Cats - new reply to old thread re: How much restriction can a Cat be?

[tberk@mindspring.com (T Berk)]

Rick Kellner wrote:
> 
>     I am in the process of replacing my entire exhaust with a TT system and
> a TT down pipe so everything is off including the catalytic converter.  I
> have never take this one off and was surprised to see how it was put
> together.  It is just a can filled with screens!  I know people replace
> these with high flow cats but how much restriction can these be?  Anyone
> really notice a difference between the stock and an upgrade or even a
> straight pipe?
> Rick Kellner.
> 84 8v
> 

Rick,

Sorry for the delay, I am just now going back over some unread list mail
from October. 

Your look down the cat looks like it's screens but what you are seeing
is a matrix or a ceramic type substance. Note how the holes are
parallel, they are like long thin tunnels packed close together, side by
side.

A good cat doesn't restrict too much, and only really aids HP gains when
in the near redline area. 

'Upgrading' to straight pipe should only be done if it comes without
introducing restrictions or changes in diameter. Hollowed out cats are
worse than good cats because of this reason. 

If you are in California or some other state/area that cares you won't
want to get caught without a cat in a car that came with one.


hth,
TBerk