Installed X Pipe = Instant DRONE

[NacsMXer]

So I have a 2.5 inch mostly mandrel-bent true dual custom exhaust system on my 5.4L supercharged 2V truck. Stainless JBA shorty headers into a pair of Catco 2200 series high flow cats, through the piping and into a Magnaflow DIDO 11379 4x9 oval 11" body muffler. At the time of the install a couple of years ago, my exhaust guy's Magnaflow catalog incorrectly indicated that the 11379 muffler had a perforated Tru-X core. In other words there was an X pipe built into it. Well I found out that's not true, as the 11379 11" body muffler is actually two straight through pipes. Only the 14" and 22" mufflers contain the Tru-X core in the DIDO configuration. So I have basically been running divorced true dual pipes with no crossover. Fast forward to last friday, where I had my exhaust guy install what was supposed to be a Magnaflow 10791 2.5" Tru-X X pipe crossover into my existing system. He spliced it in, rebent one of the pipes to fit, and repainted the pipes black. He said the X pipe might make it a little quieter, and reduce interior drone a bit. Previous to the X pipe install with the divorced duals, it had a nice aggressive exhaust note but an extremely tolerable level of interior drone. Adding the X pipe to the system alone, it has a louder idle, a less aggressive/more muddy exhaust note, and 3X the interior drone! Holy crap is the drone unbearable. It buzzes through the interior right after take-off, and gets extremely bad in the 1600-1900 RPM range. What gives here, seems like it works fine for everybody but me? I'm gonna have to have it remodified again and go with an H pipe instead. I thought X pipes were supposed to help reduce drone. And correct me if i'm wrong, but the X pipe he installed doesn't look like no Magnaflow Tru-X to me.

[avfrog]

New one for me...

[NacsMXer]

The X pipe he installed doesn't look like a Magnaflow unit. Notice how it's square-shaped in the center. The Magnaflow Tru-X has defined pipe shapes that intersect at the center to truly look like a X.

I had a Ebay special X pipe that looks similar to the one I just got installed. It had the square shaped center and also droned like a mother. It seems like that square open chamber would promote drone in the same way a hollow open chamber Flowmaster muffler would. And I think it has become way worse in my case since this X pipe is sitting right under the cab of the truck. Without the X pipe it was quiet when you needed it, and loud when you wanted it. Thoughts on my theory?

Here's what a Tru-X looks like (i'm sure you already know)

[4.6 Punisher]

Yeah, I noticed an increase in drone too when going from an H-pipe to the X. I still like the overall tone that the X-pipe helps make.

[SSCULLY]

It was not S/C, but my 2001 5.4L NA Screw I installed the Lightning Bassani Dual system on, with the X pipe. Had to cut the factory Y out and change to a system that looked more like the L / HD system with the dump in front of the rear wheel. The Bassani X pipe was more defined in the round X look, rather than a stamped box look to it.

The Bassani X pipe with 2 SI/SO mufflers did not cause cab drone. It was loud at WOT, but at cruising it was mellow.

[NacsMXer]

Thanks for the input fellas, keep it coming if you could. I'm leaning towards changing the setup to a H-pipe.

Here's the before/after X-pipe videos if you want to hear the difference the X-pipe alone makes. Watch with headphones for best quality.

Before
http://www.youtube.com/watch?v=CFUi3...&feature=g-upl

After
http://www.youtube.com/watch?v=ZjxyO...&feature=g-upl

[NacsMXer]

It seems like with the X pipe the idle and low RPM exhaust note became a bit beefier, but it seems to have lost some of its aggression revving it into the higher RPM's.

What do you guys think, should I just go with an H-pipe and be done with it?

[SSCULLY]

From what I recall, the H pipe did not add anything with the scavenging effect, it was only an equalizer.

The other thing, the '03 and older L and the HD had the X pipe right at the front of the dual SI/SO mufflers.

The kit in the picture above is installed as it would be on a L or HD, and the additional pipe is added to the front ( had I got a HD version, the pipe would have been in the kit ).

Don't know if this still holds true on a S/C 5.5L 3V motor or not, just know what I had found out before.

[beechkid]

Here's my 2 cents....an inexperienced muffler guy.....to find the correct spot to place either an H or X, is to run a small line of paint down the side of the exhaust pipes 9both pipes), drive the truck for 10-15 minutes. Where the paint has blistered is where the "area of confusion" is......meaning that is where to install the H or X. Incorrectly placed when combined with thinwalled pipe (less than 16ga), the reverb(drone) is going to be increased and heard.

[aussiekeeper]

I think they both sound like crap.................Who would want to listen to that?

[avfrog]

My X and H sounded identical at idle and low RPM. At mid to high RPM is where the difference was. X is not as choppy sounding, and sounds a little smoother.

Now thinking back, I also had no crossover to start with. The H and X both made more rumble in general over no crossover at all, but to me they sound a lot better than no crossover.

Long story short, I think you will have the same problem with the H pipe.

[tarajerame]

Originally Posted by beechkid

Here's my 2 cents....an inexperienced muffler guy.....to find the correct spot to place either an H or X, is to run a small line of paint down the side of the exhaust pipes 9both pipes), drive the truck for 10-15 minutes. Where the paint has blistered is where the "area of confusion" is......meaning that is where to install the H or X. Incorrectly placed when combined with thinwalled pipe (less than 16ga), the reverb(drone) is going to be increased and heard.

[beechkid]

Originally Posted by tarajerame

Thanks, guy! I know I am old, but regardless of all the CAD engineering, mfg, etc, etc (which is very good- don't get me wrong) sometimes the ol fashion way of doing things may not be "cool" or even "High tech", but it always seems to work when everything else fails.

[NacsMXer]

So today I took the truck back to the exhaust shop and had the stamped X-pipe cut out and had a H-pipe section fabricated in its place. They used a short 3" long section of 2.25" pipe flattened into an oval shape to create the crossover between the 2.5" pipes. The crossover is a bit further forward than the X was, and is as far forward as possible which is good.

Interior resonance is still worse than the crossover-less /divorced duals configuration but a bit less than the X-pipe. It is also in a slightly narrower RPM range now. Having a crossover is better than none so I figure i'm going to have to deal with what drone there is. Heck, I may even switch the setup for a pair of SISO Magnapacks down the road who knows

After H-Pipe sound clip:
http://www.youtube.com/watch?v=MojZUhEsKyI

[NacsMXer]

Here's a couple of pics of the H-pipe





11379 4x9 11" body DIDO muffler