Cats, can I get away without one?

HyperOnExperience

Well-Known Member
Joined
Mar 12, 2010
Location
Chapel Hill
I found a lot of threads about people asking whether they need them, but how many of you guys are getting away without them?

I think my cat is about clogged and I really don't feel like putting a new one on since my truck is just for fun and to get from point A to B, where A to B is no more than a few miles.

Truck is a 1990 isuzu pickup, so the average muffler shop probably knows one should be on it, but do any just not care?
 
if you dont have a o2 sensor behind it, ream that bugger out, you will probably fail visual without it
 
Gut it that model year is only a safety & visual inspection
 
As an x-nc inspector you are supposed to have it in place. But like they said no rear o2 sensor gut it and put it back on and call it a day.
 
Like they said, at that year it is only a visual inspection, so cut it you fail, gut it, you may be fine.
 
My cat looks like crap and has holes in the heatsheild, so it's almost worth not gutting cause the whole thing is probably about to rot to crumbs. I tried looking online for just a heat shield to create a mock but not really finding any for sale. what do you guys think about bolting on a heat shield around a straight pipe? haha...
 
HyperOnExperience said:
My cat looks like crap and has holes in the heatsheild, so it's almost worth not gutting cause the whole thing is probably about to rot to crumbs. I tried looking online for just a heat shield to create a mock but not really finding any for sale. what do you guys think about bolting on a heat shield around a straight pipe? haha...
Click to expand...

Im a inspector and I dont look close enough to tell if it has a cat in the sheild or not so I would go for it if I were you
 
^ that's what I would use if I was in your situation.
 
LOL that last paragraph in the description is hilarious. The outside diameter of my exhaust is 2" so do I want the 2" or 2.25" allflow?

Or actually an easier option may be finding a 'midpipe' with 4 bolt flanges on the ends. I can't find one though, but it would 8 bolts off 8 bolts on and I got a straightpipe. Repeat once a year for inspection to put the crappy cat back on, assuming they don't care about the putting from backpressure which will be back when the cat is on.
 
HyperOnExperience said:
LOL that last paragraph in the description is hilarious. The outside diameter of my exhaust is 2" so do I want the 2" or 2.25" allflow?

Or actually an easier option may be finding a 'midpipe' with 4 bolt flanges on the ends. I can't find one though, but it would 8 bolts off 8 bolts on and I got a straightpipe. Repeat once a year for inspection to put the crappy cat back on, assuming they don't care about the putting from backpressure which will be back when the cat is on.
Click to expand...
You would want the 2". The exhaust tubing is measured/called by it's outside diamter, those fake cats look to have the inlet/outlet swedged open to fit over the 2" tubing.

I may, or may not :rolleyes: have a 89 Mazda B2200 that had horribly clogged cats. It had two of them, the first is bolted directly to the manifold with a really weird flange, and the second was in line with the pipe under the truck. When I cut the 2nd one off, a huge pile of the material from the first cat fell on the floor, the pipe was FULL of it. I think the 2nd cat was still good, just full of trash from the first one, but I left it off anyway because I was in a hurry. The first cat I knocked the remaining material (not much), and a steel chain mail looking mesh that I had never seen in a cat before, out, then just ran a straight pipe back to a muffler. Sounds good and quiet, it had just passed inspection with the clogged cat, so I'm good for a year, I guess then I will just worry about it as it comes. I figure it will probably pass just fine because it has a stock/quiet sounding exhaust, and the first cat is still there, so it "looks" like it will pass visual inspection, unless the guy is a mazda expert and knows there should be two cats. The truck runs 10x better now too, and MPG jumped instantly up about 3.5 MPG on the next tank compared to the clogged cat tank of gas.

I also DD'd a 98 S10 2.2L that got a clogged cat, I knocked all the material out of it and "fooled" the rear 02 sensor, it made it through 2 inspections just fine with the visual, and getting plugged into the machine.

Knocking the cat's out is a good option to get you by, but they sound like :poop: as the huge open chamber becomes an expansion chamber, echoing the sound around. The little tiny precat on the Mazda didn't make much of a sound difference as it was 1.75" pipe expanded into maybe a 3" chamber and back to 1.75, but the S10 had 2" pipe expanded into a 3"x10"x18" (guessing here) and it sounded like a Honda with a fart can after that. Something like that link I posted would be a better option, or if you are handy with a welder you can make your own out of your cat's heat shield and some tubing. I have no experience with that link I posted, other than I saw it before, got a kick out of it, and stored it in my wealth of random useless (usually) knowledge.
 
well before I bother with my cat could you guys give me some insight, here is my exhaust:

http://www.youtube.com/watch?v=L2VjfBExRGs

Hear that popping?

Is that backpressure, or bad timing, or ????

I kind of assumed it was backpressure because it isnt rhythmic with the engine so I figured it's gotta be the exhaust.

I just replaced my cat-back with that cheap o glasspack because there was a hole, so moving forward I would suspect the catalytic converter to be the issue.
 
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