Muffler Flow Ratings

jroc07gt · Mar 19, 2010

I did some searching and found a list of quite a few popular muffler flow ratings. If anyone knows the flow rating of some more mufflers, please post it up and I'll edit the list.

All muffler flow ratings are with a 2 1/2" offset inlet/offset outlet and measured at 28" H2O

Here goes:

3" Straight Pipe 705 CFM

2 1/2" Straight Pipe 485 CFM

Pypes Violator 453 CFM (louder than the Race-Pro)

Pypes Race-Pro 453 CFM

Magnaflow 436 CFM

SpinTech Pro Street 427 CFM

Borla 427 CFM (not stingers)

SpinTech Sportsman Street 402 CFM

SpinTech Truck/RV 391 CFM

Pypes Street-Pro 349 CFM

DynoMax Super Turbo 344 CFM

Hooker Aero Chamber 344 CFM

DynoMax Turbo 320 CFM

Flowmaster 40 series 273 CFM

Flowmaster 50 series 213 CFM (Jesus these things suck...)

For every 2.2CFM, 1 horsepower is restricted or unrestricted. That means it takes 880CFM (440x2 mufflers = 880cfm) of flow to support 400whp. Of course that is an approximation, it's not an exact science but is a pretty close estimate.

Sound Levels

No Mufflers - 91db@Idle - 103db@2000RPM - 120db@WOT

SpinTech ProStreet - 87db@Idle - 97db@2000RPM - 116@WOT

Hooker Aerochamber - 87db@Idle - 94db@2000RPM - 114db@WOT

Flowmaster - 82db@Idle - 93db@2000RPM - 115db@WOT

Magnaflow - 82db@Idle - 91db@2000RPM - 114db@WOT

Greg Hazlett · Mar 19, 2010

Which Borla-stingers or the normal one?

cdutchess78 · Mar 19, 2010

Does the restricted air flow also corelate with how loud they are as well? If not,do you happen to have a chart for that as well?

jroc07gt · Mar 19, 2010

There is a decibel chart too, I might be able to find that one as well.

Edit: Updated topic with sound levels for the ones I could find.

Greg Hazlett · Mar 19, 2010

As a side note..my car was dyno'd with 300 miles on it with the JLT intake/tune on it and the stock mufflers; had the Stingers ready to install so while it was on the dyno they were installed and there was no increase/decrease in numbers so the stock mufflers are not a restriction.

cdutchess78 · Mar 19, 2010

thanks

jroc07gt · Mar 19, 2010

Greg Hazlett said:
As a side note..my car was dyno'd with 300 miles on it with the JLT intake/tune on it and the stock mufflers; had the Stingers ready to install so while it was on the dyno they were installed and there was no increase/decrease in numbers so the stock mufflers are not a restriction.

Obviously, you don't have enough mods to make your engine flow more air than the stock mufflers can flow. You would most likely have to make 350whp or more to start to see even the slightest gains from changing out the stock mufflers.

I don't have the flow ratings for the OEM mufflers, but I'd have to guess it's at least 375CFM. That would put it at 340whp, so the stock mufflers are more than enough for a bolt on s197.

Edit: On a sidenote, most dynos seem to reflect these flow ratings as flowmasters lose power while magnaflows gain power. Flow rating alone cannot show you everything however, such as: does the muffler come with mandrel bent piping, does the muffler use a chambered design or a straight through design, and does the muffler's tip restrict flow?

The flow rating alone does not tell you if you will pick up power, but it's one more piece of the puzzle that can help you figure that out.

SirKnightTG · Mar 19, 2010

This is a cool thread.

I find it funny how poorly the flowmasters do given their name and all.

I have Boomtubes so I guess they would be about 450 maybe.

jroc07gt · Mar 19, 2010

SirKnightTG said:
This is a cool thread.

I find it funny how poorly the flowmasters do given their name and all.

I have Boomtubes so I guess they would be about 450 maybe.

