Last week we covered what and how turbochargers work. This week we’re telling you how another popular method of squeezing more power out of your engine operates. The supercharger creates more power by shoving more air into the engine. This is similar to a turbo, but how the two devices go about it is completely different.
How do they work?
While a turbocharger uses wasted exhaust gases to produce more power, superchargers operate off a different part of the engine. Superchargers are powered mechanically by the belt or chain that goes to the crankshaft. They force more air into the engine so that more fuel can be burned, which in turn creates more energy. Superchargers increase air intake by compressing the air above atmospheric pressure.
A supercharger draws its power directly from the crankshaft. Most of them use an accessory belt, which is wrapped around a pulley that is connected to a drive gear. Once the drive gear rotates, it rotates the compressor gear. The compressors job is to draw in more air and squeeze it into a smaller space. This is then discharged into the intake manifold.
The drive gear has to be bigger than the compressor gear in a supercharger. This is because the supercharger must spin faster than the engine itself to pressurize the air. Some superchargers can spin at speeds of up to 65,000 rpm, far above any normal engine.
Like a turbocharger, the compressed air created by the supercharger becomes hot and loses its density. This means that it can’t expand as much during the explosion period, which reduces power produced. An intercooler is responsible for cooling the hot air before it enters the intake manifold. Cool air or water is sent through a series of pipes that cool the compressed air as it is passed over them. This reduces the density and makes for more power.
Advantages and Disadvantages
A superchargers biggest advantage is obviously creating more power. Turbochargers do the same thing, so why don’t we just use those? Another advantage of superchargers is that they do not suffer lag like turbo’s do. As we covered in the ‘How does a Turbo Work?” article, turbo lag is where there is a delay between putting your foot on the throttle and the turbo’s spooling up (velocity of gases reaching sufficient level). Superchargers have no problems with this because they are driven directly off the crankshaft.
Another benefit of Superchargers is that they can be fitted to an engine easier. Turbochargers require extensive modification to the exhaust system, while superchargers can be bolted to the top or side of an engine.
One last benefit is that they can be shutdown normally with the engine. Turbochargers usually have to idle for about 30 seconds prior to shutdown, so the lubricating oil has a chance to cool.
Now on to the disadvantages. A superchargers main drawback is that it has to steal some power from the engine. This is because the crankshaft drives them, although most people see the trade-off as beneficial. A supercharger may steal up to 20 percent of the power from an engine, but can create around 40 to 50 percent more power over the standard engine, making the trade-off worth it.
Another disadvantage is that a supercharger can adversely effect the reliability of an engine. More parts means more things to go wrong and more power can put additional strain through the engine that it was not intended to take. Supercharged cars generally cost more to maintain and most manufacturers suggest a higher octane fuel is used.