CAI Filter Adapter for Mini Cooper S Stealth

thingiverse

This piece is designed to mount a K&N cone filter securely within the stock airbox. The John Cooper Works (JCW) performance package comes with a similar intake system from the factory, but for those who opt out of this feature, this mod offers an effective solution. Once reassembled, the modification is completely invisible. In addition to installing this adapter, I also used a holesaw to enlarge the stock cold air inlet on both the bottom half of the airbox and the cowl. A 2.5" grommet will be needed to seal it properly; fortunately, an old r53 lower steering column boot fit perfectly in place. It's essential to note that you'll likely require a tune to fully realize any power gains from this modification, but the noticeable difference in noise alone makes it well worth the effort. The supercharger now lets out a loud scream when driven at full throttle, especially with the window open, whereas before it would whine loudly under rapid throttle inputs. This change suggests that the intake system is indeed functioning more efficiently. A comprehensive tutorial outlining this modification can be found online, which utilizes an ABS plumbing elbow. I purchased one but ultimately decided against using it due to its sharp narrowing at the filter opening. In contrast, this adapter offers about 10% more diameter at its narrowest point and features smooth transitions throughout its length. To ensure optimal durability, I printed this adapter in PETG, a material known for its fatigue resistance. ABS would be my second choice if PETG wasn't available.