Removing Cat guts = Exploding Muffler!

douglas vincent · Post by **douglas vincent** » Mon Jun 16, 2003 3:10 am

So when I gutted the two cats, the car had more power but was louder and now backfired when letting up on the gas. I could live the backfiring, or so I thought.

Today I was up in the mountains and was shooting down a straight away about 90 in third and instead of shifting into fourth, I let up on the gas because the turnoff I wanted was coming up fast.

Now the reason for the backfiring in general most likely is because the extra fuel is getting into the exhaust and not getting burnt in the catalytic converter. Instead it is building up in the exhuast and exploding, ie the backfire.

So this time, it was a big fucking backfire which immediately resulted in a blown exhaust sound. I coasted to a stop and let the car idle. The sound was a low extremely loud rumble. Stepping on the gas was extremely loud. I checked out the whole exhaust from front to rear and could not find the damage. Until I checked the side of the muffler. It was opened up down the crease line (where the top and bottom come together) about 16-20" long and about 2" wide. One big ass resonator now.

The car still ran fine, but I had to drive about 80 miles back home. I am slightly deaf now in the left ear.

Note to self - replace catalytic converter!

JasonGrahn · Post by **JasonGrahn** » Mon Jun 16, 2003 3:31 am

get stronger walled muffler! leave cats out. maybe lean out the car a tad.

Post by **Legacy777** » Mon Jun 16, 2003 2:29 pm

hahaha....sorry.....that was a funny story.

What possibly happened is that some of the cat material got lodged in the muffler and that heated up, causing your backfiring.

I think temps would have dropped sufficiently enough by the time they get to the muffler that they shouldn't ignite the fuel.

paf · Post by **paf** » Mon Jun 16, 2003 5:52 pm

should I gut my cats... just cuz I want to...
I shouldnt have to worry about mvi's cuz this is my last year with this car

subiekid · Post by **subiekid** » Wed Jun 18, 2003 6:28 pm

gut one and see how you like it.

JasonGrahn · Post by **JasonGrahn** » Wed Jun 18, 2003 6:43 pm

no, you SHOULDn't gut your cats. that is against emission regulation laws.. unless of course you canuks dont have those.. then by all means, have at 'em!

teaguespeed · Post by **teaguespeed** » Wed Jun 18, 2003 6:57 pm

how would one go about gutting cats? there are no emmissions tests where i live so it sounds cool. i remember someone saying theres chemicals and stuff in there.

JasonGrahn · Post by **JasonGrahn** » Wed Jun 18, 2003 7:28 pm

plasma torch, pry bar, and some beer.

or get a hacksaw and a broom handle...

There are many different methods, i prefer the plasma torch.

Brat4by4 · Post by **Brat4by4** » Wed Jun 18, 2003 8:38 pm

The muffler you want is a regular old "cherry-bomb" glasspack. Straight-through design, nothing to blow up. And it doesn't sound bad or loud on a NA Subaru engine. I have one on my Brat (EA82) and I love it, no it does NOT sound like a big block with a glasspack.... our engines are much smaller and it makes a cool sound. Call me crazy 'till ya try it

!

georryan · Post by **georryan** » Tue Jul 01, 2003 10:07 am

hahaha nice story....

I had a 74 nova with a 350 back in high school, but right after I got it it started running bad and backfiring. I drove it for a while until I rebuilt the engine just after my senior year. But before that happened, I was on my way to pick up a friend and my car was running exceptionally bad that day. Exhaust felt real restricted, and for the first time it backfired lightly a couple times while I was accelerating.

I wasn't sure at all what was going on and when I'd let off the gas to slow down it sounded like the exhaust was plugged and would be quiet for a bit before it would backfire.

I had just turned onto the main road leaving my neighborhood and came to a stoplight and as I stopped a little geo metro stopped next to me. There was a cute girl in that car and I glanced at her just as my car let off the most defaning crazy loud backfire I've ever heard to this day. It was so loud I litterally jumped in my car and my head hit the roof, I kid you not ( and I don't scare easy). The light turned green and I can say I've never seen a geo take off so fast. haha

I had a big fat circular exaust that was capped at the end with a hole coming off that cap (some big old stock exaust), and had almost blown that capped end off. After that though, the car would set car alarms off in a parking garage.

