Unique exhaust issue...

[vkyolv]

Ok, so here is what is going on...I could use some opinions.

I had my custom exhaust done about a year to year and half ago. I went with a straight pipe from the cat w/ no resonator to dual magnaflows. I can't remember the pipe size that the muffler shop used but I don't recall it being abnormally large.

I never really noticed the exhaust sounding bad until recently, but then again I am never outside of my car to hear how it sounds. My wife happened to take the car to work one day and I was outside watching her leave when I first noticed the sound issue. Now that I am paying closer attention to it, it seems as though the bad sound (sounds like a fart can...real tin'y) only happens when the car is cold, once it warms up the fart can goes away and the mean sound comes back.

So yesterday I stopped by a new shop closer to home and was going to have them look at it, but time didn't permit. Since the car was warm the issue didn't exist when I was having the guy look at it. The guy did look at the piping and said that he thought it was too big and that having the larger piping (with little back pressure) might have damaged my cat. He went on to say that it could be the internals of the cat are looser when it is cold causing the fart sound and when it warms up the internals expand thus causing it to stop sounding horrible.

I was thinking of scrapping the system and going with a Nismo or Greddy system, but financially it is out of the question for now. So, I think I will probably get the piping replaced...and maybe the tips too.

To be honest, I am a little scared that I may have to replace my cat now...What do y'all think?

[Hussain]

is it a 2.5 or 3.5? and straight pipe means no muffler. if you have magnaflows and no resonator i'd assume you mean magnaflow mufflers.

[vkyolv]

Hey Hussain,It is a 2.5.

This is semantics...but yes I have no resonator and dual Magnaflow mufflers.

[vkyolv]

Hey Hussain,It is a 2.5.

This is semantics...but yes I have no resonator and dual Magnaflow mufflers.

I wanted to apologize for my snarky comment.

I was have the epitome of a bad day yesterday, which actually was carried over from a nasty argument w/ my wife the night before. Heh, she even went out of her way to wake up early just to catch me before I left for work @5:00 am to continue yelling. Then, things got better in the Helpdesk yesterday.

In any case, I am sorry.

Having said all of that, does anyone have any thoughts or opinions on my exhaust issue?

[mrodrig2]

Any muffler setup regardless of brand, stock or custom is going to sound different when the engine is cold compared to warm. If I were you I'd just live with the momentary raspiness. If it really bothers you, get the resonator installed.

Also, I doubt that your cat is damaged from larger pipe size. That's bs.

[vkyolv]

I agree that it will sound different depending on what the system is...but even cold i've never seen an exhaust system have such a dramatic difference.

Of course the sound really bothers me (i mean the car is sexy but not when it sounds like pure rice), however, I am concerned with the possibility that it is the cat that is causing it. In my youth I blew up an engine because of a faulty cat. I'd rather not go through that again...

[mrodrig2]

If you want to change the exhaust sound you can change 4 things: pipe size, pipe routing, resonation and muffling. If you want to have them weld in smaller pipe, go ahead but then you might as well go with a new full system. You said money is tight so I figured a resonator is the cheapest thing to solve your problem.

The only realistic way the cat can blow an engine is if it is absolutely 100% completely clogged. If you are posting in this section, your car is no more than 2-3 years old so I really doubt that. Let's think about what's happening here. You may have changed the air velocity through the cat but that will not harm it. Additionally, less back-pressure can't add extra strain on the cat.

Unbolt the exhaust at the cat and look in there yourself. If the honeycomb is not clogged and intact then you have nothing to worry about and no mechanics trying to steal pennies from your pocket. By the way, if a primary cat is messed up, you will most likely get a CEL related to the O2 sensor or some other emissions code.

[vkyolv]

If you want to change the exhaust sound you can change 4 things: pipe size, pipe routing, resonation and muffling. If you want to have them weld in smaller pipe, go ahead but then you might as well go with a new full system. You said money is tight so I figured a resonator is the cheapest thing to solve your problem.

It's not the overall sound...once it warms up it is pure sex. The resonator was the first option I was looking to, but according to this guy a resonator is only going to quiet the sound, not keep the inital fart can from happening.

All I know is when it is cold I am almost embarrassed to be seen in the car.

[mrodrig2]

You are not going to be able to prevent having the warm-up/cool-down noises. All you can do is dampen it with your muffler or tune it out with a resonator.

The resonator WILL help with raspiness. A resonator may muffle a little but its primary purpose is to cause resonance and wave interference for certain frequencies to help the exhaust acoustics.

It sounds like you have already made up your mind so I'm not sure what else to tell you. Maybe someone else can chime in because IMO, until you unbolt your exhaust and get proof that your cat is damaged, this problem is in your head and its not worth spending time/money/effort to 'fix' 3 minutes worth of exhaust sound while the car is warming up.

[t0e]

I have a nismo exhaust on my car and about a month ago i had to replace my cat under warranty b/c the cat was leaking for some reason. so you should definitely check out your cat first. hope that helped probably not though lol.

[vkyolv]

You are not going to be able to prevent having the warm-up/cool-down noises. All you can do is dampen it with your muffler or tune it out with a resonator.

The resonator WILL help with raspiness. A resonator may muffle a little but its primary purpose is to cause resonance and wave interference for certain frequencies to help the exhaust acoustics.

It sounds like you have already made up your mind so I'm not sure what else to tell you. Maybe someone else can chime in because IMO, until you unbolt your exhaust and get proof that your cat is damaged, this problem is in your head and its not worth spending time/money/effort to 'fix' 3 minutes worth of exhaust sound while the car is warming up.

It's not so much that I have made my mind up or its in my head , but rather just cause to be worried about damage when several different shops are saying the same thing (without me priming them with info from other shops). Granted I see what you are saying and I probably could live with the horrible sound, but not if it is going to possibly damage my vehicle.

Can anyone else chime in?

[CoupeVQ35CVT]

OK, I'll bite. I went the same kinda route with my Sentra 1.8.

Custom exhaust piping (2.25" vs stock 1.75") and aftermarket resonator (12" long) and aftermarket muffler (Flowmaster 40). It will, when cold, sound different than when it is hot. It does actually sound a little like a fart can type exhaust at times.

I USED to have an aftermarket header also, and that REALLY kicked up the raspy sound, almost embarrassing. I had to have the resonator installed just to muffle some of that drone inside the cabin and get rid of some of the raspy-ness.

Our 4-cyl engines are just prone to that kind of noise. However with that said, make sure your cats are not busted causing whatever this is. I had a Magnaflow cat installed when i had the ebay header on there, and after a year the honey comb had separated from the cat's walls and rolled around inside, sometimes blocking exhaust flow (yes that meant my car took 10 seconds to get to 40 mph). Now I'm not saying that is the problem you have but it is one possible issue.

I definitely recommend the resonator option too, it will get rid of any raspy sounds and quiet it a little bit. Good luck!

[vkyolv]

Thanks for offering up your input...I couldn't take anymore of it so I replaced my system with a Greddy Ti-C. Still a little raspy when cold...but way better sound and performance overall.

Thank you for all of the input...

[CoupeVQ35CVT]

Ah yah I realized I posted 2 months too late.

Isn't the Ti-C the dual fart can setup? Or am I thinking of another GReddy system? Hehe.