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Exhaust

Sullie

NAXJA Forum User
Location
el paso tx
1988 XJ, 4.0L manual transmission...

I just bought this truck, and when she runs the exhaust is really loud, looked under it and seems to have a muffler but no cat back...
Here's some pictures, let me know what I can do as a cheap fix to soften the noise.
c8ea2e55659c99625c1053a8491b09f7.jpg

64c81f1c9df3a3c2699bf830667733fb.jpg



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Unless your state requires it I wouldn't bother with a cat. Cat back just means the exhaust system from the catalytic converter back (muffler and tail pipe I posted up). The cat is just another failure point. A decent muffler and full length tail pipe will reduce the noise.
 
You're probably going to have to cut it a couple inches off the muffler then attach if you keep the old muffler. If you get a new one it'll bolt right on with some clamps. 2.25 inch exhaust stock by the way on the diameter
 
That extension after the muffler looks a little bigger than 2 1/4". Measure its outer diameter first, it might be 2 1/2". Either way, the previous answers are correct, you need to run a tailpipe out to the back bumper, the muffler looks in really good shape, I would not change it. Keep the muffler and just add that tailpipe, it will make a huge difference. I just went through this same situation. Also, if you go with a stock 2 1/4" diameter tailpipe, you will lose some torque because a narrow tailpipe takes away a bunch. I went up to a 2 1/2" tailpipe and love it. Great sound with a little extra torque over stock!
 
That extension after the muffler looks a little bigger than 2 1/4". Measure its outer diameter first, it might be 2 1/2". Either way, the previous answers are correct, you need to run a tailpipe out to the back bumper, the muffler looks in really good shape, I would not change it. Keep the muffler and just add that tailpipe, it will make a huge difference. I just went through this same situation. Also, if you go with a stock 2 1/4" diameter tailpipe, you will lose some torque because a narrow tailpipe takes away a bunch. I went up to a 2 1/2" tailpipe and love it. Great sound with a little extra torque over stock!

You have it backward. Torque is increased with more backpressure, not less. HP, on the other hand, is increased with less back pressure. There are limits on both too.
 
Does anyone know why my spark plugs are getting fowled up,
Brand new...
Plugs
Wires
Distributor cap
Rotor
Fuel filter

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You have it backward. Torque is increased with more backpressure, not less. HP, on the other hand, is increased with less back pressure. There are limits on both too.
and outputs are directly related to engine operating RPM.

I'd get stock a cat, muffler and tailpipe from rockauto or amazon and you'll be happier. Motor and environment will be too.
As an aside, Dan told you a good thing! It is against forum policy to advise deleting federally mandated emission control equipment.
 
Hey Sullie, regardless of what anyone says, including Bill Nye the Science guy and Deputy Tree Hugger (above), just enjoy your Jeep.....that is the main thing we all want!
 
Hey Sullie, regardless of what anyone says, including Bill Nye the Science guy and Deputy Tree Hugger (above), just enjoy your Jeep.....that is the main thing we all want!

Why the name calling? If you disagree, go make friends with a dyno operator and s/he can give you the run down.
 
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and outputs are directly related to engine operating RPM.

As an aside, Dan told you a good thing! It is against forum policy to advise deleting federally mandated emission control equipment.
He didn't tell him to break the law. He said if your region doesn't require it ....

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