I've read THE exhaust guide and about 50 other threads and listened to about 25 youtube videos and I'm still not sure which way to go. I'm probably overthinking things but just want to get it right the first time.

I'm stock except for the DWV intake mod and Eastern Tru Performance cats (cats not installed yet, going to do it all at once). I'm going to add a SCT tuner w/ custom tunes after the exhaust is done. May add some long tube headers in the future but doubtful.

• Priority 1: Low end performance boost
• Priority 2: No drone
• Priority 3: Low rumble, not raspy, mild tone

• Option A: MF 2.5/2.5" Y-pipe. 2.5" intermediate. 2.5" SI/ 2.5" DO
• Option B: 2.5" DI/DO with built in X-pipe. Remove stock Y & run dual 2.5" throughout. Maybe add an H-pipe also(?)

I've narrowed it down to the Borla Pro XS or Magnaflow. Leaning toward the MF because they sound a little more mellow and have more size options.

The hardest choice is SI/DO or DI/DO (not true duals, the DI/DO with built in X-pipe). Cost wise it won't be much more for the DI/DO but will I gain anything in performance, drone, or tone vs. the SI/DO?

Is the built in X-pipe a dumb idea because the X should be closer to the transmission?

Will that X hurt the tone and make it louder/more raspy vs the SI/DO?

I originally wanted the H over the X for the lower tone and torque gain vs the X. Can I still add the H and locate it near the tranny with the DI/DO muffler or will that somehow mess things up to have two crossovers?

 

For exhaust drone, I would defer to a posting I made a couple of years ago...............

https://www.f150online.com/forums/ex...hour-trip.html

With regards to mufflers.....

I would recommend saving a lot of money & go with Allied resonators......available is any muffler shop nationwide, are of excellent quality, 1/2 the price of “performance Mufflers”, available in any length from 10" to 38" (IIRR), flow as good as Borla or most any of the "Race Mufflers”, tone is deeper and you get a nice rumble (low) with no drone and none of the tinny "ricer" echo. Allied has been made for at least 30 years and available in just about any diameter you would require (I have personally run these for since the 1970's....nice low rumble on acceleration & deceloration, no drone, deep tone.

On my 2006 Mark LT (5.4), I run duels (made my own wye pipe), you can easily run 38" long units (single or duel).....this will make no difference in flow/performance.

H vs X pipe

With regards to “H” versus “X” pipes, the “H” was originally conceived to balance the two separate exhaust pulses to create 1) smoothness & 2) reduce the “brapp” sound, later marketing guys started promoting the performance benefits although at the time and as verified in later dyno tests, there was little to no performance gain. The “X” pipe is in essence trying to simulate the effects of a 180 degree exhaust system whereby discharging the exhaust on opposite pipes creates a “vacuum” effect literally sucking the next exhaust pulse out, creating less back pressure etc….and it is effective. There are several ways to verify the location of where it should be installed and swag is not a good thing & can actually have a negative impact. Typically the install would go about ½ way between the mufflers & header/manifold…..the location, you can either use an IR gun and look for the hottest spot or take a swag of where the location is, take sone paint & paint a thin line down that area….drive the car for about 10-15 minutes with a couple full throttle short accel’s, then look for where the paint is blistered….this is the “area of confusion” and where the x-pipe should be installed.

 

There is very little need for a true dual style exhaust on these trucks, but for low end torque if you go with dual pipes you will want mandrel bent 2.25" exhaust. The muffler with a built in X does not perform as well as an X as close to where the original Y was.

If you really want a calm note with longtubes you may want a muffler up to 24"s in length.

 

I am probably going to go with longtubes so I'm leaning toward the true dual exhaust. But, only because I can use the H-Pipe and two 24" mufflers to tone things down.

Also, which is quieter... 5x8x24 or 5x11x22? I know that shorter is usually louder but the 22's are 3" wider so that should make for more sq. in. of acoustical dampening.

I am a little concerned about the cabin noise from the engine bay/longtubes. That's the only reason I'm not completely sold on them yet. I recently spent a lot of time and money to sound proof my entire cabin with CDL/CCF/MLV. A little extra noise out the *** end doesn't bother me but I'm not going to be happy with it coming from the engine bay. I found a few posts on Vette forums where some guys went longtube then removed them and went back to stock because the extra noise from the engine bay was too much. Can anyone who's installed OBX LT's on an F150 comment on the additional noise from the engine bay?

I get the reasoning for the 2.25 mandrel bent system but I'm not going to want to spring for the extra cost of mandrel bends. It probably doesn't work this way but I was thinking that 2.5 crimp bent pipes would have about the same flow as 2.25 mandrel bent, no?

 

Changed my cats... going with the metallic spun MF's that have 200 CPI instead of the 300 CPI ceramic Eastern cats.

Also not going to do the longtubes right now. Maybe in the future. But, I am still going to do an SCT tuner with some custom tunes after the exhaust is installed.

Going to go with the SI/DO 24" MF. Before I pull the trigger on parts I just have a few more quick questions...

2.5" all the way or 2.5" DI to 3" SO Y with a 3" intermediate pipe to a 3"/2.5" SI/DO muffler?

Keep the stock Y or replace it with the MF Y?

 

The Magnaflow Y is a full flowing transition much better than the OE connection joint. I would certainly replace it if your willing it. I have a 3" midpipe coming out of my Y pipe and into my 3" in/out muffler. Then I have another Magnaflow Y for my 2.5" tailpipes. Fully free flowing. Feels about where stock is on power. I can imagine low end torque would be stronger with a 2.5" midpipe. I would go with fully 2.5"

Earlier I remember seeing you say 2.5" regular smooth bent may be similar to 2.25" mandrel, it is and isn't. My 2004 was a 2.5" smooth bent system. I feel the systems pipe size was fluctuated too much and caused it to run worse than a mandrel system, even a full 2.5" system.

 

Thanks. I don't want to lose any low end and any gains would be a bonus so I'll go with the 2.5 mid pipe.

I can do the MF Y if it will help. Don't want to mess with it if there's not going to be any/much performance gain for the cost. I'm going to check more shops but the quote I got from the one shop I used before was much higher then I expected. My pipes are in fine shape so I'd like to keep what I can to keep the cost down. My cats need replaced anyway which is the main reason I'm doing the other mods to the exhaust while I'm at it.

I get the 2.5 vs 3 thing and I get the fluctuation with crimp vs smooth bent pipe. What I don't get is the 2.5 dual tailpipes. If the goal is to keep the pipe size/area down, wouldn't I want to go with dual 2.25" tail pipes, even if they're crimp bent? With one 2.5" pipe the area is 4.91. Two would be 9.82 while two 2.25" pipes would be 7.96. Does it not matter as much since it's almost at the end of the run?

EDIT: I couldn't understand how the MF Y could be that much better then the factory Y by looking at the outside but I found this photo and now I get it. LOL



Yeah. I'll do the MF Y.