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Discussion Starter · #1 ·
Please excuse my inexperience, but my new altima is the first car I've owned that I've even thought of "enhancing". Mine is a 2.5s, with the inline 4, but I'd like to see what the best performance I can get out of it would be.

Now I fully understand the value of replacing the stock intake with a cold-air, easier breathing intake. I've searched the threads here and am aware of most of the options. Thank you all for posting your modifications, ideas, and thoughts on that subject.

But what exactly is a "cat-back" exhaust? Could it mean replacing the stock pipes and muffler from the catalytic convertor back with smoother and less restrictive alternatives? Will a less-restrictive muffler be louder (as heard in the car)? Or is it a brand name specific exhaust option? Can someone point me to a web site or catalog with more information? Is there an 02 Altima-specific version out there for purchase?

Watching Horsepower TV today, they took a fairly stock little Honda and upped it's horsepower about 13% with just a new intake and exhaust. Can I expect that same increase with new intakes and exhaust on my 2.5s?

Again, please bear with me. I'm a rooky.

OpalBlue
 

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"cat-back" means you replace the exhaust piping with typically larger diameter pipe from the catalytic converter to the end of the tailpipe. hence from the "cat back".

You probably won't gain much if anything from a cat-back exhaust on a QR25, but I'm no expert here. For performance parts for that engine, you'd probably be best off heading to a Sentra site such as www.b15sentra.net or something where this engine is the "performance option" instead of the "grocery getter standard engine" that it is here. The guys after performance here all seem to have the 3.5 engine. So you might have better luck at a Sentra site as far as learning performance parts go ;)
 

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More On Cat-Back...

You also want to make sure that the piping is mandrel bent.
This ensures that the airflow remains at a constant velocity
going through the bends. Less constriction=faster airfolw.

Also make sure that your piping diameter is adequete for
your application. The goal is to move more air efficiently
without sacrificing too much backpressure. In other words you
don't want overly big piping. All too often you see the Hondah
boys outfitting their civics with 3 inch piping. Loud, You bet!
Better performance? Doubtful.
 

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Re: More On Cat-Back...

SE-Rious said:
All too often you see the Hondah
boys outfitting their civics with 3 inch piping. Loud, You bet!
Better performance? Doubtful.
True. Overly large piping will result in lost backpressure and lots of low-end torque for only a minimal gain at the top-end.

BTW, it's Honduh ;)
 

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Re: Re: More On Cat-Back...

SteVTEC said:
True. Overly large piping will result in lost backpressure and lots of low-end torque for only a minimal gain at the top-end.

BTW, it's Honduh ;)
As a Honda Owner, I appreciate your proofing
my "hondah" error. You, my friend are correct
its, "Honduh". Present company excluded of course! ;)
 

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Discussion Starter · #6 ·
Now there HAS to be performance parts for the 2.5 4. My thinking is that the Altima will gain a reputation and respect for the V6 in it. People will notice mine's a 4-banger, and underestimate it. If I can tweak maybe 25 more HP from it, it will compete well against everyone else's V6's. Now THAT (a V6 accord owner getting beat by an I4 Altima owner) would be embarassing.

OpalBLue
 

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OpalBlue said:
Now there HAS to be performance parts for the 2.5 4. My thinking is that the Altima will gain a reputation and respect for the V6 in it. People will notice mine's a 4-banger, and underestimate it. If I can tweak maybe 25 more HP from it, it will compete well against everyone else's V6's. Now THAT (a V6 accord owner getting beat by an I4 Altima owner) would be embarassing.

OpalBLue
DO IT! The Sentra guys are more into mods over there than Altima owners are over here. See what you can find and share it with this forum. I find a lot of info lurking over at Maxima.org, because they share the same engine with the Altima as well.
 

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Discussion Starter · #8 ·
by Altimat DO IT! The Sentra guys are more into mods over there than Altima owners are over here. See what you can find and share it with this forum. I find a lot of info lurking over at Maxima.org, because they share the same engine with the Altima as well.
I plan to. It already occured to me that the 2.5i4 in the Altima is basically the same engine in the Sentra sport model. I haven't seen under a Sentra's hood. I suspect the layout is close, but not exactly like under the Altima's hood.

Hopefully, some of the companies making aftermarket performance parts for the Sentra will see the potential and modify them slightly (if necessary) to work in Altimas. All I need is pateience, I'm hoping.

I'll gladly post here any mods or improvements I find out about. Can't hardly wait!

OpalBlue
 

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Here is a page with what I have done with my 2.5 S exaust.
 

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OpalBlue - Yeah, definitely head over to the Sentra forums. The Spec-V guys have the same engine, and hopefully the engine bay layout is such that any mod developed for them would work for you also. If there are any performance company reps over on the Sentra forums, definitely get into contact with them and let them know that you're interested in getting the parts to work on the Altima too.

OpalBlue said:
If I can tweak maybe 25 more HP from it, it will compete well against everyone else's V6's. Now THAT (a V6 accord owner getting beat by an I4 Altima owner) would be embarassing.
I've got respect for the 4-banger 5spd's. My V6/auto is heavier and stuck with a less efficient auto tranny and that can make a big difference. Accord L4/5spd's, properly driven can hang right with an Accord V6/auto up to 60 mph and through the 1/4 mile (about 88 mph) because they have better gearing. After they have to upshift to 4th (94 mph) is when we pull many many cars on them though because we still have a lot to go in 3rd gear (116 mph) so I can stay in the power gear for longer until I have to hit an overdrive gear there there's no power.

The new Alty 2.5S/5spd has even more power though, and about the same weight as an Accord L4/5spd with 150 HP. I wouldn't be surprised at all if a 2.5S could take an Accord V6 stock.

I've got a couple of mods that might say otherwise in my particular case though (but my car is wrecked :( )

Check out THIS THREAD. I took a look at 2.5S/5spd performance in it and it looks very good - you might ahve missed it.
 

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As of right now, there are no aftermarket performance parts yet for the QR25 Altima. And you can only use the Spec-V as a guide. Eventhough they are the same engine, the engine sits differently in the 2 engine bays. So CAIs, headers, catback systems are going to be different because of hte physical layout. And even if after metket companies make stuff for the Spec-V, that doesn't necessarily mean they're going to make it for the Altima.

Here's an example.... I have a '01 SE. I've been hitting up Hotshot to make a header application for the 2nd gen Altima since they already have one for the 1st gen. It's the same engine and platform, but yet they don't want to do it.

Greddy makes a catback exhaust for the 1st gen Altima. And I tried hitting them up to make one for 2nd gen. Again, they don't want to make one.

If you really can't wait to make modifications, the the current option you have is going custom.

Take a look at the link below. It'll help you make a performance exhaust.

http://www.altimas.net/forum/showthread.php?s=&threadid=19218

And I think you can fit the Jim Wolf popcharger or NissanLunatic's generic WAI. With enough ingenuity, I think you can manage to make your own CAI.

Be creative and have fun with your ride. :D
 
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