Has it been decided yet that for anyone w/ an '04-05 f150 wanting to run SI/DO or a single muffler DI/DO setup should run 2.5" pipe all the way through for the best performance? I am thinking of finally doing the SI/DO or DI/DO setup, not sure which. To do the DI/DO I'd have to cut the factory y pipe out and run the pipes directly into the muffler and back out. Does anyone know what this would do to performance.....hurt it or help it or any difference at all??? Or would it be best to stick w/ the SI/DO setup and keep the y pipe in place? Does anyone know how these 2 ways effect sound and performance, anyone heard any of these trucks set up like this?

fourpointsix will be proud, I'm going to get an imco muffler.

 

Higdogg...I've been patient, and I AM proud!

With a DI/DO muffler 2.5 inch is the biggest I would go. SI/DO I would go with a 3" in, 2.5 outs. However, some people have complained about a loss of low end with the 2.5 inch pipe on SI/DOs. I'd talk to an exhaust guy that really knows his stuff on that one. 2.25" would probably be the way to go UNLESS you plan on supercharging. I'm considering switching to true duals on my truck after I get headers and I'll be running dual 2.25 inch pipes.

 

In general dual 2.5" for the 5.4L and dual 2.25 for the 4.6L. I do not know how good the OEM y-pipe is on the 2004+ models, but it was terrible on the 97-03 trucks.

If you do (or have a shop do) any custom exhaust, it's a crap shoot on any performance changes. Spend the $375 on a Magnaflow system if performance is the priority.

 

I think I read that 2.5" is good for any SI/DO applications on bigger engine trucks like these. I think my '93 302 has 2.5 in/ 2.5 out, SI/DO application. Can you guys tell me what the deal w/ going 3" in/2.5" out is? Is there any advantage over 2.5" in/2.5" out? I was actually considering having the y cut off, running the factory 2.5" pipes from the engine into a single DI/DO muffler, and running 2.5" pipes out of the muffler. Fourpointsix, what is your application and pipe sizes, I forgot and I don't feel like searching?

 

Higdogg, I have the 4.6L so 2.25 inch pipes would work well for a true dual setup on my truck. On yours it would probably be a good balance to go with true duals with 2.5 inch pipes. BTW there's pics of the IMCO installed in my gallery if you want to see how small those suckers are.

 

I'm not going w/ true duals. True duals to me means 2 true mufflers (dual mufflers). I'm thinking of a DI/DO (1) muffler. There will be a difference in flow between that and true duals. So I was just wondering if there's a difference in flow/performance between the DI/DO setup and SI/SO setup.

 

Yes there is more flow with the DI/DO setup. By the way, the DI/DO should flow the same as true duals. Many of the DI/DO mufflers have an X pipe built in too so you won't need to put a separate one in. What DI/DO muffler do you plan on using?

 

Really? I didn't think a di/do muffler would flow the same as true duals. If that's the case then maybe I won't go w/ it, because I've heard rumor of our trucks possibly doing better as far as performance w/ a single style muffler. I just thought it would have been a clever way to get the y pipe off there and keep things flowing smoothly instead of it coming out of the engine w/ 2 pipes into 1 stopped up hole (like a y pipe) and into a muffler and then back out into 2 pipes (si/do). It goes from 2 to 1 back to 2. I figured if a man put a di/do muffler on, it would stay w/ 2 pipes the whole time and never lose any 'flow' and possibly do better performance-wise.

 

Higdogg, I would do the DI/DO. Getting rid of that Y pipe would be a plus. You won't lose any performance as long as your pipes aren't too big.

 

fourpointsix, what is your opinion on the backpressure w/ a di/do setup? Supposedly these trucks run best w/ a certain slight amount of backpressure, or so I hear....?? Seems like the di/do setup and cutting out of the y pipe would eliminate a lot, I'm just wondering if its too much. Need an exhaust technician to answer this question. I'd probably go w/ all 2.5" pipe all the way if I did it like that.

 

I recently had true duals w/ H-pipe custom made for my '04 F-150 5.4L. Pipes are 2.5" mandrel bent w/ Flowmaster Super 40 mufflers. I definitely DID NOT lose any power and the sound is great. Gas mileage increased approx. 1 MPG so far. I would not go any larger than 2.5" for this engine if you go with true duals.

 

Getting rid of the stock Y pipe is a plus, adding an X pipe or getting a di/do muff with an X pipe built in would also be a plus. Backpreasure would not be an issue as long as you dont go too BIG on the pipe(like some of the other guys said). I would do the true dual, with X pipe and two mufflers or a di/do w/X pipe built in, doesnt matter its going to be true dual set-up regardless, one is more compact than the other. If you want it loud get small mufflers if you want it be more toned down get BIG mufflers, either way when you really get on it it will rumble .
Good Luck
Later
M V

 

i have a 4.2 v6 and i'm running true duals and a K&N FIPK in my 2001 f-150. i run my duals 2 1/2 inches, and have no loss in power at any range. there is a nice increase to my performance at all rpm's. i wouldnt mind rounding things out with some nice mac headers eventually! personally i have had a total of three exhausts on this truck. first was a SI/SO setup with a delta 40 flowmaster. a little more power, but too quiet for my liking. so I upgraded to a flowmaster 40 series SI/DO, with a 3 inch inlet, and two 2 1/2 inch outlets, coming out the back at a 45 degree angle. still too quiet for my taste. And then my current exhaust, which is a true dual setup: ditched the y-pipe, and put in a pair of glasspacks. very nice

 

Cant believe ive missed this thread. I just recently had my truck dualed out. Its a true dual off the cats with 2.25 pipe. I have a magnaflow muffler sitting in my back seat and im just waiting to put it on. Its very loud with out a muffler so thats why i bought one. I think it sounds great and definetly sounds mean. I had my friend do some runs while i was behind it and when he would cost doing 25 by me and hammer it, when it kicks down its daamn loud.

Anyone know how much different it will sound if i put the magnaflow DI/DO on?