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Hey guys I've recently got the headers and catback of my exhaust done but have read about members recommending to replace the old cat with a hi flow cat as they're usually buggered. Given that my car has done 190,000 kms I figured this would be a good idea. Just wondering if there would be a difference to sound (I dont want a raspy noise but I would love a volume increase if possible), and a performance gain. Perhaps a 200 cel cat or a 100 cel cat would help increase the sound ? Any recommended brands, seems like xforce or magnaflow are the general choice. Thanks !

THere's a sound increase, but it's only slight,
The note changes a bit more.

Currently I have a 50 or 80-cel cat on mine (cant remember) and OEM everything else, only the tiniest bit louder than stock (seriously you'd not pick it) but it does sound a little dirtier, less smooth.

My old setup had a straight thoughm muffler and the cat made that npticably louder, and a lot rougher sounding, also shot a little flame occationally.

hks_kansei wrote:Currently I have a 50 or 80-cel cat on mine (cant remember) and OEM everything else, only the tiniest bit louder than stock (seriously you'd not pick it) but it does sound a little dirtier, less smooth.

My old setup had a straight thoughm muffler and the cat made that npticably louder, and a lot rougher sounding, also shot a little flame occationally.

Wow that 50/80 cell cat must be pretty hi flow.
My car with no cat used to shoot a flame out the exhaust on overrun (thanks to crappy installer tune) however once I fitted a 200cell cat it arrested the flame, so that only smoke puffed out.

It's only very rarely that it would pop a flame, and would only do it after me having given the car a lot of stick for a decent timeframe (so everything was well and truely hot)


I don't actually know what the cell count is, I bought it secondhand but the guy I got it from said it was a 50 or an 80 (I forget which he said)

I know though that you can see through it pretty easily, each cell was like a macdonalds thickshake straw.

TBH though, I felt no power change once it was fitted, it was all just noise (which really describes my car on the whole)

Thanks for the info, seems like a 200 cel cat is the way to go..any increase in sound is worth it !

any recommended brands without breaking the bank ? I suppose they're all quite similar in performance so I guess i'd be looking at sound. The metal cats seem interesting but out of my range seeing as they go for 200+

when i installed my cat, it increased the sound quite a lot. i had a similar system to yours, and did the cat last/separately.

In what way was it increased? More raspier or a more aggressive note or the same exhaust note but the loudness being emphasised? Also what cat is it that you are running ? Cheers !

project.r.racing wrote:when i installed my cat, it increased the sound quite a lot. i had a similar system to yours, and did the cat last/separately.

Cats tend not to increase power unless it is the bottleneck in the system, Ie reducing flow.

Currently my cat is a bottleneck but I may not be able to pass the EPA test if I go for a high flow

So it stays for now.

Roadster2 wrote:In what way was it increased? More raspier or a more aggressive note or the same exhaust note but the loudness being emphasised? Also what cat is it that you are running ? Cheers !

project.r.racing wrote:when i installed my cat, it increased the sound quite a lot. i had a similar system to yours, and did the cat last/separately.

raspieness tend to come from a poor designed and flowing big exhaust. ie axles backs etc. exhaust made up of different pipe diameters and flows.

i got same exhaust note, but 20%ish louder.

i forget now what my cat was, thinking 100 or 150 commodore 2.25" version. shop said do this, cheaper option that performance brands but does same job. it worked.

what is the diff between having liek for eg 200 cell or 400 cell? I couldnt find any info on this before buying a new cat, so i just went with a 400 cell one.

I found it weird after installing new genie performance headers + cat that no difference was made in terms of sound? After I drove off out of the exhaust shop, I was quite confused, as I was expecting a louder roar once these were installed.

Extractors are more likely to change the character of the exhaust note rather than the volume and a hi flow cat would make minimal compared to the rest of the exhaust system.

I dont think I noticed much of a sound difference after the installation of headers. Perhaps slightly more boomy if at all. I'm still contemplating between a 200cell metal cat vs a ceramic cat, just not sure which one will put out less rasp on my exhaust system.