Cutting out Cat, Noise difference...?

[89ShelbyGuy]

Hey guys, i have put on a 2.5 inch exhaust on my daytona..i have a 2.5in d/p into the catty then into a glass pack tubular muffler, then out the side...i plan on getting a exhaust system from one of the vendors (anyone know who's is better or about the same?!?!) and i would like to cut out the cat and run it staight to the glass pack muffler, then out the rear...i would like to know how much louder it would be...if any, it would be...cause its preatty loud as it is right now....Thanks!

[turbovanman²]

Yes, it will be louder. How much, impossible to say as some cats are restrictive, some are not as much.

[Speedeuphoria]

some will depend on how old/cloged the cat is currently

[BadAssPerformance]

Cats block a lotta noise. I'd run 3" from the DP out the back and a larger oval muffler like the Dynomax Race Magnum oval if you care about performance and sound Have you heard my Shadow?

[2.216VTurbo]

Don't cheat yourself on the pipe that runs out back, make sure the sound pulses get out from under the car. That last couple inches can make all the difference. On the exhaust that is Zip it Gazers

[Mopar318]

Im a pretty big fan of side dumps. Have had them on all my cars. Im building a 3" side dump for my Daytona here soon.

[2.216VTurbo]

Im a pretty big fan of side dumps. Have had them on all my cars. Im building a 3" side dump for my Daytona here soon.

Yeah, but you already admitted you're 20 What works at 20 is not so fun at 40... I think a portion of my hearing loss is due to 65K miles worth of droning in my Shelby Lancer That ringing in your ears after a 200 mile day in the car, that's permanant hearing loss. Once the cillia in you middle ears is 'mowed down' by too much sound pressure, they don't ever get back up again.

[Mopar318]

Yeah, but you already admitted you're 20 What works at 20 is not so fun at 40... I think a portion of my hearing loss is due to 65K miles worth of droning in my Shelby Lancer That ringing in your ears after a 200 mile day in the car, that's permanant hearing loss. Once the cillia in you middle ears is 'mowed down' by too much sound pressure, they don't ever get back up again.

Actually side dumps seem to have less drone at high way speeds, at least in my experience. I usually run a packed muffler with no cat, then dump it behind the passenger door. Maybe Ill just run a cutout with a side dump on the Daytona for a while to see if its going to be too loud or not.

Of course for the passenger, its usually a different story. My girlfreinds have always loved the side dumps.

[GLHNSLHT2]

I have a side exit straight pipe on my ShelbyZ. It's ok inside the car. Just a deep burble at idle and an ok roar at WOT. Highway cruise you can barely hear it. That being said that's IN THE CAR. Outside the car while it's not deafening or irratatingly loud it does attract attention. I'm tired of romping on it and thinking "are the cops gonna hear me"? am I gonna get a ticket? I must be getting old at 32 because I want something stealthy. Course I just put 3" straight pipe on my 2.2 auto new yorker out the rear because I couldn't find a muffler I like yet. Same thing, quiet in the car but loud as hell at WOT outside the car. Even shoots flames on decel with the stock ECU.

Now when my GLH was 2.5" with a cat it was nice sounding although still picked up spool with the cat removed.

I'm at a crossroads here as well. Should I get a high-flow 3" cat for noise? Will it be enough? Will it kill spool?

Tom if I were you I'd leave the cat and get rid of the muffler

[GLHNSLHT2]

I have a side exit straight pipe on my ShelbyZ. It's ok inside the car. Just a deep burble at idle and an ok roar at WOT. Highway cruise you can barely hear it. That being said that's IN THE CAR. Outside the car while it's not deafening or irratatingly loud it does attract attention. I'm tired of romping on it and thinking "are the cops gonna hear me"? am I gonna get a ticket? I must be getting old at 32 because I want something stealthy. Course I just put 3" straight pipe on my 2.2 auto new yorker out the rear because I couldn't find a muffler I like yet. Same thing, quiet in the car but loud as hell at WOT outside the car. Even shoots flames on decel with the stock ECU.

Now when my GLH was 2.5" with a cat it was nice sounding although still picked up spool with the cat removed.

I'm at a crossroads here as well. Should I get a high-flow 3" cat for noise? Will it be enough? Will it kill spool?

Tom if I were you I'd leave the cat and get rid of the muffler

[The Pope]

The NY also has the .63 housing too and a stock cam. Smaller exhaust makes extra noise and so does a larger cam. My wagon with just a cat and a stock turbo with a bigger cam is a lot more noisy, with 3"

[turbovanman²]

Yep, TIII turbo, 3 inch system, tried a side dump with no muffler or cat, I couldn't even hear myself talk,

The turbo size affects how quiet/loud it is, a mitsu with an open exhaust is fairly quiet, just raspy.

[GLHNSLHT2]

The Pope thinks my .63 housing makes the car quieter Simon.

