This was posted on www.fullsizechevy.com which is a truck forum. Supposedly this review was performed by Martel Brothers...

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All tests via an independent lab
All tests @ 15” wc

2 “ Straight Pipe 283 CFM
2 ¼ “ Straight Pipe 365 CFM
2 ½ “ Straight Pipe 521 CFM

2 ¼” Typical Bent tailpipe 268 CFM
2 ½” Typical Bent Tailpipe 417 CFM

2 ¼” Inlet/Outlet_ Glass Pack Tips- No Louvers- Smooth 274 CFM
2 ¼” Inlet/Outlet- Glass Pack Tips-Louvered 133 CFM
Same as above set for reverse flow 141 CFM
2 ¼” Cherry Bomb 239 CFM
2 ½” Cherry Bomb 294 CFM

2 ½” Inlet/Outlet Dynomax Super Turbo 278 CFM
2 ½” Inlet/Outlet Ultraflow Bullet 512 CFM
2 ½” Inlet/Outlet Gibson Superflow 267 CFM
2 ½” Inlet/Outlet Flowmaster ( 2 Chamber) 249 CFM
2 ½” Inlet Outlet Flowmaster ( 3 Chamber) 229 CFM
2 ¼” Inlet/Outlet Thrush CVX 260 CFM
2 ½” Inlet/Outlet Maremount Cherry Bomb 298 CFM
2 ½” Inlet/Outlet Hooker Aero Chamber 324 CFM
2 ½” Inlet/Outlet Hooker Max Flow 521 CFM
2 ½” Inlet/Outlet Borla Turbo 373 CFM
2 1/2" Inlet/Outlet Magnaflow 284 CFM


Standard OEM 2 ¼” Inlet/Outlet 138-152 CFM
Standard OEM 2 ½” Inlet/Outlet 161-197 CFM

The madrel bending of the pipes done by aftermarket exhaust companies is good for 2-4 h.p. depending on the severity of the stock bends. Most local exhaust places dont have a mandrel bender so changing the pipes out doesnt do anything if pipe size it not increased.

My opinion, if its more noise and a little more power just add the best flowing stainless muffler to the current system and never do it again. If you increase pipe sizes, then a local shop and only stainless. Dont care about money but want ease and better gains than most local shops can offer with no pipe size increase, and aftermarket exhaust.

NOISE does not mean power, some think it does is why Flowmasters are sold in the numbers they are!!!

 

Too bad they didn't test some of the bigger sizes like 3 inch and 4 inch. I just put a Borla XR1 oval offset muffler with 4 inch inlet and oulet on my car, and I'm very happy with it. Now if I could just find a local shop that carries 4 inch stainless steel pipe, I could take out the 3 inch I pipe and adapters. I can't find a source for a 3 inch input, 4 inch output Y pipe in stainless either, so I guess I will be fabing one.

 

I think mufflex and Spintech have 4 inch setups...

 

Yes they do, but not in stainless steel.

 

Thought I would add this review too.

The results in HP order:
1.Flowtech Warlock (open) 374.2 hp/ 333.1 tq
2.Bassani Real Street 373.7 hp/ 333.8 tq
3.Hooker Maxflow 373.5 hp/ 333 tq
4.Borla XS 373.3 hp/ 332.6 tq
5.Magnaflow 372.8 / 332.5 tq
6.MAC 372.3 hp / 331.5 tq
7.Flowtech Afterburner 372.3 hp/ 330.1 tq
8.Hooker Aerochamber 372.1 hp/ 330.4 tq
9.Bassani 372 hp/ 333.5 tq
10.Spintech 371.6 hp/ 332.2 tq
11.Edelbrock Performer RPM 370.9 hp / 331.3 tq
12.Borla XR1 370 hp/ 334 tq
13.Flowtech Terminator 369.5 hp / 331.3 tq
14.Dynomax Ultra Flo 369.4 / 333.2 tq
15.Flowmaster 369.4 hp / 331.8 tq
16.Flowtech Warlock 366.3 hp / 325.3 tq
17.No muffs 365.2 hp / 330.1 tq

Sound Off in Quietest to Loudest (Decibels):

1.Borla XS, 80db at idle, 90db at 2,000 rpm, 110db at WOT.
2.Hooker Maxflow, 80db at idle, 90db at 2,000 rpm, 120db at WOT.
3.Magnaflow, 82db at idle, 91 at 2,000 rpm, 114db at WOT.
4.Flowmaster, 82db at idle, 93 at 2,000 rpm, 115db at WOT.
5.Flowtech Warlock, 83db at idle, 92 at 2,000 rpm, 112db at WOT.
6.Dynomax UltraFlo, 83db at idle, 94 at 2,000 rpm, 113db at WOT.
7.Borla XR1, 83db at idle, 96db at 2,000 rpm, 118db at WOT.
8.Bassani Street, 83db at idle, 96db at 2,000 rpm, 120db at WOT.
9.Edelbrock RPM, 84db at idle, 93db at 2,000 rpm, 118db at WOT.
10.Bassani Real Street, 84db at idle, 96db at 2,000 rpm, MAX. (120+db).
11.Flowtech Afterburner, 86db at idle, 94db at 2,000 rpm, 115db at WOT.
12.Flowtech Terminator, 86db at idle, 94db at 2,000 rpm, 119db at WOT.
13.Hooker Aerochamber, 87db at idle, 94db at 2,000 rpm, 114db at WOT.
14.SpinTech, 87db at idle, 97db at 2,000 rpm, 116db at WOT.
15.MAC, 87db at idle, 98db at 2,000 rpm, 119db at WOT.
16.No Muffler, 91db at idle, 103db at 2,000 rpm, MAX. (120+db).

