MJ Dual Exhaust

[MJoldman]

I have a 1991 MJ 4.0L, 5 sp standard which I plan on installing duel exhaust from the new duel exhausr header I installed. I want to run the duel exhaust all the way from the header duel outlets, thru glasspacks, all the way out the rear of the truck. Does anyone have any good or bad info on such a project? 

[Jeep Driver]

I would go 2-1 at the header and then 1-2 after the x-member.

 

And it's dual, unless you are expecting a gun fight.

[onlyinajeep726]

And it's dual, unless you are expecting a gun fight.

 

:rotf:

[MJoldman]

I would think that going 2-1 then back to 1-2 would not deliver the same sound or improved performance, then I would be prepared for a gun fight. Doesn't hurt to be prepared.

[johnj92131]

I would think that going 2-1 then back to 1-2 would not deliver the same sound or improved performance, then I would be prepared for a gun fight. Doesn't hurt to be prepared.

 

A duel has rules.  Each participant is permitted a single shot at the same time.  Google "Aaron Burr vs. Alexander Hamilton"  Aaron Burr was the Vice President of the U.S.   Alexander Hamilton was the 1st U.S. Secretary of the Treasury and his likeness is on the $10 bill.

 

BTW, sound and performance are 2 different things.  But who can forget the sound of a Jaguar XK-E?  Now that was sound, high performance, and still very sexy looks.

[Eagle]

I would think that going 2-1 then back to 1-2 would not deliver the same sound or improved performance,

That's correct. Keep dual pipes all the way, or don't bother.

[gogmorgo]

If done correctly, you can get some scavenging and a performance advantage going 6-2-1, vs duals from the collectors back. Splitting again after the muffler won't change much beyond sound unless your muffler is effectively flow-through.

[91Pioneer]

Stay in school.

[Jeep Driver]

I would think that going 2-1 then back to 1-2 would not deliver the same sound or improved performance, then I would be prepared for a gun fight. Doesn't hurt to be prepared.

There is a reason for X-pipes or H-pipes you'll find on just about every performance exhaust on V8s, to balance the pressures from the left bank to the right bank. Also has to do with the scavenging effect....positive and negative pulses........way beyond my pay grade but I do understand the basics.

 

Also, go look at the amount of space you have at the x-member......now.......imagine squeezing two 2 1/4" pipes through there....imagine two pipes bent perfectly from the header THROUGH the chassis and x-member perfectly as to not rattle or put stress on the header. To get that right......you'll need to find a REAL speed shop that specializes in performance exhausts......and that'll probably run you about $800 or more.

 

Keep it simple, balance the front three cylinders with the back three.

[Stacks]

When I had my exhaust built from the Clifford dual outlet headers back to the stacks it cost me right at $200, with a balance pipe AND tied into the factory exhaust hanger at the CAT flange and the utilizing the factory tail pipe hanger to support the mufflers.  If I had wanted the pipes clear back to the rear bumper it was another $125.  Pretty much any muffler place in this area could do it for those prices.  The REAL performance exhaust shops wouldn't even touch it for me.  Different areas of the country obviously!!! I have no rattling exhaust pipes. There's plenty of room over the x member on my MJ for some reason.  A little trick I noticed on mine was that to keep the pipes from possibly rattling together they put short pieces of about 1/4" round stock between the pipes at the mid point between the support points and welded the 1/4" rod to both pipes so the can't touch each other.  Neat, cheap fix!! :)   Going from 2 into 1 and back into 2 kills the real sound of an inline 6 with a split manifold.  It doesn't sound bad at all but you lose the split manifold sound!!

[onlyinajeep726]

Y'all have me intrigued here about true duals on the 4.0... I have a single in/dual outs on a Cherry Bomb Pro and it sounds pretty good, but I'd be lying if I said I haven't wondered what the sound and performance would be like with true duals.

[gogmorgo]

A quick google brought up this:

 

Sounds like a teenager's V6 fwd sedan with a rust-opened downpipe that he thinks makes it cool...

[Jeepman]

WOW that's Bad first speed bump and that exhaust is gone....

 

I considered for about all of 1 second ok maybe 3 seconds about true dual exhaust but the pipes would need to be around 2" to get everything tucked up

and out of the way nice then the muffles and cat's but I just might be a little more finicky then most and really I couldn't see the actual advantage with an

inline engine so 2" Mandrel all they way...

 

I am happy with how mine turned out and would love to hear a MJ with true duals that is not a hack job and see how it sounds...

[Dadinator]

Unless you are doing some major work on it, you aren't going to see much of a performance gain with 1 system vs another on a 4.0 jeep. Just get what sounds good to you.

[gogmorgo]

To go to duals and stay with similar flow to the stock single-pipe, you'd need to drop exhaust size anyhow. Maybe even as low as 1.75".

But still, as keeps being pointed out, not all that much to gain on a stock motor.