It's a 5.9 and with the current clogged catalytic converter, and plenum issue I'm sure anything will increase my gas mileage. I'm now looking for replacement gaskets and stage 8 bolts so i don't have to replace pacesetters in the future. Any reccommendations? And how long will my o2 sensor have to be to reach the new location in the lt headers.

 

LMAO, we can Go 'round and 'round till the sky falls down buddy.

Too much Back pressure is bad, Not enough is equally bad.
These 5.9, unless modified, are not your Granddaddy's carbureted Power wagon.
They are for the lack of any other thoughts injector fed comp controlled crap!

I would love nothing more than to just the 5.9 Maggie down and rip every sensor and comp controlled plastic POS out of Ours, and then rebuild it to be more like the 1978 360ci EH1, and either stuff a stick in it or go with a good ole Borg T-10.
That is just to much time and money for the family DD to be inoperable.

All BS aside, wants, preferences, and theories aside......you are in part dead wrong do to excessive ECU reliance of modern Mopar.

Standard OE O2's should be fine, since they themselves have a little more reaching room than they really need on their lines. Any direct fit you use SHOULD keep your O2 bungs within 2 inches of OE placement.

This giving extra fuel to further my aggravated rant on BP good or Bad--->Clogged Cat= excess backpressure, and by definition causes a borderline flood scenario, or a very a rich burn. Considering you mentioned a plenum leak that just compounds the issue since it would be suckking extra air that the ECU will want to compensate for by tossing more fuel at it.
I totally get where your already not good situation definity gets ugly fast.

 

No. Back pressure is bad. Period.


If you put too big an exhaust on too small an engine it will actually create more back pressure, in a way. The exhaust gasses will expand and slow down.


What you want is scavenging.


Not sure why you seem so angry at the little plastic sensors. These engines run forever and engine management is a significant factor why.



Anyway,

A single 3in pipe has been well known to work well with these engines.

 

Thanks I will eventually go 3" all the way back but for the moment it will be 3" up to the cat and 2.5 after. Any recommendations on what gaskets and bolts I should use?

 

I can say first hand you will lose low end with that modified of an exhaust, the low end does like some back pressure. I had the full exhaust done on my durango 5.9l with 3.92s. I had JBA cat forward headers, JBA Y-pipe that collected to 2.5" and had it go 3" from there to the rear using a spintech muffler and no cat. The college I go too is at the top of a large hill. Before the exhaust I could set the cruise at 55mph and it would do that hill in O/D without down shifting up until 70 degrees outside. After the exhaust it had to be under 20 degrees out for it to do the hill with cruise at 55mph without downshifting. But from 2500-4000 rpm it had a substantial increase in torque. So build the system to your needs. If I were doing my truck I would do the headers and have at least single 2.5" to the muffler to preserve some back pressure because lets face it these trucks are heavy and need that low end torque, personally I don't drive above 2500rpm very often.

I would use fel-pro gaskets and Caterpillar exhaust bolt. Any cat dealer will have a bunch of them on hand, they are expensive though like $4 a bolt, but they last forever.

 

What he said....^^^^

 

[QUOTE=Double Oh Dodge;3292481]You didn't indicate if the reverence is to a I6 cumins 5.2 or 5.9.
the only issue with jumping from having the OE config of 2.5>2.25 pipes to running 3" from head to tail, is there is likely to be a noticeable fuel consumption increase, ESPECIALLY in the 5.9's.
I have noticed they love their backpressure perhaps a bit too much. QUOTE]
1. Well for one he posted links to pacesetter headers so that alone is apparent it's a v8.
2. Stock config is 2" ypipes into the cat then 2.5 back, and 2.5 out the muffler with 98+ having a 3" tailpipe. Not being rude just not quite sure what you meant by "2.5>2.25". 2.25 isn't even found in the stock system.
3. Backpressure. Rid your brain of that term, it's completely inaccurate. Backpressure is the force exerted by an exhaust pulse that pushes BACKWARDS in on the system. This is caused by blockages/restrictions. Your statement of these engines loving backpressure implys that crimping the end of the tailpipe would be the ideal system. The real secret to ALL exhaust systems is keeping flow velocity up to increase scavenging, the effect where a pulse is moving quick enough to create a slight vacuum behind it to pull the next pulse with it thereby making it easier for the engine to breathe and making it more efficient, and keeping flow capacity high enough to not choke out at an intended rpm. For a higher hp, higher rpm engine, 3" is a PROVEN good pipe size with virtually any muffler when using headers and a cat. Both of which the OP plans on using. Sure with stock manifolds it's not ideal. 2.5" will keep more of your low-mid range tq though at 4+ it won't perform like the 3", though most of us that doesn't matter because we're not turning 5k regularly.
Honestly idk that I would go 3" if your truck is pretty much stock. I wouldn't even do longtubes for mostly stock. The problem with those pacesetters other than the fitment with the driveshaft (and quality control with burred edges and bent pipes) is that the primary tubes are simply too big. Knocking it down to 2.5 afterwards will help but the tubes are still quite large, for an otherwise stock truck. I'm assuming your's is mostly stock so if I'm wrong my bad.

 

Now that is a good explanation!

 

Thx man! I learned all that back when I was 18 and I KNEW it ALL. Now I'm 20 and know nothing

 

And lets not forget tube diameter, and length as well. (on headers....) Unfortunately, we don't get a large selection when it comes to headers, for long tubes, we get the pacesetter, with large primaries..... which kinda beats up low-end torque, but, does nice at mid-range, and above. But, on our trucks, the intake chokes 'em out above around 4K, so, no real point to them.

Shortie headers are actually better (out of what we have available) for the low end grunt that you want in a truck. That actually kinda surprised me, till I looked at the tube diameter on the pace setters..... If only I could find a reasonably priced set of 1.5" primary longtubes, with three inch outlets.