brdavis9

I wish I could recall the source, but I do remember reading thread recently mentioning that if there was a smell after putting in a new cat, the computer or sensors or something wasn't cooperating with the cat.

Make sure your system was sealed properly when you put it back together? Pull your negative cable on your battery?

Other than that, I got nothin'.

...my new cat install had no odd smells of any kind ...starting, running, or off after a drive.

Cherokeekid4x4

Yes it smells like rotten eggs and no its not the cat. Idk where ts at

Nickmuller

I have a 2004 grand Cherokee wj with the 4.0l i6. I want to know what the best sounding muffler would be and will it really raise my mileage by 2 mpg?

snopro700

Everyone seems to like the flowmaster 40 or 44 on their 4.0s, and your mpg will most likely decrease because you'll want to keep hearing the motor and putting more skinny pedal into it.

Jmb94

Flowmaster. And no, a muffler will not increase gas mileage. Period.

Tom95YJ

Read up on how an airpump works. A engine is an airpump if it breathes better it becomes more efficent and making more power and noise is a side effect

jamorrowxj

^true, the hotter the air coming out of the exhaust is the easier it is for the engine to push the air out. Making your engine work less is more efficient so a muffler that keeps your air hot or if you heat wrap your pipes you will get an extra but of efficiency.

snopro700

Agreed, every little but helps. But it just won't be noticeable unless you start eliminating major restrictions, like the factory manifold, crushed downpipe, cat, and make it all 2.5" vs factory 2.25".
My brothers XJ has a full banks system on it, and that thing will smoke the tires with much less pedal into It thank me will with a stock exhaust....his mpg sucks though, because it sounds too good to ever wanna let off the pedal.

dvd_fuller

so i already have the pace setter header but before i buy anymore, what do you guys think of going 2.5" though the cat and then making it split to dual 2.25" with the muffler (magnaflow). also the whole exhaust (except that pacesetter header) will be stainless steel. i also want to have it exit out the sides behind the rear tires but i think it would be much easier to avoid the rear axle and put the exit right before the rear tires.
so as asked, what are your thoughts?

austinjoe13

Well, I think you have really deep pockets

dvd_fuller

hah i wish, the header was a gift as well as the muffler. the cat will only cost about 75 and the pipes are $40 for 5 feet. then i have friends in shops that will help me with bending and other things.

austinjoe13

Well, it's been done before. And cats are only $40 on performancecurve.com. $70 if you want a metallic catalyst. That's what I have, and I went from no cat to this and felt no lag. Also, it sounded great straight piped with it.

dvd_fuller

will i still be able to pass inspection with no cat? it is my DD

99superjeep01

No, it's illegal to not have one.

austinjoe13

Ditto
I had it straight piped WITH the cat.

Ceramic: http://performance-curve.com/410250.aspx

Metallic: http://performance-curve.com/25thund...ter415250.aspx