High Flow Cats, worth it?

[Anwyll]

I've been collecting some quotes on a new exhaust system (headers to the tips) and noticed the single biggest cost in these systems are the cats (since the VY has two of the bastards).

Is it worth replacing the factory pieces or do they flow well enough for the average cruising mobile (I'm not racing the thing)? No doubt there would be some restriction alone with the size of the entry and exit pipes to the factory cats.

Most of the quotes have been around $1900 fitted although usually $800 of this is due to the cats alone.

I browsed the exhaust threads in the FAQs but they were more about sound and few specifically dealt with cats.

[Not_An_Abba_Fan]

On a V6 with twin cats anyway, no, the stock cats will flow plenty. It's only when going forced induction will you need to go with high flow cats.

As a comparison, I do 200cpi metal high flow cats at $198 each.

[ss905l]

On a V6 with twin cats anyway, no, the stock cats will flow plenty. It's only when going forced induction will you need to go with high flow cats.

As a comparison, I do 200cpi metal high flow cats at $198 each.

What do u do stock 5 litre cats for?

[sixes]

I can't justify the cost of buying new cats. All depends on what you plan on doing for modification wise but in your case just get your original cats opened up if you are concerned. By that, get larger in and out pipes welded on. They flow well when this mod is done and costs bugger all to do and saves you cash for other things

[ss905l]

they do make a difference high flow cats, unless u got a 355 the 5 litre cats flow fine & actually have better low end take off with stock cats as sopposed to the high flow which have a bit more top end give on a 5 litre.

[MR_VX]

i have a supercharged vx and was wondering if a hi flow cat would help with the back pressure problem im having, car revs up as i push the clutch in

[sixes]

For sure they make a difference but its cheaper just to open up your stock cats as they perform very well

[Delish-VY]

For sure they make a difference but its cheaper just to open up your stock cats as they perform very well

remember that gutting ur cat is illegal so if cops check that out ule get canaried...but at the same time unless ur exhaust is whistling like a ferrari I doubt they"re gonna go to the effort of dismantling them just to see if u gutted them

[Vt_vic]

remember that gutting ur cat is illegal so if cops check that out ule get canaried...but at the same time unless ur exhaust is whistling like a ferrari I doubt they"re gonna go to the effort of dismantling them just to see if u gutted them

i think he means opening the flanges up not gutting them

[sixes]

Thats right, I didn't say gutting
All you do is get the original pipes / flanges cut off to where they meet the actual body of the cat. Then larger pipes or flanges welded on. This mod increases flow while remaining perfectly legal Have done this mod on the last few cars I have had and not only does it save you huge $$$ over buying new cats, but is a cheap way to gain more out of stock ones which do flow well with larger pipes put on.

Be aware too that some of the metal cats actually do not pass EPA. They can flow too much so they don't work as well converting the toxic nasties allowing the plod to whack on a nice sticker if they check it.

[Delish-VY]

i think he means opening the flanges up not gutting them

Thats right, I didn't say gutting

My mistake gents, a mate of mine suggested I gut my cats about 3 weeks after I got my car n he explained it gives more power n all that, n I was like..oh yeah sounds like a good idea, then hes ....but its massively illegal lol

[sixes]

If you were going to gut your cats, get a pipe welded through the cat so it flows straight through. Not doing so causes the exhaust gas to swirl in the empty cat and slowing the exit, it can also makes a funny noise. And yes, not running cats is illegal and there are some big fines, especially for your guys down south. The NT doesnt have EPA nazis as such

[a1k3m1]

remember that gutting ur cat is illegal so if cops check that out ule get canaried...but at the same time unless ur exhaust is whistling like a ferrari I doubt they"re gonna go to the effort of dismantling them just to see if u gutted them

lol the coppers have temperature sensing gadgets now, its as easy as a press of a button to work out if they've been gutted

[ss905l]

yep & a known fact is that with a gutted cat your Mild Steel exhaust will rust on the surface or possibly inner a hell of alot quicker.

[Vt_vic]

gutting it would give you stuff all of a gain anyway at 200 for a high flow cat you dont really have much to lose

[showxpony]

On a V6 with twin cats anyway, no, the stock cats will flow plenty. It's only when going forced induction will you need to go with high flow cats.

As a comparison, I do 200cpi metal high flow cats at $198 each.

+1 on that. V6 doesnt need em. V8 then it would help.