Does removing cats improve sound
Race Director
Joined: May 2002
Posts: 10,306
Likes: 15
I can't answer exactly what it will do but it will smell. I'd get some random technology cats. Honestly, though, you are only going pick up 5-10 HP if that so I'd leave them on.
Thread Starter
Pro
Joined: May 2002
Posts: 590
Likes: 0
From: Fisherville Kentucky
I am not concerned with any hp increase, I would like the car to get a bit louder, not sure if I should remove all cats, only the pre cats, or just the main cat...need advice from anyone who has done this
Le Mans Master
Joined: Aug 2000
Posts: 8,838
Likes: 31
From: Australia
The main cat acts as a very efficent muffler. Removing it increases noise level a lot but I wouldn't say it is deep throaty sound; more raspy if anything 
I would start with a new front Y pipe without the cats and see what you think
I would start with a new front Y pipe without the cats and see what you think
Team Owner
Joined: Aug 2009
Posts: 21,491
Likes: 3
From: Detroit MI
You'll smell a lot of unburned gas when you're stopped. Your car will be louder, but not necessarily a "good" louder...sometimes it's a "that car has a hole in the exhaust" louder. You'll also possibly get a lot of black residue on the back of your car over your exhaust pipes, and on your driveway where the car is parked.
I did it to a car once and it lasted a couple weeks before I put a new cat back on. It's really not that much of a hp gain for the sacrifices you make. For a track car it's worth looking into; for a driver, it's not, in my opinion.
I did it to a car once and it lasted a couple weeks before I put a new cat back on. It's really not that much of a hp gain for the sacrifices you make. For a track car it's worth looking into; for a driver, it's not, in my opinion.
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Melting Slicks
Joined: Sep 2006
Posts: 3,194
Likes: 27
From: Monroe Twp, NJ
My 84 has gutted cat and flowmasters with custom Y pipe. It is very loud and has a crispy tone to it without and any distortion. I do however have plenty of the black stuff on the rear of the car even after short trips. I am not sure if that is because the cats gone or because it runs a little rich with all the mods done on this engine by last owner.
Burning Brakes
Joined: Oct 2006
Posts: 778
Likes: 0
From: Fort Worth Texas
I replaced my front Y with one without precats.
At the same time, I replaced the main cat with a high flow cat from one of the sponsors (sorry, don't recall the specific vendor).
I Really love the sound now (much deeper and throatier).
I don't get the raspy sound or "hole in the exhaust" sound.
I can still pass the Texas inspection just fine.
No black residue......no funky smells.
I will not be going back to the stock setup any time soon.
At the same time, I replaced the main cat with a high flow cat from one of the sponsors (sorry, don't recall the specific vendor).
I Really love the sound now (much deeper and throatier).
I don't get the raspy sound or "hole in the exhaust" sound.
I can still pass the Texas inspection just fine.
No black residue......no funky smells.
I will not be going back to the stock setup any time soon.
Safety Car
Joined: Sep 2002
Posts: 4,971
Likes: 9
From: The reason time exists is so everything doesn't happen at once
Drifting
Joined: Dec 2008
Posts: 1,254
Likes: 3
From: Souderton Pa.
I wouldn't necessarily say that ditching your cats will make your car any "louder" than it is now, more like it just "enhances the tone" of your existing exhaust system. Basically, it allows you to better hear what was already there. It "enhances" the tone. Think of you exhaust as a speaker. There are a bunch of different speakers out there and they all have different sound characteristics from one speaker to the next. Some are bass heavy, others neutral sounding while others yet are very "bright sounding" - just like exhaust systems....
I guess the best way to describe it is, imagine standing in front of a speaker which has a really thick cloth grill over the front. You can still hear the sound perfectly fine, but removing that grill will allow you to hear the sound exactly as the speaker produces it. Whether that's a good or bad thing, depends on your speaker and what kind of sound you're looking for...
The mid and high frequency tones will come out a lot "cleaner" sounding than before. If your speaker is naturally "bright sounding" from the beginning, it will sound more so after the cloth grill is removed. Of coarse, some may think they sound "harsh" afterwords and prefer the sound with the grill on because it absorbs a lot of the "harshness" of the higher frequencies the speaker produces, while others feel the opposite and prefer hearing the sound with the grill off because they see the sound as being "crisp" rather than "harsh" as others might. To each this own.
