Looking to change my exhaust, thinking glasspacks. 05 FX4 Screw. Anyone running these?

 

Please dont. Dynomax bullet is the new winner.

 

x2, Bullets will sound much meaner and deeper, and more respectable. Unless the crackle and rasp is in your taste, steer clear from Glasspacks.

 

thanks guys,
which muffler is it? i checked out the dynomax website, the only "bullet" it shows is a race bullet. Is that the one you are talking about?

 

yea, thats the one

 

dont order directly from dynomax. order from summit racing.

 

Please be advised that the term "glass packs" would include:

Allied
Edelbrock
Borla
Magnaflow
Hooker

All of which use packing material which although is not fiberglass (as no one has used in 20 years), they each use a sound material absorbing design. Even conventional "glass packs" are proven in flow testing to out perform many of the so-called "Free Flowing Real Mufflers". For reference, WyoTech, Hot Rod Magazine has numerous published articals on this. On the net, please read:

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


http://www.popularhotrodding.com/eng...../index1.html (this is an in-depth article that tests not only the mis-conception of flow demand but also how placement of a muffler (a glass pack in this dyno test) can actually "fool " the system into thinking that it is essentially a straight pipe.

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

MUFFLER FLOW TEST

MUFFLER Flow at 28-in H20
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


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.


MUFFLER HP TORQUE 2,500-6,000rpmAverage
Hooker Competition 397.4 381.1 286.8hp/351.9 lb-ft
Thrush Boss Turbo 407.1 384.9 292.1 hp/357.5 lb-ft
DynoMax Race Magnum 409.5 394.3 298.8 hp/366.9 lb-ft
Flowtech Afterburner 409.7 391.2 294.8 hp/361.7 lb-ft
Thrush Glasspack 409.5 389.8 297.7 hp/365.3 lb-ft
Summit Turbo 411.5 386.3 291.5 hp/357.4 lb-ft
DynoMax Super Turbo 412.7 387.2 292.6 hp/358.6 lb-ft
Hooker Super Comp 413.8 387.2 292.8 hp/359.0 lb-ft
Summit Fully Welded 415.4 390.7 295.6 hp/362.4 lb-ft

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-$40) each and available at any muffler shop) installed backwards in independent test flowed 90%+ of a "race spec muffler". Others using other brands consistantly showed similar results.

 

Dynomax bullet not glasspack! Or should I say, if you go with glasspacks, go with the bullet!