Decat – removal of catalytic converter
When a catalytic converter blocks up, it is more cost-effective to decat the car, than to replace the exhaust manifolds. There are various shapes and sizes of manifolds and each has its own procedure for repair. In this instance, we’re showing you what the average E90 N46-engine manifold looks like. The one on the left is the original shape.
The catalytic converters are filters inside the canister-sections. These canisters are cut out and replaced with straight pipes, as can be seen on the right. Otherwise the sound of the exhaust is quite tinny and hollow. On some other manifolds, the smaller canisters are merely cut open and the cats removed, before the manifold is welded closed again. Software upgrades are also required when decatting the car, usually on models from 2005 onwards.