Question about a full de-cat

[zippee]

My chim has had the rear box conversion done along with pre-cats removed and I'm now considering replacing the Y piece with a hollow de-catted one. Whilst I know this will then sound IMHO awesome and allow the car to spit flames etc, what other affects are there? I've heard rumours that it can actually decrease power, is this right as I'd have though removing the main cat would actually help the engine breathe a bit more freely?
Is fuel consumption likely to increase as a reault? Especially with the probable increase in pops and bangs on the over-run.
Any comments/advice would be much appreciated.

[Cider Andy]

zippee said:

I've heard rumours that it can actually decrease power, is this right as I'd have thought removing the main cat would actually help the engine breathe a bit more freely?

The exhaust system (as a whole) is designed to work with the engine. Pressure within that system (sometimes referred to as back-pressure) is desired - I don't know enough about it to explain why, but no doubt someone who does know will be along soon. By modifying that system (in your case by removing the catalyst) that pressure will change which may then affect the way the engine runs. Some years ago I started my Mk II Cortina with nothing but the exhaust manifold fitted. As well as the deafening racket it made, engine power was reduced to about two-thirds.

As far as the exhasut note goes, I spoke to a Griffith owner yesterday who took the cat out of his car. He didn't like the new sound at all - he said it was too shrill and hollow, so he opted for a custom 'Y' piece with a narrower chamber.

[Hughesie2]

Mines fully decatted, sound is, well lets just say loud, MPG is affected but you counter act that by not going as fast due to excessive noise

Mail me off line if you want a chat about it, i'll let you have my number that way...

Justin

[victormeldrew]

The sound with the full decat has a "bag of nails" quality to it when listening at the sharp end. The exhaust gases seem to bang about in that hollow chamber, and it sounds like pinking or loose tappets. Glorious at the blunt end though.

You can fit a cone inside the chamber to stop this apparently. I didn't, as mine is a full replacement Y-piece without cat from TVR, so it has never been opened up and rewelded - it looks 100% original, and I still have the catted one to put back on if needed.

I just missed a stainless ACT decat Y-piece on eBay today, which looked tasty. It went too close to the new price for my liking. It went to a Griff owner, they have more money than sense, obviously.

>> Edited by victormeldrew on Monday 24th October 18:22

[mack]

Cider Andy said:

As far as the exhasut note goes, I spoke to a Griffith owner yesterday who took the cat out of his car. He didn't like the new sound at all - he said it was too shrill and hollow, so he opted for a custom 'Y' piece with a narrower chamber.

Hi Andy ,have you had chance to try the new part yet?

As already mentioned,I initially tried a full decat using the existing original manifolds and 'Y' piece.The metallic noise from the huge empty can was awful,I thought it would be a cheap way of decatting but wouldn't recommend it

I went for JP exhausts' manifolds and 'Y' piece in the end (see profile pic) and,although they're not exactly cheap,they're worth every penny for the sound IMHO