Cars

The Way You Think About Horsepower Is Completely Wrong

Published On 05/20/2016 Published On 05/20/2016

As a car-obsessed child, horsepower to me was religion, and the more-is-better doctrine one of its fundamental tenets. I worshipped cars like the 898hp Callaway Sledgehammer Corvette as if they were idols. The thing is, the way I thought about horsepower -- and likely the way you think of it, too -- was completely and utterly wrong.

If you think that horsepower is a true measure of a vehicle's performance, it's time to realize that it's only one component of many. And if you think more horsepower is the key to unlocking the fun-as-hell driving experience like you see on TV, I hate to break it to you, but that's mostly the marketing talking. Truth is, horsepower is just a number.

Horsepower is first and foremost a marketing tool 

First things first, let's talk about what horsepower actually is. In reality, it's nothing more than a number meant to define an engine's capacity for work. The concept of comparing machines to horses was refined into a scientific formula by James Watt -- one of a handful of people who spearheaded the industrial revolution with his work on the steam engine in the mid-1700s, and the guy for whom watts (as in kilowatts) are named. Watt needed a way to market his steam engine to people who normally used horses to get stuff done. Through observing how much work a horse could do and applying some relatively simple math (HP= (Torque X RPM)/5,250), the concept of horsepower became marketing gold. 

It was incredibly easy to understand: this 10-horsepower machine means you'll need to take care of 10 fewer horses. In its simplest form, it remains unchanged, and as you see in countless car commercials nearly every single day, it's still marketing gold. Just... with a shitload more horses.

Courtesy of Mercedes-Benz

The car with the most horsepower isn't always the fastest

So horsepower is just a number, and that number does tell you a lot about how fast a car can accelerate. But that is just one slice of the pie. The engine's torque, the gearing in both the transmission and the differential, available traction from the tires, aerodynamics, and the sheer amount of the car's mass all have telling roles in performance. (That's the ultra-basic version, of course.)

For most cars, accelerating in a straight line -- which is what horsepower does for you -- is the single least impressive aspect of performance. Throw all those other factors in, and it's absolutely possible for a car with less HP to outperform a car that has more. 

Think about the force throwing you into your seat when you hit the accelerator. If you're in one of today's higher-end sports cars or sport sedans -- an M3, 911, or the like -- you can expect to go from zero to 60mph in roughly 3.8 seconds. That translates to an average acceleration of just over 0.7 G's.

Even the world's fastest production cars still fail to hit one full G of acceleration, but during cornering, cars like the readily affordable Camaro SS are hitting a full GIn corners. On a basic level, having all the horsepower in the world is a moot point mid-corner, but possessing a good bit of driver skill is absolutely vital.

Flickr/Tom Ellis

Case in point: a Mini can keep up with a Mustang

Let's talk about mass, for example. There are two things to remember here: first, horsepower is a function of work, and a lighter car requires less "work" to accelerate at the same rate as a car with more mass. Second, reducing a car's weight (mass) improves not just straight-line acceleration, but its braking and cornering ability as well. If you want to see the clearest display of a heavy car with very high horsepower racing against a very light car with little power, check out this race between a Mustang and a Mini.

The original Mini won the legendary Monte Carlo Rally three times. It won the European Touring Car Championship. Twice. Britain's top road car racing series? Five-time champion. Light cars are fast cars.

Courtesy of GM

HP is actually pretty boring, once you get past the novelty of acceleration

The very first time you floor a car with 700 horsepower, it feels like a jump to hyperspace. Your sense of balance is thrown off, and your brain struggles to keep up with the rate at which the scenery is becoming increasingly blurred. The second time? It's still cool, but the more you do it, the more it becomes routine. I would know. I've been there.

When Motor Trend's Randy Pobst first tested the 2015 Z06, a car built with the sole purpose of being blisteringly quick, he had but one complaint: "Honestly, I want another hundred more [horsepower]. It's stable enough. You don't feel threatened." To be clear, he's talking about a 650hp beast of a car. A generation ago, that much power could have triggered a need for a change of underwear as you desperately tried to keep it on the road, despite the tires shouting their obvious intent to kill you.

But the cars of today are engineered so incredibly well, they can take that kind of power and turn it into something so easy to wield, that manufacturers can sell the cars without wild accusations of being irresponsible. Case in point: when I took the 640hp Cadillac CTS-V out on track, the climb from 70mph to well over 150 was downright serene.

After you've put your right foot down enough times, that kind of acceleration becomes routine, and you realize there are more things in life than horsepower.

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Aaron Miller is the Cars editor for Thrillist, and can be found on Twitter. He's had heavy cars with plenty of power, and light cars with no power. His personal preference is to add lightness whenever possible.

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