# cat back?



## b14sleeper (Dec 31, 2004)

okay, so i went and got my muffler installed today. anyways, i also had the muffler shop make a custom cat back for me, and then put the muffler on. it sounds extremely loud, and i am afraid to drive it because of the loud noise. i had a muffler on before but now i have a cat back. it is 2.25 inch piping on a 96 b14 sentra. the problem is, i think i have no cat, i think that they just cut the cat off and put piping. i am not too good with engine parts, so if someone could help me. where the hell is the cat located, before or after the sensor that is located under our cars. their was a box(something, dont know what) that was after the sensor, but it is not their anymore, please help, my question is, where the hell is the cat?


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## B14Nizmo97 (Jun 4, 2005)

the o2 senser on my b14 is directly mounted to the cat. on the driverside. im pretty sure if you look under your car the cat is before the seats, under the car, its shaped something like a football when the headshield is removed, but with the headshield on it should look like a big metal plate with little holes thats the best description i can give. your car might be louder cause they probably took off the resonator thats right after the cat. if they took the cat competly off the CEL might come on cause no o2 senser.


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## wes (Apr 30, 2002)

It is loud because they removed the resonator. Have them weld in a resonator direstly after the cat. and it will sound much better! 

It is illegal for them to remove the cat FYI.


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## Twiz (Aug 24, 2004)

Assuming these guys at the muffler shop are " PROS "... at some point there could be a leak somewhere in your exhaust system... that gets quite loud. Or the resonator just like Wes mentioned ... you wanna make sure you have that in too, the exhaust sounds horrible without it.


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## b14sleeper (Dec 31, 2004)

is 2.25 really that big on a N/A ga16de?


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## Acceler8ter (Feb 5, 2005)

b14sleeper said:


> is 2.25 really that big on a N/A ga16de?


Not really. But its bigger then you need. You're not trying to eliminate back-pressure, just reduce it. If you get it piped too big and you eliminate back-pressure (or reduce it more then it needs to be) you lose power.... which is the opposite of what you're trying to do.

Example: I took the pipe that connects the cat to my header off when I was doing a clutch job on my B14 and test drove it. I noticed a SIGNIFICANT negative affect on my performance. I mean, it was horrible. I would have been cannon fodder for a Geo. This is why they recommend 2 inch for NA cars and 2.5-3 inch for turbo cars. I don't think 2.25 is gonna affect you to much... just get more air in that motor and more exhaust out and you should be good... but it'll be expensive and take you a while. =P


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## Token Moron (Mar 28, 2003)

Acceler8ter said:


> Not really. But its bigger then you need. You're not trying to eliminate back-pressure, just reduce it. If you get it piped too big and you eliminate back-pressure (or reduce it more then it needs to be) you lose power.... which is the opposite of what you're trying to do.
> 
> Example: I took the pipe that connects the cat to my header off when I was doing a clutch job on my B14 and test drove it. I noticed a SIGNIFICANT negative affect on my performance. I mean, it was horrible. I would have been cannon fodder for a Geo. This is why they recommend 2 inch for NA cars and 2.5-3 inch for turbo cars. I don't think 2.25 is gonna affect you to much... just get more air in that motor and more exhaust out and you should be good... but it'll be expensive and take you a while. =P



lol...  
2.25" is a lil big for an N/A ga16de...2" is optimal. its not about back pressure..back pressure is BAD..B-A-D. you mean exhaust velocity...you want to increase that.


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## Acceler8ter (Feb 5, 2005)

cHoPs said:


> lol...
> 2.25" is a lil big for an N/A ga16de...2" is optimal. its not about back pressure..back pressure is BAD..B-A-D. you mean exhaust velocity...you want to increase that.


Oh is it? My bad. Sorry, I'm used to working on Muscle cars... so for me 2.25 is really small, haha. But you do have to have a BIT of backpressure, why do you think you don't wanna go larger then a certain size? It makes sense if you think about it. I'm not calling you wrong though, if thats what your thinking.


