hey guys i have a 2004 f150(new body style) that is straight piped and y's right before the axel. all it has is catalytic converters. i'm needing a muffler to build back pressure to make my truck run a little bette at least thats what my mechanic said. is there any truth to this? it seems to make sense. but i'm wanting to fix it for fairly cheep and i'm wanting a muffler to keep somewhat loud but more of a deep sound, not a annoying glass pack sound.

i've heard a magna flow will sound good and a flow master super 44 will keep loud but more of a glass pack sound. somebody please give me advice! lol i'm taking it in tomorrow to get aligned since i put a leveling kit on today and they are the top notch exhaust place in my town so i'm gunna get some prices and see what can be done

 

dynomax bullet or magnaflow magnapack

/thread.

 

Back-pressure is a myth. You can tell that to your mechanic.

As Mig already suggested, Bullet or Magnapack.

 

ok then. bottom line, which would you choose? i'm even consider having them dumped. and even tho its a myth, will it help a little?

 

I would choose the Magnapack.

I highly doubt just removing the muffler is causing it to not run properly.

 

well for the most part it runs fine. he just said it'd help a little bit. i just found your youtube videos. haha but would it still sound good with only magnapack and then y out or would it be puny sounding?

 

i would chose bullet because its cheaper and imo it sounds better in a single exhaust vs a single magnapack. duals on the other hand, i would hands down go packs.

 

i LOVE the sound of 4.6 Punishers truck. so i should ask about the dynomax bullet? i just the want the best sound price isnt to big of a factory but i dont wanna shell out for true duals and then still buy two mufflers. i wanna keep it the same just add a muffler.
what do y'll think about having it dumped after the muffler?

 

buy 1 dynomax bullet online through summit racing. dont dump it. put it out the side before the rear tire. my sig has that setup.

 

is summit the only place you can buy them? and to be honest, i've never like pipes out the sides before or after the tire. just my opinion so don't take any offense.

 

All I can say to the mechanic is BS- the cats create more backpressure than any muffler- and the oem ECM can more than adapt the very small fuel mixture change requirement.

For mufflers: Iwould recommend Allied- it is a straight through design, excellent quality, any (literally) muffler shop will have their products (they have been around for 30+ years), flow as well as any of the "performance mufflers" and cost (installed depending on the size) anywhere from $50 to $90. They have a deep tone, throaty, light rumble, no drone.

General muffler info:

broaderperformance.com/muffler_flow_tests.htm (Independently tested cfm flows of the more popular mufflers, glasspacks and resonators @ 15” wc:
2 ½” diameter straight pipe 521
2 ¼” diameter straight pipe 365
2” diameter straight pipe 283
2 ¼” diameter tailpipe 268
2 ¼” round glasspack- no louvers 274
2 ¼” round glasspack- with inward punched louvers 133
2 ¼” round glasspack- inward punched louvers/installed backwards 141
2 ½” inlet/outlet Dynomax SuperTurbo 268
2 1/4” inlet/outlet Thrush CVX 260
2 ½” inlet/outlet Flowmaster 2-chamber 249
2 ¼” inlet/2 ½”outlet Cherry Bomb turbo 249
2 ¼” inlet/outlet Flowmaster 3-chamber 229
2 ¼” inlet/2 ½”outlet Maremount Super C (OEM Replacement) 149
2 ¼” inlet/2” dual outlet Maremount 183
2 ¼” inlet/outlet California Turbo 229
2 ½” inlet/outlet Hooker Aerochamber 324
2 ½” inlet/outlet Hooker MaxFlow 521
2 ¼” inlet/outlet Maremount Cherrybomb Vortex 298
2 ½” inlet center/outlet offset Borla Turbo 373



I have listed here a muffler shootout test done by CAR CRAFT:

The Mufflers

DynoMax Race Magnum 528.64 cfm
Thrush Magnum Glasspack 507.40 cfm
Summit Fully Welded 343.38 cfm
Flowtech Afterburner 342.20 cfm
DynoMax Super Turbo 333.94 cfm
Hooker Competition 232.46 cfm
Hooker Super Competition 320.96 cfm
Summit Turbo 331.16 cfm
Thrush Boss Turbo 297.36 cfm

MUFFLER Idle dB WOT dB
DynoMax Super Turbo 89 123
DynoMax Race Magnum 94 133
Flowtech Afterburner 92 124
Hooker Competion 92 122
Hooker Super Competion 90 125
Summit Turbo 89 124
Summit Fully Welded 92 125
Thrush Boss Turbo 90 123
Thrush Magnum Glasspack 92 128

DYNO TEST
All mufflers were dyno-tested on a 355-cube SBC with 10.0:1 compression, Air Flow Research 190 aluminum heads, a CompCams 292 hyd. a Victor Jr. intake, a Holley 750-cfm double-pumper, and 1 5/8 Headman headers.

While there are mufflers that will out flow a glass pack design, it also depends on the design. Does the glasspack use "louvers or perforations" - Louvers reduce the flow by as much as 50% but Allied resonators (that sell for $20-$50) each and available at any muffler shop) installed in independent test flowed 90%+ of a "race spec muffler". Others using other brands consistantly showed similar results.

