stock downpipe

nyxj42 · May 31, 2007

Let me start by saying that i searched for a couple of days for my answer b-4 deciding to post, no luck, so just let me appologise in advace for being a noob and for my poor grammar and spelling..... I changed the oil in my 99xj sport the other day and noticed a sizable depression in what i'm gonna call the down pipe just above the u-joint on the front diff, at first i thought i smashed it wheelin' but then i looked under my dad's 94xj and its the same story so i have to assume that this is normal OEM jackassery. Does anyone know why this was done?....clearance at full stuff perhaps? but the u-joint is about 3.5" away from the down pipe and its only about 2.5" the bump stop to the spring seat. if clearance is not an issue could one assume that putting in a custom downpipe and say a flowmaster 40 series would be a comparable performance increase to just putting on a header that reuses the stock downpipe?
thanx in advance for any help y'all might have for a confused noob.

j99xj · May 31, 2007

You are right that its the factory mistake. Everything should be fine in theory but if you want a little more horsepower you can put a bigger pipe in thats bent a little different so it doesn't get hit.

Even though the bumpstop is closer to "hitting" than the ujoint, you must take into account that the bumpstop compresses. (and quite a lot too)

ren · May 31, 2007

Yeah, the bumps compress all-right. I changed my pipe to a normal, round one, went wheeling, and had a normal factory flat spot in mine. Most likely from the D/S, I guess.

Crawler · May 31, 2007

nyxj42 said:
Let me start by saying that i searched for a couple of days for my answer b-4 deciding to post, no luck, so just let me appologise in advace for being a noob and for my poor grammar and spelling..... I changed the oil in my 99xj sport the other day and noticed a sizable depression in what i'm gonna call the down pipe just above the u-joint on the front diff, at first i thought i smashed it wheelin' but then i looked under my dad's 94xj and its the same story so i have to assume that this is normal OEM jackassery. Does anyone know why this was done?....clearance at full stuff perhaps? but the u-joint is about 3.5" away from the down pipe and its only about 2.5" the bump stop to the spring seat. if clearance is not an issue could one assume that putting in a custom downpipe and say a flowmaster 40 series would be a comparable performance increase to just putting on a header that reuses the stock downpipe?
thanx in advance for any help y'all might have for a confused noob.

The keywords: "downpipe clearance" gave me two pages of post topics, some of which contained your answer, and on the first try. It took me all of a few minutes to go through them, but I digress...

The "pinch" was engineered(?) to clear your front driveshaft from near to full suspension compression. You can have someone fabricate a new pipe up to 2.25" that will clear fairly easily, but usually only as long as your track bar is stock and/or at stock adjustment. Anything larger in diameter or compensating for front wheel tracking after a lift and there's a good chance you'll find yourself fabbing it up again... don' ask me how I know... ;^]

I believe "Dr. Dyno" got away with fabbing one up out of 3" mandrel bent angle sections, but his stroked and highly modified XJ is still sitting at close to stock hight.

Crush · May 31, 2007

The keywords: "downpipe clearance" gave me two pages of post topics, some of which contained your answer, and on the first try. It took me all of a few minutes to go through them, but I digress...

Bit pointless now.Impressive yet none the less pointless.

JNickel101 · May 31, 2007

Ah, just typical NAXJA

"use the search function" jackassery...which is very similar to OEM jackassery

Crawler · May 31, 2007

But not to be confused with the JACKASS "jackassery" of those who criticize without bothering (being able?) to address the question(s) asked... right?

To answer some of the rest of the question(s):
Fab up a downpipe, install a flowmaster muffler, increase to a 2.5" tailpipe, and you'll notice the difference.
Bore your throttlebody out and fab up a cold air intake and you'll notice even more.

Best wishes and have fun... ;^]

nyxj42 · May 31, 2007

thx for the info guys and for not beating me up much for my less than brilliant search function usage.

stock downpipe

nyxj42

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j99xj

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ren

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Crawler

NAXJA Forum User

Crush

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JNickel101

NAXJA Forum User

Crawler

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nyxj42

NAXJA Forum User

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