blueZenki

Alright, so I bought a 3 inch catback system for my s14, its a ka24de n/t, and I also got OBX long tube headers+downpipe+test pipe, those parts are all 2.5 inch, are the flanges going to meet up, or should i take out the test pipe, cut the flanges and weld in a 3"-2.5" adapter??? Any Ideas, i havents seen the header down yet so I dont know, im just trying to get prepared for this weekend to do it.

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jsu1012

will not mount up, or at least when i've had this setup it didn't . if you want to keep the 2.5 i suggest taking it down to the local exhaust shop and have them fab you up something.

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blueZenki

Well, im good with welding thats why i said i was gonna just take the 2.5-3 inch adapter, weld a 2.5 inch peice of exhaist to it to make it the full 12.5 inches of my actual test pipe, then weld it in so the placement is good.

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Kallixtos

Not trying to sound like a douche or anything, but why are you running 3" on a non turbo setup?

teh smithers

Because 2.5" exhausts are for dumb people who want proper back pressure on their N/A motors.

blueZenki

Well, see son, theres a time in everyones life when it is time to have more then one car, this is my n/a and its also my wifes car, but she misses how my car sounds, and she wanted this exhaust. Just making sure its going to fit, needed some FRIENDLY advice, not jackassery.

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vipergtsr1000hp

i got obx longtube header + 3" test pipe + 3" isis catback. all bolted up fine. sounds loud and deep.

drftngs14

Im running the same as viper, OBX header, isis resi test pipe and isis dual n1, everything bolts up no problem. Only had to retighten after first couple heat cycles

blueZenki

yeah i know if i had a 3 inch it'd be fine, but im wondering if the flange on a 2.5 inch is the same as the flange on a 3 inch.... lol man, we were getting way off topic up there. Only on ZILVIA!

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drftngs14

got ya, misread man just trying to help out... My last 96 240 I had the obx header with stock cat and it bolted right up with no issues, not sure of the size on flange on stock cat but maybe that will give you an idea

blueZenki

not you man, the other dude, lol the one who said "douchebag"
anyways, yeah im just curious if someone has a 2.5 inch OBX header laying around they could measure the flange from the center of both bolt holes. I just wanna know if its gonna seat flush or if im gonna have to go get my welder out of storage...

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mmmS13

The flanges should be the same size, only difference should be the inner diameter of the piping. (3in vs 2.5inch)

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vipergtsr1000hp

yes, this is true. flanges are the same. depending on brand or ebay, the flanges might be off centered. thats why my exhaust doesnt line up like i want it to lol. but flanges are the same, inside diameter is smaller.

fliprayzin240sx

Yup, flanges are the same size so they should all bolt up after the cat. I was running a 3" Blitz Nur Spec on my NA KA for a good 3 yrs before I swapped and never had an issue other than it ca be too loud sometimes for an NA car. But thats what silencers are for...

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blueZenki

okay so, they meet up, no leaks, depending on the brand? I just dont wanna have absolutly NO back pressure, so sketchy lol

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fliprayzin240sx

Why would have no back pressure? Never mind, I'm not even gonna get into it. Just know this, larger 3" exhaust will cause you to lose low end power but you'll gain more on the mid to top end of the NA KA powerband.

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Frank_Jaeger

From what I've read, the dyno sheets I've seen, and what I personally have experienced, you do not lose any low end on a KA by going up to a 3" exhaust.

codyace

While we never dynoed it, the Altima with 3" vs 2.5" trapped 2 mph more everytime. That (to me) shows an improvement.

I agree, exhausts can be over sized, but 2.5 to 3" on that setup isn't hurting it. Same with SR20, we saw HP and torque across the board on that dyno, no loss.

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Redleader540

so do these long tube headers bolt directly to the cat? And can I use a stock cat?

fliprayzin240sx

Yes, every KA header I've seen will sit right where the old manifold and cat would meet.

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