So I got obx headers and now I'm going to get a racingline high flow cat; however the obx header y pipe is a weird size. I've measured it and it looks about 2 3/8 inches, but the inner diameter looks closer to 2 1/4 inches. The cat is offered in a 2.25 inch, 2.5 inch, or 3 inch inlet diameter. Should I get the 2.25 inch or the 2.5 inch?

 

Does anybody with OBX headers have any idea?

 

You can always step up from the headers back.
2.25"headers>2.5" cat>3" catback.

 

So are you saying that the size of the outlet of the y pipe and the inlet of the cat don't have to perfectly match up? And I plan on keeping my stock catback just because I don't like the obnoxious noise that aftermarket ones make. And also because my car is an I35 and it seems like the aftermarket ones made for the maxima would be too short for my car.

 

Cats are a waste of money. Gut it or leave it as is if you can't get away with a test pipe. A high flow won't do jack **** for you with stock exhaust lol.

In fact, the headers were pointless, too. You should have just gutted the stock manifolds.

 

I was under the impression that the stock catback was rated to 250 whp. And I could definitely get away with a test pipe, but I just don't want a nasty smell, because then I would have no cats at all. If the smell isn't that bad though, I would definitely do it.

 

If there's a smell..it's behind you.
You'll be fine.

 

There is no smell except on cold start from running rich.

You would have to be standing right behind it on a calm day to tell.

Stock muffler will flow up to 250whp, IIRC. With the small diameter piping all the way I doubt that you can get near that.
I'm sure you're making awesome torque down low, though.

 

I thought that catbacks didn't do much to increase power, maybe 5 hp at best.... I thought they were just there for the noise?

 

We don't have 3" catbacks for the noise
Okay, that's partially a lie

Of course, it is mod dependent.
2.5" catback on an otherwise stock car wouldn't yield much. It should be like 10 whp with I/H, no?

 

Isn't a 3 inch catback too big unless you're turbocharged, because there's not enough back pressure???

 

No.

 

So do you think that my obx headers, with a racingline high flow cat, and a 3 inch BRM catback would be a good setup? I've also got NWP spacers and will be doing an sri intake with a midpipe and 6 inch velocity stack with 6 inch aem dryflow filter.

 

Why stop there?
Get a piggyback tuner and some 440cc injectors with a 4" MAF housing.

After that

 

Not much help in here. Just a bunch of speculation. FWIW, you usually get the foul smell from removing the cats when cams are involved and you have duration overlap. Not a big deal with these cars. That being said, since the OBX are 2.25, I would get a 2.25 cat, and mount it as close to the front as possible. The closer they are to the exhaust valve, the faster they get up to temperature and do their job. Then I would purchase the 2.25 catback off ebay for 120 shipped, and you would have a nice sounding, free flowing exhaust, that bolts up, and is no headache. Leave the 3 inch stuff for the posers and speculators.


There are no drawback and all positive results from headers. There is a lot more to it than HP, most don't understand the benefits. There is absolutely nothing wrong with putting a catalytic converter on your car. It is the responsible thing to do, and it will kill a lot of the drone that most complain about.

 

Who pissed in your fruit punch to go around name calling?
Glad you are the self proclaimed know it all.

 

Go look at most of these replies to any of the tech threads.....no help. Same guys spewing the same crap. MOST of the time with irrelevant info, if any info at all. Mainly name calling and just plain old dumb posts.


You're welcome for giving good advice and tech'ing up the 5th gen section. I don't know it all, but I post about what I do know, instead of just speculating and telling guys that are looking for help a bunch of dumb childish thigs. If you see me as a know it all, that's fine. Post up where I am wrong. I will gladly learn something new.

 

It sounds like OP is going for fitment and performance.
You can always step up a half inch easily.
Gaskets do their job.

That being said, the easiest transition from the 2.25" headers to a 3" exhaust would be a 2.5" cat or test pipe.

Test pipe is ideal of you want all the power you can get and you don't have a strict state emissions test.
I don't feel that smell is an issue with a test pipe.

I don't recommend getting a cat to get rid of drone, but rather a large resonator will do the job and not rob any power.

And I would like to see proof from the guy that said aftermarket headers on stock exhaust shows no gains..I don't understand that one..gotta show some..just will show more if able to exhale better.

 

I didn't say no gain, but I can bet money that it would be virtually identical to gutted cats. Small piping plus that crushed section in the B pipe isn't very good for flow haha.