Thinking of your cats as really thick cloth "speaker grills" - may give you a better idea of what to expect by removing them.
Take them out, and the sound get's a little bit more "harsh" (aka: raspy). You'll hear your exhaust a lot more clearly which may or may not be a good thing. Depends on how your mufflers sound. If they're naturally "raspy" sounding, then ditching the cats will make them even more so. If your mufflers have a deeper tone to them, then you'll still get a good bit of raspiness but the mufflers deep tone will offset a lot of the raspiness and you'll have a good balance.
When I ditched the cats on my '92, my exhaust definitely sounded more raspy, but because I'm running Corsa mufflers which do a really good job at muffling unwanted noise , I think the raspiness lends itself well to the overall sound. The key is, you have to run mufflers that aren't all that raspy sounding to begin with, or it will sound too raspy afterwords, but some may prefer it that way.
Probably the biggest difference I noticed in regards to sound, was that you can hear all the exhaust "popping" upon de-acceleration, where as before it was masked by the cats. Personally, I LOVE the sound, but to each his own.
Although I'm running Cosa and not the B&B exhuast you have, here's a sound clip of my car. You can hear that it has kind of a "raw", "pissed-off" kind of raspyness to it when you hit wide open throttle. . You know right away it's not running cats. Ditching them has the same effect on the exhuast tone regardless of what engine/exhaust you're running. It's your mufflers that ultimately decide how you car is going to sound, ditching you cats will only "magnify" or "enhance" what's already there...
Hope that helps.
I guess the best way to describe it is, imagine standing in front of a speaker which has a really thick cloth grill over the front. You can still hear the sound perfectly fine, but removing that grill will allow you to hear the sound exactly as the speaker produces it. Whether that's a good or bad thing, depends on your speaker and what kind of sound you're looking for...
The mid and high frequency tones will come out a lot "cleaner" sounding than before. If your speaker is naturally "bright sounding" from the beginning, it will sound more so after the cloth grill is removed. Of coarse, some may think they sound "harsh" afterwords and prefer the sound with the grill on because it absorbs a lot of the "harshness" of the higher frequencies the speaker produces, while others feel the opposite and prefer hearing the sound with the grill off because they see the sound as being "crisp" rather than "harsh" as others might. To each this own.
Thinking of your cats as really thick cloth "speaker grills" - may give you a better idea of what to expect by removing them.
Take them out, and the sound get's a little bit more "harsh" (aka: raspy). You'll hear your exhaust a lot more clearly which may or may not be a good thing. Depends on how your mufflers sound. If they're naturally "raspy" sounding, then ditching the cats will make them even more so. If your mufflers have a deeper tone to them, then you'll still get a good bit of raspiness but the mufflers deep tone will offset a lot of the raspiness and you'll have a good balance.
When I ditched the cats on my '92, my exhaust definitely sounded more raspy, but because I'm running Corsa mufflers which do a really good job at muffling unwanted noise , I think the raspiness lends itself well to the overall sound. The key is, you have to run mufflers that aren't all that raspy sounding to begin with, or it will sound too raspy afterwords, but some may prefer it that way.
Probably the biggest difference I noticed in regards to sound, was that you can hear all the exhaust "popping" upon de-acceleration, where as before it was masked by the cats. Personally, I LOVE the sound, but to each his own.
Although I'm running Cosa and not the B&B exhuast you have, here's a sound clip of my car. You can hear that it has kind of a "raw", "pissed-off" kind of raspyness to it when you hit wide open throttle.
. You know right away it's not running cats. Ditching them has the same effect on the exhuast tone regardless of what engine/exhaust you're running. It's your mufflers that ultimately decide how you car is going to sound, ditching you cats will only "magnify" or "enhance" what's already there...Hope that helps.
Team Owner
Joined: Dec 1999
Posts: 34,873
Likes: 487
From: Lacey WA RVN 68-69
NCM Sinkhole Donor
The cats on the 92 are welded in place and as mentioned, a muffler shop will not risk the 5-figure fine by the feds if they got caught removing them. And the car will fail an emissions test without them.
