For a supercharger to work at peak efficiency, the compressed air exiting the discharge unit must be cooled before it enters the intake manifold. This means that it can't create as much power when it's ignited by the spark plug. Hotter air is less dense and can't expand as much during the explosion as cooler air. Atmospheric pressure at sea level is 14.7 psi, so a typical boost from a supercharger places about 50 percent more air into the engine.Īs the air is compressed, it gets hotter. That's 6 to 9 additional psi over the atmospheric pressure at a particular elevation. Superchargers can spin at speeds as high as 50,000 to 65,000 rotations per minute (RPM).Ī compressor spinning at 50,000 RPM translates to a boost of about 6 to 9 pounds per square inch (psi). Making the drive gear larger than the compressor gear causes the compressor to spin faster. To pressurize the air, a supercharger must spin rapidly – more rapidly than the engine itself. 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. The drive gear, in turn, rotates the compressor gear.
Most are driven by an accessory belt, which wraps around a pulley that is connected to a drive gear. Unlike turbochargers, which use the exhaust gases created by combustion to power the compressor, superchargers draw their power directly from the crankshaft. 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. Supercharging adds an average of 46 percent more horsepower and 31 percent more torque. With the additional air, more fuel can be added to the charge, and the power of the engine is increased. This forces more air into the engine, providing a boost. Superchargers increase intake by compressing air above atmospheric pressure without creating a vacuum.
If you want to set records in the quarter-mile, however, you'll need to add more air so you can add more fuel. When you need more power, such as accelerating to pass on the highway, the air-fuel ratio is more like 12:1. When idling or cruising at a constant speed, the mixture is 14.7 parts of air to 1 part fuel. But you can't simply pump more fuel into the engine because you need an exact amount of oxygen burn a given amount of fuel. Getting more fuel into the charge would make for a more powerful explosion.
0 kommentar(er)
