De-Catting

[Ikemi]

I'm not hugely mechanically minded, but the willingness to learn is there ... I'm currently helping a mate rebuild an engine, which is expanding my knowledge greatly, as well as being lots of fun! Anyway, I'm thinking about de-catting my car this summer and have found a straight through pipe on Hangar 111 for £40! Bargain!

Firstly, are they relatively easy to fit? Do I have to remove the access panel underneath to reach the CAT? Is it easy to find amongst the other components? Also, are there differences in more expensive straight-through pipes?

Cheers

[Dixie]

Easy job if it's done regular. First time will be a bit of a pain. Careful not to smash the cat filament to bits when your clubbing it to death with a hammer!


Anybody know what the actual gains are for removing the cat other than a much noisier exhaust note?

[RichQuy]

Pretty simple as long as you have the access underneath.

Ideally, to make things easier you want the car up on ramps at the back. You will need to take the undertray off (the S2 has two parts so only the rear most section need come off, the S1 may be different) and obviously do this when the car (exhaust) is cold!

You won't be able to miss the CAT - it'll probably be rusty and is the bulky, ugly-looking pipe between the downpipe from the manifold and the exhaust back-box. From memory it is connected at each end with 3 M10 bolts, and by now will probably have seized on. Either try some penetrating oil to loosen them, or more likely a dremmel to cut the bolts off.

Once off keep the CAT to one side as you will need it come MOT time. Simply put the straight through pipe in the CAT's place, making sure that you've replaced the gaskets (which should come with the de-CAT) and used enough exhaust sealant paste, use fresh M10 bolts which are nicely copper-slipped (so that they come off easier come MOT time!) and job's done! I don't think the S1 requires messing with a post CAT lamba sensor like the S2 does.

Anyone - feel free to correct where I may have gone wrong!!

[village idiot]

do remember that it 'could' invalidate your insurance as it 'technically' makes the car unroadworthy.

never come across anyone who has fallen foul of it before (my own insurance company were not too bothered when i had one fitted to mine, but couldn't 'officially' sanction the modification), but i guess if you were driving in front of a cop car in the summer and if they had their window open, they might object to having headaches and streaming eyes!

[Ikemi]

Dixie said:

Anybody know what the actual gains are for removing the cat other than a much noisier exhaust note?

That's the only reason I need! I believe it also allows more power out of the engine, although the difference may be marginal ... However £40 and a couple of hours work sounds pretty reasonable to get a louder exhaust note and more (well, more than I get at the moment) 'popping' on overrun

Yeah, that is the only downside. I have heard the same when it comes to insurance. My insurance renewal is next month so I'll ask about it then and find out their opinions ... Otherwise I guess it is not that noticeable from the engine bay, not like an induction kit would be!

ETA: Cheers RichQuy for the in-depth instructions! Much appreciated

Edited by Ikemi on Thursday 17th April 16:23

[Mr_B]

A ramp would be great, but jacking the car gives enough room to work. Remove the rear most undertray and then it's just a case of removing 6 nuts on the cat. The problem is they are liable to be rusted on pretty good. Get some decent ( not WD40 ) penetrating spray and give it plenty. Having a Dremel type tool on hand is also a good idea just in case you need to cut any off. Re-fit with stainless bolts.
Some reading for you ....


http://www.elisenet.plus.com/Exhaust.htm

http://www.elisenet.plus.com/CatBolts.htm

[Mr_B]

Oh, and stuff some rag around the tail pipes when removing the cat, as the exhaust will flop about and could damage the paint where the pipes exit.

[Pied Piper]

Was the least satisfying modification I made to my car, an absoulete PITA come MOT time (crawling under car in Feb not nice at all), and not a massive difference in sound.

Replaced mine with a sports cat much better sound and no problems with MIL and constant resets of stack,

[bencollins]

Ikemi said:

Dixie said:

Anybody know what the actual gains are for removing the cat other than a much noisier exhaust note?

That's the only reason I need! I believe it also allows more power out of the engine, although the difference may be marginal ... However £40 and a couple of hours work sounds pretty reasonable to get a louder exhaust note and more (well, more than I get at the moment) 'popping' on overrun

Yeah, that is the only downside. I have heard the same when it comes to insurance. My insurance renewal is next month so I'll ask about it then and find out their opinions ... Otherwise I guess it is not that noticeable from the engine bay, not like an induction kit would be!

ETA: Cheers RichQuy for the in-depth instructions! Much appreciated

Edited by Ikemi on Thursday 17th April 16:23

Cats gobble significant power, so wont be marginal, +12%, also fuel economy +12%. But it is illegal.

[Tin Hat]

Cats are also pretty heavy!

[The Pits]

surely you need a bespoke remap on a rolling road to get any benefits out of decatting?

I decatted my tuscan and even after a chip modification it still produced less power than a sports catted tuscan with bespoke map.

[MRTOAD]

Do you need to reset the ECU by disconnecting the battery after de-catting?

[LivinLaVidaLotus]

All those posts and not a single one about cats, soft-tops and hair? I'm disappointed.

[S Works]

Personally I wouldn't bother. Have you got a decent induction kit? If you want it more 'noisy', £40 towards that is a better spend IMO.

[Mr_B]

Changed mine back to a de-cat after the MOT the other week. Had the roof off nearly every day this week and I have to say it's worth the effort - car sounds soooo much better. I didtched the K&N filter kit, that was just too much noise and not even a nice sound.