The 2012 Porsche 911 Carrera S can churn out nearly 400 horsepower, but it'll set you back close to $100,000. Want to feel just as much power for half the money? Buy a Ford Shelby GT500.
Thanks to improved engine technologies that produce higher horsepower, and lighter materials that lower a car's curb weight, the latest generation of relatively affordable, mass-market sports cars can go as fast if not faster than many of the fancier vehicles blazing down the highway, according to auto experts at Edmunds.com.
Quantifying speed can be tricky. Automakers have been steering clear of advertising a car's top speed for legal reasons, explains Bruce Harrison, a research director at IHS Automotive. So what about zero-to-60 times? That measures acceleration, and the significance of that number is waning, some experts say.
"The numbers are getting so close and so good," says Edmunds analyst Ivan Drury. "The fact that the Toyota Camry can go from zero to 60 mph in 6.5 seconds is kind of mind-blowing compared to the muscle cars in the '60s doing the same time," he says.
So what's the best way to determine a car's speed? Horsepower and weight: the lower the ratio of power to curb weight, the faster the car, experts say. Based on that metric, researchers at Edmunds.com helped us determine the fastest cars under $50,000.
One surprise: U.S. automakers sweep the top five spots.
The Chevy Camaro takes fifth place among the fastest cars under $50,000. The Camaro gets 426 hp, but at $33,180 for a two-door coupe with a 6.2 litre, eight-cylinder engine, it's the least expensive among the top five.
If you need more speed than a Camaro can offer, you'll have to pay about $10,000 more. The two-door Dodge Challenger SRT8 392 has a power-to-weight ratio of 8.9 compared with the Camaro's 9.1, and it can reach up to 470 hp, Edmunds says. But the Challenger will cost you about $45,000.
Ford makes the two fastest cars under $50,000, and the automaker isn't shy about what makes them go.
The Ford Shelby GT500, which tops our list, gets 550 hp. To put that in perspective, in the 1990s, a Ford Mustang got an impressive-for-the-time 300 hp while minivans today can too, notes IHS analyst Harrison.
The two-door Shelby is priced just below our threshold, at $49,605.
"The Shelby GT500 has so much power that each 'horse' only has to move 6.9 pounds," notes Drury of Edmunds, meanwhile each "horse" out of a Dodge Ram 1500 engine's horsepower needs to push 12.3 pounds, the analyst says.
Ford doesn't make Shelby fans do the math, however. The automaker admits that the GT500 can reach 200 mph, the company says -- with a caveat.
"Safety is our first and top priority, not overall speed and acceleration," says Ford power train spokesman Richard Truett, who adds that, even at high speed conditions, the GT500's brakes, chassis and suspension work just as effectively.
Among the imports on our top 10 list, the Subaru Impreza hatchback comes in 10th place, with a horsepower-to-curb weight ratio of 11.1. Its engine packs 305 horses and costs a lot less than some of its competitors at about $36,845.
And the Nissan Infiniti G two-door coupe, which makes ninth place on our list, gets the best gas mileage among our top 10, at a combined city-highway rating of 22 mpg. And with 330 horses, it's got a more powerful engine than the Impreza as well.
A big part of why horsepower, and therefore speed, has improved so drastically in recent years is that stability control, antilock brakes, and even the more complicated details of fuel injection, variable valve timing and turbocharging or supercharging are now being facilitated by computers, says Harrison of IHS.
"There are so many other factors that go into it, how big are the brakes, how many speed transmission is it, what gear ratio is in the vehicle, what kind of suspension helps it get around a corner. There are so many different variables that go into it," Harrison says.
For instance, Ford says it uses electric power assisted steering instead of engine-driven hydraulic pumps that use up a lot of power. "These changes also enable better engine performance because more of the power output is directed to the wheels," says Truett of Ford.
But cars are getting faster across the board, across all brands as well as price ranges.
"I wouldn't say that advances are impacting low-priced cars more than high-priced vehicles, but I do think that, as economies of scale kick in, it's easier to put some of the more advanced technologies on the less expensive vehicles," Harrison says.