I've listened to a few audio clips of coupe exhausts, and the de-cat systems both sounded significantly better than the others.

Is is a feature of the de-cat or is it something to do with the exhaust more generally.

I have a supersprint system. Would a de-cat make a major difference to the exhaust note?

Steve

Also, what is inside the section of a decat system that looks from the outside like a cat? I think that the inside of the pipe at that section has perforations in it. What is the purpose of this.

a de-cat will make a different sound!!

the de-cat will open the flow of the exhaust system up!

a super sprint de-cat is around £50 on here, worth a pop, put it on and see if you like it!

i think Nigel ran with a super sprint decatted system!

also, the de-cat sounds the nuts on the coupe!!!

Got the supersprint decat. Nice sound bit louder than with a cat. Does smell though and sometimes you can get a whiff in the cabin. probably a mild increase in power too.

Eh? I have a full supersprint with De-cat, I cant ever smell anything! sounds lovely too, not intrusive at motorway speeds though, and it fits the bumper cut out perfectly too.....

I have one of the decats with a silencer hooked up to a Ragazzon cat-back.

Performance wise there was a marginal increase, sound wise there was also an improvement making the 20VT sound more like the NA 20V version with a crisper exhaust note with the odd pop on overrun, and not too much louder than with original cat...also it seemed to make the gas pedal feel slightly heavier to operate, but that could be due to my imagination!

mr cooper: De-cat = louder + potentially more power. The bit on a de-cat that looks like a cat is probably a silencer, which also has the perforations inside as these allow the gas into the silcencing material and generally deaden the sound and slow the gas down.
De-catting can ruin your turbo seals on a normal turbo. bit of a gamble, a nornmal turbo might be ok with a de-cat or it might let-go in a few thousand miles.
Really need a hybrid turbo with uprated seals to runa de-cat.
Also incase you didn't know you would need to put the cat back-on for the MOT.

You could get a custom cat pipe made with or without a silencer but with a sports cat, this would provide better gas flow, better sound and more power but would also be MOT friendly. Mine cost £200 (stainless 2 1/2" with silencer and sports cat).

mine's decatted now and really sounds great imo - done by paul at Motormech for not much money, and accompanied by the supporting bits is a worthwhile venture imo.....

not sure my neighbours agree at 5.30 am, however

as for power, i fitted a de-cat and a chip to my car and the rolling road print out showed a gain of 9bhp which i was happy with!!

I see. What is the silencing material?

Mrcooper if I remember you have a blueflame on yours? Well all I would say ever since I put that full blueflame system on mine with no cat I distroyed my standard t28 in hours under normal driving, play in the shaft wasn't even close! So for the short story if you decat the coupe buy a uprated turbo too, there's no way round it, don't even bother driving it on the standard t28, I'm now £1500+ lighter over these that 4 months

Proccy, yours sounds mint, chap, good reason to persist with the car

The sound of a decat really depends on the exhaust you have. Size of silencer, diameter of pipe, and material of the rest of your system really plays a part on how it will sound. Stainless steel will generally sound raspier compared to mild steel (supersprint).

I would advise using a silencer in place of the cat rather than just a straight pipe. A straight pipe will be stupidly loud! I used to set off car alarms when starting up with the straight pipe.

Arh that take me back my first UNO turbo had no boxes, it sounded like a tractor on start up but total manic on full boost

This is what mine sounded like the last time without the silencer.
Video
Only thing i really missed about it is the gurgles and pops I get on the over-run. Ahhh..

Yeah I remember when I first picked up my Coop the de-cat pipe was fitted at the time. It sounded great for a few months but the constant drone eventually got to me . If I wasn't using the Coupé daily then I would just leave it with the de-cat and straight-through exhaust but I like to listen to music now and again despite how nice the 5-pot burble is.

Here's an old video of my 20VT Coupé with the de-cat on,it's tempting me to stick the pipe back on for SICD now

Baz

So are they not too great on the motorways?

Sounds nice Kelv. Shame the supersprint is mild steel, I do like the raspier notes - very supercaresque

I have a Supersprint decat on a Powerflow 2 box system. It really does sound great, and there is no drone at motorway speeds.

Difficult to put this into words but they get better with mileage too, mine has quietened down a fair bit after it's been on a couple of thousand miles.

I wouldn't go back now, it really isn't obtrusive (on my system) and does free more power. I'm pretty confident that I wouldn't have achieved over 300bhp without it..

Ive always fancied this. But isnt it a huge pain in the rear end to get the cat put back on at MOT time?

Booming on motorways is one thing...shame its just stupidly loud even on normal roads!

If you like raspy just go for the stainless steel option. They last longer too.

Not if you weld flanges on both ends. Then its just a case of undoing the bolts and presto!

Well, I just fitted my stock mid section including cat upto my larger bore down pipe as had her mot yesterday.

My aftermarket system comprises of a decat straight through silencer and a backbox.

The car with a cat and few more silencers now sounds much quieter and less intrusive at normal speeds but definately miss the noise on throttle.

What i did want to add is that my car is running a superspool at 1.3 bar with a sip and fmic. With the cat back on ive noticed not much difference in outright performance but... Turbo Spool up is now definately taking longer.


Oh and car went straight through mot, so am a happy bunny.

here's a video of my car full 3" system with decat and a supersprint back box. Not loud on motorways at 70mph or just general driving but, when accelerating its gets rather loud.

http://s805.photobucket.com/albums/yy332/mrlmgeddis/?action=view&current=VIDEO0071.flv

That made me chuckle - looks like your camerman mate is waiting for you to come back..

lol couldn't be bothered to edit it

I really want my Coupe back after reading this thread.

I have a full 3" stainless with 4" end can no silencers straight all the way and love the noise mine makes on full chat

from the ones I've seen it has been glass fibre.

woah, totally fell off the end of the thread there, didn't see two pages.

sound deadening material is usually glass fibre (to answer a much earlier question)

Thanks, er, stinky!