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Discussion Starter #1
so how much louder will my exhaust get if i get rid of the secondary cats? i want to make my own "Test Pipe" i know it shouldnt throw a CEL because its after the 02 sensors....any performance changes?
 

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It will get a little bit louder but I dont think you should be able to tell that much but you will get an increase in power.
X2
 

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can you just clear the cat out so you can see through to the other side and wont it work the same way ??
 

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yes but what your clearing out is precious metal including platinum and rhodium. if you cut it off then you should be able to get a lil bit of money.the prices wereup but they have dropped but are rumored to go back up again
 

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You're in Kalifornia? I wouldn't do it.
 

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Discussion Starter #7
yea im california...why wouldnt you do it?..i already have headers, and my 240sx is completely illegal...302WHP... my truck sounds nice just want a bit more power and a bit louder would be nice. also i want to make my own test pipes for that same reason incase i get a referee ticket. i can slap the stock secondary cats back on.
 

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Go for it then, as long as you know what you are getting into..... do a write up so we can all see your progress. That would be great.
Get an UpRev dyno tune while your are at it so you can take full benefit of the modification.
 

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Generally a gutted cat is not the best direction to go. In your case you might just think about a test pipe in place of the second cat. A straight thru pipe is going to have better d\flow than an large open(gutted) cat would have. Plus you would still have your good cats just in case you ever needed them for emissions testing or to make it easier to sell your truck down the road.
 

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Discussion Starter #10
yea thats what im planning on doing.. i wanted to see if anyone here had done it. and yes a "straight test pipe" would be better flowing than a gutted cat. and i would have the stock cats "just in case"...gotta love cali with these stupid laws..ill let you guys know when i finally do this probably next month.
 

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Take lots of pics... If it turns out well, I may have you make me a pair! :)
 

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[snip]...gotta love cali with these stupid laws...[snip]
Just a FYI. It isn't a "cali" thing to require catalytic converters. It's federal/EPA regulation.

That's not to say "cali" might not have more stringent laws on said subject.
 

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The real dumb thing is that Cali counties are different as well. When I lived in Sonoma the test was a sniffer on the tail pipe. When I moved to Sacramento, they flagged my Ranger as a "gross polluter" and I had to have it put on a dyno, it didn't pass the "visual" test even though it passed the dyno and sniffer. I had to place the warm air tube from the exhaust to the intake back on and it ran WORSE but passed the visual! :thatswck:
 

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2 things,

1. I'm not sure you need to "delete" any of the cats, Nissan pinches down the Y-Pipe to slow the exhaust gas flow to heat it up so the cats will get hotter and work better. Restriction for the cats at that point is minimal.

2. IF you want to do it, years ago I had a German Ford (Merkur Scorpio) and it started rattling. I tracked it down to the cat. I had a small garage shop and cut the cat in half with a bandsaw, removed all of the honeycomb material (it had broken loose), and welded it back together. Worked great.

As far as I'm concerned, there may not be much of a gain in removing the second cat. Of course there might be a small power gain... Removing any restriction, or reducing any friction is good for a power gain, however the secondary cat removal may not give much.

JMO...
 

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Discussion Starter #15
yes i know the whole emissions law thing. and yes your right its not a cali thing i just say cali because they have the strictest laws for this. its rediculous what they can pull you over for out here. and any little hose no matter what its for (emissions wise) has to be the right type of hose routed properly or it will fail visual. the dyno testing isnt too bad

yea i know the power gains if any will be minimal, i just figured i have the volant intake and full gibson exhaust its nice and quiet i wouldnt mind if it was a bit louder. and like i said i would be able to swap them in and out quick.

but i will definitely keep everyone updated
 

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Punched the 2nd ones out in mine, after the o2 sensor. - made a Ltr per 100kms difference for the better. - That alone made it worth it.
 
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