This is the first thing just about anyone will tell you when you say you want to up your horsepower. It's kind of like those minty-fresh gum commercials with the ice swirling around, and the price is only a smidge more than a pack of gum. A kind of big smidge, but still. The idea is that cold air is more dense, so more air gets into the cylinders to mix with the fuel. More air means more combustion, and more combustion means more power, to the tune of a realistic 5- to 7-horsepower in a typical engine. This only works if the air intake is the limiting factor, however. If your engine is already sucking in big breaths of cool, fresh air, then try one of the other tricks on this list.
No cats need be harmed in the increasing of one's horsepower (how did so many animals make it into this tip?). This means that you straighten the pipes from the catalyst in the exhaust tubing to the back of the car, at the bumper. "This will loosen up the entire system," said Jeff Zurschmeide, author of "The New Mini Performance Handbook." "It pushes the exhaust gases out easier." Getting those gases out ASAP means more room for more air and fuel, and more air and fuel means more power. Zurschmeide notes that "new catalysts are less restrictive than they used to be, and they're designed to work with the engine. They're not such a bar to performance anymore." If your car is, ahem, vintage, you might want to check out tip number 3.
When cars were first required to have catalytic converters, manufacturers rushed to slap them into place. They didn't do one's performance any favors, though they did help the air we breathe some. It took decades for catalysts to improve, with even cars from the 1980s and 1990s getting gummed up in the converters. And if you added leaded gas to that equation? Well, you were lucky if you could make it up a hill. Try this: Swap an old catalyst out for a modern aftermarket high-flow number and feel the difference in the pedal. Do this along with a cat-back exhaust, Zurschmeide says, for the biggest bang for your buck. He also notes that it's illegal to remove a catalyst that's not broken -- and there are some hefty fines for punishment. Do not, under any circumstances, knock a hole into your catalytic converter with a wrench you happen to be holding, requiring it to be replaced, perhaps by a high-flow catalyst. You hear that? Do not knock a hole in it.
Believe it or not, there are a bunch of tweaks you can make to your tires to increase the feel of power in your car. Zurschmeide suggests starting with a more aggressive alignment. Dial out the toe-in that manufacturers specify so that the wheels are pointed straight ahead for more straight-line speed. Swap out the regular tires for a set of shorter tires to increase acceleration. Sure, this will make your speedometer read incorrectly, but it's a small price to pay for a quick time off the line. You can always get a new set of light weight wheels to mount those short tires on, too, but be careful here if you're pinching pennies. A set of carbon-fiber wheels may lighten your load, but they'll lighten your wallet by far, far more.
Reflash! Ah-aaaah! Savior of the universe! Reflashing your car's computer merely changes its programming regarding timing, fuel-air mixture and other horsepower-upping inputs. The benefit of a reflash, besides the added power, is that it can be undone if you need warranty work done or have to have your car inspected by the state environmental department. The downside is that it really only works if your car is turbocharged or supercharged; reflashing a normally aspirated engine will only get you an extra half a horsepower, Zurschmeide says. And as with some of the others on this list, it only nets a big power boost if the factory programming is the limiting factor for your engine. Swapping out the stock computer for an entirely new module could help -- but that, Zurschmeide says, "has a very high price of entry."