I know the 3" in dual out flowmaster has caught alot of crap for not flowing worth crap. On the HOT ROD Power Tour I went to the DYNOMAX trailer where they had a flowbench with about 6 mufflers and the flowmaster was about the worst of the designs. But I asked the guy, where was the Magnaflow setup? He took me outside and explained there was a reason there was not a Magnaflow on the bench and it was because it outflowed all of their mufflers. He said next year would be a totally different story.... and since I had a Magnaflow on my LS1 car to just keep it. I can appreciate honesty like that.

Anyways, back to my point. On my LT1 car I am running the Mufflex 4" in 4" out single pipe setup and the car with just heads/cam/nitrous/suspension/LT's/Mufflex ran 10's all day long. So I am under the assumption it flowed beautifully for a stock internal block LT1 to run so well. Not to mention, I am head over heels about the sound.

Well, I have added LT's to my 3" Magnaflow catback on my LS1 car and I think it sounds pretty ratty at WOT. With manifolds it sounded pretty wicked (different than any other system out there). So, I just purchased me another 4" Mufflex with the Flowmaster muffler. Right now, the car is just a bolt on car, but I have Heads, cam, and nitrous for it, and it will be going on within the next couple weeks.

So I guess what I am asking, has anyone ever tested or compared the 4" 1 in 1 out design Flowmaster to anything else? Gains, losses?

 

I think the flow issues from Flowmaster have mostly to do with the crossflow 80 series design. I think the single in-out systems probably flow a lot better. I don't have any numbers, but I haven't really heard anyone complain about flow qualities on the single in-out mufflers.

 

I was thinking the same thing, and hopefully that holds true. I have yet to see the internals of the 4" in/out design.

 

I agree. I think this especially holds true with the 1-chambers like I have. Good luck, and I bet that 4" kit w/ a flowmaster will sound awesome!

 

It will sound good but again flow not the greatest. Just get a 4in cut out if you want the extra power. just my opinion.

 

Results based on 5.0 Mustang Magazine December 2002 issue (page 55). Test car is a ’90 Coupe with 370 HP and 11 second potential. A number of 66 pulls were made to compile this information. Where does your muffler stack up?

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).
__________________

 

hmmm, that would be expensive to hack up a 4" catback but it would dispell or prove any flow issues if done on a dyno.

 

the single chambers arent bad

 

I have a Magnaflow on my WS6 with no cut out...469rwhp, I am happy with it

 

About the same price as hacking up a 3" catback.

 

Good info!

Do you happen to know if the test car had cats or not?

 

I'm pretty sure that was with the 3" catback dual exhaust for the flowmaster though. However, that is some pretty impressive information to have.

 

True, true!!!

 

Even though it's 4", it probably won't flow very well because it still has the same chambered design I believe. There's nothing like a straight through muffler for flow/power.

 

On some flowmaster mufflers you can almost see the internals from the outside. I have had a couple of flowmaster mufflers and usually I could see the heat affected area thorugh the outside of the case where the baffles are welded inside. This can give you a general idea of whats going on inside. Even if the single chambers don't flow quite as well as a straight through muffler, they can sound pretty wicked!

 

Hmmm.... I find this rather interesting. Notice that no muffler was down about 10hp from the top 5. So, think about all the guys on here running 3" Bullets with dumps (which is pretty much no muffler at all). Are they actually leaving power on the table?

 

that was with a mustang, i think our bigger motors and more power we move so much air it wont hurt us

 

Yeah so by not having mufflers one loses HP?

 

FWIW I've got a Hooker cat back, 24" Dynomax in the I pipe, and a cut out Behind the Dynomax. With the cut out closed vs cut out open there is 4 rwhp difference. I was surprised the difference was so minr, I guess it shows the Hooker does flow well.

 

Hi FRDnemesis, I have the flowmaster and would like to scrap it. What exact part number of the Magnaflow do you have. Just want to get the right one, thanks.