Rear Cat Delete

[SC Cheesehead]

I know that deleting the rear cats is typical exhaust system mod, but is there any real benefit other than sound?

Will deleting them result in increased HP? Getting ready to do my exhaust work, and I'm on the fence about the rear cats. I actually prefer a quieter car, and if I'm not going to see increased power from deleting the cats, I may just opt to leave 'em on, as I've got res-delete tips installed and don't want to up the db level substantially.

[musclemerc]

Cheesehead check out some of my old exhaust threads.

Your doing the FRPP's right?

If yes then you need to get a 99~04 Mustang downpipe **YOU CANNOT USE A MM DOWNPIPE ON THE SHORTY HEADERS**. Either Stock Cobra, H, X, or Prochamber, these will be 2-1/2" dia. pipes. Even if you get a stock Cobra pipe they have high flows on it from the factory, if you want to go with one of the others then get an "off road" setup and order a set of Magnaflow High flow cats *pm me for some info* Adding the high flows to an off road pipe will make up the diffrence in the length needed to connect to the stock mufflers.

[Blackened300a]

I know that deleting the rear cats is typical exhaust system mod, but is there any real benefit other than sound?

Will deleting them result in increased HP? Getting ready to do my exhaust work, and I'm on the fence about the rear cats. I actually prefer a quieter car, and if I'm not going to see increased power from deleting the cats, I may just opt to leave 'em on, as I've got res-delete tips installed and don't want to up the db level substantially.


I didn't notice too much of a power increase, but the sound increase may make you regret this mod if you prefer a quieter car.
GWLDJ-WUQZI

[SC Cheesehead]

Cheesehead check out some of my old exhaust threads.

Your doing the FRPP's right?

If yes then you need to get a 99~04 Mustang downpipe **YOU CANNOT USE A MM DOWNPIPE ON THE SHORTY HEADERS**. Either Stock Cobra, H, X, or Prochamber, these will be 2-1/2" dia. pipes. Even if you get a stock Cobra pipe they have high flows on it from the factory, if you want to go with one of the others then get an "off road" setup and order a set of Magnaflow High flow cats *pm me for some info* Adding the high flows to an off road pipe will make up the diffrence in the length needed to connect to the stock mufflers.

Yup, doing the FRPP shorty headers, and have already worked through the details back through the mufflers. I have the Magnaflow front cats already, and the installer's probably going to go with a custom fab for the downpipes. Only thing I'm iffy on is the rear cat delete. If there's not a HP increase to be gained by deleting them, I'll most likely leave them in place to keep the noise down.

[Marauderman]

Yup, doing the FRPP shorty headers, and have already worked through the details back through the mufflers. I have the Magnaflow front cats already, and the installer's probably going to go with a custom fab for the downpipes. Only thing I'm iffy on is the rear cat delete. If there's not a HP increase to be gained by deleting them, I'll most likely leave them in place to keep the noise down.

Your too doubtful to take them out--so leave them on -you can always do it later if you want--or after driving someone else's like it-----enjoy!

[LANDY]

if you want a quiet exhaust use your shortys, high flow cats, magnaflow integraded x-pipe in muffler, then 18 magnaflow and dont delete the resonator on the tips. you wont regret it.

[justbob]

Or do like me and have two sets of downpipes:P Actually, I missed diagnosed my car thinking I had plugged cats when in reality it was numerous coils AND a fuel pump on the way out. ( I truly hate when dealing with two problems at once, especially sporatic ones!!!!)I had allready removed the rear cats in the stockers and Travis bent over backwards to help me when in need and jobless! He gave me a deal of a lifetime that I will never forget..:beer:
Anyways, after instalation, the car ran better indeed, untill my issues came back....

So now I rotate out downpipes every few months depending on what mood i'm in:)

Thanks again T!!!!

[musclemerc]

Very cool Bob, Rex, your gonna be hard to catch with all the work you've gotten done.

Great Job Guy's!

[fastblackmerc]

If you want a quiet exhaust then don't change the stock setup.

Delete the 4 cats and replace them with 2 hi flo cats, increase in sound, increase in HP, increase in mpg since the factory cats are a restriction in the system.