-Ryan

Redline Dreamz · Post by **Redline Dreamz** » Tue Jul 01, 2003 10:35 am

your car shouldnt be that loud in the first place. You shold be able to run an OPEN downpipe and still be able to drive it w/o too much noise. The turbo alone quiets the exhaust more than any muffler ever could right off the header. Keep it up and youll blow the blades off your exhaust wheel.

vrg3 · Post by **vrg3** » Tue Jul 01, 2003 12:45 pm

Douglas' car isn't a turbo, I don't think.

Post by **Legacy777** » Tue Jul 01, 2003 1:57 pm

No it's not.

Redline Dreamz · Post by **Redline Dreamz** » Wed Jul 02, 2003 7:18 am

o well then hes gonna blow his valve seats and burn holes in his valves. Andys car doesn thave a muffler... sounds mean

970subaru · Post by **970subaru** » Wed Oct 29, 2003 9:05 am

dont think the cat has anything to do with the extra gas. ever seen a flamepipe? lotta people can spit huge flames without blowing anything up.

91White-T · Post by **91White-T** » Wed Oct 29, 2003 4:08 pm

Redline Dreamz wrote: The turbo alone quiets the exhaust more than any muffler ever could right off the header.

I had a turboback straightpipe and it was ridiculously loud, I can't explain just how loud it was, my ears would literally hurt if I opened her up in an underpass, it took less than a month before I got pulled over and had to put a muffler on... now I kinda wish my gutted cat would make it explode...

ShinobiSilver · Post by **ShinobiSilver** » Wed Nov 19, 2003 9:21 pm

georryan wrote:hahaha nice story....

I had a 74 nova with a 350 ....

Lol, My dads 72 nova backfired so loud once that it made a nearby horse jump its fence and run down the road! (which the backfire also blew apart both mufflers)

TurboLegacy · Post by **TurboLegacy** » Tue Mar 02, 2004 5:54 pm

will my exhaust sound level increase significantly if i only hollow out one cat?, will it do this without backfiring a whole lot?. i only want to hollow out one cuz it will be alot easier. thanks

JasonGrahn · Post by **JasonGrahn** » Tue Mar 02, 2004 6:28 pm

TurboLegacy wrote:will my exhaust sound level increase significantly if i only hollow out one cat?, will it do this without backfiring a whole lot?. i only want to hollow out one cuz it will be alot easier. thanks

Wow, welcome to an old thread. But THANK YOU! I'm glad that you have rekindled the discussion instead of starting a new thread.

Hollowing out a cat will cause your sound levels to increase. Your definition of "signicantly" may be different then mine, but I don't think it's too bad.

Post by **DLC** » Tue Mar 02, 2004 7:36 pm

Besides, it's a boxer, and they sounds soooo gooooood...

QuickDrive · Post by **QuickDrive** » Wed Mar 03, 2004 2:37 am

http://quickdraw.dynu.com/sounds/exhaust.wmv

I removed the 2nd cat on the midpipe, replaced it with a flexpipe, and a new muffler = the sound you hear.

Legacytuner · Post by **Legacytuner** » Wed Mar 03, 2004 6:02 am

I once had a 92 lagacy n/a and threw on a 10" glasspack it sounded very similar to the scooby sport system that i have on my 91 turbo

LegacySport4L · Post by **LegacySport4L** » Wed May 05, 2004 1:17 am

Glasspack on my WRX (Both require quicktime):
from inside even at WOT it's relatively tame (sound only - 92kb)
from outside at WOT...

(sound/vid - I did not choose the background music!

- 448kb)

my wrx is...or was until today catless with TurboXS uppipe, downpipe, race pipe, midpipe, and my custom axleback with cherry bomb. The WRX is getting sold and the exhaust is going on my legacy turbo.

Another spin on the exploding muffler...
Having such an open exhaust with a cork on the end (aka stock muffler) will put a lot of extra pressure on the muffler and this can lead to it splitting. i've seen this happen before.

warlord · Post by **warlord** » Thu May 13, 2004 8:11 am

man you guys shold see the flames my twin turbo legacy can spit when bouncing off my 112mph (180 kmh) speed limiter

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Removing Cat guts = Exploding Muffler!

Removing Cat guts = Exploding Muffler!

what if i only hollow out one cat?

Re: what if i only hollow out one cat?

glasspack