Cat Info

[Trough Lolly]

was after a bit of info on the stock cat, ive been pricing around numerous exhaust shops in mildura and they tell me the stock cat is a single 3' input to twin 2 1/4 outlets. to get a highflo cat that splits into twins is alot more pricey, so what I would like to know:

would a single 3' high flow cat be enough for 290atw? im aware the stock system goes into twins at the cat, if I go this path ill get them to make it go into a duel system just after the cat.

and if I go the single route, is 3' big enough or should I go 4'?? even though the dump pipe is 3' I think going 4' is a waste of time with what I plan on doing.

I wanna keep the stock exhaust but just change the cat and centre muffler.

any info appreciated.

and what cats are mainly used? I tried the stupid search feature and as always showed up everything I DIDNT want to read about! lol

thanks guys

[bugster70]

I'd be keen to know more about aftermarkets cats too - tried starting a new thread on this a while back but didn't get very far.

On a similar note, does anybody know (approximately) what the stock cat is good for? Would, say, 260rwkw be beyond its capabilities?

[Xtreme F6]

Ok guys, ill put this here for you its a topic I have somewhere else but ill post it here for you aswell, take it as you like. Hope it helps

Well its come to a head with the testing ive been doing and its almost competed.

Ive been asked by a few customers about how my F6 can make 340 + rwkw's with a stock exhaust.. heres why

Firstly guys with XR6T's and F6's. From the cats back of your exhaust unless you change the cat to one that flows OVER 560 cfm, your exhaust isnt going to be a restriction.

Lets break it down, Stock Cat = 300 cfm.

Centre Muffler with pipe work = 560 cfm

Rear assemble the same as above.

Now, do we see where this is going? The cat is the restriction on these 2 cars.

But why do Boss engines pick up from just a zorst change with stock cats. Well that's easy they have 2 cats... 2 x 300 cfm cats = 600 cfm worth of flow. Centre muffler flow = 560 .. Small restriction. ...Most after market cats still dont flow over 500 cfm so they arent going to be putting pressure on the rear muffler. Hence why when I tested the removal of the centre muffler it made ZERO change on my wifes 12 second xr6T. Her cat only flows 460 cfm.... and the note was shocking.

Now if you use a SMB cat for example you will have a cat capable of flowing 660 cfm. Now if you cars making the power to still be seeing it utilising that to its full potential then you will make gains from changing your exhaust. So am I using my exhaust to its full potential at 340 rwkw's? Well lets find out, In the next 2 weeks ill test just that by using a more free flowing exhaust on my car and see if it actually is going to make any differance to my power.

Anyways guys for those that are interested hope you enjoy this sort of stuff as I do.. I live for R&D and finding the best bang for YOUR bucks I can.

Now as for the power level of the stock cat I wouldnt really put a figure on it, I would say but the more restiction in the cat the less boost it will make and shorter period of time it will make it for.

Edited 01/08/05 08:09 AM by GTP-330

[Trough Lolly]

again, is a aftermarket 3' cat good enough to flow 290-300atw?

the exhaust will then be a dual system strait behind the cat.

[Xtreme F6]

again, is a aftermarket 3' cat good enough to flow 290-300atw?

the exhaust will then be a dual system strait behind the cat.

.......... What cat... what flow???? what core?????? Its not that smple....

Hence why I posted the above reply... You need to be more specific. If it flows 460 cfm then it will support 300 rwkw's.

[shiftyxr]

I have a hi flow cat and a stock exhaust it makes 308rwkw easy,with the stock cat was giving up around 250rwkw.

[Xtreme F6]

I have a hi flow cat and a stock exhaust it makes 308rwkw easy,with the stock cat was giving up around 250rwkw.

yep I have a stock exhaust also @340 rwkw's but I have a good cat.

[Flukey]

I have a hi flow cat and a stock exhaust it makes 308rwkw easy,with the stock cat was giving up around 250rwkw.

What was the cost to upgrade your Cat? I am at 245atw and have run out of puff so will probably need to change mine.

[Xtreme F6]

I have a hi flow cat and a stock exhaust it makes 308rwkw easy,with the stock cat was giving up around 250rwkw.

What was the cost to upgrade your Cat? I am at 245atw and have run out of puff so will probably need to change mine.

the best ive seen and tested is the SMB option, they are around the 400.00 mark

[Trough Lolly]

can anyone suggest a cat under $350??

the SMB is a 4' isnt it? waste of time me getting that if its gunna be redused back to 3' strait after