Catless Race Downpipes

A catless (race) downpipe removes the catalytic converter from the first section of exhaust behind the turbo. It flows the most of any downpipe type and lowers the backpressure the turbo pushes against, which is why it suits track and competition builds. Expect more sound, rasp and exhaust smell than a catted pipe.

Catless and high-flow downpipes and other emissions-related parts are intended for off-road and competition use and may not be legal on the street where you live. A high-flow converter is not the same as a certified replacement part, so check your local laws and inspection rules before you buy or install one.

Plan on one. Without a converter the rear oxygen sensor reads differently and a check-engine light may occur. Many listings recommend a supporting tune, and the brands quote their gains with proper tuning. Talk to your tuner before you order so the software and hardware match.

Cold starts and idling smell noticeably stronger without a converter, and the tone gains rasp. Drone, the steady boom at highway cruise, is shaped more by the mid-pipe, resonators, mufflers and valves than by the downpipe alone, but a louder downpipe gives the rest of the system more to deal with.

Most downpipes reuse the factory oxygen sensors, so have an O2 sensor socket ready; seized sensors are common on older exhausts. Some pipes add sensor bungs, extensions or heat shields that change how the sensors fit, so check the listing for your part, and inspect the factory clamps and gaskets while everything is apart.