Test Pipe Inside Gutted Cat?

[suprbuick7]

Who is running a gutted cat with a pipe welded inside? I'm in NJ would like to run a test pipe but don't want to not have a cat on the car ( with my luck a cop will impound it). Will the car pass NJ emissions with maybe an emissions chip and no cat?

 

[Murt TTA]

emissions chips usually work to pass emissions. My tta actually passed emissions with no cat.

You could always put a test pipe on the car, and then when u need a sticker, put the cat back on for a day.

But if you are concerned about getting pulled over and a visual inspection, u might wanna just hollow the cat out, seems like the same thing as putting a test pipe in the middle of it, just simpler.

I got pulled over once by a state trooper and pointed to my flex pipe as a "high flow cat".

~Murt

 

[WakkoSS]

If your car is running right you won't need a cat to get it to pass. Might be easier to take a cat, cut it in half with a plasma cutter, and weld the shell over a test pipe. Quite easy and if the welds are done fairly cleanly (spot welds would work) it'll look just a like a cat unless someone puts the car on a lift and looks super close.

 

[Missouri T]

Take the time to put a test pipe in there......

Please take it from me...
The hollowed out cat makes for an oddball "echo chamber" in terms of exhaust note AND it is a source of turbulence in the exhaust.
What happens when the high pressure wave of hot exhaust hits that open chamber?
Is it going to magically "find" the open door at the other end?
No.
Swirl and possibly even reversion are going to happen.

It may sound like a pain in the rump but take the time to put a test pipe in there.
It MAY save you the goofy exhaust note, a citation (or impound?!!?!??) from the emissions Nazi's and even a HP or two.

I don't have emissions testing where my car is titled so, THANK GOODNESS, I'm eliminating the hollowed out cat the previous owner of this car installed and installing a test pipe.
Hopefully tomorrow.

Best of Luck.

 

[iamjeff]

my car isnt running yet, but here is what i did... i hollowed out my cat, and then cut/trimmed the ends so that i could take a hammer and board and hammer a 3" pipe through the cat.. then i just welded it back up. the result is a test pipe that looks a whole lot like a cat.

-jeff

 

[Missouri T]

Now THAT'S what I'm talkin' about!

Right on, Jeff.

You've got the right idea.

Hey, as long as they see a cat shell, they're happy.....THEY meaning the emissions Nazi's......

3" inside, too?
YOU da man!

Good Job.

 

[iamjeff]

it was a pretty snug fit but it went in pretty well. i put the pipe in it because i dont like the "echo" of a hollow cat. this cat along with my 3" atr exhaust is basically the same as a straight pipe isnt it? it might be a little noisey...just the way i like it.

-jeff

 

[GN ERGY]

Thats what I did 10 yrs ago. Cut the tubes off the cat shoved a piece of 3 inch pipe thru it and rewelded it and you can't tell.
Tarey D.

 

[Freedster]

Originally posted by iamjeff
my car isnt running yet, but here is what i did... i hollowed out my cat, and then cut/trimmed the ends so that i could take a hammer and board and hammer a 3" pipe through the cat.. then i just welded it back up. the result is a test pipe that looks a whole lot like a cat.

-jeff

That's what my dad did with his GN. It's been that way for almost 10 years now, and he passes inspection every year. Of course, they don't actually sniff your exhaust in Virginia...

- Freed

 

[Missouri T]

Ahh....I'm a "Test Pipe" person now....

Has anyone thought of the OTHER benefits of having a test pipe versus a cat?

Look how much easier it is to get to EVERYTHING related to the transmission on the passenger side now!
And how easy it is to clean under there.

My old cat looked horrible....even if it was empty.

My mufflers were toast as well.
Replaced them with some Dynomax Welded race mufflers.
A bit loud but not TOO bad.
The price was right.