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Thread: Muffler flow tests and Exhaust theory

  1. #1
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    Default Muffler flow tests and Exhaust theory

    http://www.allfordmustangs.com/Detailed/70.shtml

    According to the recent Mustang poll, more than 1/2 of voters would or did spend their first modification dollars or exhaust. Easy decision on what to do, but the real decision lies in whose exhaust to buy. With more than a dozen companies making cat-back systems alone for Mustangs, the trying to figure out how it will work with your combination can be overwhelming. Don't fret we're here to help.

    We obtained 10 different after-cat exhaust configurations for 1987-1993 Mustangs (1979-1986 can use the same setups if converted to true dual exhaust). The goal is to illustrate key points of each system and explain how it worked on the test car to help you make an informed decision on what system might be best for you.
    Last edited by V8Demon; 03-29-2009 at 11:02 AM.
    -- 05 Mustang GT-Whipplecharged !! -- 87 5.0 Trick Flow Heads & Intake - Custom Cam - Many other goodies...3100Lbs...Low12's! http://www.fquick.com/V8Demon

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    Nice.

    I wish they had used an SPL meter for a quantitative measurement of sound. Noise is an important figure of merit for me.

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    Is the Quiet Thunder the system that has the removable baffles for the exhaust tips?

    Garrett H.
    '94 F250 XLT- 4x4, 5 speed, 7.3 IDI Turbo Diesel, 4" intake, 4" exhaust, 5" turnout stacks, manual hubs, etc.
    '87 Thunderbird Turbo Coupe
    Engine, wheels, tires, etc!
    Exhaust sound clip
    Another clip

  4. #4
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    I have no idea....One thing that could have been done was to note the manufacturer's part # for each respective setup. A search on Bassani's website showed no results for a foxbody car concerning the quiet thunder system.
    -- 05 Mustang GT-Whipplecharged !! -- 87 5.0 Trick Flow Heads & Intake - Custom Cam - Many other goodies...3100Lbs...Low12's! http://www.fquick.com/V8Demon

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    Here's my favorite muffler shootout article - just the all-important comparison tables




    And the dB levels for Jeremy:
    11.96 @ 118 MPH @ 3700lb, 1.6 60' (1.564 best)

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    Perhaps you can enlighten me as it seems you have the actual article.....I've seen those results before, but am leery about them because I am unsure what other changes were taken into account on the exhaust system.

    http://www.foxtbirdcougarforums.com/...ad.php?t=17505

    With the other test it's shown the same headers and X-pipe were used throughout. With the "Muffler Shootout I've never heard if this was the case and if so what components were used.

    The test car is a mildly modified 1990 LX 5L (details here). The rest of the exhaust for the testing was comprised of MAC 1 5/8" EL headers into a Bassani 2.5" offroad X-pipe. Weights were included where possible. OK, now let's get started.
    I would very much like to see that info concerning the magazine test if it's available. It would be appreciated.

    The ultimate test would be the mufflers on some type of flow bench with as little piping as possible to show true flow #'s of the mufflers themselves.
    Last edited by V8Demon; 05-16-2008 at 01:25 PM.
    -- 05 Mustang GT-Whipplecharged !! -- 87 5.0 Trick Flow Heads & Intake - Custom Cam - Many other goodies...3100Lbs...Low12's! http://www.fquick.com/V8Demon

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    I've read the entire article and the test was a remove and replace on the same car - I can't find the entire article now though as I had a link to it but it's dead. I would much rather have them test mufflers on a 370 RWHP car than a 225 HP 14 second car due to differences may be more visible due to higher airflow. Comparing ET's is not that scientific if you ask me. Flow rates are available and straight-through like the Magnaflow flow best(?), but in the real world with exhaust pulses causing resonances in the muffler, simple flow rates may not tell the whole story. This is not the first time I've seen a test where no muffler gives less HP - there can be issues when a sudden change from a closed pipe to free-air occurs. Also see the AFR tuning comment in the article review I've posted below. I've seen some reputable racers on Hardcore5.0 claim to go the same ET with a muffler versus without. These are typically high-HP cars too.

