How much HP will a 4" mufflex with Flowmaster muffler support?
Thread Starter
Joined: Jan 2002
Posts: 398
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From: St. Charles, IL
How much HP will a 4" mufflex with Flowmaster muffler support? 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
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
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.
Thread Starter
Joined: Jan 2002
Posts: 398
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From: St. Charles, IL
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.
Thread Starter
Joined: Jan 2002
Posts: 398
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From: St. Charles, IL
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.
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.
Thread Starter
Joined: Jan 2002
Posts: 398
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From: St. Charles, IL
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 **** together and make something flow well while sounding good.
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I love my Mufflex with Magnaflow. I get compliments all the time, it's a very unique sounding setup.
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Thread Starter
Joined: Jan 2002
Posts: 398
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From: St. Charles, IL
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.
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.
Thread Starter
Joined: Jan 2002
Posts: 398
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From: St. Charles, IL
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......
Launching!
Joined: Mar 2004
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From: SUGAR GROVE TOWNSHIP ILLINOIS
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...
Thread Starter
Joined: Jan 2002
Posts: 398
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From: St. Charles, IL
Probably will be stuck going back to true duals......
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.