pros and cons on removing cats

Running no cats especially with a rich tune (supercharger, etc) will almost guarantee a strong odor. I've run several applications (stangs, vettes) with dyno tunes by some of the best tuners and always got a rather strong odor especially at idle. Ever been behind a car at a stop light with an obnoxious odor? Probably catless. Stay behind it long enough and you'll be changing your clothes. One of the very top tuners in the midwest will tell you that going in. He recommends against it.

that's what I thought.. it has to smell.. its logic

Aerofinz said:

Running no cats especially with a rich tune (supercharger, etc) will almost guarantee a strong odor. I've run several applications (stangs, vettes) with dyno tunes by some of the best tuners and always got a rather strong odor especially at idle. Ever been behind a car at a stop light with an obnoxious odor? Probably catless. Stay behind it long enough and you'll be changing your clothes. One of the very top tuners in the midwest will tell you that going in. He recommends against it.

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I like that smell, reminds me of the old days with dad filling up the Chevelle. If you're worried about drone you can always mid-mount some resonators or smaller straight through mufflers. I would stagger them a bit too, but I didn't. I also don't tend to keep the rpm's ever below about 2300 so I don't get into that drone zone very much.




I mounted mine right before the axle.

Did that really help the drone? Did it make the exhaust a bit quieter? I've been thinking about doing this to mine to reduce the drone and make it a bit quieter.

MrAwesome987 said:

Did that really help the drone? Did it make the exhaust a bit quieter? I've been thinking about doing this to mine to reduce the drone and make it a bit quieter.

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Yes, but it didn't eliminate it. I think it would have done better if I staggered them a bit. It did not make it noticeably quieter but it did change up the tone. Made it a little more refined and less raw. I've seen guys mid-mount stingers on there with good success also.

I get rid of drone by down shifting and giving it more throttle. But it's usually not an issue as my transmission shift points are set pretty high.

07 Boss said:

I like that smell, reminds me of the old days with dad filling up the Chevelle. If you're worried about drone you can always mid-mount some resonators or smaller straight through mufflers. I would stagger them a bit too, but I didn't. I also don't tend to keep the rpm's ever below about 2300 so I don't get into that drone zone very much.




I mounted mine right before the axle.

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I mounted my pair of 304 stainless Pypes M80's ( $52 at AM) just before the axle, welded in, (oem clamping flanges cut off in bandsaw) identical to your setup. Drone @ 1900 rpm is still there... but WAY down from b4. Exhaust note went to a lower pitch. I didn't stagger mine either.

The story I got on cherry bombs, (on their site) is that they use.... 'aluminized steel'... which is a concoction of steel + aluminum alloy. Local mustang buddy had an old dodge super bee ( hot rod version of a coronet) with a 440 magnum... and LT's. He welded in a pair of cherry bombs..right at the ends of the LT's. Red paint burnt off, then the insides burnt out in < 3 weeks !

What mufflers do you have Pentalab?

If you have access to alcohol-free premium, the smell really is like the old time muscle cars. My S197 had Flowtech Red Hots on it- without cats there was some drone but man it sounded sweet! I ended up combining the Red Hots as resonators and using MBRP axle backs- the tone was great. A little too quiet, but zero drone. My experience was that even though a measurable HP increase is gained by removing the cats, unless you combine that with other mods you won't really feel a difference.

MrAwesome987 said:

What mufflers do you have Pentalab?

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FRPP ... FRS-500's. On my 2010, the FRS-500's have 3.5" OD tips that are 1" longer, vs the 05-09 FRS-500.
The FRS-500's sounded superb, zero drone. That all changed when I had the JBA 'titanium ceramic coated' LT's installed.... + mating JBA catted H section. (1 5/8" primaries, 2.5" collector) The hi flow cats were apparently what was causing the exhaust to then have bad drone.. + WAY too loud !
Got busted by local cop (who pulled a gun on me for getting out of the car) for speeding. He was also gonna impound the car for.."too loud". I had mashed it, going through an intersection. Stupid loud... so in went the pair of M80's... problem solved.

