DIY Cat Bypass

[aston@ultrasw.c]

I have an old cat that I plan to cut open and make a cat bypass.

So how's it done?

Remove the guts and substitute a straight tube?

Add a perforated tube?

Baffles etc....

This is mostly a track car.

I don't mind noisy but I don't want obnoxious.

I plan to change the chip when I install.

Cheers!

[MotoSook]

Just punch and dispose of all the stuff in the cat and bolt it back up...no need to do anything else to it. Lots of guys run with a "gutted cat."

[Oh Haha]

Originally Posted by Soukus

Just punch and dispose of all the stuff in the cat and bolt it back up...no need to do anything else to it. Lots of guys run with a "gutted cat."

+1

If you are running a stock muffler it won't be much louder.

[aston@ultrasw.c]

Originally Posted by Oh Haha

+1

If you are running a stock muffler it won't be much louder.

I have a Flowmaster #80 1 in 2 out.

Sounds raspy!

[rnln]

What do u mean by punch? Keep drilling holes until it's all gone?

Originally Posted by Soukus

Just punch and dispose of all the stuff in the cat and bolt it back up...no need to do anything else to it. Lots of guys run with a "gutted cat."

[Oh Haha]

Originally Posted by aston@ultrasw.c

I have a Flowmaster #80 1 in 2 out.

Sounds raspy!

Sweet. You will love the new sound but you may end up capping one outlet.

[MotoSook]

Even if you run a euro premuffler with that Flowmaster it won't make it much quieter. The euro premuffler is essentially what you are proposing to replicate with your welding.

You can pick up a use Fabspeed or Dansk premuffler for less than $300 if you want to go that route.

To be honest a premuffler and a stock muffler is loud enough and has little to no effect on power. I don't know why some folks want an offensively loud exhaust. Save that for the track or for hanging out with the ricers at the local Friday night after the football game hangout.

[Oh Haha]

Originally Posted by rnln

What do u mean by punch? Keep drilling holes until it's all gone?

Punch, break, smash. Just verbage meaning to get all of the honeycomb material out of the case.

I used a piece of rebar to remove the insides of the cat on my late model Z28.

[rnln]

rebar? A steel rod? With a hammer I assume?
Did you that stuff is that soft.
Thanks oh haha

[Oh Haha]

It breaks up pretty easily. Once you get it started it should breakinto small pieces.

Get medievel on it!!

[175K911]

Originally Posted by Oh Haha

Punch, break, smash. Just verbage meaning to get all of the honeycomb material out of the case.

I used a piece of rebar to remove the insides of the cat on my late model Z28.

That's what I've done in the past. The ceramic honeycomb in there will break apart with a bit of force. I use a piece of steel conduit and a hammer. Assuming you leave the cat on the car to gut it, just make sure to fire it up before you put the muffler back on or you'll end up with a bunch of little pieces stuck in the muffler baffles and have to live with the rattles.

[rnln]

thanks guys.

[175K911]

Option for you- I have a gutted cat sitting in my basement. It's not an OE cat but an aftermarket type. Functions and fits the same, but looks different. I gutted it and used it until I got my headers on. I'd consider selling it if you were interested, then you could keep your original cat intact. No idea what it's worth though.

[ben parrish]

A broom handle will work fine. I bought a used/clogged cat and used a broom handle to break apart the insides; kept my original one in case I need it in the future.