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

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

Tools required

• 10 - 19mm sockets and spanners. A deep 14mm socket may well be needed to get to under the bottom nut securing the cat to the turbo housing
• 12mm and 14mm single hex drive sockets - as with any exhaust parts, they get hot and are always a b@st$rd for rounding off using conventional sockets
• Penetrating oil (?) I didn't use any, but I probably should have soaked everything first
• Drills up to 6.5mm - for when the heads shear off at the cat to elbow!
• 8mm x 1.25mm tap set - see previous!
• 5 new bolts for above. (Though, I'm inclined to use studs and nuts just in case I need to open it up again in the future).
• Dust mask, goggles and gloves. The safety kit is especially important when doing this job
• Engine oil - soaking the internals of the cat and leaving for several minutes will aid in removal

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.

• I suspect that this would come out in one piece if heated - submerged in boiling water on a stove for half an hour or so if single/living with or married to understanding 'other-half'.
• Oh, I removed the front bumper, too. It isn't necessary, but I always do when I'm messing under the front of the car - gives me a bit more room to manoeuvre/one less thing to bang my head on and lets a bit of light in - good for seeing with!