BTW... the old '5.0' magazine tested ad nauseum, no cats vs 'hi-flow cats', with all tests done between 2-6 krpm. ( S197 4.6L) and at most their was a 0-2 hp difference across the rpm range. Sometimes 1-2 hp in favor of no cats...sometimes 1-2 hp in favor of hi-flow cats. 75% of the time, there was no difference between the two.

But there would be more of a difference between high-flow cats / no cats.... vs OEM cat's. Hi- flow cats are typ 4" OD..and really short vs OEM cats..which are a lot smaller diameter..and a lot longer.

Macman45 said:

Finished as in no good? I removed mine years ago and love it. It's LOUD but I enjoy it. Probably 8ish HP, not a ton. You will need a good tune or MIL eliminators or you'll have a Check Engine for the O2 sensor. Smell is not bad at all I dont think, you cant smell it in the car and have to be behind it for awhile to notice

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You'll need for a tuner to turn off the rear 02 sensors in the calibration tune or install a pair of spark plug non-foulers in the rear 02 sensor ports. Mil eliminators will not work on 2005-10 S197 models due to the Spanish Oak ECM.

MrAwesome987 said:

Mine is MUCH louder without the cats, and it does smell a bit at stop lights, but its not that big a deal to me. The power gain is negligible. The most annoying part for me was the CEL was on for the o2 sensors. Beware, bama and other email tuners won't disable the CEL (although they can, they just won't). I ended up living with the CEL for months until I got the car dyno tuned.

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You may want to consider Brenspeed. I know when I ran their off-road tunes, they turned the rear 02 sensors off in the tune, but I don't know if they still do or not? So you may want to check with them just to make certain. You could also find out if Lito turns off the rear 02 sensors in his tunes as well.

MrAwesome987 said:

Also, the exhaust is much raspier without cats.

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If running an X crossover without cats? most definitely much raspier. An off-road H, not so much. When I ran an off-road Prochamber, there was no raspiness at all but does smooth out the exhaust pulses and provides a more refined, deeper sound.

RLF9409 said:

I had to put cats back on mine. It was to raspy and created a trumpting around 2k rpm that i couldn't stand. Also I hated the smell of exhaust on my clothes after driving.

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Are you running an X or H crossover? If you're running an off-road X mid pipe? they're well known for being raspy and trumpeting. Off-Road H crossovers have deeper, lower tones. As for the smell, make sure you're 02 sensors are secured tightly, otherwise, you will get exhaust fumes inside the cabin when at traffic lights, stop signs when at idle.

Pentalab said:

Is it true that Montreal is the pot hole capital of North America ?

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I can't speak from personal experience about Montreal, however, when it comes to the U.S, Pittsburgh is considered pot-hole capital U.S.A lol.

Aerofinz said:

Running no cats especially with a rich tune (supercharger, etc) will almost guarantee a strong odor. I've run several applications (stangs, vettes) with dyno tunes by some of the best tuners and always got a rather strong odor especially at idle. Ever been behind a car at a stop light with an obnoxious odor? Probably catless. Stay behind it long enough and you'll be changing your clothes. One of the very top tuners in the midwest will tell you that going in. He recommends against it.

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After finding out that one of my rear 02 sensors was responsible for the exhaust odors from being loose, I didn't notice any more smell from my O/R ProChamber setup after tightening up the rear 02 sensor. I did notice however on a few occasions smelling strong odors from being behind a car at a stop light in which I could tell right off the bat was running catless lol.

sc517hp said:

If you have access to alcohol-free premium, the smell really is like the old time muscle cars.

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Local Chevron sells 94 octane..with NO ethanol. Buddy was behind me in his truck..and told me he could smell it... when I mashed it, with blower on. (AFR is 11.7 with blower on.... 14.4 in NA mode). Nobody has ever said that before...or since. I don't smell anything inside the car, with windows down... nor idling, and going to back of car. Been using the same 94 octane...sans ethanol since 2011.

