[Diy_efi] Re: Can constant WOT operation destroy a muffler?

[Scott C]

Well, there *IS* combustion going-on inside the Cat, which I'm assuming 
is *just* ahead of the muffler in the pic, out of the frame. Heat-cycling 
from this, coupled with condensation and corrosive exhaust byproducts 
(which are probably aggravated by extended heavy loading of the engine), 
could quite possibly weaken and fatigue the metal.

Couple that with a (possibly) poorly-routed exhaust system, that places a 
heavy stress on the middle of the muffler - all that could do it.

I don't really have a solution for you, though.

Have you tried a different brand/style of muffler? 

-Scott C.


-----Original Message-----
From: Andy Harvilla <higrafey at gmail.com>
To: diy_efi at diy-efi.org
Date: Thu, 15 Jun 2006 10:49:33 -0400
Subject: [Diy_efi] Re: Can constant WOT operation destroy a muffler?

> Those are some good exhaust mounting tips.  It's true the exhaust  
> systems on these Jeeps aren't set up very well.  The cat and muffler  
> are within six inches of each other, there being a support at the cat  
> (into the transmission mount) and one behind the muffler on the  
> body.  Even so, I'm not sure if it's really a lack of suitable  
> mounting that's causing the mufflers to blow out (the motor mounts  
> are pretty new, too).  Here's a picture I took this morning showing  
> how the metal is degrading.  The silvery band along the center is  
> usually first to deform; the arrow shows where it typically develops  
> a crack.  The pipe ends never give me trouble, only the metal  
> underside of the muffler.  In another month I'll be ready to replace  
> this one again (good thing for lifetime warranties!).
> 
> http://www.pitt.edu/~ajh32/etc/yjmuffler.jpg
> 
> This being an off-road vehicle and all, sloshing through the mud and  
> muck isn't good for the exhaust... especially water, which cools down  
> the metal relatively quickly.  However, the four-wheeling in my area  
> has all but dried up in the past year and I haven't been out in quite  
> sometime.
> 
> Depending on the situation, I see a wide range of rpm at full pedal.   
> Driving up a steep hill, I'd usually be in third gear and turning  
> maybe 3000-3500 rpm.  Highway driving at 65 mph is around 2500 rpm in  
> fifth, but most often I'm using fourth gear (3000 rpm) because  
> there's not enough power.  I've already regeared from 4.10's to  
> 4.56's (what a difference!).  On-road driving is the only power issue  
> I have with the Jeep.  Off-road, there's more than enough juice to  
> get around due to all of the gearing.
> 
> Again, I've only started having this problem after I installed a  
> converter.  The original muffler lasted 65,000 miles with a hollowed  
> cat, but I'm on my fourth muffler only 30,000 miles later.  Just  
> kinda seems weird.  I'm wondering if it's possible for a cat to heat  
> up enough to damage a muffler... or maybe if prolonged high  
> temperatures (aggravated by a cat) can kill it.  Assuming I'm  
> entering WOT mode, of course.
> 
> Andy
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