EX­PERT’S GUIDE TO... SU­PER­CHARG­ERS

Forc­ing com­pressed air into a mo­tor is an ef­fec­tive way of ramp­ing up per­for­mance. But how does it work?

Motorcycle News (UK) - - Garage -

THE EX­PERT Sean Mills The boss of Big CC Racing in Wok­ing­ham has been fit­ting su­per­charg­ers since 2004 af­ter he caught the turbo bug in the 1980s with a ‘crappy’ Suzuki XN85 and then a Kawasaki 750. Shov­ing com­pressed air into an en­gine is a sure-fire way of boost­ing the per­for­mance per cc, and there are two types of com­pres­sor avail­able for do­ing such a task: tur­bocharg­ers and su­per­charg­ers.

A tur­bocharger uses the ex­haust gases so there’s a cer­tain amount of turbo-lag, but su­per­charg­ers are dif­fer­ent in that they use a me­chan­i­cal drive via a gear, belt or shaft from the en­gine’s crank­shaft.

A cen­trifu­gal su­per­charger is sim­i­lar to a turbo as it com­presses the air inside the su­per­charger case via an im­peller, then dis­charges it into the mo­tor and comes with a cer­tain amount of lag.

But that’s a good thing. Imagine go­ing around a mini round­about at 3000rpm, then crack­ing open the throt­tle... you’d be side­ways all the time. A cen­trifu­gal charger is more us­able on a bike, pre­cisely be­cause it builds the boost pro­gres­sively with the rpm of the en­gine. Typ­i­cal power out­puts are be­tween 230-320bhp on fore­court fuel.

A cen­trifu­gal su­per­charger com­presses air inside the case via an im­peller

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