Cat Back

[AMPlibby06]

Has anyone ever heard a MBRP cat back on a KJ? Just came across the brand, and checked streetfire and youtube. Sounds great on TJs and Dodge Rams, but haven't heard one on a KJ.

Thanks

 

[Powerslave]

They are expensive, but if you know the right muffler shop, they can custom make you one a LOT cheaper. I had one made for a Geo Tracker, Cat back... $90.00. I have seen some direct fits the Liberty for 400.00 or more...
http://shopping.yahoo.com/s:Exhaust Systems:22606-Model=Jeep Liberty:22607-Year=2006

With the right people, a TRUE DUAL exhaust can be made as well. Each bank has a PreCat, then into the main cat, then back to the muffler and tail. To keep it somewhat legal, you would need to small cats, from a 4-cyl MFR car that will work. Then, you have the two banks, two pre-cats, then two cats, then out. AS long as it meets EPA emissions. Thing is, how many times will it take to get right...

States like PA, you won't pass emissions or inspection with true duals on a vehicle that was not equipped with it, but other places, it can be done.

 

[tjkj2002]

They are expensive, but if you know the right muffler shop, they can custom make you one a LOT cheaper. I had one made for a Geo Tracker, Cat back... $90.00. I have seen some direct fits the Liberty for 400.00 or more...
http://shopping.yahoo.com/s:Exhaust Systems:22606-Model=Jeep Liberty:22607-Year=2006

With the right people, a TRUE DUAL exhaust can be made as well. Each bank has a PreCat, then into the main cat, then back to the muffler and tail. To keep it somewhat legal, you would need to small cats, from a 4-cyl MFR car that will work. Then, you have the two banks, two pre-cats, then two cats, then out. AS long as it meets EPA emissions. Thing is, how many times will it take to get right...

States like PA, you won't pass emissions or inspection with true duals on a vehicle that was not equipped with it, but other places, it can be done.

It depends on the year on how many cats you have,some have 3 and others have only 2.The years that have 3 cats('02's and some '03's) actually may have 1 of 4 different set-ups.Also most exhaust shops will not touch your cat-forward system until 8 years old or 80,000miles since that is the federal warranty period for '96+ vehicles and will tell you no or go to the dealership.


Plus true duals will kill the little bit of low end torque the 3.7 has,and to do it right would cost very big $$$ to not loose power,many times on a dyno and many different exhaust systems will need to be made and tested on the dyno.Could run past $10,000 to get it right.



Best bet is just have a good muffler welded in place of the OEM one,the tail pipe is plenty big enough for the 3.7.Or you could do what I did and for go the tail pipe all together.

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I ran the Thrush turbo muffler(top one) then switched to the MagnaFlow UltraFlow Race muffler since I need the space when I SFA my KJ.

You must be registered for see images attach

 

[Powerslave]

True duals would not kill the low end if you restrict them to the same specs as the original exhaust, for more back pressure to compensate. I don't know of any cams out there that would help either.

The 3.7, I have noticed, doesn't have the higher end torque. Lowering back pressure will move the torque curve up to a higher RPM range. I would be satisfied with that. It won't take much to equalize it with a good intake, and a little more free flowing exhaust.

I have a good fiend who owns an exhaust shop, been there for 20+ years, and knows all the tricks, so I will be good to go....

 

[tjkj2002]

True duals would not kill the low end if you restrict them to the same specs as the original exhaust, for more back pressure to compensate. I don't know of any cams out there that would help either.

The 3.7, I have noticed, doesn't have the higher end torque. Lowering back pressure will move the torque curve up to a higher RPM range. I would be satisfied with that. It won't take much to equalize it with a good intake, and a little more free flowing exhaust.

I have a good fiend who owns an exhaust shop, been there for 20+ years, and knows all the tricks, so I will be good to go....

The 3.7 makes it peak power in the higher RPM range(above 4000rpm's).Yes you can make true duals make power but on a KJ the pipes would be like 1" in diameter,kinda odd looking.Freeing up back pressure you will loose low end power which the 3.7 can't afford.The PCM is pretty smart also unless you get it reprogrammed it will learn the new mods and adjust to cancel them out anyways.Your buddy with 20 years making exhaust systems may know how to make them,make them sound good but do they actually make power? Bet not without a dyno to test before/after.It has been proven on dyno's that single exhaust can make more power then duals with these newer computerized engines.Plus the cats in our systems are pretty high flow already(amazingly high flow) so just replace the OEM muffler with a higher flow one for sound and be done with it.Adding true duals will add nothing but bling factor.I whell my KJ and true duals is a big no-no for lack of space,and I need all the low end power I can since I spend most of the time on the trail going only 2-3mph crawling over big rocks.

 

[AMPlibby06]

Best bet is just have a good muffler welded in place of the OEM one,the tail pipe is plenty big enough for the 3.7.Or you could do what I did and for go the tail pipe all together.

You must be registered for see images attach

I ran the Thrush turbo muffler(top one) then switched to the MagnaFlow UltraFlow Race muffler since I need the space when I SFA my KJ.

You must be registered for see images attach

How does your magnaflow ultraflow sound? The main reason I want the cat back is for a nice sounding low growl, in addition to some more power. But I've been reading that the power difference really isn't that great without a tune (and I don't wanna pay money for a dyno tune for my automatic SUV). Is there anyway you could send a video clip or something? Thanks!

 

[trailman]

Thanks!

If you just click on the second pic, it's actually a video.

 

[rockymountain]

If you just click on the second pic, it's actually a video.

I'm more interested in the whine I hear from the front!!!

 

[tjkj2002]

I'm more interested in the whine I hear from the front!!!

That would be the resonating exhaust on the tin roof of my carport.

 

[AMPlibby06]

so is that race muffler attached directly to the cat? i don't know exhaust at all so I cant really tell whats going on

 

[moparman]

I can answer that. Yes. The bulge in front of the flange is the catalytic converter. As for dual exhaust, aside from tuning issues, there really isn't that much room there, certainly with 4WD. Believe me, if anybody wants dual exhaust it is me. But I have been under my KJ and ruled it out. And if you were offroading it would be more pipe to bend up.