The secret to making power in an internal combustion engine really boils down to how much air can be stuffed into the cylinders on each power stroke. With more air comes more fuel. Add more air and fuel, and combustion produces more heat, energy, and pressure. Higher pressure exerts greater push on the piston and rod; the crank spins faster, resulting in higher power output at the flywheel. This is the idea behind big cams, ported heads, and stroker cranks.
Even with those improvements, a normally aspirated engine relies on atmospheric pressure (14.7 psi at sea level) and the vacuum created by internal piston suction to draw air and fuel into the engine. Ultimately, this limits how much mixture can be burned on each power stroke. Adding a compressor can force-feed a denser fuel/air charge into the combustion chamber for increased power.
Automotive engineers refer to such a compressor as a supercharger, regardless of the way its driven; however, gearheads commonly use the term supercharger or blower to refer to a compressor thats driven by a belt, gears, or a chain. This distinguishes them from exhaust-driven superchargers, known to car crafters as turbochargers or turbos.
Car Craft covered turbos back in the Feb. 01 issue. In this installment, with help from Blower Drive Service, Kenne-Bell, Vortech, and Paxton, well take a look at three common belt-driven supercharger designsthe centrifugal, the rotor (positive-displacement or Roots-type), and the twin-screw compressor.
Check 'em out in the sidebars below.
The "secret" to making power in an internal combustion engine really boils down to how much air can be stuffed into the cylinders on each power stroke. With more air comes more fuel. Add more air and fuel, and combustion produces more heat, energy, and pressure. Higher pressure exerts greater "push" on the piston and rod; the crank spins faster, resulting in higher power output at the flywheel. This is the idea behind big cams, ported heads, and stroker cranks.Even with those improvements, a normally aspirated engine relies on atmospheric pressure (14.7 psi at sea level) and the vacuum created by internal piston suction to draw air and fuel into the engine. Ultimately, this limits how much mixture can be burned on each power stroke. Adding a compressor can force-feed a denser fuel/air charge into the combustion chamber for increased power.
Automotive engineers refer to such a compressor as a supercharger, regardless of the way it's driven; however, gearheads commonly use the term "supercharger" or "blower" to refer to a compressor that's driven by a belt, gears, or a chain. This distinguishes them from exhaust-driven superchargers, known to car crafters as "turbochargers" or "turbos."
Car Craft covered turbos back in the Feb. '01 issue. In this installment, with help from Blower Drive Service, Kenne-Bell, Vortech, and Paxton, we'll take a look at three common belt-driven supercharger designs--the centrifugal, the rotor (positive-displacement or Roots-type), and the twin-screw compressor.
Check 'em out in the sidebars below.