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Old 08-19-2012, 10:20 PM   #1
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No Cats vs High Flow Cats

I have a 2007 Mustang GT and I was bound and determined to remove the cats. I had them removed and a smaller pipe added in (for back pressure) and I love the sound, a tad bit too raspy around 2500-3000 rpm, but I'm happy with the sound. Well I'm dumb and started looking into laws after I did it and realize the fines are way bigger than I thought (up to $10,000 living in Georgia). So now I'm thinking I need to get some high flow cats, probably from American Muscle so I'll be legal again but have the sound. I'm just wondering if it's gonna sound anywhere close to how it does now. It'd be perfect if it just reduced the rasp a little but still had that mustang "growl" and was still loud. Also, the inevitable check engine light is on now so when I get this changed out I need to get the light reset, right? Or should it go off on its own? And I'm running x pipe and 40 series flowmasters. Hoping someone reads this that has gone from no cats to high flow.

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Old 08-19-2012, 10:27 PM   #2
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Quote:
Originally Posted by dPayne003
I have a 2007 Mustang GT and I was bound and determined to remove the cats. I had them removed and a smaller pipe added in (for back pressure) and I love the sound, a tad bit too raspy around 2500-3000 rpm, but I'm happy with the sound. Well I'm dumb and started looking into laws after I did it and realize the fines are way bigger than I thought (up to $10,000 living in Georgia). So now I'm thinking I need to get some high flow cats, probably from American Muscle so I'll be legal again but have the sound. I'm just wondering if it's gonna sound anywhere close to how it does now. It'd be perfect if it just reduced the rasp a little but still had that mustang "growl" and was still loud. Also, the inevitable check engine light is on now so when I get this changed out I need to get the light reset, right? Or should it go off on its own? And I'm running x pipe and 40 series flowmasters. Hoping someone reads this that has gone from no cats to high flow.
If you put cats back on it will make it more raspy. I have Pypes h pipe with no cats and pypes muffler deletes. Loud and mean sounding. Lower growl. My buddy has the same pypes muffler deletes with a x pipe and high flow cats. It is very loud and very raspy. And also get a tuner and you can keep thay cel from coming on. And have ALOT more[COLOR="Silver"]

---------- Post added at 10:27 PM ---------- Previous post was at 10:26 PM ----------
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Old 08-19-2012, 10:33 PM   #3
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Originally Posted by Jake
If you put cats back on it will make it more raspy. I have Pypes h pipe with no cats and pypes muffler deletes. Very Loud and mean sounding. Lower growl. My buddy has the same pypes muffler deletes with a x pipe and high flow cats. It is very loud and very raspy. And also get a tuner and you can keep thay cel from coming on. And have ALOT more power.
Yeah I plan to get a tuner but I'm worried about this first. I know it's rare to get caught but it's not worth any $10,000 fines. And I've definitely never heard of cats making more raspy. They usually reduce the rasp.
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Old 08-19-2012, 10:36 PM   #4
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Well me and my friend, he has 06 i have 07, have the same axlebacks, both have cai and tuned. He has high flow cats and x pipe, i have h pipe with no cats. My car is loud, deep, and throaty, his is very loud and very raspy. Im not comparing through a video im telling you exactly what i hear in person. But ya know i may be just stupid.
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Old 08-19-2012, 10:46 PM   #5
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Originally Posted by Jake
Well me and my friend, he has 06 i have 07, have the same axlebacks, both have cai and tuned. He has high flow cats and x pipe, i have h pipe with no cats. My car is loud, deep, and throaty, his is very loud and very raspy. Im not comparing through a video im telling you exactly what i hear in person. But ya know i may be just stupid.
Yeah might have something to do with the muffler deletes on your friend's. Heard that sounds horrible on our cars. All I know is with cats it wasn't raspy but now it is raspy with the same setup just minus the cats. Just trying to find out if high flows will sound way better than stock cats or if I would be wasting my money.
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Old 08-19-2012, 10:51 PM   #6
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Originally Posted by dPayne003

Yeah might have something to do with the muffler deletes on your friend's. Heard that sounds horrible on our cars. All I know is with cats it wasn't raspy but now it is raspy with the same setup just minus the cats. Just trying to find out if high flows will sound way better than stock cats or if I would be wasting my money.
We both have Pypes Muffler Deletes. So how would his have anything to do with it??
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Old 08-19-2012, 10:56 PM   #7
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What county in GA do you stay in?
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Old 08-19-2012, 11:00 PM   #8
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I don't think it's the cats that make the raspy sound it's the x pipe on your buddies stang that might be the culprit. Mines kinda raspy because of the x pipe on it
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Old 08-19-2012, 11:06 PM   #9
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Originally Posted by Alonzo.dargan1
What county in GA do you stay in?
Henry county

