Technical question about CAT

[frenchalex]

I have a question which to the TVR pros out here will make me sound like a numpty, but I am new to this game. And in my view the only stupid question is the one you don't ask.
I keep reading about exhausts that are cat or pre-cat or de-cat. What does it mean? Has is got to do with a bypass of the catalytic converter? What do you gain out of all the different options?

Thanks for your help.

[shpub]

Pre-cat exhausts do not have cats in them. Cat exhausts do have them. Decatted are cat exhausts where the cat has been removed.

Removing cat makes the car gray on legality (emissions, insurance) but louder. Power increases are usually myth or are caused by the cats being dead originally.

All Chimaeras are post 1993 and should have cats.
Griffs 4.x are pre-cat and don't have them. Griff 500s have them.

Steve
www.tvrbooks.co.uk

[Roobarb]

What a STUPID QUESTION !
Nah, only joking
When the Griff was launched it was not law for new vehicles to be fitted with cats, so TVR didn't bother, obviously the act was finally passed and TVR did bother. Thus the term pre-cat for early Griffs. The cat does act as a muffler to an extent, so removing it creates a louder exhaust note (racket), thus de-cat. It should be noted that these need to be replaced for MOT's. I don't think removing the cat alters performance but then I'm sure someone will.

Steve, beat me to it by a minute!!

>> Edited by Roobarb on Monday 10th March 12:01

[GreenV8S]

Roobarb said:Thus the term pre-cat for early Griffs.

Just to add to the confusion, a 'catted' car has one main cat in the 'Y' piece, and two smaller cats in the manifolds which are known as 'pre-cats'.

[tony Hall]

And if the cat up the street dumps in my garden one more time i'll stick a boot up its **** and de cat it!

[frenchalex]

Thanks for your replies, its all clear now.