Muffler Internal Damage?

[Sylvanite]

According to an inspection report from about 7k mi ago (before I owned it), there is "internal damage" to the muffler. Now, if the muffler's damaged, I want to replace it, but I'm a little skeptical of the report. I guess my question is can the muffler get damaged internally, other than if the cat is damaged (mine apparently isn't, it just passed emissions). Could you tell if it's internally damaged from the outside? I don't know how the mechanic would known if there was damage other than this since the muffler is halfway to the cat and around the bend to tailpipe opening, I mean it's not like you can just look in there.

[fixkick]

i think they meant, when they bump the cat, it rattles, and is sign if its about to breakup inside.
most just run it, let it do as it wants.

they did the bump test, bump, rattle rattle, test.
i had a jeep that did this every 75k miles, like clock work, (I6 shacks it to death) i sent many cats to the road side dust bin. chuck by chunk....
i know one guy that screws a huge screw into the side if cat to it stops rattling,,, but might make it fail , so is risky.

[Sylvanite]

Hmm, so you think the mechanic heard pieces of the cat rattling in the muffler? I hope the cat's not failing (although I'm surprised it's not failed already after overheats, the engine running rich from a cracked ex. manifold, and I think a PO driving maybe over 5k mi in limp home). Other than risky screwing, are there any other (legal) ways to fix/ prolong the life of the cat?

[fixkick]

its a first thing check on cats, bump it, if it rattles in side, its going to breakup soon. seen many.
ive even driven 50,000 with one rattling. then one day, bam, gone. then 100k more.... (before p0420s were invented.)

sure keep the engine from shaking. the only sure way, and no limp
but these cars, No limp, will go 150k or more on a cat. easy. the older cats were stronger too.

[cosmic_splatter]

Will the car run properly if you eliminate the cat? I read somewhere that the system needs the back pressure. I'm going to live somewhere where they dont do emissions checks. It would be good to know if it can be taken out if it failed.

[fixkick]

the 8v dont like a missing cat. the 8v uses engine VE + MAP+ IAT = fuel required.
so if destroy VE , fueling is wrong,
what is VE, its pumping efficiency, volumetric Efficiency, that is 400CC are sucked in , each intake stroke, = 100%
changing exh , causes the valve overlap flow to change, the MAP does not measure air flow, it does so indirectly, using VE as the magic to get flow.
my guess, is it will only happen near WOT and at WOT, this lean out. for sure around town not, the throttle is near closed and VE is bad then, anyway ,(huge pumping losses)
but in acceleration mode, it might go lean.

the 16v has a MAF so never fails. it measures air flow no matter what you do . to exh.
the EGR dies, and valves run hotter. last less long.
the EGR does 3 things,
1: lowers NOX (smog)
2: lower valve temps, big time.
3: and reduces pumping losses, (more MPG)

the EGR is dead at idle and WOT.

on the 8v , just leave it in, unless it melts, it will not be a problem.
do not use large diameter exhaust as that will kill low end power. (you want high velocity exhaust, this allows savaging to work , more power.)

[Sylvanite]

Watch out, running without a cat is a federal crime if I'm not mistaken

[fixkick]

not outside USA> i.m not sure where anyone lives. not me..
change federal crime to USA Federal crime.
http://www.fixkick.com/smog/2011-7910.pdf

in the USA all parts related to smog, are not to be removed or replaced with non certified parts, in Calif make that 10 times, more hard. (they get visual checks too.....)
this is a nice condensed review.
http://www.racingbeat.com/mazda/performa...sions.html

In USA federal states 1996 and newer cars have to pass only a few tests.
CEL out. and fuel tank leak down rates.
oh, and one more the smog station wiggles the CEL from scan tool to see its been monkeyed with. (or removed)
and if car is about 2002 or newer there scan tool can see if the ECU CODE is not messed with..... "Checksums"CVN checks.!
but they don't view the cat (eye balls), unless your in calif. (some states run CALIF rules (new york?)
this is my experience.
With the cat removed 1996 an newer, the ECU/PCm will SET DTC P0420s for ever.

but if testing below, 1996, you must get a tail pipe sniff test. and it will fail if the cat is missing. (there are 3 GAS tests to pass)
so......
more. my smog page... can save you lots of cash.

http://www.fixkick.com/smog/smog.html

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CAT life
on the suzuki the orig, cat is very robust.
i had one full of oil and antifreeze. (blown engine)
so i replaced the whole cat back system, (it was dripping oil and smoking and had to)
the cat I kept,
i was running STOICH , Closed loop and engine turned to max.
this gets the CAT nice and warm, and it baked dry in 1 day.
and guess what, it passed the P0420 tests, and was and original cat, 1996. 150k miles too.

just stay out of limp home (FAILSAFE) and it will last. over 200k,,, easy
and keep all air leaks away from the front 02 sensor.
the 16v MPI engine loves to crack the #4 exhaust tube just before the collector, shields off.
to pass smog do that and make darn sure your EGR works,(ask how)

http://www.fixkick.com/look/96-num4-cracked.JPG

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what car, what engine what year>?
shop can do many tests. and don't read reports as truth, it can be lost in the translation from mech, to clerk , reading it (hen scratch) and typing it in to the billing report...

id read that report as "SOME Thing wrong with exhaust" and nothing else.!!!
he can shake it and make it rattle.
he can see vacuum is acting odd, just like huge exh, back pressure. (classic signs, read the vacuum gauge , instructions page, its there, to read)
he can see cranking exh back pressure too high (pressures gauge applied to the front 02 bung port)
he can do same at 2500 RPM and sees over 2PSI (its in the FSM this fact) pressure.
he might see cracks, or other damage there.
IF the clerk reads all that and types it all wrong. bingo.
better, do that tests your self. the tools are dirt cheap. (free really) just working 1hr on car saves you $100, , so the tools are free. see?

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no car ever stated.
so all answers are ( wrong?)
we get posts here from cars in , deep South pacific, with JDM engines, and no smog parts at all, I call them slicks and are tuned with Carbon Monoxide resistor blocks.
that car has no 02 sensors at ALL.
so my answers are wild guesses. all i really know is car has cat.