2005MustangGT

After months of searching for an off road h-pipe, I finally broke down and did it my self. Instead of removing the cats all together, I just knocked out the inside and reinstalled them. It sounds just like the older body Mustangs now. It only took 1hr and 15 minutes from start to finish. The sound is incredible, I already had Flowmaster 40 series mufflers, but it wasn't loud enough, it only gave the car a different tone.
The car is a whole lot louder now on the outside, but still quiet enough on the inside to be a daily driver....probably b/c the mufflers are at the back on this model.
-just figured I would let everyone know about this, and it didn't cost one dime.
-no check engine light either (yet)!!!

LilHog

Can you explain how you gutted them? And how about performance, any loss in power?

Retro GT

"Yet" is the key word. Your SES light will soon be turning on with a couple of possible faults. I would bet that you will set a 'Catalyst efficiency failure". If the Engine Computer doesn't see a difference between the upstream oxygen sensor and the downstream oxygen sensor, it knows that Catalyst isn't doing its job and will turn the light on. Sorry to be the bearer of bad news.

2005MustangGT

Oh well, by the way, I don't think I've ever had a Mustang that had a Catalytic Converter doing it's job, b/c I've never had a mustang w/ catalytic converters..... I've owned over 10 Mustangs, so I'm used to all of my mustangs having check engine lights on, as for power, you can't tell a difference, I'm sure it will need to be reflashed for any power increase, but the sound is so much better...it's what I'm used to hearing from a mustang.
-as for how to hollow out the cats, all you have to do is remove the h-pipe and use a tire iron or long hard object that will fit into the opening and break up the inside and start dumping it out, it took about 30 minutes to do, i used a jack handle to break up the inside of the cats, you will also need a pair of needle nose pliers to pull out a metallic like fabric that is in there,
-there is nothing to it, simple hour long job.

S197 GT

Any sound files Bucky??

Also, I live in CA and I know that's definately illegal. Are there any physical signs that your cats have been punched?

Mongoose

Oh my goodness. One of these days you are in for it. Not only are you in violation of federal law but here you are confessing to the whole thing It is going to cost mega bucks to replace them when you are caught.

2005MustangGT

there are no physical signs that they are hollow now, just louder....but you won't pass an emissions test this way.

LordBritish

I live in California so this would be a no, no.

If u live in state without emissions tests then it might be ok but think about the environment !!!

Stang281

Never thought i'd hear Mustang owners talking about the environment.

LordBritish

Come to L.A. and you'll know what I'm talking about.

Stang281

My brother's been, said the smog was horrible.

HOTLAP

And thanks to stricter vehicle emissions regulations/testing the air is cleaner than it was 25 years ago - despite there being more people here.....

05stangkc

FYI The replacement Cats are $1648.33 MSRP

KC

acadian

You won't have to replace them with stock. I live in Louisiana where are no emissions testing and was thinking about doing this... if there are ever tests, then you can easily buy an aftermarket catted X or H pipe for 2 or 3 hundred bucks. You'd have to spend that much to get an off-road mid pipe anyway. So, it's not too bad of an idea. I think thouhg, after plenty of thought, that I'll actually be patient for once and wait until Magnaflow comes out with their off-road x-pipe, or spend the money on a MAC pro-chamber off-road. That way, I'll have the stock one to throw on in case.

RRRoamer

I'm with you acadian. I'm all for improved power and if I can keep the car "clean" at the same time, great! I can't wait until we see a couple of consumer dyno tests of the Magnaflow hi-flow cat x-pipe. If the results hold up under the light of consumer testing, this might be the perfect foundation for a very quick NA car.

I think I need to start working a second job so I can save up for hop ups....

2005MustangGT

i was with you too at first acadian, I was planning on keeping the stock h-pipe incase they ever start testing around here, but It's been 4 1/2 long months w/ a quiet mustang, I'm not use to that. plus i figure if they ever start testing around here it will be years away and you should be able to pick up a stock h-pipe on ebay for less than 100 bucks

acadian

Yep, you are right. If I do wait though, it's not even about waiting for Magnaflow or someone to come out with a decent priced non-catted mid pipe, but I gotta save up for it too. So, it might be a while. I may very well break down and core out the stock cats. I have a question for you though, Bucky... did you use a socket wrench to get the nuts off of the bolts connecting the cats to the headers? I was down under the car yesterday just to see exactly what was involved with this, and I didn't have a long socket that fit the nuts up there by the headers. Not to mention, it looks really tight up there. Did you just use a socket wrench with a long socket, and if so what size socket was it? My socket set is pretty basic, but I don't want to have to go out and buy a whole set if you happen to know what size it is. I can just get a single socket from the hardware store if I decide to do this one day.

And by the way, how much louder is it exacty? Are we talking a good bit, or just something noticeable?

2005MustangGT

Oh yeah, It is a "GOOD BIT" louder, but not rediculously loud.
-all of the bolts/nuts are 15mm, I used a deep well 15mm socket w/ 2 12" extensions to get to the header flange bolts
-this is definitely the easiest Mustang H-pipe I've ever taken off before.

acadian

Thanks a lot, Bucky. I think I'll swing by the hardware store and get a 15mm deep socket. I might just do this afterall.

2005MustangGT

the sound was well worth the money, wait i didn't spend a dime, that's what makes it better....LOL
-let me know how it goes, and if you have any questions