Replacing cat with higher flowing part.

[Z2TT]

Hi,

I have a 1989 Toyota Soarer GZ20.

I currently have a 2.5" Catback, the pipe from the turbo dump pipe to the catalytic converter is stock, the catalytic converter is also stock. Very soon I am going to get the pipe from the dump to the cat replaced with a 2.5" pipe just like the rest of the exhuast, this will cost me $250. For a new hi flow cat it will cost me $350.

Instead of spending $350 for a new hiflow cat, would it be a good suggestion to find a higher flowing unit from another car?

Which cat would be a good one to buy?

Thanks.

[forey]

decat unit from ebay?

[Gary]

i quite glad i went highflows for mine, i dont think ill have it another way now

higher flow seems to have had a lessened sound muffling effect, i get a lightly more pronounced bark to revs now, i love it. cars more willing to kick down and generally runs a little bit better

stock cats that i hear flow good; 5L commodore cats (as new as you can get em i guess, so VT), and GTR cats (any model). if you know any good exhaust place have a chat with them see what they say

[Z2TT]

Thanks.

I might look into getting a cat from a 5L Commodore.

Any other suggestions?

[#rolla boy]

smash the guts out of yours or get another with biger flang and smash that and keep yours as a spare this is the cheapest easiest and most reliable option

[Golberg]

smash the guts out of yours or get another with biger flang and smash that and keep yours as a spare this is the cheapest easiest and most reliable option

And the most illegal too

[oldcorollas]

smash the guts out of yours or get another with biger flang and smash that and keep yours as a spare this is the cheapest easiest and most reliable option

you forgot the bit about Toymods not condoning or promoting illegal behaviour.
please keep those comments for boostcruisin and PF.


when you are looking for a higher flowing stock cat, you need to look for two things.

first is shape. the oval cross-section cats are almots always ceramic core.
the round ones (like i posted recently) are almost always metal core.

the ceramic core need larger size to get the same flow as a metal core.

the ST202 celica cat is a two stage (two different catalysts) metal cat with 3.5" core.
it was also nearly cheapest in the toyota range

get under some cares, and measure the outside of th ecats. there will prolly be 3-4mm of metal on the outside of them at least (excluding chields), so.. minus about 8-10mm to get the size of cat.

there may nto actually be much difference in the actual size of the cores, as there are not many catalyst makers, so the main differences are likely to just to be in the flanges...

basically, if you can find a car with similar output to what you want, then their stock cores will flow enough, and you can increase flange size easily on them. the prices may vary wildly between companies tho. shop around.

[Z2TT]

Thanks.

So should I be looking at cars like ?

VN Onwards V8 Commodores
JZA80's
Skyline GTR

So its a tossup between those 3, anybody know which one would flow the best?

By the way I found this on this website :

http://www.bestmufflers.com/Informat...er_PH5000d.htm

The factory original catalytic converters VN to VQ
V6 or V8 are on of the best available, they flow better
than most 'hiflow" cats and very rarely fail if
installed correctly.

Is there any vehicles that come with 2.5" cats from factory?

[LeeRoy]

smash the guts out of yours or get another with biger flang and smash that and keep yours as a spare this is the cheapest easiest and most reliable option

That is also detrimental to power along with making an exhaust sound horrible.

[NORBY]

i heard your meant to go .5" bigger than the rest of your system where possible? So if your running a 2.5 inch system run a 3 inch cat? (obviously the flanges would need to be correct)

[oldcorollas]

please don't miss the point here

the flow of a cat is goverened by the core (max flow).
putting a 3" flange on a 3" core doesn't mean shit, it is the size of the core that is the problem

those commondore cats pictured above are ceramic core, and they have TWO for the output of a V6 or V8 commodore? so thats? 150kw each?

compare the size of the ceramic core with other cars... cutting and changing flanges is easy.

[Z2TT]

They look larger than my soarer cat, apparently the sizes of the V8's and V6 commodore cats are the same.

Has anybody ever taken a look at a JZA80 stock cat?
I might go and ask in the Nissan Forums for the GTR Cat.

By the way I hear of many people gutting the cats who claim it increases power,

Leeroy why would it decrease power, is it because the internals of the cat help maintain a linear flow? where as if you gut the internals it becomes a restriction as the gas flows all over the cat? Just a guess as I've never taken apart a cat.

Thanks.

Thanks.

[oldcorollas]

well, it may get you a slight increase in power (but may actually not, unless it is too small in the first place....

but it could get you a $10,000 fine from the EPA for interfering with emissions gear in a deliberate manner....

you might wanna check on that in your state...

[Z2TT]

No way i'd have a gutted cat on a street car, that's not a good option for me or anyone.

Might just settle for a Skyline GTR Cat.

[oldcorollas]

why skyline?
go and freekin measure the size of cats in cars at a wreckers.