TUR­BOCHARG­ING

HWM (Singapore) - - Learn -

The term and name turbo is syn­ony­mous with go­ing faster. Some of you might re­mem­ber old PC sys­tems with a “Turbo” but­ton that can in­crease its clock speeds. How­ever, the turbo in such com­puter sys­tems is noth­ing like the turbo used in au­to­mo­biles. For one, you can­not just push a but­ton to activate the turbo, and the per­for­mance boost that a turbo pro­vides does not come in­stan­ta­neously. To un­der­stand why, it is nec­es­sary to look at how a turbo setup is like and how it works.

Sim­ply put, a turbo is re­ally just a de­vice that has a tur­bine that is spun by ex­haust gases. Since this tur­bine is con­nected

to the com­pres­sor, as the tur­bine spins, so does the com­pres­sor, which forces more and more air into the in­take of the en­gine. The tur­bine in a turbo can spin as high as 150,000rpm. And be­cause they are driven by ex­haust gases which would have other­wise been wasted, tur­bos are com­monly said to in­crease an en­gine’s ef­fi­ciency.

How­ever, be­cause a turbo is driven by ex­haust gases and spins so fast, it also gen­er­ates a lot of heat. Heat de­creases the den­sity of the charged air and re­duces the po­ten­tial per­for­mance gains that can be had. To rec­tify this, a turbo setup also in­cludes some­thing called an in­ter­cooler. An in­ter­cooler can be thought of as a ra­di­a­tor that helps cool down the mass of charged and com­pressed air that is en­ter­ing the en­gine.

An­other downside to the turbo is lag or more com­monly known as “turbo lag”. Re­mem­ber that the turbo is driven by ex­haust gases? For a turbo to start be­ing use­ful, the en­gine first needs to get up to speed to gen­er­ate enough ex­haust gases to spin the turbo, only then can it ef­fec­tively gen­er­ate “boost” and force air into the en­gine. This is al­ways why the power and torque graphs of a tur­bocharged car of­ten have a very steep and sud­den in­crease.

The time that it takes for the turbo to spin and gen­er­ate op­ti­mal boost is there­fore re­ferred to as “turbo lag” and this is gen­er­ally un­de­sir­able es­pe­cially for track driv­ing as it makes the car some­what un­pre­dictable, es­pe­cially when cor­ner­ing. On the other hand, turbo lag makes driv­ing turbo cars ex­cit­ing, which is very true for cars with huge tur­bos since driv­ers of­ten wait in an­tic­i­pa­tion for the boost to kick in; the car then ex­pe­ri­ences a dra­matic surge in power and torque.

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