Image: Boxster
Porsche
If engineers want to quicken a car like the $47,550 Porsche Boxster, they must add a bigger engine, bigger brakes, bigger wheels and bigger tires to compensate for the increase in speed. That can throw off the entire design.
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updated 8/18/2009 7:11:47 AM ET 2009-08-18T11:11:47

The Mercedes-Benz SL550 will get to 60 miles per hour in 5.3 seconds, but that kind of speed will cost you — to the tune of $98,500 big ones.

If you can settle on a car that will get you to 60 mph just one-tenth of a second later, the savings can be significant. The Mercedes SLK350 costs only $50,950. It's not the exact same car (the SL550 has one of the most luxurious, high-tech interiors of any vehicle), but it's certainly close.

Several other cars also deliver speed without the price of an F1 race car. They hail from all the usual suspects, such as Audi, BMW, Lexus and Porsche, as well as American automakers Chevrolet, Ford and Saturn. There's a reasonably priced speedster to suit just about any taste.

For our list, we used Kelley Blue Book data to identify vehicles currently sold in the U.S. that cost less than $50,000 but have quick zero-to-60-mph times. We then pared down the list to the top 10 fastest under $50K.

The $46,325 Ford Mustang GT500 tops our list with a blistering zero-to-60 time of 4.3 seconds. Close behind, the $31,040 Chevrolet Camaro SS, hits 60 mph in 4.6 seconds. BMW's $36,675 135i coupe comes in third.

Martin Birkmann, BMW's motorsport manager and manager of product and price planning, says fast cars must successfully balance weight, velocity and control.

"For us, speed is something that should have a sensory component for the driver," Birkmann says. "It should be something that can be experienced but also something that [the driver] feels being in control of."

That control creates safety — a responsiveness that's available when accelerating, cornering and stopping is not about achieving breakneck speed, but about preventing a crash.

Cars like Lexus' $37,580 IS 350 are more expensive than their slower counterparts because it takes stronger, lighter and more durable components to give vehicles that extra control at high speeds.

If engineers want to quicken a car like the $47,550 Porsche Boxster, they must add a bigger engine, bigger brakes, bigger wheels and bigger tires to compensate for the increase in speed. That can throw off the entire design.

"We just don't put a bigger engine in something and say, 'OK, now you go faster,'" says Dave Engelman, a spokesman for Porsche. "It's back to that balance thing. We really don't compromise giving one thing up to get another. It all has to work together."

Certain kinds of engines provide a speed advantage, as well. Turbocharged engines, for example, force more air into an engine's chambers than usual in order to push the pistons downward faster. This helps increase displacement while using less fuel. A turbo-boosted V6 engine uses less gas than — but achieves the same power as — a V8.

The Ford Flex crossover, for instance, uses a twin-turbo 3.5-liter V6 engine that gets 355 horsepower and 350 ft.-lb. of torque. That configuration improves fuel economy by 10 percent to 15 percent over a V8 in the same class with no sacrifice in speed.

Even with national average gas prices $1.45 lower than they were a year ago, fuel economy is as important as raw speed, says David Paja, the director of marketing for passenger vehicles at Honeywell. The New Jersey-based company makes turboboosters for Ford, BMW and Jaguar.

"Customers are more and more looking at turbocharging as the key technology ... to meet some of the conflicting priorities over the next few years," Paja says. "They are trying to make affordable cars that meet lower fuel-consumption standards."

At any rate, our list supports the notion that you don't have to fork over your life savings, or even more than you can easily afford, to go fast. Options abound, even within our list: BMW's 135i uses a 3.0-liter turbocharged 300-hp V6 engine and costs thousands less than the $46,575 BMW Z4 — and it reaches 60 mph from a standstill half a second faster.

Sometimes you can have your cake and eat it, too.

© 2012 Forbes.com

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