Here are our tried and true crank pulleys, the ones we’re all familiar with. In this series, additional power gains are seen from the underdriving of all the accessories (which accounts for about 15% additional gain).

However, we do not push the amount of underdrive for two main reasons. First, it is important to keep charging systems, air conditioning, power steering, and water pumps moving fast enough for every day driving. Second, not much horsepower is gained from extreme underdriving.

In most applications all of our underdriving is done with the crank pulley, not the accessory pulleys. This is done so maximum weight loss can be achieved at the crank where most of the horsepower gains are found. Most Ultra Series underdrive crank pulleys are available in natural polished aluminum as well as black, red, and blue anodizing.
 

Unorthodox Ultra S Underdrive Crank Pulleys
An idea or a need arises. The result? Unorthodox Racing Ultra Street lightened underdrive crank pulleys. Our pulleys are CNC-machined from lightweight 6061-T6 aluminum billet. Premium U.S. made 6061-T6 aluminum billet ensures the consistency of the material's strength and balance. Tolerances are held to within .001", and numerous machining steps are used to ensure the lightest possible design. In addition to fit, finish is just as important and each piece is representative of this. Every pulley is inspected multiple times from machining to anodizing to stocking and finally at shipping time. If at any point a pulley does not pass inspection it is pulled from production.

Unorthodox Racing lightened underdrive crank pulleys on average can provide gains of 5 to 12 HP and 4 to 8 lbs.-ft. on normally aspirated engines and 8 to 16 HP and 8 to 18 lbs.-ft. on forced induction engines. Higher gains are possible. For example, a Nissan 300ZX twin-turbo saw gains as high as 37 HP and 45 lbs.- ft. on the dyno just by replacing the stock crank pulley with our Ultra S lightened underdrive crank pulley.

Power gains are obtained in two ways. First, and most important, is the weight loss. An average of 2.7 HP is gained from every pound lost off the crank shaft. 85% of our gains are from weight loss.

The rest of the gains are from underdriving, which accounts for about 15% of the total gains. We do not push underdriving for two main reasons. Our main reason is to keep charging systems, air conditioning, power steering, and water pumps moving fast enough for every day driving. Second, not much horsepower is gained from extreme underdriving. In most applications all of our underdriving is done with the crank pulley, not the accessory pulleys. This is done so maximum weight loss can be achieved at the crank where most of the horsepower gains are found.

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http://www.unorthodoxracing.com/