Just trying to figure out the most efficient way to replace my stock setup. I've already ordered the Pacesetter LT's - and my muffler is the magnaflow 15609 setup, which I believe is 3" pipe. So the question that has been brought to my attention by another member of this forum is weather or not to use 2.5" or 3" high flow cats. His idea was to get the 3" and weld them right onto the LT's, then downcovert to 2.5. He didn't know what muffler setup I had though, so i'm wondering, why would I downcovert to 2.5 and then back to 3? I've also read posts that people who go all 3" lose low end torque..So in that case, maybe its best to have the 2.5" cats, so the LT's go from 3" to 2.5, then at the muffler back to 3"??? If it makes a difference, I'm going with the spun cats.. the cost seems negligable over the other type, and I just like the idea.

Help me out here, please!

 

Are you doing true duels? If so from what I've read an x-pipe should be used. I am also just getting all my stuff together to put on a set of LT's and do the rest of the exhaust while I'm at it. I am using OBX LT's and they come with a Y-pipe that the Headers T into. I've gone with with a 3" SI and a 3" DO Magnaflow. I believe that any loss of TQ by going this route won't be noticed. Just letting you know what I've done.

 

I'm not doing duals just yet, but won't rule out that mod for the future. I think i'm just going to go with the 3" cats and see what happens!

 

I found a magnaflow with 3 inch in and out. I have the 2005 5.4 will this be ok on my truck to just replace the muffler....??? by the way the muffler is 18inch oval with 3 inch in and out.

 

Ok. Shouldn't be bad since your getting LTs. Why not catted LTs? Save some hassle.

Your stock exhaust is 2.5" so it will need adapters, but it would be easiest to find a 2.5" muffler.

 

Thats why I went with the magnalflow catback kit.. It incldued the muffler, plus all the piping. It was more expensive, I htink i paid about $370 from performance peddler, but it was super easy bolt on, and included a reducer pipe to go from 3" to 2.5".

If you go with just hte 3" muffler, you will have to do a little work to get it to fit, like cutting the pipes -- unless the new muffler is exact same size as old muffler, but you will still have to integrate a reducer somewhere.

 

So if I get a reducer from 2.5 to 3 and then just run a 3 inch out I am good to go?

 

What engine do you have ? I can't remember everyones motor - I know I have to ask you every time - why don't you list it somewhere like most people do - Hell it's not even in your profile.

If you not going to make a sig with your info or don't want to display it in the top right corner or anywhere else for some reason - The least you could do when you start a new thread is tell us what you have for a motor - Setups vary from one motor to the other.

I hate asking this so much , I spent 5 minutes looking for your engine size, that sucks.

Just put it in your sig or info somewhere - it's just a couple #'s and a decimal point . ???

 

Kind of.. you will still have to do alot of pipe cutting if you just get a new muffler and a reducer. Check out pictures of the magnaflow kit I got 15609. It has a muffler, a pipe that goes from the muffler to the cats which starts at 3" at muffler and then goes to 2.5" (this goes on w/ clamps) and then a mandrel bent piece that goes from the muffler out the side of truck, and has exhaust hangers and an exhaust tip. I still ran into an issue as I couldn't get the pipe off that ran from my old muffler to my cats -- it was pretty well stuck and I had to bring it to a shop to have them put a torch on it. THey got that off, and I was able to go home and finish the job. So again, if you just buy a muffler, your going to have to cut the pipes to get your muffler to fit exactly, including the reducer. If your new muffler is smaller than your old muffler, your going to have to buy new pipe somewhere. The other thing is that the pipes supplied with the kits are slotted so you can use clamps. If you just cut your pipe and try to mate it up to the muffler, I think it will have to be welded.
TO be honest, i'm not the best person to be answering this question, and I hope i'm not too far off. WOrst thing that happens is you just order your muffler and can't get it on, and bring it to a shop to do. I can't imagine a shop charging more than $40-80 to do this, so your still ahead of the game.
Hopefully someone else with more experience chimes in on this question.

 

 

If your stock no tune - Remember you have a Big a$$ 3" Flange that you want to slide into over the top of (Top of preferably) You have that collector (4 chambers ) Right there as well. A 3" cat into the header will smooth up the . Your improving scavenging big time with those LT's.

If you reduce to 2.5 at the header flange , all that air movement is going to hit a brick wall directly after the collector. You don't want that. You want that air to move in that area.

You want a smooth transition . The header feeds into a 3" cat opening/ No bumps in the road. Your air hit the converter cone/ flow is reduced/ cat is then reduce to 2.5 at the rear / Flow is reduced a little more/Run 2.5 an stick with it - Don't open it up , you have plenty of flow . Bumping up to 3" after the cat WILL hurt the torque.

For the sound your looking for (not loud) and to maintain torque ++++ / SISO~2.5 X 2.5 Offset. Borla, Maggy, Roush. - The biggest one you can get. - I have a 22" inch and mines to loud for me. I don't here anything at cruising speeds tho.

 

Flange/ Slip fit/ Clamp if you need to run to the shop to get her welded



Ready to weld up. -



Collector/ Flange/ O2/ Modified heat shield -



Another pic -