Forced Induction: Charging For Boost - How It Works
You probably know that in an automobile engine the pistons go up and down, and this makes the wheels go round and round. It's the downstroke that sends the driving force to the wheels, and the more powerful the downforce, the more horsepower you have.
The way to get more powerful downforce is to have a more powerful explosion at the top of the piston, and the way to do this is to force more air and fuel into the cylinder at each cycle.
Normally aspirated engines draw in outside air by the vacuum caused by the piston going down as the vapor in the cylinder is exhausted. If you push more air in, and compress it so it's more dense, the explosion increases. Force-feeding the engine in this way is Forced Induction, the general name for the whole family of turbocharging and supercharging devices designed to boost the engine power.
The science of air compression and pumping was in use before the internal combustion engine was invented - if you're interested take a look at our History of SuperCharging page for the big picture.
Forced induction as applied to automobiles is a simple concept: put an air pump into the fuel-air delivery system to force in more air under pressure so the denser air in the cylinder makes a bigger bang per cycle. The basic requirement is to pump air faster than the engine does, but the complications come with the need to do this across the whole range of rpm, and without absorbing too much of the extra power produced, and especially without producing too much extra heat, because heat is bad for the engine and more significantly, prevents the very density you want to achieve. See more about this in our Supercharger Heat page.
The solutions are diverse. Read on to our Superchargers Compared page.