exert, while horsepower defines how quickly that work can be delivered. But to quote Carroll Shelby, the famous car designer and Formula One racer, “Horsepower sells cars, torque wins races.”
If you need a used performance car with loads of horsepower or a high-torque truck that has mastered the art of towing, trust in our Blue Springs used car dealer to get you on your way. We have a variety of pre-owned vehicles for sale, from coupes and sedans to SUVs and pickups, as well as some of the best used car specials around Kansas City.
Contact McCarthy Pre-Owned Supercenter at (816) 256-2632 or swing into our Blue Springs used car lot at 3030 NW South Outer Road to take a test drive.
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