The first generation MINI Cooper S, built between 2001 and 2006, is powered by a supercharger. The supercharger in the first Cooper S provides more oxygen to the engine and consequently more fuel. This increased oxygen and fuel distribution to the Cooper S engine produces higher power output. However, you can still get more power from MINI’s aftermarket parts like the smaller supercharger pulleys.
Aftermarket pulleys typically come in three different styles: 15%, 17%, and 19%. What do these percentages mean? They simply refer to the difference in size between the aftermarket and the original pulley. For example, a 15% pulley is 15% smaller than the one that comes standard on the MINI. The smaller the pulley, the smaller the belt; And the smaller the belt, the faster the supercharger turbines turn. When the turbines rotate faster, more oxygen is supplied to the engine and the engine produces more power output. What does this amount to? More torque and horsepower.
On the R53 MINI Cooper S, expect to capture a gain of about 15 HP after installing a 15% pulley. (Remember, the pulley percentage does not correspond to the gain in HP – this is just a coincidence.) With 17% an increase of 20 HP is expected and, with 19%, an increase of 25 HP. All HP earnings vary based on MINI condition and previously added performance parts.
When considering the cost of an aftermarket pulley ($ 100 to $ 150) and the amount of additional HP gained, it’s one of the most cost-effective aftermarket upgrades to the R53 MINI. MINI performance parts, like bulky intercoolers and exhausts, cost around a thousand dollars and don’t offer the HP increases that performance pulleys offer. In essence you get an extra 15-25 HP with a two pound pulley and less HP gain with various performance parts that are heavier and more expensive. This is why many enthusiasts are rushing to make an aftermarket pulley installation their first MINI upgrade.
But which pulley should you buy? 15%, 17% or 19%?
Looking at the HP gains produced by each pulley, it seems best to go with 19% for the highest HP gain. The 19% pulley, however, is not the most practical. 19% provides the most boost, but also provides the most wear to the internal parts of the vehicle. 19% is good for short circuit or time trial races, while 15% is good for endurance, long races and daily energy cravings. Putting this in perspective, 17% is a compromise between the two. It offers a higher than 15% HP increase, but makes the internal components wear out a bit faster. Overall, 15% is the most recommended pulley for everyday R53 MINI Cooper S drivers looking for a substantial power gain.