SU­PER­CHARG­ING

HWM (Singapore) - - Learn -

Like tur­bocharg­ers, a su­per­charger is a de­vice that also forces more air into the en­gine. How­ever, un­like tur­bos, a su­per­charger is pow­ered by a belt that is di­rectly con­nected the crankshaft. Be­cause of this, they are gen­er­ally more re­spon­sive and do not suf­fer “lag” as badly as tur­bocharged cars do. On the flip side, since they are driven di­rectly by the en­gine, they tend to sap power from the very en­gine it’s sup­posed to boost. But since they gen­er­ate more power than they use, the trade-off is con­sid­ered worth­while. An in­ter­cooler is also used in su­per­charger set­ups to fur­ther in­crease the den­sity of air and im­prove its over­all ef­fec­tive­ness.

There are three main types of su­per­charg­ers: roots, twin-screw and cen­trifu­gal. Roots and twin-screw types of su­per­charg­ers use mesh­ing lobes to com­press air, while a cen­trifu­gal su­per­charger uses an im­peller, which sucks in air.

Roots su­per­charger are very old in de­sign and have been in ex­is­tence since the early 1900s. It con­sists typ­i­cally of ro­tors with three or four lobes that, when in ro­ta­tion, trap air in sur­round­ing pock­ets around the lobes and move them to the in­take tract of the en­gine. For this rea­son, they are of­ten re­ferred to as blow­ers.

Twin-screw su­per­charg­ers are some­what sim­i­lar in de­sign but use mesh­ing lobes that re­sem­ble worm gears to com­press air in the hous­ing. They are more ef­fi­cient than Roots su­per­charg­ers and pro­vide very good re­sponse be­cause boost is pro­duced al­most in­stan­ta­neously at very low en­gine speeds. How­ever, twin-screw su­per­charg­ers usu­ally cost more too as they need to be built with close tol­er­ances and high pre­ci­sion to en­sure op­er­at­ing ef­fi­ciency.

Fi­nally, a cen­trifu­gal su­per­charger uses im­pellers to draw more air into its com­pres­sor hous­ing, which is not that dif­fer­ent from a tur­bocharger, ex­cept that it is driven by the belt in­stead of ex­haust gases. Be­cause of this, cen­trifu­gal su­per­charg­ers are more ef­fec­tive and will pro­duce more boost as en­gine speeds in­crease. On the flip side, they are less ef­fi­cient and un­re­spon­sive at low en­gine speeds.

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