---------- Post added at 12:06 AM ---------- Previous post was at 12:02 AM ----------

Quote:
Originally Posted by Jake

We both have Pypes Muffler Deletes. So how would his have anything to do with it??
I didn't catch that in your first message, sorry. I'm now learning the x pipe is causing rasp. The little rasp it has doesn't sound bad. I'm not all that worried about that. Just worried about if the exhaust is gonna sound just like it did with stock cats or if it's still gonna have a pretty good sound like it does now.
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Old 08-19-2012, 11:13 PM   #10
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Hi flows shouldn't change the sound too much. They'll be legal so no worries.
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Old 08-19-2012, 11:15 PM   #11
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Originally Posted by 2007pullinaway
Hi flows shouldn't change the sound too much. They'll be legal so no worries.
Thanks, that's all I was looking for lol. I appreciate it.
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Old 08-19-2012, 11:17 PM   #12
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Originally Posted by dPayne003

Thanks, that's all I was looking for lol. I appreciate it.
No prob bro
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Old 08-19-2012, 11:19 PM   #13
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You should be good if your county doesn't do emissions checks. My setup is Lts offroad-x and pypes violators and I live in troup county. Btw I when next to cops I light step on the gas pedal.
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Old 08-19-2012, 11:23 PM   #14
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Originally Posted by Alonzo.dargan1
You should be good if your county doesn't do emissions checks. My setup is Lts offroad-x and pypes violators and I live in troup county. Btw I when next to cops I light step on the gas pedal.
Same here just don't wanna get on it hard and there be a cop I didn't see lol. My county does emissions but I plan on getting MIL eliminators if I leave the setup I have now. And I'll just go to a shop that doesn't do a visual check.
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Old 08-20-2012, 06:56 AM   #15
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It probably is the x pipe, but i thought i read that you have an x pipe?? So if you have an x pipe with high flow cats it will be raspy. He ran x pipe with high flow cats for about a month before he put the muffler deletes on. And dont get me wrong, im not saying it sounds bad at all. His car sounds sick, but it is raspy! If you want deep and throaty go h pipe
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Old 08-20-2012, 07:40 AM   #16
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Quote:
Originally Posted by dPayne003
I have a 2007 Mustang GT and I was bound and determined to remove the cats. I had them removed and a smaller pipe added in (for back pressure) and I love the sound, a tad bit too raspy around 2500-3000 rpm, but I'm happy with the sound. Well I'm dumb and started looking into laws after I did it and realize the fines are way bigger than I thought (up to $10,000 living in Georgia). So now I'm thinking I need to get some high flow cats, probably from American Muscle so I'll be legal again but have the sound. I'm just wondering if it's gonna sound anywhere close to how it does now. It'd be perfect if it just reduced the rasp a little but still had that mustang "growl" and was still loud. Also, the inevitable check engine light is on now so when I get this changed out I need to get the light reset, right? Or should it go off on its own? And I'm running x pipe and 40 series flowmasters. Hoping someone reads this that has gone from no cats to high flow.
I'm running o/r H and I ordered high flow cats from AM last week. I'll be putting them on this weekend, I'll explain why and post videos of before and after.
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Old 08-20-2012, 08:03 AM   #17
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Oh so you have a h pipe?? Okay so that wont sound too bad!
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Old 08-20-2012, 05:38 PM   #18
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Originally Posted by Jake
It probably is the x pipe, but i thought i read that you have an x pipe?? So if you have an x pipe with high flow cats it will be raspy. He ran x pipe with high flow cats for about a month before he put the muffler deletes on. And dont get me wrong, im not saying it sounds bad at all. His car sounds sick, but it is raspy! If you want deep and throaty go h pipe
Thanks I probably will. I'm learning a lot about exhaust here lately. Just came from a 350z that I didn't care as much about sound but I wanna get the best sound out of the stang.
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Old 08-20-2012, 05:47 PM   #19
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Re: No Cats vs High Flow Cats

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Originally Posted by dPayne003 View Post
Yeah might have something to do with the muffler deletes on your friend's. Heard that sounds horrible on our cars. All I know is with cats it wasn't raspy but now it is raspy with the same setup just minus the cats. Just trying to find out if high flows will sound way better than stock cats or if I would be wasting my money.
Why dont you just knock out the guts of the cat,,and put it back on,,that way you will have visual..From the outside it looks like you have the cats..If you get a tuner ,,you can turn off your back o2 sensors and the engine light will go out
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Old 08-20-2012, 05:59 PM   #20
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Yeaa man i would just say rip everything out and put the case around the pipe and clamp them on for inspection then rip them off oooo amd i just got an h pipe no cat with flowmaster 10 series and they sound great soo i would stay with ur set up and get it tuned
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Old 08-20-2012, 08:54 PM   #21
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Quote:
Originally Posted by dPayne003

