You have california emssions, but, are not in california, so, check local laws, and see what they have to say. For the most part, it is generally "If it came from the factory with it, you have to leave it there.".....

Now, if you have inspections..... that might become an issue, however, they may, or may not be concerned about how many cats you have, just that you have them..... and the O2 sensors are there. If you don't have inspections, then you can do basically whatever you want, or, in this case, whatever you can convince you exhaust guy to do.

If you can bring the truck in, minus the third cat, and relieve him of some legal obligations, then definitely go for it. Will make both your lives a tad easier... (or, if he actually owns the shop, ask him about paying cash for the job, and no receipt.....)

If you replace the front two cats with magna flow HP cats, leaving the O2 sensors in place, (probably have to weld in some bungs for them......) you should actually GAIN some power, with NO loss of low end. They will probably be as quiet as the current system, depending on which mufflers you go with. (on my bird, I REALLY like the way it sounded with the exhaust ENDING after the cat....... just couldn't drive it that way.)

If you are replacing a bunch of pip, post-cat, just go with 2 1/4 inch pipe. Will be more than adequate to the task, and won't give you any power loss issues. (ok, shouldn't....... there are no guarantees in the real world.)

 

It seems that you are asking what size pipe to run with the true dual system. Correct?

You are actually very lucky to have cali emmisions if you want to run true duals. This allows you to have a precat O2 sensor in each bank which will give much better readings than one O2 on one side as some people run.

Since a cali motor is the same as the rest of them you should be able to follow what other people have done and get similar results. With the 5.9L, 2.25" or 2.5" true duals are usually the best size for fairly stock vehicles (yours applies). Since you really want torque play it safe and go with the 2.25.

My suggestion stands for any cat/muffler combo you decide to go with. On these trucks it really doesn't matter to much despite what you hear. Most of these trucks really aren't "high performance" (high performance is far more than bolt on's to the rest of the world) and you should go with whatever sound you like. Also high flow cat's don't really seem neccesary for your truck as you have two factory ones already which is twice what most trucks on here have. I would save your money and leave them on if they are working properly.

Make sure you have an h-pipe or x-pipe in the system. I have heard that h-pipes make more torque but don't have any facts to back that up.

Great article by the way. It is amazing how many people have no idea what they are talking about when it comes to exhaust particulary backpressure.

 

uh-oh... I'm absolutely lost again because of your sentence highlighted in blue.. I'm asking because I truly don't know- but why should there be an X or H pipe? Is it balancing flow or some such?

And I've learned far more about exhaust in the past several hours than I have in the 38 years previous combined.. that article actually made the rest of what I've read make better sense..

thanks for the input guys.

 

I believe X and H pipes allow one bank of exhaust to scavenge the other bank. David Vizard explains that the pipes can only help power so why not. I don't think h-pipe have much actual exhaust flow through them, they simply balance the pressures in the exhaust. Both crossover pipes will help sound quaility also. (make it sound like a V8 not 2 I4's)

 

I suggested replacing the factory cats with the magnaflows, simply because they flow better. Not absolutely necessary... but hey, every little bit helps.

H/X pipe makes the 'collector' length of the headers longer, and improves scavenging, which is always a good thing.

 

Drew,
That IS a cat. I have the same set up. I pulled the number off it and took it to Dodge. It's a third, unmonitored cat. If you check the Magnaflow web site it will give you a diagram of what exhaust system you have. (I think the Magnaflow number is 45206.)

California sucks when it comes to most things, especially emmisions control. Outside CA shouldn't need to keep that third cat, but you might have a hard time finding someone to cut it out.

As for running true duals in California... it won't happen. Not "legally" that is. If it isn't the way it came from the factory, and if it doesn't have a "California Air Resources Board Approved" sticker on it, it's illegal.

 

heheheheheeeeee- Pard, that WAS a cat...

I appreciate your help. A little work on it, and it somehow disappeared... from my peripheral vision I think I saw it swallowed by a vortex aka black hole.. But it's gone now.. I hope I don't miss it.. :-)

 

Good for you.

I hate California.

 

Well, you know how cats are.... what with their independent attitude, their "I couldn't care less." lifestyle.... you can just never tell when they are going to up an disappear..... Shameful things really.

 

will a dual-in/dual-out muffler accomplish the same thing as a x or h pipe?

muffler in question is a flowmaster super 40, single chamber- two in, two out.. i found one new for $45, and that is cheaper than a magnaflow x... and kills two birds if it will accomplish the same thing.. I can't see why it won't, but I figured I'd ask cause it's not uncommon for me to look right past the obvious..