In order to install the “Green Cat”, we had to cut the factory cat off the 90-degree elbow and flex joint.
With the factory cat removed, RareFab installed V-band clamps to make the exhaust more modular like we did in Project E90 M3, where we made the factory cats interchangeable with straight pipes. After experiencing the ease of unbolting exhaust and making changes like we did on the M3, it’s hard to not install V-bands on any custom exhaust work.
Will then welds the V-band to the original exhaust elbow.
After welding the other V-band on to the cat, they are bolted together and test fit to determine the ideal length for the 3” pipe that will connect to the Corsa cat-back.
The Kooks Green cats come in 2.5” in/out and 3” in/out. Since we were bolting the cat to the factory 2.5” exhaust, Will from RareFab chose to get the 2.5” and chop the reducer on the back end off at 3” to weld to our 3” pipe to effectively make a 2.5” in / 3” out cat.
The stock muffler (above) is larger in diameter and length than the Corsa resonator that replaces it. The stock exhaust uses 2.5” pluming that makes an “S”-bend in the muffler, while the 3” Corsa has a less restrictive straight shot.