dual exhaust using two stock exhausts?

[Willcall]

First and foremost, the only thing that I know about the exhaust system on my vehicle is that it is restrictive from what I hear. And I also understand that if you can make it less restrictive, your mpg will increase. So, I was wondering if it is possible to just cut the exhaust line that comes off the driver's side of the engine and just weld on another exhaust line (with cats and tailpipe) from a junkyard explorer to have a dual exhaust setup that isn't as restrictive. I have a 1998 X 4x2 with the 4.0L OHV.
Thanks
-Will

 

[lounge lizard]

you would have to move the gas tanks and a few other things to get the pipe down the driver side of the truck

 

[Willcall]

But what if you just ran it next to existing stock one and had it branch off in front of spare tire? There appears to be enough space if you move the existing cat over a bit or ran the new one to overlap it.

 

[ranger7ltr]

Which exhaust manifold do you have?

I replaced my engine last spring and noticed the exhaust manifolds were blocking part of the exhaust port...The manifolds looks like the right picture...

The manifolds I am replacing the original ones are from a 97 Explorer... The ports are more than 19% larger than the ones from my 99 Explorer...You can see the difference between the two...1.7" vs 1.4" inches in diameter...

Now about dual exhaust...The 3rd picture is the current 2.5" pipe coming off the second rear cat into a single muffler and a single pipe out the back...
The muffler I have a stainless steel Mangaflow dual-in/dual-out 2.25" ports that is the same physical size as the single 2.5" muffler on there now...The piping will not be any further outside the envelope of the muffler and two pipes should fit without issue on the passenger side in the space that one pipe is resting in now...

After replacing the manifolds, I am going to replace the cats in the primary pipes and the 2 downstream cats as well as using a Magnaflow dual-in/dual out muffler and running the exhaust pipes out the back like the single pipe runs out...I plan to run 2.25" pipes throughout the system to maintain exhaust velocity and run the 2 cats in parallel[ one in each pipe instead of both in series] and add the back O2 sensor to one of the rear cats...I will run the pipes down the passenger side and not need to move any components under the truck...

I am also looking to run an X-pipe at the junction of the two primary pipes and the rest of the exhaust system before the secondary cats...

 

[2000StreetRod]

port mismatch

That's interesting about the ports on the 99 exhaust manifold not matching the head ports. I wonder if there were problems with the manifold cracking and Ford decided strength was more important than flow.

My SOHC V6 is most restrictive at the down pipe bends between the exhaust manifold and the cats. I only have two cats - one for each down pipe. Pipes from the cats (also with restrictive bends) feed a dual in/single out muffler. I believe my tail pipe is 2 inches in diameter. The system appears to be original equipment although other Sport members have said mine doesn't match theirs.

Since the OHV V6 doesn't rev as high as the SOHC V6 (stock max rev on mine is 6350 rpm) I just don't believe true dual exhausts are justified unless the engine has a turbo or super charger. Even then, a single 2.5 or 3.0 inch diameter tail pipe is probably adequate. I think the crossover pipe may improve performance if it provides good bank cross flow from upstream to downstream but that requires D type fittings that are uncommon. I believe the T fittings have poor upstream to cross bank downstream air flow.

 

[lounge lizard]

on my v-8 I have dual exhaust, dual cats till I get to the muffler, then it's dual in and single out.

on mine there is too much gas parts that are on the driver side even under the spare tire