okay about a week and a half ago I installed a high flow cat on my car. It's a magnaflow replacement cat # 23473. My exhaust as you can see in my registry is a megan racing catback. Well since I added this cat it's gotten alot louder and droans alot in the car going down the road and even got a slight bit of rasp on initial start up when cold or when idleing for a while and building moisture in the exhaust pipe. Would a resonator be worth my time it would it still be fairly loud and droan in the car?
Cat installed.
Before I added the cat.
http://www.youtube.com/watch?v=2M_E6K_BrEY
After I added the cat
http://www.youtube.com/watch?v=esaKd4rVfyk
WOT in the car after cat. Alot of noise but not really going anywhere although it made a slight difference as the car wouldn't do this before.
http://www.youtube.com/watch?v=XOYZYObjJAA
2009 Ford Mustang V6
I had thought about a resonator and a borla pro xs muffler. But I think that the muffler I have would look great behind and tucked in a LS sport bumper.
2009 Ford Mustang V6
i have a magnaflow 18" magnapack, sounds great.
12.33 @ 111.67 mph [Oct 2009]
Dyno'd on 08/02/09 - Mustang Dyno:
327.6 WHP 333.6 WTQ [10.1 AFR]
You could do a diff muffler.
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Wait until you get a header, lol. Youll definitely want a resonator if you get a header, yours isnt too bad now though. If you want cheap get a glasspack, or if you dont mind spending a bit more go magnaflow or something.
I actualy have a 12" long 2.25" straight through aerospeed or something brand resonator sitting around if you want it. It wont quiet it down too much but it will take away the rasp. $5 lol
You've got a few options. I'd probably just get a good resonator. You could give the silencer a coat or 2 of matte black paint, then put it in. If you get a resonator, go 1/4 inch bigger thatn your exhaust piping to account for the louvered holes in the resonator.
My buddy has a custom 2 inch cat-back with a megan racing muffler. He put a header on it last week and the cat was shot, so he had to weld in a piece of straight pipe until he could find a high-flow cat. It's LOUD.
I thought the megan pipes were larger than factory pipes.
If you got the factory replacement, then you may be pinching things.
But, the recomended catconvs from magnaflow are the 90435 (2.25"), 90436 (2.5")
They're actually a little longer and should handle the sound issue.
I have the 2.5" version, 2.5" piping all the way back on my 2.4, no resonator (or header)
My rasp comes from my hollowed out muffler,.
Otherwise its plenty quiet.
Quick answer, get a nice resonator.
Less quick answer, opt for another cat. Then add the resonator if need be.
-M
Remember....syringes go in the RED waste basket.
Haha, welcome to the freeflowing world of exhaust upgrades.
Just get a Dynomax SuperTurbo with a nice tip and you'll be done.
Or get a good magnaflow muffler.
That would cease any and all raspiness you're having and may quell your droan.
But when you lessen the backpressure given to you with what the factory gives you, this is going to happen.
I actually enjoy that droan and volume to my exhaust. I wouldn't have it any other way.
It's music to my ears and lets me know things are purring right along where they should be.
Good luck with it and hope you get it the way you want.
Misnblu.com
Newbie member since 1999
Thank you Dave and JBO! 
Hmmmm have been looking around and have came across the vibrant catback. I must say I like the sound of it and the looks as well dont seem to be that bad. Maybe I'll put away for that and sell my megan racing.
2009 Ford Mustang V6
Michael Antle wrote:You've got a few options. I'd probably just get a good resonator. You could give the silencer a coat or 2 of matte black paint, then put it in. If you get a resonator, go 1/4 inch bigger thatn your exhaust piping to account for the louvered holes in the resonator.
My buddy has a custom 2 inch cat-back with a megan racing muffler. He put a header on it last week and the cat was shot, so he had to weld in a piece of straight pipe until he could find a high-flow cat. It's LOUD.
thats the point of the louvered holes........youll have sounds worse than rasp if you have a section of pipe thats a bigger diameter feeding a smaller diameter
More worrying then the noise is the did you lose low end power? With my old OHV, I found that it's very easy to kill your low end torque by having a high flow cat combined with larger exhaust and a stright through design muffler...going back to a normal (but 2.25") cat helped return a lot of this lost power.
Don't buy from MANTAPART!!
Use the removable resonators that cmae with the mufflers that is what they are for.
FU Tuning
