Cats or no cats

MPScott1 · Jul 13, 2009

Will taking off my catalytic converters make my exhaust louder? I know it is illegal in some states, i just want to know if the exhaust will get louder.

Pokageek · Jul 13, 2009

Yes. A LOT.

BlackVert · Jul 13, 2009

removing them will also make your exhaust smell like a lawn mower's exhaust

302GTS · Jul 13, 2009

Before putting on my Flowmasters, I had just a BBK o/r x-pipe with stock catback on my car. It was louder, but not obnoxiously loud. It's actually very tame. It gets loud if you go WOT and at around 2,200 rpms it starts to get a nice raspy growl to it, but at idle and at normal cruising rpms it's really not bad at all. And yes, it does make it stink.

Pokageek · Jul 13, 2009

I hate it...the stink and the noise that is. The car can sound really good without being super loud and stinky-ous. The z06 or Cobra and many other sports cars put out boatloads of power without attracting negative attention, cops and waking everyone up - why can't we.. The trouble is, I have yet to see ANY tests showing results in terms of rwhp loss from no cats TO---> HIGH flow cats like that old muffler decibel shootout chart we once had. I cannot find any companies to tell me which is amazing since they sell untested products! So at the same time, who wants to plug up 30rwhp!

302GTS · Jul 13, 2009

Pokageek said:
I hate it...the stink and the noise that is. The car can sound really good without being super loud and stinky-ous. The z06 or Cobra and many other sports cars put out boatloads of power without attracting negative attention, cops and waking everyone up - why can't we.. The trouble is, I have yet to see ANY tests showing results in terms of rwhp loss from no cats TO---> HIGH flow cats like that old muffler decibel shootout chart we once had. I cannot find any companies to tell me which is amazing since they sell untested products! So at the same time, who wants to plug up 30rwhp!

I personally can't feel any life altering difference after putting my offroad exhaust on, but I havn't had any track times yet to compare to my times with stock exhaust. I'll be sure to update anyone wondering though next time I hit the track. As for my exhaust though it's really not as loud as I'd have imagined. Put it this way, my old 4 cylinder Ranger ran with no muffler on it for a month, just the 2 cats that were on it stock, and it was louder than my Mustang was with stock catback and o/r x-pipe.

turbogt · Jul 13, 2009

302GTS said:
I personally can't feel any life altering difference after putting my offroad exhaust on, but I havn't had any track times yet to compare to my times with stock exhaust. I'll be sure to update anyone wondering though next time I hit the track. As for my exhaust though it's really not as loud as I'd have imagined. Put it this way, my old 4 cylinder Ranger ran with no muffler on it for a month, just the 2 cats that were on it stock, and it was louder than my Mustang was with stock catback and o/r x-pipe.

Off road mid-pipe plus any aftermarket catback= LOUD

302GTS · Jul 13, 2009

turbogt said:
Off road mid-pipe plus any aftermarket catback= LOUD

With a catback, definitely true! An o/r x-pipe with Flows behind it are enough to wake the neighbors any bright and sunny Monday morning.

Venom351R · Jul 13, 2009

Mine was pull me over and arrest me loud w/ an O/R H pipe so I put a catted X pipe on and it sounds 100X better

final5-0 · Jul 13, 2009

How about I throw up a fork in the road of our discussion

For now ... lets get off the path of ... Sound
and
Travel down the road of ... Performance

Yes ... the OEM 4 cat mid pipe is VERY restrictive
but
A set of cats built for high flow/volume will hold you back very little

Just wanted to offer a thought about a different option

Grady

Pokageek · Jul 13, 2009

final5-0 said:
How about I throw up a fork in the road of our discussion

For now ... lets get off the path of ... Sound
and
Travel down the road of ... Performance

Yes ... the OEM 4 cat mid pipe is VERY restrictive
but
A set of cats built for high flow/volume will hold you back very little

Just wanted to offer a thought about a different option

Grady

Thanks Grady but I am looking for specific evidence of this for high rwhp combos. Anyone who can find this pm me. Not that this statement is - but when I put universal cats on my car, it killed the HP so bad it was ridiculous. Sorry I just realized I am :OT:

nmcgrawj · Jul 14, 2009

U guys arent using good gas if your exhaust smells like a lawn mower

I like the smell of gas.....not in the cabin though. Which is why i dont care for dumps. But at car shows....races....premium gas and turbo blue smell like heaven to me

Pokageek said:
Thanks Grady but I am looking for specific evidence of this for high rwhp combos. Anyone who can find this pm me. Not that this statement is - but when I put universal cats on my car, it killed the HP so bad it was ridiculous. Sorry I just realized I am :OT:

What cats are you using? Not every universal cat is created equal.

On N/A applications i have always thought the exhaust is a minor part in comparison to other stuff in the big picture compared to say, turbo'd motors. So if u are losing 30rwhp, i'd guess that it was extremely restrictive. I mean, what do u gain if u put on a set of 40 series flows, compared to running bassani/dynomax/magnaflow straight through (less restrictive) mufflers?

I've never heard of a 450rwhp N/A car gaining/losing 30rwhp over flowmaster mufflers. I HAVE heard of it on a turbo car. So that just makes me guess that those cats you have suck and dont flow worth a crap.

You brought up cobras and vettes....why not get a vette replacement cat, or cobra replacement cat, and compare the structure?

Or pay the money for a quality cat that flows well. I havent been up there in the high HP set ups but have u spent time on Z06 boards? There's gotta be answers out there somewhere.....

final5-0 · Jul 14, 2009

Pokageek said:
Thanks Grady but I am looking for specific evidence of this for high rwhp combos. Anyone who can find this pm me. Not that this statement is - but when I put universal cats on my car, it killed the HP so bad it was ridiculous. Sorry I just realized I am :OT:

Sorry

I should'a been a bit more specific

I was NOT thinking about anything more than OEM block NA bolt-on or h/c/i

Sure ... the % is gonna be higher on a higher hp combo

Grady

Pokageek · Jul 14, 2009

Darn, lol. I was hoping you were going to come back with some charts or something. I mean that in a good way tho. Many times you find what we are looking for.

revhead347 · Jul 14, 2009

Removing your cats is illegal in all states. The EPA restricts the removal of emission control devices on the federal level.

Taking your cats off makes a huge difference. You can put the best flowing cat in the world on your car, and it still takes all the throttle response out of it. I've never really had a Mustang with cats on it for a long time, but I remember the day I took them off this car it was night and day.

Kurt

MPScott1 · Jul 15, 2009

Thanks for all the responses, it seems like a majority say better with o/r x-pipe. The main reason i want them off is i think they might be clogged anyway.

Pokageek · Jul 15, 2009

MPScott1 said:
Thanks for all the responses, it seems like a majority say better with o/r x-pipe. The main reason i want them off is i think they might be clogged anyway.

Not sure what you mean by better. Your OQ was will it make it louder. If louder is better then yes.

desertcox05 · Jul 15, 2009

as a bit of a added plus. when I added my offroad h, I picked up about 1-2 mpg.

302GTS · Jul 15, 2009

desertcox05 said:
as a bit of a added plus. when I added my offroad h, I picked up about 1-2 mpg.

I picked up 1, maybe 2 mpgs with my exhaust on. Remember though, that doesn't mean you can go WOT and pick up some mpgs. It's all about how you drive your car. Personally, I shift at 2-2,300 rpms and run cruise control anytime I possibly can, and I end up usually with around 18 mpg in the city.

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