Custom Exhaust for Maximum Torque - 4.0 Sohc

[Explorer Power]

Hi there,

Since our 4.0 Sohc v6 engines dont like freeflowing exhaust systems with big pipe diameters and need backpressure to produce low end torque, true duals seems to be out of the question, almost all low end torque seems to be lost...

So what exhaust setup for our 4.0 Sohc engines will produce the most low - mid range torque...? Without losing top end horsepower...?

That is the question. :scratch:

So the pipes from the back of the headers to the cat's, these are about 2 inches diameter stock, i think.
Will it have any use to replace these?

Then the cat's... These will be removed of course. :

Should the pipes then be brought togheter with an Y- pipe? or use a dual in muffler?

Wich muffler should best be used?

If dual endpipes are preferred, wich diameter should be used? 2,5 inch? or even smaller?

Thanks in advance.

 

[IZwack]

It might also be worthwhile looking at the other side of the system - the intake manifold (and not bolt on "intakes" cones or tubes from PepBoys, but the actual manifold/plenum system). And I wouldnt remove the cats unless you have systematically determined that it significantly hinders system performance.

But since you asked about mufflers, look at NACA report 1192 - its old but its is a good starting point for muffler design.

 

[Elessar65]

Haha, NACA... That takes me back, to way before I was born, lol. From the good old National Advisory Committee for Aeronautics days before NASA.

 

[stangman82]

I just had my exhaust done on my 2000 sohc. y'd the pipe right after the rear cats to a single in single out flowmaster 40. all stock piping including resonator. I LOVE IT!!!! great sound (for a sohc) and excellent torque.

 

[Explorer Power]

IZwack:
I'm already looking at the intake
Oh and i'm not gonna design my own muffler
I did get some custom made mufflers:

Wanted to use them in my exhaust setup, have 4 of them (wanted to do true duals, but have been told that i will lose a lot of torque. )
Back o2 sensors are already removed (and simulated), so i can lose the cat's without problems (don't live in usa so emissions won't be a problem).
Tell me what you think will be the best setup for maximum torque.
(would like dual tailpipes ).

Elessar:
Can you tell something about your custom exhaust?

Stangman:
ok thanks for your input
Did you keep the original cat/resonator (you know the dual in, single out muffler)?

 

[ranger7ltr]

Here is my solution to this issue

I wanted to replace the exhaust on my truck since I didn't really know what the condition of the convertors were and the engine seemed to not be breathing as well as it could..

I had the rear catalytic convertor replaced with a dual in-dual out hi flow unit and then a Magnaflow dual in-dual out muffler with dual tailpipes out of the back of the truck...

The convertor has a O2 bung because I had to keep the rear O2 sensor and the 2.25 inch diameters of the muffler and 2" diameter of the convertor keeps the velocity high so the exhaust can flow out and not hurt performance...

There is speculation that the oem is a high flow unit but after 165k and 10 years on it I suspect that it has worked hard enough and needed to be replaced... I will also replace the front convertors for the same reason...

 

[Axial32]

I ran two seperate mufflers per pipe witha "H" connector before the mufflers to even out the pressure... and kept the 2 1/4" pipe and 3" tips. It seems to do fine torque wise... but my 35's don't help I can get a one wheel peel goin though with the 35's soo..

the pictures don't show with the 35's

 

[stangman82]

IZwack:
I'm already looking at the intake
Oh and i'm not gonna design my own muffler
I did get some custom made mufflers:

Wanted to use them in my exhaust setup, have 4 of them (wanted to do true duals, but have been told that i will lose a lot of torque. )
Back o2 sensors are already removed (and simulated), so i can lose the cat's without problems (don't live in usa so emissions won't be a problem).
Tell me what you think will be the best setup for maximum torque.
(would like dual tailpipes ).

Elessar:
Can you tell something about your custom exhaust?

Stangman:
ok thanks for your input
Did you keep the original cat/resonator (you know the dual in, single out muffler)?

Yes I kept all the stock piping including the resonator. all I did was cut the old muffler out and y the dual in pipes into one. then the muffler was welded in. (single in single out flowmaster 40)

 

[Elessar65]

Its pretty basic really. Dual 2.5" inlet single 2.5" outles Hooker Aerochamber muffler, and 2.5" pipes from the cats back into the muffler, following the stock routing. Single tailpipe 2.5" exits at the stock location. I am pretty happy with it, it was only $200 (plus the price of the muffler, I think like $70 from Summit) to have a shop bend it up and weld it. If I had to do it again the only thing I would change would be to add a 2.5" resonator on the tailpipe somewhere. I get a little bit of drone at part throttle from about 2000 to 2600 rpms.

 

[Axial32]

Here's the sound of mine...

http://www.youtube.com/watch?v=Q3AtiYJHjKs