 

I gotcha.

 

Fitment and performance is exactly what I want. And I'm definitely down for a 3 inch BRM catback; however, I don't want to be heard from a mile away when I am just driving in the city. There's another guy on here who has an intake, headers, high flow cat, and the BRM 3 inch exhaust and said that the sound was unbearable. He ended up getting a 30x6 magnaflow resonator. I asked him if it worked, but I haven't heard back. If the 30x6 could quiet it down a considerable amount, then I'd be down.

 

Going from 2.25 to 3" isn't going to give any measureable difference. It won't hurt, but the 2.25 is the restriction. Don't get caught up in the hype, unless you just want 3" for the looks and cool factor, which I totally understand.

 

That's completely false.
3" shows gains over a 2.25" any day.

 

Another 10whp over 2.5" for a lot of the curve, iirc,

 

LOL.....nope.......but, hey.......believe whatever makes you happy. It's like the blind leading the blind around here.

 

Prove us wrong.
There are dyno charts everywhere that will inform you.
Seriously,

Gains are to be had in the higher RPM's with a 3"+.

I would look it up for you, but you seem to be the one that needs to learn, it will do you some good to search and read.

 

The BRM catback is similar to my MES catback on both the 3rd and 4th Gem Maxima(s)...But the similarities stop here!!!! The main cause of drone in most systems are poor resonator /muffler size choice!!!! BRM's system went for the looks of Magnaflow's street/racing tipped 14" mufflers cause they do look nice and are beautifully done...But too FREAKIN SMALL!!!! If you get their system talk to them to sell you a tubing kit! Then you incorporate a 22" long x 4" x 2.5" (inlet/outlet) or the 18" x 6" round x 3" (inlet/outlet) and last but not least 22" x 11" x 5" dual outlet rear muffler....Then you'll be happy with the sound....

 

He suffers from trolliosis.

 

Yeah, I was actually wondering if they would just sell the tubing. I'll hit em up and ask. What about just getting the whole cat back from BRM, and not getting a resonator from them, since they have that option. Then getting a 30x6 magnaflow resonator? There's a guy on here that's selling his 30x6 magnaflow and he said that it really helped quiet it down. There's also another guy that had the BRM setup with headers and said that the sound was unbearable; so, he got the 30x6 magnaflow. I asked him if it helped, but I haven't heard back.

 

LOL........so.....affixing a 3" pipe behind a 2.25" pipe is going to make a 2.25 inch pipe flow more?????? If the setup was 3" from Y all the way back, then.......but in this case, it is not....Sorry.


OP......just try to sort through the dribble, and come to a logical conclusion of this mess. Good luck.

 

:

You can't really be that dumb, and I'll just assume you're trolling from here on.

 

LOL....the question is.....do stupid people know that they are stupid.....No, they don't.


I'm headed to go get a 6" exhaust tip, so my muffler will flow better....thanks for the advice.

 

I'll act like you're serious and just dense.

The OP has headers and is looking to upgrade from there.
He doesn't need 3" headers<~lol or a y like you suggest..or for the 3" to bolt to the y~gradual steps up are best.
OP wants a performance cat or test pipe and to kill the possible drone wants an extremely long 3" resonator.

Every catback system that is larger than OEM is designed to bolt up from the cat back~meaning after the y and the cat and that does free up the restriction due to it replacing over half of the exhaust.
You're stupid if you think a tip is what anyone was ever talking about in this thread.

See your way out.

 

Lol......You mean the tip won't work? But you taught us all so much......


Is your car slow too? Or is it just you? I bet both...

 

Mr. WTF, you have some learning to do.



EDIT: I'll save you some time. Info has been out there for years.
https://maxima.org/forums/dyno-discu...44-ft-lbs.html

 

 

 

You know people are mad when they do ........ ........ after every word or just throw in a ton of LOL LOL LOL and smileys like they ain't mad but they really are.

 

Can't believe I missed this post. Exellent read for some of you fellas. This gentleman seems to know what I am hinting too.


Again, just affixing a 3" catback does not mean more power, as a matter of fact, it rarely does...why not? I am really losing faith in some of you. Do you guys really believe that a bigger exhaust behind a smaller exhaust flows more? Explain........hint......it could......why?


FWIW.....I been doing this......engine building/tuning/dynoing.....since before these maximas were new....

 

LOL....saved.