exhaust flow

[lowfat_hg]

how much flow is enough?
I am ordering a new Cat and need to know how big it needs to be. I can get a skyline item that flows 550cfm or a bigger metal core item rated at 880cfm. I was planning to use the original items (1UZ) in parallel but think i will run out of space and for the sake of $200 it might be worth getting a new one that fits better.
So, what do i need and what are my options?
thanks!

 

[XR8tt]

You have almost answered your own question...
If you cannot fit one on each side then one big single...
Btw this may not be an issue for you up there...
The metal cats don't work as good as ceramic cats
for EPA testing...

 

[JBrady]

You have almost answered your own question...
If you cannot fit one on each side then one big single...
Btw this may not be an issue for you up there...
The metal cats don't work as good as ceramic cats
for EPA testing...

Depends on the cat. My stock 1999 LS400 has metal cats from the factory and is rated as a LEV (low emissions vehicle).

Aftermarket will vary. Stock cats are not available used in the USA which is too bad because Lexus used them from 1998-2001 on the V8s.

Pic of stock metal core.

 

[Zuffen]

If you want the dual cat setup don't try to put them side by side.

Stagger them a little and you can reduce the width of the package to one cat width plus the diameter of the pipe of the other. This can save 75mm in the total package. Also look at the option of turning the cats on their side if ground clearance allows.

Mine were staggered and rolled on their sides in my Rover swap to make room for them.

My latest swap (still in my Rover) will see a separate system down each side of the transmission.