So I'm asking Santa for true dual exhaust on my 2005 5.4 Supercrew 4x4. I'm thinking of going with 24" Magnaflows, because I don't want it loud, just a rumble, and having a local shop weld it all up. My question is what diameter pipe should I go with? I know that the bigger the pipe the deeper the sound, which is what I want, but I'm also very concerned about losing low end torque from having too much flow. So what do you guys think I should go with? 2? 2.25? 2.5 just seems way to big for a completely unmodified engine. Thanks for the input.

 

I think you'd be good with 2.5" pipes. That should keep enough back pressure on it to keep your low end torque happy, but should also allow for a good throaty tone and the flow that you're in search of.
I just checked Magnaflow's site, and they too are using 2.5" pipes on their cat back systems.

 

Thanks for the reply. I saw that on their website as well, but I think none of theirs are true dual setups, they all start after the y pipe and split again at the muffler. My thinking is that the single pipe, however big it is stock, between the y and the muffler would give you the required back pressure, regardless of the pipe diameter after the muffler. But I don't know much about this stuff, which is why I'm calling for help.

 

So is your plan to terminate the factory exhaust right after each cat, and then fab up from there?

 

I think so. After pricing things I could either get a SISO catback from Magnaflow, or a true dual setup with Magnaflow mufflers for close to the same price or even a little cheaper at a local shop. I'm not dead set on true dual either, I just thought that since I was having the work done by a shop, I'd get the "better" setup.

 

"Better" is relative. Is the shop going to use aluminized pipes or stainless steel? Seeing that you're in UT, I would think that you'd want to stay away from aluminized.
Also, the MF pipes will be mandrel bent. Is your shop using a conventional pipe bender, or mandrel pipes?
Just something else to ask the shop, if you haven't already.

 

I actually haven't called just yet, I wanted to get an idea of size before getting a quote. But I've got a call in now, he's calling me back with a quote in 20 minutes, so far he's talking about doing a standard dual after the y pipe setup. Says that it's hard to make things work around the transfer case. So we'll see I guess. I'm open to anything, the only things I have set in stone are that it needs to be a big magnaflow muffler and stainless steel.

 

Good grief, just got off the phone with the shop. They won't do true duals because it's too hard, they'll either do SI/SO or SI/DO catback, they only offer aluminzed, mandrel bent pipes and will charge me around $350 or $550 for the respective Magnaflow systems. Does that sound right?

 

Personally, I would walk. You get a good amount of snow and ice in UT right? The road salt/chemicals does some serious damage on anything other than SS. My aluminized pipes on my previous Explorer last 7 years here in VA, and we only get salt treats one week out of the year, normally.

 

Turns out that it's kind of hard to get stainless steel around these parts. And the prices are higher than I thought. I guess it's back to the drawing board. Maybe I'll just have to wait for a killer deal on a Magnaflow catback system and install it myself.

 

Check out the Banks cat back system also. I got one last year and it is all stainless and pre-welded from Banks. Now it is SISO and I kept the same exit point as the factory tip but it also comes with a 2.5 inch system with a huge chrome tip.

 

I thinking that the best route is going to be buying a 22" or 24" Magnaflow and have a shop weld it in. That way I keep my perfect condition factory stainless steel, mandrel bent tailpipe and get the better flow/sound for cheap. I'm going down to the shop now so they can see what style of muffler to order. I'll report back.

 

that should save alot of money and it wont be loud. myself, i like it to turn heads when im getting on it. if you keep a single stock pipe out the rear and only change the muffler, your going to want to go with a loud muffler because that system is going to quiet it down alot. i have an edelbrock SDT dual exhaust and i got it off ebay shipped to me for $200. i put it on myself and after about 2 months of driving it started to get its tone and sounds good now.

 

oh yeah in my area $375 is a good price for a flowmaster catback installed, the high side is $500 or so but this is not SS

 

Spoke to a couple of shops. I can buy a 22" Maggie muffler (12577) for like $80 off of the interwebs and have it welded up for around $65. So much cheaper than any other option and most of the benefit. Thanks for all your input guys. As soon as I get it done, I'll post a video or something.