What are underdrive pulleys?

The objective of an underdrive pulley is to slow down the accessories in order to reduce the parasitic power loss on the engine. This is achieved by using a crankshaft pulley with a smaller diameter than stock, which slows the serpentine belt.

Do underdrive pulleys increase torque?

The GFB lightweight under-drive pulleys do not increase the amount of torque or power developed by the engine. They simply reduce the amount of mass that the engine must accelerate. Therefore, the faster the engine RPM is increasing, the greater the benefit will be from reduced pulley mass.

What does a 25 underdrive pulley do?

So what do underdrive pulleys do? Underdrive pulley systems increase engine horsepower by reducing the amount of power required to drive external engine accessories. For example, the alternator, power steering, water pump and air compressor rob horsepower from your engine.

Are underdrive pulleys bad?

Poorly engineered underdrive pulleys can cause unwanted side effects; this is due to not spinning the alternator, power steering, and/or air conditioning fast enough. This leads to low alternator voltage, weak or no power steering assist, and weak or no air conditioning effectiveness, especially at idle or low RPM.

Do lightweight pulleys increase HP?

A lightweight pulley accomplishes this simply by reducing rotational mass – or in leymans terms, because it weighs less, it takes less horsepower to spin the pulley, so more horsepower gets to the wheels.

Does a lighter crank pulley do anything?

A lightweight pulley accomplishes this simply by reducing rotational mass – or in leymans terms, because it weighs less, it takes less horsepower to spin the pulley, so more horsepower gets to the wheels. Consider that stock crank pulleys typically weight 4-10 lbs… this varies depending on manufacturer and engine size.

Can I put a bigger pulley on my alternator?

Yes, you can increase your alternators overall output as well as increase power output at engine idle speeds. Check the size of the pulley on your alternator. If you are having problems with overall alternator output or charging at engine idle, maybe a smaller pulley is all you need.

Do all engines have a harmonic balancer?

The harmonic balancer is an engine component found on virtually all rotating internal combustion engines and plays an important role in protecting the engine from dangerous harmonic vibrations and potential damage.

Does a bigger pulley increase speed?

By changing the diameter of the pulley wheels, speed can be changed. A smaller pulley turning a larger pulley results in the larger one moving more slowly but with more shaft power.

Do light weight pulleys increase HP?

What does an underdrive pulley do for a car?

Underdrive pulleys usually are a performance enhancing item that increases the torque and horsepower output of an engine by reducing drag caused by belt-driven accessories. Horsepower gains from underdrive pulleys alone are usually around 4-7 hp. These are some of the best HP improvements enthusiasts can find for their money.

Can a crankshaft pulley be changed for underdrive?

As mentioned earlier, to accomplish an underdrive ratio, you can change either the crankshaft pulley or the accessory pulleys. As there is more than one accessory that often needs to be underdriven, pulley kits start with a smaller crankshaft pulley. This gets all of the accessories close to the underdriven goal, with a single pulley change.

How long does it take to install an underdrive pulley?

5. The cost of underdrive pulleys is relatively low compared to the gains received. You can install an underdrive pulley on your vehicle in less than an hour. They create power on virtually any system you have, even though the biggest enthusiasts tend to own Ford Mustangs.

What happens when you increase the diameter of an accessory pulley?

When the diameter of an accessory pulley is increased, the revolutions per minute of the pulley decreases, which cuts down on parasitic drag of the component’s demands. As much as 15 horsepower gains can be realized at the wheels with an underdrive pulley kit, depending upon the number of accessories involved.