    OK, I found another source for the article's info with a review of the methodology too! It's just one man's opinion, but I think it's a good one:

    Quote Originally Posted by Steve A.
    The best muffler comparison I've seen to shed light on available choices based on that criteria was in the December 2002 5.0 Mustang and Super Fords magazine. 15 pairs of performance mufflers were tested on a highly-tuned, naturally-aspirated, EFI 306 Mustang making about 370 RWHP. Peak power is in the mid-6000 range, peak torque mid-5000 range. Tests were run back-to-back in a single day on Rick Anderson's dyno (Anderson Ford Motorsports). Horsepower, torque, and various sound levels were recorded in the most consistent manner possible for valid comparison. Four pulls were made with each pair of mufflers, and an average used for the reported numbers. Sound was measured with a decibel meter at idle, at 2000 rpm light-load cruise, and then at wide-open throttle maximum.

    None of the mufflers produced hugely-different power results, ranging from 366.3 RWHP to 374.2 RWHP, and 330.1 lb./ft to 334.0 lb./ft. torque.

    There were, however, a lot of differences in sound levels produced...both in quantity and subjective quality. Sometimes the loud mufflers produced more power, and sometimes they didn't. I've listed the mufflers below and the suggested retail price EACH as given in the magazine (rounded to even dollars). In the brackets with the price, I've indicated their construction: SS for stainless steel, AS for aluminized steel, and MS for mild steel. Next is the measured sound-level results in decibels, followed by power numbers (to compare relative efficiency). Re: the decibel numbers...the first number after the muffler name is decibels at IDLE, the second number is 2000 rpm CRUISE decibels, and the third number is WOT decibels. RWHP & RW torque are listed last. (Note: OMS means "off the sound meter's scale... too loud to measure):

    NO muffler ($free!): 91/103/OMS/365.2 RWHP/330.1 RWT
    Bassani QT ($186 SS): 83/96/120/372.0 RWHP/333.5 RWT
    Bassani Real Street ($186 SS): 84/96/OMS/373.7 RWHP/333.8 RWT
    Borla XS ($130 SS): 80/90/110/373.3 RWHP/332.6 RWT
    Borla XR1 ($168 SS): 83/96/118/370 RWHP/334.0 RWT
    Dynomax Ultra Flo ($80 AS): 83/94/113/369.4 RWHP/333.2 RWT
    Edelbrock RPM ($179 SS): 84/94/118/370.9 RWHP/331.3 RWT
    Flowmaster 50 series SUV type ($135 MS): 82/93/115/369.4 RWHP/331.8 RWT
    Flowtech Afterburner ($43 AS): 86/94/115/372.3 RWHP/330.1 RWT
    Flowtech Terminator ($59 AS): 86/94/119/369.5 RWHP/331.3 RWT
    Flowtech Warlock ($75 MS): 83/92/112/366.3 RWHP/325.3 RWT
    Hooker Aerochamber ($69 AS): 87/94/114/372.1 RWHP/330.4 RWT
    Hooker MAXflow ($69 AS&SS): 80/90/120/373.5 RWHP/333.0 RWT
    MAC Flowpath ($80 SS): 87/98/119/372.3 RWHP/331.5 RWT
    Magnaflow ($84 SS): 82/91/114/372.8 RWHP/332.5 RWT
    SpinTech ($80 AS): 87/97/116/371.6 RWHP/332.2 RWT

    Rick Anderson wisely points out in the article that (as always) you shouldn't look only at peak HP/torque figures but rather at AVERAGE power production figures within the engine's powerband. Best in that regard was the (very loud) Bassani Real Street, followed by a virtual four-way tie between the Magnaflow, both Borlas, and the Hooker MAXflow.

    FWIW in scientific procedure commentary: Because the open-pipe version was lowest in power, my opinion is that the car was well-tuned for mufflers and the injectors went slightly lean at max rpm when the exhaust was opened up. That would suggest that a couple of the most open, high-flowing mufflers MIGHT have made a few more ponies on top with the A/F optimized for them. They're all so close, though, that this is nit-picking.

