Gut a Cat!

What is a cat?

A catalytic converter. In simple speak, converts nasty exhaust gases to harmless gases and vapours.

Does my car legally need a cat?

If your car is registered later than August 1994 then you need a cat. By law a cat must be fitted. Click here for the MOT test stations check off chart. A cat will help you to pass the emissions tests that are becoming more and more stringent...

Why do I want to gut my cat?

In order to produce more power the exhaust must flow as freely as possible, i.e. as little restriction as possible. Since the cat sits almost immediately under the turbo it presents quite a restriction for the exhaust gases to freely flow out of the turbo and away down the exhaust. Gutting the cat removes a large part of this restriction resulting in improved turbo spool up time and greater output power.

Why is it so restrictive?

The cat presents a very large surface area to the oncoming gases, and as such takes on a honeycombed effect. If you examine the picture closely you can see this honeycomb and how densely packed it is within the cat.


The cat material The restrictive "honeycomb"

Before you start

The cat contains hazardous to health materials. Ensure you observe all the relevant safety precautions e.g. face mask, gloves, goggles etc

Tools required

How do I gut it?

Remove the heat shields and the upper support bracket from turbo (between alternator and turbo elbow), and also the upper exhaust manifold
  Remove the 2 front engine "under trays"
  Remove alternator cooling duct, unplug oxygen sensor, unbolt it from the cat and stick it in a safe place out of the way
  Undo exhaust down pipe nuts (and front-centre section clamp on Scorpion system and remove front pipe) and move the front pipe to one side
  Assuming they are still present, loosen turbo cat elbow nuts x4
  Looking from the front of the car, remove the left hand support bracket bolts from engine block, and also the right hand support bracket
Undo turbo-turbine elbow nuts and remove cat and elbow from below the car
Undo the five bolts (read - snap heads off!) that hold the cat to the elbow
  Hack out the cat material from inside the cat using a hammer and screwdriver/chisel. This produces toxic dust!!! Please wear a dust mask, goggles and safety gloves and any other relevant safety equipment

Update - * Soaking the cat internals with old engine oil will assist in its removal *

  Using new seals and gaskets reinstall everything in the reverse order.

Many thanks to Julian Hankinson for supplying this article