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

Andy Harvilla higrafey
Thu Jun 15 14:49:33 UTC 2006


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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