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Exhaust Collapse?

M

Mudshack

NAXJA Forum User
Location
Billings, Montana
While under the truck for something else, I notice what looked like the exhaust collapsed. Right below where the exhaust pipe flange connects to the heder flange, it looks like the exhast collapsed. It looks like a straw that you suck on while your finger plugs the other end. Is this normal, or am I going to have to replace the intie exhaust from the flange, back?
 
The little crimp the factory put in the pipe so the stock suspension can cycle without the drive shaft hitting the pipe ? Normal.

.
dent.jpg
 
Yep, seems to me the front DS will hit it without the dimple. If you lift your XJ enough the issue goes away and you can change out the downpipe if it bothers you.
 
yeh, that is the dimple. didn't see where it would interfere with the DS, though. So, our 2.25 exhaust on these XJ's is not really 2.25 due to the "designed" restriction. That cracks me up. Not that these 4.0L's are lacking any power. It just seemed odd when I saw it.

Thanks guys.
 
Manifold to CAT 2.5", CAT to the rear 2.25".
 
I replaced my whole exhaust this weekend, and out of curiosity, decided to measure the area of a cross section of pipe at the crushed bend.I traced it onto graph paper and counted the little squares. Turns out its only about 1.5 Sq. Inches. A 2.5" mandrel bent piece will be almost 5 Sq. Inches. Seems a bit ridiculous.
I ran a stock 99 exhaust on my stroker for the last year, and finally replaced it with 2.5 from the header back. Man what a difference, almost more noticeable than the stroker was over stock. It also allows me to get over 4k rpm now. Before it had no extra power over 4k, and sounded like the header was going to blow off.
To me, getting rid of this restriction is more important than any other part of the exhaust, even on a stock 4.0
 
interesting.....i guess my PO already took care of that since i have no crushed bend like that. seems like a rather stupid way to design it, mine was put in without the crush and it clears the DS without issue(even when it was at stock height).......you would think jeep engineers could figure out a better way.......
 
You had me curious so I went back in the warehouse and snapped some pics.. These are pipes made by Goerlich (AP Exhaust). Does the OE pipe have the dimple in the bottom where it bolts to the converter as well? The dimple measured 2.5" x 1.5" but it was actually recessed inward so there was an even greater loss of flow area.

jeep-pipe.jpg


jeep-pipe2.jpg
 
So Jeep designed the exhaust to be 1.5" but everyone thinks it is 2.25 (more manly) lol. Must be a jeep thing.

I still don't see how the dimple up near the headers helps it clear the driveshaft. It is a good 6-9" above the shaft.
 
Mudshack said:
So Jeep designed the exhaust to be 1.5" but everyone thinks it is 2.25 (more manly) lol. Must be a jeep thing.
Click to expand...

WTF??? Every high school auto shop student knows that any kind of exhaust restriction = less power....

While the l6 does a decent job of making torque, and pushes the XJ down the road pretty well..... What the hell is wrong with a little more power???


Guess I'll continue my search to become "more manly" elsewhere......


xcm.... That is, hands down, one of the most disturbing videos I've ever seen.......... Thank You.
 
Mudshack said:
I still don't see how the dimple up near the headers helps it clear the driveshaft. It is a good 6-9" above the shaft.
Click to expand...

Here's a downpipe that came with no dimple. That dimple was made by the front shaft at the joint. Stock height, occured pulling into a driveway in 4WD last winter. I'm thinking that's why there was a dimple there from the factory.

Image005.jpg
 
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