Lightened crank pulley reduces the inertia and load placed on the engine, therefore reducing parasitic loss on the engine power. It doesn't increase power, but you will feel that the engine is much more easier to rev and accelerate.
If you are planning to get LCPs, just make sure that they are the exact same size and dimensions as the original pulley. Undersizing or oversizing will cause damage as it has different circumferences and cause the auxiliary components such as air cond compressor, power steering pumps etc to rotate in RPMs outside of their designed specs.
---------- Post added at 02:00 AM ---------- 6 hour anti-bump limit - Previous post was at 01:57 AM ----------
may i know, why when i use lighten crank pulley, i can hear like the sound 'tok..tok..tok' seems like belting...or another pulley sound... why its happen ? should i use back the original or how to solve ? thanx
Chances are either the crank pulley was not fixed properly or the belt tensioner or the other pulleys are worn and needs to be changed. I doubt its due to improper belt tension as belts usually squeek rather than create knocking sounds.