On my recently purchased XJ, I noticed a huge dent in the down-pipe coming off the exhaust manifold (it's in the wierdest place). Anyway, it looks pretty restrictive. Would this be hurting my engine performance?

Thanks in advance.

How much do you think the dent reduces the cross-sectional aarea of the pipe at that point?

It's a least half of what the diameter should be.

If it LOOKS restrictive I'd replace it. But LOOKS may fool you. While observing the dent think about the area inside the dent and conclude whether or not it is simply a change in SHAPE or if it actually is squeezing the exhaust at that point and lessening the flow.
If the flow is lessened...GET A NEW ONE!!
Big JIm <img src="/forums/images/graemlins/pfft.gif" alt="" />

If that's the case, it is definitely affecting engine performance, particularly in the top half of the rpm band. Get a new one.

Mine was dented the same way, at the same place.
The previous owner had wrecked the xj, and i believe the dent was caused by the front drive line.

I straightened it out, and never noticed any difference in performance, or mileage. I'd say dont worry about it, because there are already factory bends in the pipe, where it also is pinched almost as much.

I'll second the ôdon't worry about itö. I have the same thing on mine too, I did a little research on it, because I didnÆt like the looks of it either, I agree it ôLooksö awfully restrictive, and I thought the driveline must have hit it with the previous owner too. Well what I found out is on the later XJÆs that down pipe runs a different path than previous years, and the dent is actually caused from the mandrel used to bend the tubing. They showed the cross section of the dented tube, and it is a little restrictive, but itÆs not really that bad. And then the article went on to say with a naturally aspirated 4.0 there was no need to worry about it. It only becomes a concern if you are installing a turbo or supercharger. So if you have money burning a hole in your pocket and you want to make it look better, replace it. If not, just drive it and donÆt think about it.

<img src="/forums/images/graemlins/cheers.gif" alt="" />

Sean

I wish I would have known that BEFORE I tried fixing it. haha.

When i finally dropped the exhaust system, i broke the plug of the rear o2 sensor. then when i pounded the dent out of the pipe, the flange doesnt line up perfect now (no biggie, cuz my header is cracked where the pipes go together anyways, so it already had a slight leak.) when putting it back on, I stripped both bolt holess that held the transmission mount/exhaust bracket to the tranny, and broke a bit in one of the bolts while trying to drill it out. Needless to say, it was a major pain in the <img src="/forums/images/graemlins/butwiggle.gif" alt="" /> for NOTHING...

It's still hard to believe that a dent that big doesn't hurt anything, but I have minimal knowledge aabout exhaust systems. So, I'm just gonna leave it alone and use that money elsewhere. Thanks for all the advice. <img src="/forums/images/graemlins/kewl.gif" alt="" />

I thought the same thing. WHAT! Someone crushed my downpipe?

They're all like that. And yes they do restrict flow. We put a Downey aluminized header(the cheaper one) and downpipe on my 98 XJ and it really opened it up. I had the auto so it's hard to tell exactly where the power band is. It stopped downshifting on every single tiny incline though. It would stay on gear much longer and felt more powerful.

K&N drop in air filter was next. No noticable diffence but sounded a bit deeper. High flow cat and larger dia exhaust pipes and muffler were last. Helped bring up my MPG a bit but it was still around 17MPG.250miles from 15 gallons instead of 220 miles. Better than the 12 or so I was getting from each fill up but the $600 I spent on the header and exhaust would buy a lot of gas.

Sounded great and quit downnshifting every time I hit a hill but as for actual HP or MPG it would have to be dyno'd.