Movin' Fast

By Sharon Naylor

August 23, 2011 6 min read

If speed is an important requirement for the next car you purchase, then knowing performance terms can help you choose a model to better meet your driving needs. Here is a brief overview of speeding terminology:

--Speed. This seems quite simple: I'm traveling at 60 mph. Keep in mind that the number on your speedometer depends on the correct functioning of your vehicle's speed sensor, or VSS.

Typically, a VSS won't wear out over time, since it operates on electrical sensors. If it is faulty, you might be traveling at 80 mph while your VSS says 60 mph. A faulty VSS can dangerously affect your cruise control and anti-lock brakes. "If you notice that it is implying speeds that are obviously inaccurate, ask your mechanic to check your VSS," says CarsLikeUs.com.

--Acceleration. The phrase "0 to 60" represents the length in seconds it takes for your car to start from standstill and reach 60 mph. This figure factors into vehicles' rankings and prices, since acceleration is what allows you to merge onto a highway, quickly reach highway speeds and perform evasive actions to avoid accidents.

For example, a sports car may reach 60 mph in four seconds, while the standard SUV may reach 60 mph at the nine-second point. If your commute puts you on freeways where you need the ability to speed up quickly, a vehicle with a higher acceleration rate may be the best choice for you.

--Horsepower. Aaron Gold, About.com's guide to cars, says that car buyers often confuse horsepower and torque when assessing a new car's power package. "Basically, horsepower measures work (force x time). It's the most common measurement of engine power because it describes how much work the engine can do," Gold says. By definition, one horsepower equals 33,000 foot-pounds per minute. "In simpler terms, horsepower is one figure to consider for mid- and upper-range engine response."

At highway speeds, the average car requires only 20 horsepower to keep it running. Vehicles that pull heavy loads will require more horsepower to fulfill its intended purposes. There's no magic number for ideal horsepower for your car, as other variables like engine torque, vehicle weight, aerodynamics and gearing all play supporting roles in the car's overall performance.

With a lighter car, you don't need as much horsepower. When you're researching vehicles, be sure to check for charts or data on a model's weight and its horsepower, as well as other factors such as aerodynamics and gear systems.

--Torque. Torque measures force, or more specifically, twisting force related to the inner mechanisms of the car's engine and speed-producing parts. It gives the car that extra oomph to help maneuver around and pass other vehicles on the highway.

"Torque is what pushes the seat into the small of your back," Gold says. "A car with lots of torque will often feel faster, although it may not actually be faster. That's why muscle cars like the Corvette and Mustang use big, torque V-8 engines."

A heavier car depends upon good torque to make a safe pass. Any vehicle with quality torque -- especially low- and mid-range response cars -- enjoys strong bursts of speed without downshifting or noisy over-revving.

--Turbocharger. "A turbocharger, or 'turbo,' is a device that increases an engine's power output," Gold says. "Engines work by sucking in air (which is then mixed with gasoline in a specific ratio), compressing it, igniting it with a spark to produce power and then pushing out the spent gasses through the exhaust. The engine 'inhales' from the vacuum created when the pistons move downward. A turbocharger is an exhaust-driven turbine that packs more air into the engine than the pistons can draw-in on their own. With more air, you can add more fuel, get a bigger bang and produce more power.

"A turbocharger allows a small engine to produce the power of a big engine. Turbos used to be used mostly for sports cars, but nowadays automakers are turning to them for fuel economy." Turbos only boost power when you step on the gas, but when you are driving gently, the turbo doesn't kick in. So the engine inhales less air and uses less fuel. "Ford, Hyundai, Kia and Buick are starting to use turbocharged engines this way. A great example is the Hyundai Sonata, which has a turbocharged four-cylinder instead of a V-6. Under heavy throttle, it produces as much power as a V-6 with similar fuel consumption. But when you are just cruising down the freeway, its fuel economy is similar to a small four-cylinder engine."

If you live in a high altitude, where the air is less dense, a turbocharger will help prevent the reduced power that normal cars usually experience when the engines get a smaller amount of air. Thinner air is easier for a turbocharger to pump.

Gold warns, "While turbos are a lot of fun and well suited to sporty cars, their wind-up-and-go power delivery can make for a neck-snapping ride. That's why family and luxury cars generally use larger engines to develop more power, instead of a turbocharger."

When it comes to speed, always keep safety first. According to the National Highway Traffic Safety Administration, speed is a factor in one-third of fatal crashes. So if you do choose a car with lots of speed, prepare to drive extra-cautiously to keep the power in your hands.

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