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Supercharging Fundamentals
Superchargers have become very popular in recent years for the following reasons, they are cost efficient, reliable, and produce lots of power. Supercharging an engine often results in huge power increases in the range of 50% to 100%, making them great for racing, towing, or just having fun in your daily vehicle. Although superchargers carry a fairly high ticket price when compared to other single performance upgrades, nothing provides more horsepower for your money. And because of the way superchargers work, they provide power only when the engine is under full throttle or under load... not under normal cruising conditions. This means that the supercharger will not affect the engine's reliability, longevity, or fuel economy under normal driving conditions.
A supercharger increases the gas (air) density at the inlet to the engine. We have all heard about how a supercharger “forces” air into an engine, or “pumps” more air in, etc. The engine of course consumes more air and, with the proportionally correct amount of additional fuel, will make more power:
- An engine will “pump” a fixed volume of air, at a given speed, assuming Wide open throttle operation. This volumetric flowrate, of course, is entirely dependent or the engine size, speed, and volumetric efficiency. Items such as tuned intake and exhaust systems, ported cylinder heads, modified camshaft profiles and the like are all designed to improve volumetric efficiency, which increases power.
- The AIR MASS flowrate through the engine is a product of inlet air density and the volumetric flowrate. So, this means that for any given engine, one very effective way to get more air through it is to increase the density of the air available at the inlet.
- With increased AIR MASS flowrate, we can now add the correct amount of additional fuel and produce more power. The important distinction is that power strongly depends on air density, i.e., the amount of oxygen available in a given volume to combine with fuel.
- Since superchargers increase the inlet air density to the engine, they are also and often referred to as “compressors”.
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