Exhaust Drone
Exhaust drone & exhaust noise while both are different by definition, both are created as a result of impactors/promoters. Exhaust drone is that which is caused by harmonics- a soundwave generated which in essence takes the exhaust sound and sends it back up the exhaust system (towards the engine) and is released or transferred into the passenger compartment. This transfer typically happens where large contact areas exist that have little to no sound dampening qualities and/or materials- as a result of the muffler construction or vehicle manufacturer.

Exhaust Noise (in passenger compartment) is what most people actually complain about. While harmonics do play a contributive role, it is not the primary cause.

Impactors/Promoters

I would love to tell everyone that “x” is the cause 99% of the time for exhaust noise complaints, but it is typically a series or combination of numerous factors which leads or develops the level of noise which is uncomfortable to the ear. The first “rule” of an exhaust system is that the noise should be generated at the point of discharge (ie tailpipe tip). Obviously, if the tip terminates at your door or immediately under the passenger compartment, the sound level will be much greater at the exhaust discharge point than if the tip exits the rear of the vehicle, but this is common sense.

Assuming that there are no exhaust system leaks and isolators are correctly installed at all mounting points, what is not acceptable by industry standards, is when an exhaust system has been installed correctly, exiting well past the passenger compartment to have substantial exhaust sound transfer into the passenger compartment at a level which does not allow a person to talk without raising their voice to well above ambient noise levels. Whether you love to hear your engine roar (which I do), stereo blast or have a conversation, this interfers with your ability to enjoy what you like.

Now for the Causes

The first problem is most muffler shop staff today have little to no knowledge of exhaust systems, the “tricks” to installing a system that will “please” the customer, and simply verbally repeat the marketing materials provided to them by the system manufacturer. As previously noted by several others, there are 3 basic muffler designs, Absorption, Diffusion, and Chamber (Resonator), no matter which one suits your ear best, the criteria for promoting unnecessary in-cabin noise is the same.

Impactors:

Exhaust system material thickness should be no less than 16 gauge- double-walled pipe was commonly available through the 1970’s until manufacturers began seeking ways to reduce costs. Many of the “Muffler Chains” who marketed lifetime warranties always used double-walled pipe before “stainless steel” became the “in-crowd”. If a shop had it available, I would choose double-walled aluminized coated steel or 14 gauge stainless steel (depending on environmental conditions or personal tastes) - it is very quiet, solid and in terms of costs, pipe is pretty cheap, depending on length, 16 gauge aluminum coated runs about $11 to $20 wholesale (depending on diameter), stainless about double for the same gauge.

The muffler should be located as close to the axle (far away from the passenger compartment) as possible, allowing at least 3” of straight run pipe before a bend occurring (if installed to the forward position of the axle), with the overall length as long as possible. In the oem location, 24" will fit fine, located at the head pipe, 30" will fit fine as well and eliminate almost any possibility of drone in this particular location due to the size, length and insulation qualities (and yes, Allied does make units this long).

With regards to the 5.4/4.6 engines, The head-pipe (the pipe installed in between the exhaust manifold and the muffler) should be no greater in inside diameter the 2 7/8”, at 3” it now becomes a contributor.

Duel Tailpipes should be limited to no greater than 2.25” inside diameter, single tailpipes 3” maximum inside diameter- tips which are larger can certainly be installed but should be limited to 12” in length and have a discharge point past any material that may “catch” a soundwave or exhaust. When you exceed these diameters, it now becomes a contributor.

Tailpipe length in general should be as short as possible, minimal bends, etc, terminating past the axle, 1.5" past the body or bumper. Lengths greater than 4 feet promote “drone” (ie harmonics), typically about 3 ½ feet past the muffler.

Pipe diameter reduction should occur before the muffler. While many muffler installers like to use mufflers which reduce pipe diameter or split the exhaust at the point of discharge at the muffler, or install reducers to connect the tailpipes after the muffler induces “noise”.

Ultimately, it is the quality of the material and the installer which 90% of the time leads to a successful installation. I would like to also emphasize that it is not necessary to spend a fortune on a muffler ($100+) or system to have an excellent sounding, performing and long lasting result.

 

i appreciate the info but some of that looked like chinese. lol i'll ask about allied. what size would i need for either dynomax, allied, or magnapack? like length? i just want to have it sound good the first try

 

Chances are, they won't have anything besides Slowmasters and their knock-offs. Summit has Bullets for $40 a piece. And if you want to dump it, do so after the axle.

 

well this place is pretty legit. i know they carry magnaflow and flowmaster in stock for a fact because i looked into puttin pipes on our 08 KR with the 5.4 but just havent felt like having it done yet, its nice to drive something quiet ever now and again. lol but i'll go by there and ask around tomorrow and see whats up. i may not even do it if they confirm the back pressure thing is a myth. and i've know the owner for awhile and he cuts me deals on everything so im sure he wont cheat me

 

i just seen a truck on youtube that has my same motor and it appears my same set up only it has big 24s on it. maybe y'll have seen it? but it has a flowmaster super 44 and i thought it sounded pretty good, i don't know how good it'll sound in person or how'd it hold up but i'm gunna go to the shop today and have them compare the dynomax, magnaflow, and the flowmaster and see what they say.