Exhaust shop confusion

[Arch_Stanton]

Hey guys, the previous owner of my truck had a hack job of an exhaust set-up done, and I wanted to get it put back to as close to stock as possible.  I got a good price on a basic Walker muffler (part#18403) and catalytic converter (part# 15634), and then took them up to a local exhaust shop.  I told the guy that I wanted the cat and muffler installed, and 2.25'' pipe run out the back, over the axle, and out between the rear passenger tire and bumper.  I also asked him if he could re-do the downpipe before the cat to take out the two 90 degree bends, and replace them with two 45 degree bends.  He seemed confused about the downpipe request, but said he'd get it up on the lift and call me in a bit.  I left it with him, and he called about an hour later saying that he wasn't sure he'd recommend the downpipe modification because it looked to be originally routed around the transmission pan for a reason, he thought maybe because of the heat from the pipe.  I told him to leave the downpipe alone then, and to just put on the cat, muffler, and pipe out the rear.  When I arrived to pick it up, he told me that the cat I brought him had a 2.25'' outlet, but only a 2'' inlet?  He said he had cut off the inlet (without asking me) and welded a 2.25'' inlet to it, then attached it with a bracket to the downpipe.  Then he says that the downpipe on my truck is only 2'' diameter.  Huh?  I thought that Comanche's had a 2.5'' downpipe that later narrows to 2.25''.  The catalytic converter I bought was listed as a direct fit for a 4.0 1991 Comanche, and the specs show a 2.25'' outlet.  Is that the right size catalytic converter after all?  Is it even possible a cat would be made with a 2'' inlet and 2.25'' outlet or did he put it on backwards or something?  I only had a minute to glance at it before I had to come to work today, but it seems like the downpipe is very narrow, smaller than the 2.25'' inlet he decided to weld on the cat.  I'm not sure what to do now, but it just doesn't seem right, looking for some guidance.  Thanks.

 

 

[daking]

The down pipe is 2.25". Except where it bends, its less then 2.25". Factory uses compression bends, so pipe gets smaller at the bends. ( I think that's why you wanted 45s?)

 

I believe the cat is 2.25" on the IN and 2.5" on exit..

 

I would leave it the way he did it. Better a bit larger then smaller. Unless your looking for a factory restore on that jeep.

 

I could be wrong, but I just pulled all that off my truck. So I could measure later.

 

I made a custom down pipe using 2.5" Mandrel bent pipe. I added a flex pipe to limit damage to exhaust header.

[Eagle]

The down pipe is 2.25". Except where it bends, its less then 2.25". Factory uses compression bends, so pipe gets smaller at the bends. ( I think that's why you wanted 45s?)

 

I believe the cat is 2.25" on the IN and 2.5" on exit..

For a 4.0L, the downpipe is 2-1/2". The catalytic converter is a 2-1/2" inlet, and 2-1/2" at the outlet from the cat body. The short pipe from the cat (which is an integral part of the cat) to the muffler necks down to 2-1/4 halfway to the muffler.

[Arch_Stanton]

I don't know how apparent it is from my picture above, but my down pipe doesn't look to be 2.5'' diameter.  Once I get home I'll look at it a bit closer to see how it connects to the manifold.  I'm not sure what the previous owner did to it, but the bend around the transmission pan looks like others I've seen, so I assumed it was an original down pipe.  I'm still unsure why this exhaust guy needed to hack off the "inlet" to the cat, since it was sold as OEM replacement direct fit.  I would expect the cat to have a 2.5'' inlet and 2.25'' output from the short pipe, but this guy is telling me it had a 2'' inlet.  I was hoping this shop, which had good reviews and has been there forever, would set me straight, but now I'm confused.  I halfway feel like he's jacking with me because I came in with my own parts.  I'll look closer when I get home.  Thanks for the help.
 

[Rockfrog]

The stock pipe on my 88 was 2.25" from the down pipe going past the trans

My 00 XJ uses a stock 99 downpipe which was 2.25" to the trans crossover where it widens to 2.5" to the tailpipe.