2.5" cat to 3" cat... worth it?

[WazR32GTSt]

this is in regards to my exhaust set-up...

currently:

- 3" dump/front-in-one (from BATMBL)

- 3" custom-made mandrel-bent cat-back with 3" cannon muffler and 3" resonator

- stock compliance cat: looks like 2.5" but has been 'high-flowed' if you know what i mean...

so my question is this:

is it worthwile spending the $200 on a 3" cat?

I have done some searches and have read many posts where people change to a 3" cat and say they feel no difference in power...

another option is to get my cat 'converted' to a 3" cat by cutting it and welding on 3" flanges and 3" pipe on either end...

is this possible? has anyone done this before or is it just theory?

has anyone chagned their cat with positive results?

with this set-up i made 132rwkw on 12psi with the auto-trans equipped rb20 (with 10-10.5 AFRs!)

Cheers,

Warren

[R31Nismoid]

upgrading to a 3" "hi-flowed" if you know what i mean is a good option.

someone told me a nice straight 3" pipe works wonders

[SLY33]

depends on how much boost your going to run, id say with your setup and only being 2litres you might not gain much. But at the end of that day the bigger freer flowing system wont hurt.

[SLY33]

depends on how much boost your going to run, id say with your setup and only being 2litres you might not gain much. But at the end of the day the bigger freer flowing system wont hurt.

[WazR32GTSt]

upgrading to a 3" "hi-flowed" if you know what i mean is a good option.

someone told me a nice straight 3" pipe works wonders

yeah would be nice...

would rather something a little more subtle though

[WazR32GTSt]

depends on how much boost your going to run, id say with your setup and only being 2litres you might not gain much.  But at the end of the day the bigger freer flowing system wont hurt.

that's what i'm thinking... i don't want to spend $200 to find it makes no difference. that $200 could go into an SAFC or something similar...

anyone else actually done a swap and noticed a difference?

[R31Nismoid]

my mate also told me just to put the cat shroud over it.

then tis sublte and still cheap

[Sydneykid]

Alternative.........spend $500 and upgrade to a 4" Magic cat, no restriction there:cheers:

[TimmyC]

Not that im hijacking the thread or anything, but since where on the subject of zorsts and size...

Is there much improvement for a 3.5" over a 3" turbo back on an rb20 making 200rwkw ??

Is the extra 0.5" really worth it ? if so how come few people have them...

[WazR32GTSt]

Not that im hijacking the thread or anything, but since where on the subject of zorsts and size...

Is there much improvement for a 3.5" over a 3" turbo back on an rb20 making 200rwkw ??

Is the extra 0.5" really worth it ? if so how come few people have them...

well, yeah you are hijacking the thread. you will get more responses if you start a new thread...

[WazR32GTSt]

Alternative.........spend $500 and upgrade to a 4" Magic cat, no restriction there:cheers:

there may be no restriction, but my question is will it make any difference in power?

being a studenti'm after bang-for-buck

$500 for a 5kW gain is not worth it in my book... however $500 for a 20kW gain is a different story... but i know in this case that's not what i am looking at

[Beer Baron]

if you have already 'high flowed' your 2.5 inch cat just stick with it. it will flow more than a 3 inch 'regular' cat. though you are breaking the law and for fine prevention it may be worth looking at a 'proper' high flow cat.

[WazR32GTSt]

if you have already 'high flowed' your 2.5 inch cat just stick with it. it will flow more than a 3 inch 'regular' cat. though you are breaking the law and for fine prevention it may be worth looking at a 'proper' high flow cat.

yeah its just a temporary measure untill i can get my hands on something better...

thanks all for you help

might just save up for a 3" cat in the next few months...

[Rolls]

how would they tell your cat had been "high flowed" though if it still has the original housing? I mean its not like a cop is going to pull you over and take your cat off and then defect you.

[WazR32GTSt]

how would they tell your cat had been "high flowed" though if it still has the original housing? I mean its not like a cop is going to pull you over and take your cat off and then defect you.

well that's a debatable point... some say they "have a method" but i have not heard of anyone getting fined

i think the $10,000 fine that you can potentially get scares some people away

[WazR32GTSt]

oh, and i don't condone "high-flowing" your own cat. i did it as a temporary measure and will be replacing it with a legit cat soon

[someonestolecc]

I thought realistically it's like 5rwkw difference?

They can just use a broomstick.

[Lazy-Bastard]

It would have to be a very long and very flexible broomstick to snake its way through your muffler, resonator and around any bends in the exhaust.....

I have "heard" of people hacking the ends of their 2.5" cat and putting a 3" pipe straight through and then welding 3" flanges on the ends.

[WazR32GTSt]

It would have to be a very long and very flexible broomstick to snake its way through your muffler, resonator and around any bends in the exhaust.....

I have "heard" of people hacking the ends of their 2.5" cat and putting a 3" pipe straight through and then welding 3" flanges on the ends.

yeah i have heard stories of it too but never actually spoken to anyone sho has done it

i think its just a myth

[Lazy-Bastard]

yeah i have heard stories of it too but never actually spoken to anyone sho has done it

i think its just a myth

you think wrong