    It's worth noting that there's a significant weight difference among these mufflers, ranging from 6 lb. for the DynoMax to 16 lb. for the long, 3 chamber Flowmaster. That's up to 20 lb. weight difference for 2 mufflers!

    The "quality" of the exhaust note produced is impossibly subjective to quantitatively express...yet every gear head can listen to different exhaust combos and...more often than not... agree on which ones sound "good" to the performance enthusiast's ear. 5.0 magazine picked the Magnaflow, Bassani QT, and Edelbrock RPM as having the "sweetest" performance notes. FWIW, this agrees with my own casual observations.

    After running all this data combined with my own experiences through my red-neck, highly-biased, opinionated, don't-confuse-me-with-the-facts-because-my-mind's-already-made-up cerebral computer, I interpret the outcome as two winners (based on our originally-stated criteria):

    If you want the quietest muffler you can get without suffering a performance penalty, the Borla XS wins hands-down. The ability to make power while generating only 110 db at WOT is amazing. It's 90 db cruise is also the quietest, as is its 80 db idle. Bonus is it's one of the lightest at 7.5 lb. T'aint cheap at $130 each, but the stainless Borla offers undisputed high quality with a nearly-forever warranty. Their sound reminds me of the stock, "factory muscle car" sound of the 60's. Conservative but classy.

    The Magnaflow offers great value, high quality, high performance, and sweet music without the mind-numbing drone or obnoxious bellow. Only $84 each gets you shrink-wrapped, flawless stainless steel that is polished so beautifully that it will make you sad to hide them under your car. At 10.5 lb. they're still on the lighter end of the spectrum. They're only 1 db louder than the Borla XS at cruise speed, and only 2 db thumpier at idle. They open up "just enough" at WOT (IMHO) to sing a well-controlled but exuberant horsepower sonata. Fortissimo passion without pain. Even though 4 db. louder than the Borla at WOT, they're still on the low db side compared to the others in the test. I've never heard anyone complain about the "quality" of the sound from Magnaflows, and only a couple complaints about "not loud enough," (mostly from 2-chamber Flowmaster aficionados, lol).

    Either of these choices SHOULD be run with an H or X pipe crossover. This will provide both better performance and optimum sound control. Either COULD be run with cats which would subdue their mildly-sonorous personalities even further.
    Last edited by Cougar5.0; 04-23-2008 at 11:04 AM.
    11.96 @ 118 MPH @ 3700lb, 1.6 60' (1.564 best)

  8. #8
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    Quote Originally Posted by the article
    Because the open-pipe version was lowest in power, my opinion is that the car was well-tuned for mufflers and the injectors went slightly lean at max rpm when the exhaust was opened up
    Quote Originally Posted by me
    it would seem the exhaust system was optimized to be used with a muffler and not wihout as evidenced by no muffler showing the lowest HP rating.
    Same end result in that particular case of no muffler.....

    Thank you. I've never seen the full article and what you added was helpful!

    Just like everything else, your exhaust system is a compromise....

    http://www.carcraft.com/techarticles...ics/index.html
    http://www.chevyhiperformance.com/te...tem/index.html
    http://sbftech.com/index.php/topic,7758.0.html
    http://sbftech.com/index.php/topic,4825.0.html
    http://www.maxracesoftware.com/pipemax36xp2.htm
    Last edited by V8Demon; 04-18-2008 at 12:48 PM.
    -- 05 Mustang GT-Whipplecharged !! -- 87 5.0 Trick Flow Heads & Intake - Custom Cam - Many other goodies...3100Lbs...Low12's! http://www.fquick.com/V8Demon

  9. #9
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    Sweet! That's a cool follow-up to the article!

    I'm presently going to remove my mufflers to maximize my power levels
    11.96 @ 118 MPH @ 3700lb, 1.6 60' (1.564 best)

  10. #10
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    You can usually guesstimate by what type it is (chambered, straight through etc...), diameter & by listening to clips someone might have posted online.
    11.96 @ 118 MPH @ 3700lb, 1.6 60' (1.564 best)

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