There is no Y-pipe as each cat is part of the two exhaust pipes from the manifolds down to the B&B resonator.
The Corsa system sounds entirely differently than the B&B and most cat-back systems have their own sort of unique sound.
Team Owner
Joined: Jan 2009
Posts: 73,568
Likes: 33
From: Somewhere in Mo
St. Jude Donor '09-'10, '14
I replaced my front Y with one without precats.
At the same time, I replaced the main cat with a high flow cat from one of the sponsors (sorry, don't recall the specific vendor).
I Really love the sound now (much deeper and throatier).
I don't get the raspy sound or "hole in the exhaust" sound.
I can still pass the Texas inspection just fine.
No black residue......no funky smells.
I will not be going back to the stock setup any time soon.
At the same time, I replaced the main cat with a high flow cat from one of the sponsors (sorry, don't recall the specific vendor).
I Really love the sound now (much deeper and throatier).
I don't get the raspy sound or "hole in the exhaust" sound.
I can still pass the Texas inspection just fine.
No black residue......no funky smells.
I will not be going back to the stock setup any time soon.
Le Mans Master
Joined: Sep 2006
Posts: 6,050
Likes: 147
From: Phoenix AZ
2021 C4 of the Year - Modified Finalist
Here's my story....'86E
In search of a cheap extra HP, I obtained an 85 front Y pipe with no cats, and a new 3 way cat. I installed the Y pipe, and cat, and the resonance is horrendous.
The answer for me is to go to LT-1 exhaust with dual exhaust with a resonator where the original cat was.
Iobtained the LT-1 exhaust, and have yet to install it, although I tried using the cast iron exhaust manifolds, and the 3 stud pattern into the 85 Y pipe does not match up, so I reinstalled the original exhaust manifolds, and will just have to be content in changing out the whole thing.
But I gotta say, with the precats removed, and just a main cat in their place, the car has really picked up mileage and acceleration.
For instance, at 70, I had to give it a lot more gas to get to 80 or 85, and now it overshoots almost 90 if I don't watch it.
The precats were either plugged up, or just the cork in the bottle.
But it is LOUD until you hit 2000 RPM, and then the resonance just melts away. Super quiet after 2000. 'Course with a 258 rear end, that is 80 mph, so you are trying to get a speeding ticket to save your ears.
I talked to a guy who had the factory LT-1 exhaust on his car with chambered pipes instead of mufflers, and it wasn't objectionable at all, with no resonance.
I have the LT-1 cats as well, so it will be a complete system when it goes on.
In search of a cheap extra HP, I obtained an 85 front Y pipe with no cats, and a new 3 way cat. I installed the Y pipe, and cat, and the resonance is horrendous.
The answer for me is to go to LT-1 exhaust with dual exhaust with a resonator where the original cat was.
Iobtained the LT-1 exhaust, and have yet to install it, although I tried using the cast iron exhaust manifolds, and the 3 stud pattern into the 85 Y pipe does not match up, so I reinstalled the original exhaust manifolds, and will just have to be content in changing out the whole thing.
But I gotta say, with the precats removed, and just a main cat in their place, the car has really picked up mileage and acceleration.
For instance, at 70, I had to give it a lot more gas to get to 80 or 85, and now it overshoots almost 90 if I don't watch it.
The precats were either plugged up, or just the cork in the bottle.
But it is LOUD until you hit 2000 RPM, and then the resonance just melts away. Super quiet after 2000. 'Course with a 258 rear end, that is 80 mph, so you are trying to get a speeding ticket to save your ears.
I talked to a guy who had the factory LT-1 exhaust on his car with chambered pipes instead of mufflers, and it wasn't objectionable at all, with no resonance.
I have the LT-1 cats as well, so it will be a complete system when it goes on.
Drifting
Joined: Jul 2006
Posts: 1,483
Likes: 3
From: Newark, New Jersey
Now i know where all that black soot around my taillights and bumper comes from. I too gutted my cats and ran a straight dual exhaust. Love the sound, but the black stuff I could live without.
Le Mans Master
Joined: Feb 1999
Posts: 6,470
Likes: 2
From: levittown pa. usa Even a bad day with my `Vette, is better than a good day at work
St. Jude Donor '10
