How STILLEN Lightweight and Underdrive Pulleys Help You Recover Horsepower and Improve Engine Efficiency

For decades, performance enthusiasts and motorsport tuners have searched for every possible way to extract more power from an engine. Most of the time, performance gains come from getting more air and fuel into the engine -- but what if you could recover power that is already being lost without adding anything at all? Here at STILLEN, we have been developing high-performance parts for a wide variety of makes and models since the early 1980s, and STILLEN lightweight pulleys and underdrive pulley sets represent one of the most overlooked yet highly effective power-recovery upgrades available.

After years of frustration sourcing quality parts from outside vendors and outside machine shops, STILLEN invested in an in-house CNC machine shop to control the entire manufacturing process. The result is a line of precision-machined performance pulleys that we are 100% confident in, from raw material selection through final packaging.

What Is a Lightweight Pulley or Underdrive Pulley?

The simplest answer is that lightweight and underdrive pulleys are exactly what the name implies. Stock vehicles come equipped with heavy cast-iron or steel crank pulleys. There is nothing inherently wrong with that, but those heavy components are not optimized for performance. Anything that spins requires power to spin it, and that means a heavy cast-iron pulley robs more power from your drivetrain than a lighter billet aluminum pulley machined to reduce as much rotating mass as possible.

Underdrive pulleys take this concept one step further by slowing the rotational speed of the surrounding accessory pulleys -- including the alternator and air conditioning compressor -- to reduce the amount of work the engine is required to perform. The less parasitic load from accessories, the more power is transferred through the drivetrain and ultimately to the tires. We like to say that lightweight and underdrive pulleys do not actually make horsepower -- they recover power that was previously being lost to excess rotating mass and accessory drag.

Why Are Performance Pulleys Important?

Lightweight and underdrive pulleys are a smart way to make your engine run more efficiently with less internal resistance. Whether you are building a performance street car or a dedicated track build, reducing the weight of rotating components is one of the most effective ways to improve overall vehicle efficiency. Whether you are reducing unsprung weight with lighter wheels and tires, upgrading to performance brake rotors, lightening your flywheel, or swapping to a lighter crank pulley, every pound removed from a rotating component transfers more of that recovered power to the rear wheels.

In addition to rear wheel horsepower gains, customers consistently tell us the engine feels like it has been freed up -- revving more freely, responding more quickly, and feeling less restrained overall. Some customers also report improvements in fuel economy as a result of the engine operating more efficiently with less rotating mass to overcome.

What Makes STILLEN Pulleys Different?

Before developing the STILLEN line of high-performance aluminum pulleys, our engineering team drew on decades of experience carrying and evaluating other manufacturers' pulleys to understand exactly what to do -- and what not to do.

Common issues we identified with competing products included improper CNC machining tolerances, improper balancing, and factory timing marks that were not machined in correct relation to the crankshaft keyway. These are critical details that directly affect how a crank pulley performs and how well the engine runs.

Here is how STILLEN approaches it differently:

• All STILLEN pulleys are designed in 3D CAD software and then analyzed in FEA (finite element analysis) software that simulates real-world loads and beyond, identifying design weaknesses before a single part is cut.
• Crank pulleys include precision timing marks machined in exact relation to the crank keyway -- a non-negotiable detail for proper engine operation.
• All crank pulleys are finished with a 304 stainless steel sleeve at the main seal contact point, matching factory design intent.
• STILLEN pulleys are machined from billet aluminum and are up to 80% lighter than stock steel pulleys, and up to 10% lighter than competing aftermarket pull
• With dyno-tested gains of up to 10+ horsepower at the wheels and both underdrive and stock-diameter applications available for most popular Nissan and Infiniti vehicles, STILLEN pulleys are a straightforward, proven power-recovery upgrade backed by real engineering. Give us a call at (866) 250-5542 to speak with one of our automotive performance specialists about which pulley set is right for your vehicle.