Raspy and way too loud exhaust, and the smell bothered me at the lights or in traffic. Put my high flows back on after couple weeks.

Lito will shut off rear O2 sensors. VMP et all, won't.

Johnstone said:

I even had put wool in the trunk under the spare tire.. surprisingly helped. the Borlas I got are grea, nice deep tone but at low rpms they resonate a little.. but hey it's a mustang not a Cadillac lol

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I finally got around to having the Pypes cut n clamp X pipe installed to the OEM cats along with the Borla ATAK mufflers. The good news, the ATAK mufflers are quiet at idle, but really come alive under part and WOT. The bad news, however, there is still noticeable drone, but only when the engine is under load and at low RPM's when driving around town. Other than that, once I'm above 60-65 MPH on the interstate, it goes away altogether. That being said, the Borla's sound much better overall since replacing the cut n clamp ProChamber with the Pypes after cat mid X pipe. Needless to say, now I can finally tolerate the amount of drone which is no longer all that bad since making the mid-pipe crossover switch. I'll also try out the wool in the trunk under the spare tire trick and find out how well it helps out as well

Screamin_dutch said:

Raspy and way too loud exhaust, and the smell bothered me at the lights or in traffic. Put my high flows back on after couple weeks.

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Are you running an off-road H or off-road X pipe? Also, do high-flow cats really make a noticeable difference with rasp, exhaust loudness and reducing exhaust fume smell?

nice. let me know.

06 T-RED S/C GT said:

I finally got around to having the Pypes cut n clamp X pipe installed to the OEM cats along with the Borla ATAK mufflers. The good news, the ATAK mufflers are quiet at idle, but really come alive under part and WOT. The bad news, however, there is still noticeable drone, but only when the engine is under load and at low RPM's when driving around town. Other than that, once I'm above 60-65 MPH on the interstate, it goes away altogether. That being said, the Borla's sound much better overall since replacing the cut n clamp ProChamber with the Pypes after cat mid X pipe. Needless to say, now I can finally tolerate the amount of drone which is no longer all that bad since making the mid-pipe crossover switch. I'll also try out the wool in the trunk under the spare tire trick and find out how well it helps out as well

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I most definitely will. Btw: is the wool you have in the trunk steel wool or as in yarn wool? Just want to make certain we're on the same page lol.

the one used to insulate walls. I did some Reno's at home and had some left over

06 T-RED S/C GT said:

I most definitely will. Btw: is the wool you have in the trunk steel wool or as in yarn wool? Just want to make certain we're on the same page lol.

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So do you mean Owens Corning Fiberglass which is used to insulate interior walls? I also wanted to give a heads up that you're Borla Touring mufflers are the quietest mufflers in the Borla exhaust line-up. Therefore if you're looking to get more volume/sound from the Touring mufflers, you'll need to either go catless which is going to increase the amount of exhaust smell or consider a high-flow catted mid-pipe from either Magnaflow, Pypes Performance Exhaust or Bassani.

If your not old enough to remember the days before catalytic convertors that entailed bad smell and possible carbon monoxide poisoning, you should read this first. https://www.abe.iastate.edu/extension-and-outreach/carbon-monoxide-poisoning-vehicles-aen-208/
Cat convertors are not only for the environment but for yours and others safety. Same goes for removal of lead from gasoline in the 70's.

yea they're not the loudest. I can of like them though.

06 T-RED S/C GT said:

So you mean Owens Corning Fiberglass which is used to insulate interior walls? I also wanted to give a heads up that you're Borla Touring mufflers are the quietest mufflers in the Borla exhaust line-up. Therefore if you're looking to get more volume/sound from the Touring mufflers, you'll need to either go catless which is going to increase the amount of exhaust smell or consider a high-flow catted mid-pipe from either Magnaflow, Pypes Performance Exhaust or Bassani.

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