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Hey guys,

So I have a Stillen Intake and headers on my car right now. I have an old Invidia muffler from my RX7 that I'm going to put on my G. The muffler is straight through, so I'm wondering if I should take off the cat while I'm at it.

Is there any significant performance benefit with removing the cat on SR20's? On turbo RX7's there are two cats and removing them makes a big difference creating less lag and more boost. On n/a RX7's, there are 3 cats so getting rid of them frees up the airflow a bunch.

It looks like there's only one cat on G20's and I'm guessing it's not too restrictive. Has anyone run a straight piping setup?? The muffler shop where I did all of my stuff on the RX7 can swap stuff in and out easily so it's not problem for me to take off the cat and return it for smog time. I'm guessing the SR20 is pretty loud with no cat and straight mufflers. I might just try it just for kicks...:p
 

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If you do a search you should be able to find out more info. My suggestion, don't do it. You won't gain any hp and it'll be horribly gross sounding and probably pretty loud too. Although probably nothing like an RX-7 w/ straight pipes :p I am pretty sure it's been discussed before too, if you're looking for more info. Hope this helps.
 

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Nooooo!

Well, first of all, the Rx-7, being a rotary, has a way different system as a regular 4cyl. The reason the rx-7 has so many cats is because they produce much more toxins, which need to be filtered out. I read once (some where way back when i had an rx7) that the rotary engine is able to produce much more horsepower than any traditional engine, but is so restricted with the exhaust that it is not able to.
As far as cats on 4cyl, they contribute to so little loss of hp, that unless you are going to do full out racing, it is really not worth it. The cats on most cars today are designed to have almost no restriction. They recently did a test on mustangs (back when i had a stang i was really interested on this too) and came up with a loss of .5 hp (out of like 275). Unless you plan on getting a turbo, and setting up for full race, i would highly recommend you keep the cat in. Not to mention if a CHP or any law enforcement checks for cats, and you have none... its a $10,000 fine.
Besides that it is really really bad for the envirnon.:knockout:
 

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Not only what they said, but your cat also has a secondary O2 sensor in it. You would have to either figure out how to trick the ECU to think it is operating and remove it or tap it into the straight pipe which wouldn't work so well.

Also, the Nissan/Infiniti cat has a large inner diameter as well. You won't notice any improvement in performance on a NA SR20DE.
 
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