Underdrive and Lightened Pulleys
In this short article, we will be reviewing the properties of lightened crankshaft pulleys and underdrive crankshaft pulleys. A lightened crankshaft pulley is a standard diameter crankshaft pulley that is made from a solid billet of aluminum. Aluminum is about 1/3 the weight of steel. An underdrive crankshaft pulley is a smaller than normal size crankshaft pulley. Usually, these pulleys are also made from a solid billet of aluminum.
The benefit of installing a lightened crankshaft pulley is that you are reducing the rotating mass of the engine. This gives the engine the ability to get up to speed faster, i.e., quicker acceleration.
The benefit of installing an underdrive crankshaft pulley is the same as a normal sized lightened pulley. Being made from aluminum, they will be lighter and allow the engine to rev up more easily. The extra advantage of an underdrive pulley is that it is smaller than the factory size crankshaft pulley. What this means is that at higher RPMs the engine will not be working as hard to turn the alternator and water pump, thus “saving” power for the wheels.
However, there is some disadvantages to using an underdrive crankshaft pulley. You will want to consider what type of driving you plan on doing with your car. Because the pulley is smaller, and will therefore be turning the water pump slower, you may experience cooling issues at idle. Say for instance, you are hammering your car around the track, full on, then you must slow down and idle for a little bit; your water pump may then have a little trouble keeping up with all the heat produced while running full out. Another situation where an underdrive pulley may not be suitable is if you spend a lot of time driving in traffic. Because your engine is spending a lot of time idling at stop lights, you may experience both heating issues, and battery charging issues. Cooling issues may also be more pronounced in hotter parts of the world. It is up to the end user to decide what pulley would be best for their situation.