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## wes (Apr 30, 2002)

Acceler8ter said:


> Oh is it? My bad. Sorry, I'm used to working on Muscle cars... so for me 2.25 is really small, haha. But you do have to have a BIT of backpressure, why do you think you don't wanna go larger then a certain size? It makes sense if you think about it. I'm not calling you wrong though, if thats what your thinking.


Because it has been dyno proven to provide the most HP and the best powerband. And your wrong abotu backpressure. What you want is an exhaust size that maintains exhaust gas velocity, so piping that is too large can hurt velocity and as a result reduce the scavenging effect of the exhaust system. 

Most old school domestic refer to this as having a little back-pressure but technically that is wrong. Then again Nascar people call camber "wedge"....


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## b14sleeper (Dec 31, 2004)

also, what is the best resonator? i am going to purchase a Cherry Bomb(red glasspack) i have heard that those are nice, and add a deep tone to the exhaust... i am not sure which length though, so if anyone can help...wes?


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## wes (Apr 30, 2002)

It doesn't matter what brand it is as long as it is a perforated core. Magnaflow makes nice ones. There is info. on this and pictures of a perforated core VS a louvoured core on the sentra.net tech. page.


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## infazorak (Jun 18, 2005)

wes said:


> It doesn't matter what brand it is as long as it is a perforated core. Magnaflow makes nice ones. There is info. on this and pictures of a perforated core VS a louvoured core on the sentra.net tech. page.


What's the deal with mandrel bent pipes? Can I just take them to my local "Muffler King" and they can install them along with the resonator, muffler and all that? Is it OK to leave the stock cat on there? Or does that need to be replaced with the whole rig. I've read the Nissan stock one is a fine cat and doesn't really need to be chaged, but does it affect performance? 

*Zorak Out. *


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## wes (Apr 30, 2002)

infazorak said:


> What's the deal with mandrel bent pipes? Can I just take them to my local "Muffler King" and they can install them along with the resonator, muffler and all that? Is it OK to leave the stock cat on there? Or does that need to be replaced with the whole rig. I've read the Nissan stock one is a fine cat and doesn't really need to be chaged, but does it affect performance?
> 
> *Zorak Out. *


Taken from the sentra.net Tech section. 

" A proper exhaust system should be fabricated from pre-made mandrel bends, not crush bent muffler shop pipe. A good fabricator cuts these bends apart and welds them together to make an exhaust with no neck downs. Normal muffler shop pipe benders crush the pipe by as much as 50% when making bends. These stainless steel mandrel bends are made by Magnaflow."

Unless they have a mandrel bender no they cannot bend the pipes for you. As the tech. points out if you wan tto custom make an exhaust you will have to order pre-bent mandrel bent pipes and have them cut and welded. Read the tech. section thoroughly and you wil learn a TON!


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## pete? (Jul 6, 2004)

for you GA guys. when you upgrade to a 2 inch exhaust buy a stock sr20 cat. i just got a cat (my b13 was catless for awile) and it was clean through. hold it up to the light and she was perfect and you cant get much for "high flow" than that. also, the opening is 2inches in and out. 

cherry bomb reses are good. i cant see how a magna flow would be any better save the higher price.


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## wes (Apr 30, 2002)

pete? said:


> for you GA guys. when you upgrade to a 2 inch exhaust buy a stock sr20 cat. i just got a cat (my b13 was catless for awile) and it was clean through. hold it up to the light and she was perfect and you cant get much for "high flow" than that. also, the opening is 2inches in and out.
> 
> cherry bomb reses are good. i cant see how a magna flow would be any better save the higher price.


Actually the B14 cats (GA and SR) are 2.75" in and out.


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## pete? (Jul 6, 2004)

wes said:


> Actually the B14 cats (GA and SR) are 2.75" in and out.


oh really? why thank you wes, i never knew that. :cheers:


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