[shadow88]

Yeah, but you already admitted you're 20 What works at 20 is not so fun at 40... I think a portion of my hearing loss is due to 65K miles worth of droning in my Shelby Lancer That ringing in your ears after a 200 mile day in the car, that's permanant hearing loss. Once the cillia in you middle ears is 'mowed down' by too much sound pressure, they don't ever get back up again.

WHAT????

Oh, I'm just kidding. The additional popping on decel is a nice touch too when going cat-free. I like being quiet enough not to raise any eyebrows. I run cat and muffled 2.5" rear exit.

[turbovanman²]

The Pope thinks my .63 housing makes the car quieter Simon.

Really, thats kinda azz backwards but ok,

[Spraynlog]

Hey guys, i have put on a 2.5 inch exhaust on my daytona..i have a 2.5in d/p into the catty then into a glass pack tubular muffler, then out the side...i plan on getting a exhaust system from one of the vendors (anyone know who's is better or about the same?!?!) and i would like to cut out the cat and run it staight to the glass pack muffler, then out the rear...i would like to know how much louder it would be...if any, it would be...cause its preatty loud as it is right now....Thanks!

If you are running a stock cat, and you cut it out, it will be a lot louder. I recently tried running a glasspack off my 2 1/2" downpipe, and it was pretty much unbearable. You can read what I did in my post about the Edelbrock SDT muffler.

[MiniMopar]

Yeah, exhaust drone varies depending on your setup: eg. which SV/DP you have, where your exit is, what size pipe your have, maybe even the type of pipe...I dunno. I like to read the various muffler threads and all I can say is there are lots of different things to try and it seems like everyone has a different experience.

All that said, yeah removing the cat will make it louder for sure. I put a 3" system on the CSX a few years ago and it still has no cat. Even with two mufflers, it's louder than the Daytona with one straight-through muffler and a high performance cat from Dynomax. When I ran the Daytona briefly with just a muffler, it was VERY loud. I don't mind somewhat loud exhaust, but a lot of highway drone drives me nuts and I also don't want to get on the neighbor's bad side too much.

When I got my CSX in '98, the exhaust was old school: stock DP and cat with 2.25" cat-back and no muffler. It was fine at idle, but loud while driving.

[turbovanman²]

I hate drone, it was ok when I didn't have to commute on the highway but when I moved, argg. The cat definately cut that out-but you could feel the power loss so now I have a extremely high flowing cat and will be trying a new muffler setup soon.

[TurboSedan]

bumping an old thread here but i just got the 3" exhaust installed on my Spirit R/T and thought i would add my .02 rather than start a new thread.

previously my exhaust system consisted of the stock pipes, however i had a test pipe welded in where the cat was and no muffler at all. the pipe actually ended right before where the muffler was (just after rear tire). it was very loud but i could still drive it around that way. it wasn't loud enough that i got any trouble from the cops or any noise complaints. the only time it was really too loud was when i floored it and let the RPM really get up there which was hardly ever.

the car is REALLY quiet now. i think it's maybe just a little louder (deeper tone) than a completely stock exhaust system. mine consists of the 3" mandrel bent aluminized system from FWDP, along with a 3" Magnaflow cat and a round 3" Dynomax Ultraflo muffler and a turn down tip. the only real reason i decided to get the cat is because i wanted the car to be very quiet (stealthy). the exhaust shop put the turn down on, which i wasn't expecting them to do but i'm actually glad they did because you can't even tell the car has a larger exhaust system just by looking at the rear of the car.

my brother has exactly the same system on his Spirit R/T except he has a test pipe in place of the cat and the exhaust tip goes straight out. mine is definitely quieter than his and it is obvious whether the car is idling but especially when driving. he has the same 3" system from FWDP, exact same muffler as well, the only difference is the cat and tip. i would think that the turn-down would make mine a little louder if anything.

i'm definitely glad i bought the cat! now that i know they cut out so much noise i will be getting one for the CSX as well.

my R/T definitely feels a little quicker now...the first time i floored it i could tell it pulled harder than it ever had before. i didn't think i would notice much difference since i am only at about ~9psi and the system that was on there was simply straight pipe with no muffler or cat.

--------------------------------
Joshua Mitchell
'91 Dodge SPiRiT R/T
'87 Shelby CSX #667
'98 Buick Regal GS

[thrashercharged]

>my R/T definitely feels a little quicker now...the first time i floored it i could tell it pulled harder than it ever had before. i didn't think i would notice much difference since i am only at about ~9psi and the system that was on there was simply straight pipe with no muffler or cat.

Anyone have any theories as to why the car would be quicker with the addition of a cat and muffler? My understanding from reading the post is that this is the same exhaust system, turbo, same boost, etc. just the addition of a muffler and cat, so there has to be more restriction. Why would the engine be making more power, especially being a turbo car?