Drive

Tweaks, turbos and air flow help boost your car's power

Whether it’s to make a sports car faster, or for better performance in an everyday car, auto manufacturers often increase the horsepower in their engines. In some cases, they’ll even tweak a single engine design to get a lower- and higher-horsepower version out of it. It’s a process that involves several methods, employed alone or in combination.

“Horsepower is the measure of work an engine can do,” says Chris Nowak, senior manager of product development for Chrysler’s Mopar division. “With any amount of fuel into the engine, it’s how much useful motion I can get out of the car.”

Most cars run on gasoline, but they mix it with large volumes of air and then burn this volatile vapour to create power. It isn’t enough to just pour in more gas.

“At some point, you will saturate the engine and it won’t run properly,” Nowak says. “You want to add more air.”

One way to do this is to add a turbocharger or supercharger. These devices attach to the engine and force air into it when more power is needed, such as when you press hard on the throttle. The engine’s computers respond by increasing the flow of fuel, which in turn increases the power.

When extra air goes in, it has to go out to make room for more, so engineers also improve how the engine “breathes.” A freer-flowing exhaust system will still muffle the sound and reduce pollutants, but it reduces back pressure on the engine. Engineers carefully balance the air going into the engine with the amount going out.

Another step is to calibrate the engine by programming its control module.

“The calibration tells the engine how to mix the air and fuel, how much, and at what r.p.m.,” Nowak says. “You could tune the intake or the exhaust alone, and that would give you an increase in horsepower, but the calibration is where you maximize performance.”

Some performance kits include a cold-air intake, which draws cool fresh air into the engine, rather than the hot air in the engine compartment. Cold air is denser, so more oxygen is drawn in, which more effectively burns in the combustion chamber to power the engine.

Race-car drivers substantially increase horsepower by rebuilding their engines with speed-specific internal components, but this can be extremely expensive. Everyday car owners can buy add-ons, such as cold-air intakes or freer-flowing exhaust systems, to get more power at a fraction of the race-car cost.

Need for speed

  • “Horsepower” was coined by inventor James Watt. It’s believed he measured a pony pulling up a 330-pound coal bucket 100 feet in one minute, which was one horsepower.
  • Engines also have torque, a measurement of the twisting force that eventually turns the wheels. A car with high torque will accelerate faster than one with low torque.
  • Auto companies “tune” the exhaust note to give performance cars a sportier sound.

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