B46 Downpipe: Unlocking Performance, Sound, and Turbo Efficiency for Your BMW The B46 downpipe is one of the most effective upgrades for BMW owners looking to boost performance, turbo efficiency, and exhaust tone. Found in vehicles such as the 118i, 120i, 218i, and X1 sDrive models, the B46 engine responds exceptionally well to exhaust flow improvements. Upgrading the downpipe can unlock noticeable gains in power and throttle response without requiring extensive engine...