That's the job of the supercharger. Superchargers increase intake by compressing air above atmospheric pressure without creating a vacuum.
This forces more air into the engine, providing a boost. With the additional air, more fuel can be added to the charge, and the power of the engine is increased.
Supercharging adds an average of 46 percent more horsepower and 31 percent more torque. In high-altitude situations, where engine performance deteriorates because the air has low density and pressure, a supercharger delivers higher-pressure air to the engine so it can operate optimally.
Unlike turbochargers, which use the exhaust gases created by combustion to power the compressor, superchargers draw their power directly from the crankshaft. Most are driven by an accessory belt, which wraps around a pulley that is connected to a drive gear. The drive gear, in turn, rotates the compressor gear. The rotor of the compressor can come in various designs, but its job is to draw air in, squeeze the air into a smaller space and discharge it into the intake manifold.
To pressurize the air, a supercharger must spin rapidly — more rapidly than the engine itself. Making the drive gear larger than the compressor gear causes the compressor to spin faster.
Superchargers can spin at speeds as high as 50, to 65, rotations per minute RPM. A compressor spinning at 50, RPM translates to a boost of about 6 to 9 pounds per square inch psi.
That's 6 to 9 additional psi over the atmospheric pressure at a particular elevation. Atmospheric pressure at sea level is As the air is compressed, it gets hotter. Hotter air is less dense and can't expand as much during the explosion as cooler air. This means that it can't create as much power when it's ignited by the spark plug. For a supercharger to work at peak efficiency, the compressed air exiting the discharge unit must be cooled before it enters the intake manifold.
The intercooler is responsible for this cooling process. Intercoolers come in two basic designs: air-to-air intercoolers and air-to-water intercoolers. Both work just like a radiator , with cooler air or water sent through a system of pipes or tubes. As the hot air exiting the supercharger encounters the cooler pipes, it also cools down. The reduction in air temperature increases the density of the air, which makes for a denser charge entering the combustion chamber. There are three types of superchargers: Roots, twin-screw and centrifugal.
The main difference is how they move air to the intake manifold of the engine. The Roots supercharger is the one that you sometimes see sitting on top of the hood of a drag car.
It uses two rotors that mesh together and compress the incoming air before sending it to the engine. The twin-screw supercharger has, as you might have guessed, two rotors that are wound together like two screws instead of gears. The screws compress air when they rotate. A centrifugal supercharger looks kind of like a snail shell, with an impeller wheel that compresses the air. Although all of these designs provide a boost, they differ considerably in their efficiency.
Each type of supercharger is available in different sizes, depending on whether you just want to give your car a boost or compete in a race.
The Roots supercharger is the oldest design. Philander and Francis Roots patented the design in as a machine that would help ventilate mine shafts. In , Gottleib Daimler included a Roots supercharger in a car engine. As the meshing rotors spin, air trapped in the pockets between the lobes on the rotors is carried between the fill side and the discharge side. Large quantities of air move into the intake manifold and "stack up" to create positive pressure.
For this reason, Roots superchargers are really nothing more than air blowers, and the term "blower" is still often used to describe all superchargers. Roots superchargers are usually large and sit on top of the engine. They are popular in muscle cars and hot rods because they stick out of the hood of the car. However, they are the least efficient supercharger for two reasons: They add more weight to the vehicle and they move air in discrete bursts instead of in a smooth and continuous flow.
Regardless of the application, turbochargers and superchargers create extreme operating conditions, placing more stress on engine oil. Click here to update settings. How turbocharger and superchargers differ Turbochargers and superchargers can sometimes get confused. Turbochargers and superchargers: The function of induction Before discussing their differences, it helps to understand what links turbochargers and superchargers from an engineering standpoint.
How do turbos work? Mercedes A — with a 2. Turbodiesels are the mainstay of the Range Rover Evoque engine line-up. Ford Puma has a 1. Volvo XC60 T8 has a turbo and a supercharger. Configure your next turbocharged car. Compare cars using carwow Compare cars using carwow. View offers from local and national dealers.
Buy with confidence on carwow. Select a car. Like this article? Share it with others! Related articles. What is GAP insurance and why do you need it? Lada Niva review: utilitarian Russian off-roader driven. That smaller engine is inherently more fuel-sipping than a larger one, but when power is needed, the forced-air system starts operating to provide it — a four-cylinder feels like a six-cylinder, for example. Sign up to receive Driving. A welcome email is on its way. If you don't see it, please check your junk folder.
The next issue of Driving. We encountered an issue signing you up. Please try again. This website uses cookies to personalize your content including ads , and allows us to analyze our traffic. Read more about cookies here. By continuing to use our site, you agree to our Terms of Service and Privacy Policy. Sign up. Main Menu Search driving.
0コメント