http://forums.stangnet.com/archive/index.php/t-392314

 

nice to see the info man, thanks!

 

I think those flow numbers are definitely goofy, how can a straight through muffler like dynomax or magnaflow flow half of what a straight peice of pipe does? don't make sense to me.

 

Logically it might not make sense but the comparison Pro Stock John posted and the one I posted are 2 totally different tests. Yet the flow numbers seem to match the kind of restriction each muffler really caused on the exhaust. The Hooker Aero Chamber flowed higher than the Dynomax and in the comparison I posted the Hooker made more power than the Dynomax. The Dynomax flowed better than the Flowmaster and in the the comparison I posted the Dynomax made more hp than the Flowmaster. The Magnaflow cfm numbers do seem low though for making as much hp as they did.

 

exactly, i've seen dyno results where a cutout only gaind 1-5 hp over a straight through design like magnaflow and the like.

 

This is an old post worthy of being dredged up, I think you just need to make proportional increases the numbers for the 3.0 mufflers vs the smaller mufflers that were part of this study.

Based on this study I went with a Hooker Aerochamber for my truck, and it's quieter than I thought it would be which is GREAT and I won't have that nagging doubt that I went with something that doesn't flow a lot more than OEM.

 

Flow is not directly proportional to pipe size since the cross sectional area of a tube is related to the square of it's radius.

 

people buy flowmaster in masses because of the sound.
while some mufflers outflow f.m they dont sound as good.
i gained 7 rwhp with just a flowmaster 80 muffler and stock pipes.
that was on back to back dyno pulls.

 

I found another flow test comparision.

http://www.svtoa.org/articles_006.htm

MODEL
Flow Rate Muffler Inlet Size

@ 20.3" H2O

+ Edelbrock 5501 492 scfm 2.25"
$ Flowmaster 42440 483 scfm 2.25"
Race Magnum Welded 17216 711 scfm 2.25"

+ Edelbrock 5511 579 scfm 2.50"
$ Flowmaster 42540 352 scfm 2.50"
Ultra-Flo SS 17263 1133 scfm 2.50"
Race Magnum Welded 17218 1000 scfm 2.50"
# Borla 40600 836 scfm 2.50"

+ Edelbrock 5505 708 scfm 3.00"
$ Flowmaster 43040 392 scfm 3.00"
Ultra-Flo SS 17296 2200 scfm 3.00"
Race Magnum Welded 17220 2200 scfm 3.00"
# Borla 40450 1400 scfm 3.00"
# Borla 40575 1100 scfm 3.00"

@ Edelbrock 5535 562 scfm 3.50"
$ Flowmaster 435409 576 scfm 3.50"
Ultra-Flo SS 17268 2200 scfm 3.50"
Race Magnum Welded 17224 2200 scfm 3.50"
# Borla 40615 854 scfm 3.50"

@ Edelbrock 5537 1400 scfm 4.00"
* Flowmaster 54040-10 634 scfm 4.00"
Race Magnum Welded 17225 2600 scfm 4.00"
# Borla 40741 1450 scfm 4.00"

+ Edelbrock General Application Series
@ Edelbrock Victor Series Race
$ Flowmaster 40 Series ( 2 Chamber)
* Flowmaster Delta Force Race Series
# Borla XR-1 Racing Series (Round or Oval)

 

I still would like to try the super turbos on my true dual setup.

 

Straight through mufflers are the best. They are relatively quiet at idle and part throttle. THen they get loud at wot, which is what u wont. Kinda like a cutout that opens when u want it 2.

I cant understand the popularity of flowmasters, spintech, or turbo mufflers. They have poor flow and are loud.

 

Your right dug, I really wanted to use Hooker Maxflow mufflers but they were just too big. Sucks not having a car that was engineered for duals.

 

I'd really like to try and run my duals out the back eventually using the same straight through mufflers I'm using now. I think it would reduce the noise level inside the car quite a bit.

 

My trans-am has no mufflers, but the stock y-pipe set up, so your saying i'd gain hp by adding a muffler? I always thought that mufflers restricted air flow for the most part which made you lose hp. I've also heard you need back pressure, but doesn't the cat do that?

 

.
What cat-back do you have which does not have a muffler? The SLP-Loudmouth is the only cat-back system I know of which has no muffler.

 

maybe he has a modified catback setup, cuz your right, LM is the only setup that doesnt have a real muffler and just has a small resonator.