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Old 05-03-2008, 04:35 PM   #1
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Default Ditching catalytic?

I got an enthuza 2.5" catback and im not reaching for big power just yet, 200hp initially.

Garrett T25 of an SR20, if it matters. So not the most efficient thing up top.

What are the pros and cons of ditching the cat? Worth the effort and supposedly the smell?
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Old 05-03-2008, 04:51 PM   #2
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Not worth it. At most its only 1-2 hp if you have a good cat. Why **** the environment, for 2hp?
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Old 05-03-2008, 05:40 PM   #3
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I've heard its a lot more than that on a turbo car.

And a miata is not going to **** the environment.

I have no smell...other than the unburnt fuel smell of running god awful rich...cons is obviously illegal.
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Old 05-03-2008, 05:44 PM   #4
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It's more than just 2hp on a turbo car.. The smell is only an issue for me when I am running it in the garage or shop, otherwise I don't even notice.
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Old 05-03-2008, 05:52 PM   #5
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I'm not concerned to much about illegal because I can just build a o2 simulator so I can pass emissions, and no one does visual inspection in NY.

I just have the chance to ditch my cat because someone can build me a test pipe as long as i can provide flanges and tubing.

So I am just curious how much advantage people are seeing when ditching the cat.

Naturally I would rather keep the cat for the car to be more environmentally friendly and its one less thing for me to wire into the car.
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Old 05-03-2008, 06:04 PM   #6
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I've had the cat off my car since I went turbo years ago. I have no complaints about the smell, buses are usually the only vehicles that the smell aggravates me.

Having a miata is already being "environment friendly". You could be driving a suburban or expedition around. Bump your karma and plant a tree once you take the cat off.

I had a guy give me the visual check for my cat. He said just swap in you cat, show it to me, then do whatever you want afterward. Whenever I need to again I still have the cat to throw on for the 30 mins or so to pass my test.

Vash-
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Old 05-03-2008, 06:14 PM   #7
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What about performance?
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Old 05-03-2008, 06:21 PM   #8
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stock cat is only 2 inch pipe. it won't flow any more than a 2 inch pipe. so no matter how big the exhaust is after the cat, you can only flow what the smallest section is. you can always get a bigger high flow cat if your worried about Envirothugs.
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Old 05-03-2008, 08:51 PM   #9
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if you don't have to deal with the sniffer for inspection, then there is no good reason to keep the kitty.
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Old 05-03-2008, 09:19 PM   #10
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How about the fact that you're not in competitive racing and that last 1 or 2 hp isn't necessary, and that you're miata is going to be plenty fast even with the cat if it's turbocharged (get a high flow cat maybe?). Add to that the fact that you'll probably be running mostly either rich or lean of stoichiometric and I'd imagine the car is not going to be as eco-friendly as it used to be......Now everyone can commence bashing me on this opinion.
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Old 05-03-2008, 09:25 PM   #11
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lol

I definitely didn't do it for any other reason than my turbo **** came with a test pipe. So when I put everything in, that was part of it.

But now ordering the new 3" Enthuza exhaust, I also am having Jason make me a 3" test pipe as well. I guess I feel like I never really had the cat, no need to add one now.

ANYWAYS!!!! Cats are the hot item on the market now. Have one on your car? Not till the thieves get to you!

Vash-
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Old 05-03-2008, 09:36 PM   #12
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just wondering.... what boost are you running with the T25? ... there may be easier ways to make more power. Also, keep in mind that the S14 T28 can be found for about 300-500 and is single ball bearing, much more efficient and slightly bigger.
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Old 05-04-2008, 12:24 AM   #13
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When in doubt ask Corky.


"Do yourself a favor and leave it alone"


get a high flow cat, but leave it in there. The ozone layer will thank you by helping to keep you skin cancer free.
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Old 05-04-2008, 12:23 PM   #14
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Quote:
Originally Posted by left field View Post
stock cat is only 2 inch pipe. it won't flow any more than a 2 inch pipe. so no matter how big the exhaust is after the cat, you can only flow what the smallest section is. you can always get a bigger high flow cat if your worried about Envirothugs.
So everyone who buys an enthuza exhaust runs a higher flow cat or no cat at all?

I would imagine that it could be a bottle neck there, but having a freeier flowing exhaust after the cat would allow it to breath easier as well.

I'm not an exhaust expert, just a guess.

Quote:
Originally Posted by 240_to_miata_OWNER View Post
just wondering.... what boost are you running with the T25? ... there may be easier ways to make more power. Also, keep in mind that the S14 T28 can be found for about 300-500 and is single ball bearing, much more efficient and slightly bigger.
Going to be running wastegate pressure initially then 12 psi after I get a boost controller.

As for upgrading the turbo, no point because I already have the T25 and if i'm gonna be buying a new turbo ill probably splurge on a GT2560.

I'm just curious if anyones done any before and after comparisons, or how many are running a stock cat.
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Old 05-04-2008, 03:27 PM   #15
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Your miata will pollute a couple of hundred times more than your average SUV without a cat. If you want extra power AND good karma, go metallic core cat.

Edit 2: Seems like a good cat takes away between 80-97% of NOx, with the higher percentage reserved for large marine diesel engines. Will see if i can find an article in english to share.

Edit 3: I give up the search for hard facts. EPA and such agencys state in a lot of articles that the effectiveness is 80%<, but they never publishes any measured values.

Last edited by Sentic; 05-04-2008 at 07:08 PM.
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Old 05-04-2008, 06:06 PM   #16
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i went no cat for $$$ reasons...

my cat was clogged and i didnt want to buy a new so i made a test pipe for $6 and learned how to weld at the same time. Dont have too bad of a smell at all to me i dont mind the smell of unburnt gas when i get out of the car because i dont hangout behind the muffler and the sound is def on the loud side for a N/A car...

to each his own
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Old 05-04-2008, 11:51 PM   #17
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Quote:
Originally Posted by Saml01 View Post
I'm not concerned to much about illegal because I can just build a o2 simulator so I can pass emissions, and no one does visual inspection in NY.

Im in Buffalo and Im the exact opposit, I get the visual but I dont think they've every done an emissions test on me.
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Old 05-05-2008, 05:40 PM   #18
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I guess ill keep it for now, and then if I am not satisfied ill get rid of it. I am not an enviro nut but I dont want to pollute if I dont have too.
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Old 05-05-2008, 05:51 PM   #19
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Why run a 2.5" DP, 2.5" exhaust, and then choke the **** out of it with a 2.25" cat? If you're going to run a cat, run a 2.5" high-flow or larger. I'm using a 3" high-flow to match my 3" DP and 3" catback.
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