Why Use Underdrive Pulleys?

Underdrive pulleys increase engine output by reducing the draw of the engine's accessories by slowing them down and reducing the horsepower (HP) they use. ... Additional and significant performance improvements can be seen by reducing the weight of the pulley versus the original pulley.

Is an underdrive pulley worth it?

Underdrive pulleys, when applied to the accessory components of a vehicle, drive the components at a lesser speed because of their increased diameter size. As far as an upgrade, they provide one of the cheapest returns for the money spent when it comes to actual performance and horsepower gains.

Do underdrive pulleys add horsepower?

Underdrive pulleys will yield a small increase in horsepower anywhere from 8 to 15 hp. This is accomplished by reducing the amount of power needed to drive the engine accessories that eat up precious horsepower.