Anybody know how restrictive the stock mufflers are?

Benchracer

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Does anybody have any evidence on how restrictive the stock mufflers are? I am shooting for 1000+rwhp and was curious how much my stock mufflers are going to choke my power down, if at all vs. an aftermarket muffler. Its a turbo car and I do not like loud exhaust so I am not going to buy an aftermarket muffler. If anything, I will run some electric cut outs. The rest of the exhaust is pretty well opened up(no cats and mandrel bent exhaust). Thanks for any info.
 

CSG

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They will kill a turbo car's power. The GT500 axle back cost me around 70rwhp where it would go dead at 550rw (mustang dyno). It was also VERY quiet with the GT500's since the turbo acts like a muffler as well. With the Magnaflow comp 3" it was comparable to the GT500 and no turbo as far as loudness. You will need cut-outs regardless for 1000rw. Good luck!
 

kona 199

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glad to here that someone besides me does not want a loud exhaust.i do a lot more driving than racing and a loud exhaust gets old quick.i got longtubes on the way from beefcake and hope to keep my factory muffers.
 

burke985

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Get some JBA'S they are even more quiet and lighter than the GT500 and have a clean sound
 

Deespeed99

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You'll never do it through stock or even GT500 mufflers. Mine started to choke out at 650 through stock mufflers and picked up 100hp just from opening the cutouts.
 

MRSUPRA

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glad to here that someone besides me does not want a loud exhaust.i do a lot more driving than racing and a loud exhaust gets old quick.i got longtubes on the way from beefcake and hope to keep my factory muffers.

Your not the only one.
If the mufflers become a restiction, a turbo kit with open wastegates(if you like the sound of a broken muffler while boosting) will relieve a lot of back pressure.
 

burke985

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No no drone with them, only issue I had was the tips stick out far so I went to a muffler shop and had them pushed back a few inches. But as far as sound goes I like them not too loud with the O/R X
 

Benchracer

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Get some JBA'S they are even more quiet and lighter than the GT500 and have a clean sound

Will they flow enough to make my horsepower goals?

It amazes me that the stock mufflers are as restrictive as everyone says. I know guys that have made tons of power running multiple mufflers in line on turbo cars to make a good sleeper. I would figure a halfway decent muffler would be fine. Guess our stock mufflers arent as great as I thought. :shrug:
 

burke985

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Will they flow enough to make my horsepower goals?

It amazes me that the stock mufflers are as restrictive as everyone says. I know guys that have made tons of power running multiple mufflers in line on turbo cars to make a good sleeper. I would figure a halfway decent muffler would be fine. Guess our stock mufflers arent as great as I thought. :shrug:

Not sure on the HP part , im at 617 with JBA's,Stock headers and O/R X, They are a chambered muffler
 

manolith

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i made 620rwhp thru the stock mufflers with an offroad xpipe at 8.5psi of boost with only 14 degrees of timing.
 

turbosha

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ive seen sleepers put glasspacks on the staights of the pipes.
I believe one nova had 3 glass packs per side!!!!
they are straight thru but have packing to absorb sound.
I thought of taking my resonators off and putting 3 inch diameter 30" long glass packs in.
 

ArtVandalay16

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What's a "non" restrictive muffler that isn't ear piercing loud? Borla/magnaflow?
Didn't realize my gt500s were that restrictive...is this also the case for sc car or are we talking strictly turbo?
 

thekanezzi

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I've wondered this as well. I have gt500s and stock oap, I've thought about going to full 3 inch id and I'm not sure which muffler and oap to go with. The problem is, I don't want it to be too loud. Any suggestions?
 

five.slow

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727rwhp with flowmasters.... Just saying.

Once upon a time I think it was magnaflow that made a quiet muffler that wasn't real restrictive.
 

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