[youngrauderlvr]

where are you going to get them done?

[BODYMAN]

Rex my 03 300A has sw LT's 1 set of cats delete rest stock It is amazingly quite and it still makes 500 to the rear. I got cutouts and when opened on dyno I lost 2lbs TQ and gained 1HP. So anyone telling you are stock stuff is restrictive its not atleast with one set of cats gone. I could for sure see were all 4 cats could restrict gotta go thru 2 on each side. On my SB when it gets built the exhaust will remain stock after cats w/ Kooks & Ill be well over 500.

[ImpalaSlayer]

If you want a quiet exhaust then don't change the stock setup.

Delete the 4 cats and replace them with 2 hi flo cats, increase in sound, increase in HP, increase in mpg since the factory cats are a restriction in the system.

i agree. going from my retardedly loud car to Rexs almost silent car it was way more fun to hear the blower then the exhaust. i didnt even know the eatons have a bit of whine to them at idle because my car is so loud

Rex, i wouldnt change a damn thing on that car but thats just me

[BODYMAN]

Yeah its actually nice when quiter. The blower is for sure more pronounced not to metion the camaro sitting at a light next to you & then you smoke him. Its also better in the fact at no time are you dealing with drone

[SC Cheesehead]

i agree. going from my retardedly loud car to Rexs almost silent car it was way more fun to hear the blower then the exhaust. i didnt even know the eatons have a bit of whine to them at idle because my car is so loud

Rex, i wouldnt change a damn thing on that car but thats just me


Yeah its actually nice when quiter. The blower is for sure more pronounced not to metion the camaro sitting at a light next to you & then you smoke him. Its also better in the fact at no time are you dealing with drone

Well, I want to get the headers on the car, so the more I think about it, will prolly just go shorty's, H pipe, and high flow cats into the stock mufflers and leave the rest as-is.

You're right about the blower whine, one of my favorite things about the Eaton... :D

[justbob]

This is going to cost you well.............
http://i300.photobucket.com/albums/nn19/marauding4life/1105101245.jpg


You were warned.

[babbage]

if you want a quiet exhaust use your shortys, high flow cats, magnaflow integraded x-pipe in muffler, then 18 magnaflow and dont delete the resonator on the tips. you wont regret it.

This is what I have now. And it's quiet. It should get a "touch" louder with my SW LT's - Dynomax super turbo mufflers flow well and are quiet. My K&N intake can easily be heard however. ;)

[DOOM]

Rex the short answer is YES!

Deleting the rear cats will gain you more HP.

BUT it's a minimal gain. (about 5hp)

[Mr. Man]

As long as your spending money Rexie scrap the shorties as you are driving a DPB and your top end is non-existant.;) Get LT's, free flo cats and 2 1/2 pipes w/ 3 1/2" tips and if you want quiet get a muffler with lots of chambers. X pipe for flow, H pipe for sound.:beatnik:

[ImpalaSlayer]

As long as your spending money Rexie scrap the shorties as you are driving a DPB and your top end is non-existant.;) Get LT's, free flo cats and 2 1/2 pipes w/ 3 1/2" tips and if you want quiet get a muffler with lots of chambers. X pipe for flow, H pipe for sound.:beatnik:


**** LTs, not worth the pain in the ass if you work on your own stuff. specialy if you are blown. ill never buy another set for anything i own

[SC Cheesehead]

As long as your spending money Rexie scrap the shorties as you are driving a DPB and your top end is non-existant.;) Get LT's, free flo cats and 2 1/2 pipes w/ 3 1/2" tips and if you want quiet get a muffler with lots of chambers. X pipe for flow, H pipe for sound.:beatnik:

#1 Gotta keep the shortys, Momma's about ready to shut down my bank book for mods (well, at least for this go-round ;))

#2 :razz:

#3 See Davie's comments about LT's. He's the MAN, and if he sez nope to LT's then I sez nope to LT's.

