How much HP will a 4" mufflex with Flowmaster muffler support?

MBC Racing · 06-29-2009, 05:20 PM

I have been searching and can't find any results...... I have heard that the flowmaster used in the 4" mufflex flows like crap. Some reports of picking up 28 rwhp by switching to a borla xr-1 in place of the flowmaster???

I had it on my car and LOVED the way it sounded. I took it off due to being heavy and trying a true dual set up with bullets. Well, the duals are going on another car and I am contemplating putting the mufflex back on this car. It will be a 6.0L heads cam motor with A4 and SS4000 yank. Hoping for 450-470 rwhp.

Question is..... how much hp can the flowmaster muffler support effeciently?? Would I pick up 25 hp with a different muffler or another true dual setup??? I don't care about 5 rwhp... however 25rwhp is a BIG deal. Anybody have a before/after dyno result?

Thanks

Black Sunshine/ 00SS · 06-29-2009, 07:02 PM

You'll have to do a search.. I know I have seen some write ups about it. Guys have also switched to the magnaflow, and been happy with the results. If my memory serves me, it was more than 5 hp gain by getting rid of the Flowmaster.

MBC Racing · 06-30-2009, 01:59 PM

I searched under mufflex and flowmaster. Find a bunch of stuff, but not what i am looking for. Plenty of how the transverse spintech sucks and the same with the flowmaster cat back. However, nothing on the mufflex with the flowmaster.

KurtRardin · 06-30-2009, 03:40 PM

Hell, if you like the way it sounds then just go with that. A cutout can take care of the rest.

MBC Racing · 06-30-2009, 03:48 PM

Quote:

Originally Posted by KurtRardin

Hell, if you like the way it sounds then just go with that. A cutout can take care of the rest.

I ran it with out the muffler for a test run down the street. It was "go directly to jail" loud comming out of the 4". I don't want to spend the coin on an electric one and want my car running and tuned dead on for on the street which will be 90% of its use. I'm not worried about a couple hp, but 25 is a big deal. I'd rather spend the money once on a good exhaust that I don't have to screw around with. I already have the mufflex, started with it before the car got to this hp level.

I don't want to do this test myself since I am buying new headers and don't want to spend money on a Y if I am going to end up true dual again.

KurtRardin · 06-30-2009, 06:07 PM

How about the same setup but with the magnaflow muffler? Mufflex sells it, but not on their web page. Several people have it, and the magnaflow design is strait thru. Someone stocks this setup for LS1's, and I can't remember who. I think it was a thirdgen store.

MBC Racing · 07-01-2009, 09:25 AM

The any of the straight through mufflers will work and flow well..... straight through is obviously minimal restriction... BUT how will it sound???? I don't want it to sound like azz or be super loud. I just wish flowmaster could get thier shit together and make something flow well while sounding good.

Grifter · 07-01-2009, 09:44 AM

I love my Mufflex with Magnaflow. I get compliments all the time, it's a very unique sounding setup.

Custom Mufflex Exhaust. *PICS*

LS1crazy01 · 07-01-2009, 09:53 AM

Just go duals, even a 2 1/2" setup will flow better then a 4" Y pipe set up.

MBC Racing · 07-01-2009, 10:04 AM

I had FLP long tubes, 2.5" y with 3.5" flowmaster merge going to 4" mufflex. After I shot the muffler off the car when it was loose one day.... I started thinking it was a RESTRICTION! Then I chopped the y, put in magnaflow 2.5" X, and ran 2 24" long dynomax bullets side by side where the single int pipe use to go. I had awsome ground clearance and it sounded good. Those headers are now looking tired (dull grey and been patched where the emissions fittings fell off) and that setup is going on my road race car. I had planned to buy new headers for the other car and since I still had the mufflex, I was going to maybe put it back on. I tried to run the duals on each side, but had a lot less ground clearance that way. Only issue I had was to make sure the drive shaft didn't come down and rub on the muffler. I may go that route again, but am not sure....... I just loved the way the mufflex sounded.

KurtRardin · 07-01-2009, 10:57 AM

Quote:

Originally Posted by LS1crazy01

Just go duals, even a 2 1/2" setup will flow better then a 4" Y pipe set up.

Are you sure? One 4" pipe has almost 22% more area than two 2.5" pipes together, and only about 12% less area than two 3" pipes. Something tells me that a 3" y pipe that merges with a single 4" pipe would outflow 2.5" duals.

MBC Racing · 07-01-2009, 11:02 AM

Quote:

Originally Posted by KurtRardin

Are you sure? One 4" pipe has almost 22% more area than two 2.5" pipes together, and only about 12% less area than two 3" pipes. Something tells me that a 3" y pipe that merges with a single 4" pipe would outflow 2.5" duals.

That is what i was thinking. IF i go with a Y, it will have the dual 3" to single 4" flowmaster merge. I'm not even going to mess with the dual 3 to single 3 stuff......

Flawless02SS · 07-01-2009, 10:22 PM

I read somewhere a while back that a Flowmaster can handle up to 260ish HP. Yeah, Flowmaster is no Flow Master at all, lol!!!!!

squale iii · 07-01-2009, 10:28 PM

i'm going to be going with that borla straight thru muffler i think on mine. I'm running LT's and an off road y-pipe with a dump right now it's it's OBNOXIOUSLY loud lol

2002SS#1811 · 07-03-2009, 01:32 PM

Quote:

Originally Posted by Black Sunshine/ 00SS

You'll have to do a search.. I know I have seen some write ups about it. Guys have also switched to the magnaflow, and been happy with the results. If my memory serves me, it was more than 5 hp gain by getting rid of the Flowmaster.

Dropped 9 hp going from a true dual to a Magnaflow and that is with adding cats. Very satisfied

The dual was about go to jail loud or let's just say it was a problem. I also have E-cut outs when I track it or feel like it.

Sounds nice without all the problems now.

I use to live in St Charles also...

Big_Bird_WS6 · 07-03-2009, 01:42 PM

sounds clips would make this whole thread better

mrsracing · 07-04-2009, 07:52 AM

I'm planning on going Mufflex but don't know whether Spintech, Flowmaster, etc? Interesting thread.

KurtRardin · 07-04-2009, 10:17 AM

Too bad Mufflex won't sell just the over-axle part of their exhaust. That's all I really need to make my own 4" exhaust.

MBC Racing · 07-07-2009, 11:00 AM

Quote:

Originally Posted by Flawless02SS

I read somewhere a while back that a Flowmaster can handle up to 260ish HP. Yeah, Flowmaster is no Flow Master at all, lol!!!!!

That is the flowmaster designed for the cat back. I talked to flowmaster and this is a 4" race muffler. They said it can handle 450-500 hp. However it is dependant on RPM since it is the volume of of the air and the velocity......
Probably will be stuck going back to true duals......

JFM-jr · 07-07-2009, 11:10 AM

I made my own muflex style setup. 3" custom Y into a flowmaster merge out to 4 inch over the axle with a Hooker max flow 4 inch muffler. This gained me 14RWHP over the SLP dual dual that had a Kooks 3" Y catless as well.