Henry county

---------- Post added at 12:06 AM ---------- Previous post was at 12:02 AM ----------



I didn't catch that in your first message, sorry. I'm now learning the x pipe is causing rasp. The little rasp it has doesn't sound bad. I'm not all that worried about that. Just worried about if the exhaust is gonna sound just like it did with stock cats or if it's still gonna have a pretty good sound like it does now.
+1 its the x pipe
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Old 08-21-2012, 01:57 AM   #22
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I don't like the way off road x pipes sound on 3vs personally I have an h n the garage I'm getting ready to put on... and high flow cat is the way to go... less hassle for inspection time... I lucked out this year but no telling what's to come
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Old 08-21-2012, 03:04 AM   #23
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Re: No Cats vs High Flow Cats

Taking the cats off then installing a smaller pipe for "back pressure" was a complete waste of time. You defeated the main purpose of removing the cats in the first place and you don't need the back pressure. That's an old myth that has been dis-proven many times over the years. (Unless these newer cars need to sense that somehow?)

Gutting the cats is not a good idea either. You end up creating an "expansion chamber" that makes them sound like crap IMO. If you need to leave a visual representation, the best thing to do is to remove the guts and run a pipe straight through the cat, welding it up to look unmolested.

Otherwise just replace them with some high flow cats and carry on.
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Old 08-21-2012, 03:23 AM   #24
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Exactly what trojan said. You can find many articles on this. Where the myth comes from is. If you get real crazy on the size of the pipe, you may lose some low end torque. But removing cats and stepping up a size definitely is not gonna hurt you. Why do you think race cars have no mufflers and large diameter exhaust. Even with to large of an exhaust you will still have higher hp gains but may lose a little low end torque. But even this can be tuned for.

I recently read something about this dude that had a high 9 second fox. He used 3 1/2" exhaust at the track. But since it was so loud , to quiet it down he put on 2 1/2. He lost (I don't remember the exact amount) but somewhere from 1/2-1 second in his 1/4 mile time.
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Old 08-21-2012, 07:45 AM   #25
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Originally Posted by Silversky545
I don't like the way off road x pipes sound on 3vs personally I have an h n the garage I'm getting ready to put on... and high flow cat is the way to go... less hassle for inspection time... I lucked out this year but no telling what's to come
I agree, im glad i dont have inspection here so i can run offroad h pipe!
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Old 08-21-2012, 09:45 PM   #26
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Re: No Cats vs High Flow Cats

I plan to keep the cats on my GT the few HP I will lose is not worth the bother come time for inspection The Cated X pipe I like is the BBK they use 2 3/4 "pipe insted of
2 1/2" all the other major brand X pipes use. The larger pipe and cats should flow a little better maybe not as good as a catless 2 1/2" X pipe but better then a 2 1/2 " X with cats
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Old 08-21-2012, 09:58 PM   #27
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05 gt stick with the cats off.. Sounds nice and a tad bit more hp. You just gotta buy the right stuff... (that fakes the computer for the emissions test)
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Old 08-22-2012, 11:04 PM   #28
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Thank god I live in Walton county! Lol
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Old 08-22-2012, 11:16 PM   #29
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You'll need the tuner for the cel... Mil eliminators are for previous years I believe... Someone will correct me if I'm wrong
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Old 08-23-2012, 02:23 AM   #30
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I'm running a high flow cat x pipe with Long tubes and stingers in the back and it sounds sweet, not too loud, not too quiet and definitely not raspy.
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Old 08-30-2012, 07:55 PM   #31
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Re: No Cats vs High Flow Cats

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Originally Posted by Jake View Post
Well me and my friend, he has 06 i have 07, have the same axlebacks, both have cai and tuned. He has high flow cats and x pipe, i have h pipe with no cats. My car is loud, deep, and throaty, his is very loud and very raspy. Im not comparing through a video im telling you exactly what i hear in person. But ya know i may be just stupid.
X pipes produce a raspier sound H pipe is deeper.
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Old 08-30-2012, 08:09 PM   #32
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X pipes produce a raspier sound H pipe is deeper.
Exactly what i said
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Old 08-30-2012, 08:30 PM   #33
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Even with cats on an x pipe don't you still get a little hp gain vs stock exhaust
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Old 08-30-2012, 08:56 PM   #34
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Even with cats on an x pipe don't you still get a little hp gain vs stock exhaust
Yes, with cats on a x pipe you will still see gains because stock is a very restrictive h pipe with cats, so the x pipe with cats will flow much better. Now an aftermarket or h pipe you will see good gain too
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