I think the Boomtubes are pretty much a straight pipe with a 4" tailpipe that has some baffling, so it would flow the same as a 2.5" straight pipe.

shatter · Mar 19, 2010

This was taken from http://www.mustang50magazine.com/te...rd_mustang_muffler_comparison_test/index.html
The test vehicle was a 1990 Mustang with a 5.0, built as a 306 with Twisted Wedge heads, Thick Flow Track heat manifold, 75mm throttle body, AFM N-91 cam.
The Borla XS was the best performer, but at over $150 each, out of the reach of most. Next on the top of both low end Torque AND High end HP, is the Magnaflows, and with a choice of coated steel, or stainless.

shatter · Mar 19, 2010

This was taken from http://www.broaderperformance.com/muffler_flow_tests.htm

This is a chart of popular performance and a few stock type mufflers I have tested on our flow bench. These were all the most popular mufflers sold and installed at a local exhaust shop. Straight pipes have been tested and are used to compare these mufflers to "potential" flow of a muffler. When running a performance muffler on the street there are many more things to consider then just good flow. For instance pleasant tone and enough sound reduction to avoid any "unwanted" attention from local authorities. One thing to keep in mind is how restrictive tailpipes are. You can have a great flowing muffler but if your tailpipes are restrictive you may not be getting any gain from loud, high flow, and not to mention sometimes "expensive" mufflers.

shatter · Mar 19, 2010

This was posted on www.fullsizechevy.com which is a truck forum. Supposedly this review was performed by Martel Brothers...

*******************
All tests via an independent lab
All tests @ 15” wc

2 “ Straight Pipe 283 CFM
2 ¼ “ Straight Pipe 365 CFM
2 ½ “ Straight Pipe 521 CFM

2 ¼” Typical Bent tailpipe 268 CFM
2 ½” Typical Bent Tailpipe 417 CFM

2 ¼” Inlet/Outlet_ Glass Pack Tips- No Louvers- Smooth 274 CFM
2 ¼” Inlet/Outlet- Glass Pack Tips-Louvered 133 CFM
Same as above set for reverse flow 141 CFM
2 ¼” Cherry Bomb 239 CFM
2 ½” Cherry Bomb 294 CFM

2 ½” Inlet/Outlet Dynomax Super Turbo 278 CFM
2 ½” Inlet/Outlet Ultraflow Bullet 512 CFM
2 ½” Inlet/Outlet Gibson Superflow 267 CFM
2 ½” Inlet/Outlet Flowmaster ( 2 Chamber) 249 CFM
2 ½” Inlet Outlet Flowmaster ( 3 Chamber) 229 CFM
2 ¼” Inlet/Outlet Thrush CVX 260 CFM
2 ½” Inlet/Outlet Maremount Cherry Bomb 298 CFM
2 ½” Inlet/Outlet Hooker Aero Chamber 324 CFM
2 ½” Inlet/Outlet Hooker Max Flow 521 CFM
2 ½” Inlet/Outlet Borla Turbo 373 CFM
2 1/2" Inlet/Outlet Magnaflow 284 CFM

Standard OEM 2 ¼” Inlet/Outlet 138-152 CFM
Standard OEM 2 ½” Inlet/Outlet 161-197 CFM

antonio1988 · Mar 19, 2010

very interesting read... I have the Magnapacks, which are a resonated straight through design, I'll assume they flow close to the 2 1/2" piping rating?

SirKnightTG · Mar 19, 2010

jroc07gt said:
I think the Boomtubes are pretty much a straight pipe with a 4" tailpipe that has some baffling, so it would flow the same as a 2.5" straight pipe.

Yep. But I figure the baffling may slow it down just slight. That's why I'd estimate it to be a little under straight 2.5" pipes.

gmantheman · Mar 20, 2010

Flowmaster A/T just may affect performance. Two of my friends with S197s went to the 1/8 mile strip. Both were running constant 8.7XXX at 81.XXX. The next time at the track one of my friends replaces his stock axlebacks with flowmaster A/T. He was now running 9.1xxx to 9.2XXX at 79.XXX while my other friend was still running 8.7XXX at 81. The only difference was the flowmasters.

Kankakee · Mar 20, 2010

Hmmm, I have flowmasters.. ruh roh.

gmantheman · Mar 20, 2010

Kankakee said:
Hmmm, I have flowmasters.. ruh roh.

But with a procharger it is probably a moot point.

jroc07gt · Mar 20, 2010

gmantheman said:
But with a procharger it is probably a moot point.

With a procharger, it makes an even bigger restriction. He's probably losing 20-30whp with those flowmasters.

kevinatfms · Aug 24, 2011

any numbers on the stock mufflers?

UltraKla$$ic · Aug 24, 2011

jroc07gt said:
I don't have the flow ratings for the OEM mufflers, but I'd have to guess it's at least 375CFM. That would put it at 340whp, so the stock mufflers are more than enough for a bolt on s197.

.

kevinatfms said:
any numbers on the stock mufflers?

Close enough I'm sure.

Muffler Flow Ratings

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