[ImpalaSlayer]

#1 Gotta keep the shortys, Momma's about ready to shut down my bank book for mods (well, at least for this go-round ;))

#2 :razz:

#3 See Davie's comments about LT's. He's the MAN, and if he sez nope to LT's then I sez nope to LT's.


i wouldnt say all that but hated my lts on my car and my truck, nothing but a pain in the ass

[DOOM]

Might as well get glen in here now!

:popcorn:

[SC Cheesehead]

Might as well get glen in here now!

:popcorn:

Yeah, I was hoping he'd chime in.

[LANDY]

**** LTs, not worth the pain in the ass if you work on your own stuff. specialy if you are blown. ill never buy another set for anything i own are you ok bro? i tought you were part of the LT's family, LOL

[DOOM]

are you ok bro? i tought you were part of the LT's family, LOL

He changes his mind every 2 seconds! :lol:

[ImpalaSlayer]

There's no doubt lts prefor better, no arguing that, its a fact. But when you have a blower on a stock motor that limited to hp what's the point in spending the coin? Rex could go lay down 450 if he wanted to tomorrow

[Vortech347]

Do it! I have no 2nd cats and res tips. Car sounds like it should from the factory. I use it for business and haul clients around all the time. I always get positive comments and never hear anything negative. You don't notice any difference at cruising, just when applying the power.

Deleting rear cats and an intake spacer I picked up 10rwhp 12ft-lbs tq.

[Jesse]

I did that to my car. She really roars!

[SC Cheesehead]

I did that to my car. She really roars!

Don't want roar; want more power while keeping it quiet.

[RR|Suki]

There's no doubt lts prefor better, no arguing that, its a fact. But when you have a blower on a stock motor that limited to hp what's the point in spending the coin? Rex could go lay down 450 if he wanted to tomorrow

Good point. Heck honestly if 450 is the max, that can be done no problem with the stock manifolds.

[SC Cheesehead]

Good point. Heck honestly if 450 is the max, that can be done no problem with the stock manifolds.

I've already got the shorty headers, high flow cats, and a Mac Pro Chamber is on the way. I'm on the fence about deleting the rear cats as I don't want to increase cabin noise substantially

I'm interested to see what HP these mods will add to my current set up. I've got a conservative tune that's putting out 423 rwhp at 11 lbs boost now, and a more aggressive tune in the x-Cal that'll push 430+ easy.

[Blackened300a]

I've already got the shorty headers, high flow cats, and a Mac Pro Chamber is on the way. I'm on the fence about deleting the rear cats as I don't want to increase cabin noise substantially.

Rex, I took the plunge and its louder then I expected. You have 4" non-res tips as well. I don't mind it too much cause I don't drive the car that often. If I drove it all the time, I would put the rear cats back in. For the minimal hp gain, the noise isn't worth it.

[musclemerc]

Hmmm... ;) Sounds like a setup simular to mine. I'm running JBA shorty's, Magnaflow high flow cats, and a Mac Prochamber. My setup is grumbly at idle and throught the rpm range, without any drone. I don't have the deleted tips though.

I think you will be quite pleased when its all done Rex. :burnout:

[Vortech347]

You guys seriously think stock mufflers with no rear cats is loud?

[justbob]

Good point. Heck honestly if 450 is the max, that can be done no problem with the stock manifolds.
Really? No way?:D

[SC Cheesehead]

Rex, I took the plunge and its louder then I expected. You have 4" non-res tips as well. I don't mind it too much cause I don't drive the car that often. If I drove it all the time, I would put the rear cats back in. For the minimal hp gain, the noise isn't worth it.

Thanks for the advice, Paul. You're right about the res-delete tips, and Doomie said about the same thing regarding HP. Think that I'll leave the 2nd set of cats in for now. Can always pull them later if I really I need that extra couple HP.

[Vortech347]

With a higher forced induction car you'll prolly pick up 10 horsepowers... :)

[JOEMERC]

i like to do a rear cat delete but no shops will do it for legal reasons .anyone in philly area willing to do it?

[SC Cheesehead]

i like to do a rear cat delete but no shops will do it for legal reasons .anyone in philly area willing to do it?

PM DOOM, he's in Maryland, but can prolly give you the name of the shop that did his exhaust system (which, IIRC, included a rear cat delete).