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    1. #1
      Join Date
      Sep 2010
      Location
      Martinez, CA
      Posts
      142
      Country Flag: United States

      Can a muffler be too large diameter to effectively silence the exhaust

      In my Chevelle I have a 3.6 liter engine with a 2.5 system, an X pipe and dual 2.5 in/out mufflers. The mufflers are 50 series Flowmasters.

      For comparison, a 1970 Cadillac Deville with a 7.7 liter engine uses a 2.5 system with wye pipe to single 2.5 in/out muffler. Probably a pretty darn restrictive muffler too.

      My car is too loud for me as a driver. Mostly drone. And being a V6 its not like is has a real good sound anyway.

      Ive seen mufflers that have smaller outlets than inlets and wonder why. Im also wondering if dual 2.5 system is too large for 3.6 liters.

      Im leaning towards Dynamax Super Turbo mufflers and am wondering if I should stay with 2.5 or reduce down to dual 2.25 or even 2.

      If I do change mufflers size it will be just the mufflers. The rest of the system will stay 2.5. Will my tail pipes to the bumper amplify sound from a smaller outlet muffler?

      Any experience or thoughts?
      1966 Chevelle, 3.6L/217 CI, 4 cam direct injected V6, 6 speed auto, full Hotchkis suspension, 4 wheel Wilwood discs, white w/red interior, cowl hood. 3260 lbs w/full tank. Built for 35 mpg. So far 32.

    2. #2
      Join Date
      Apr 2009
      Location
      Michigan
      Posts
      265
      Country Flag: United States
      2.5" duals are overkill for ~300 hp, but they won't really hurt anything (besides adding weight and maybe decreasing ground clearance). There's no reason to change muffler inlet/outlet size if your mid and tailpipes remain 2.5." Many of the lower cost turbo mufflers use 2" or so pipes internally regardless of the inlet/outlet sizes to save cost. Sounds like these cheapo mufflers would be perfect for your application - even though most guys hate them because they "choke down" their 2.5" or 3" exhaust.

      The mufflers with the smaller internal piping will be quieter and obviously flow less, but that's not the biggest concern for you. Go to the muffler shop with a flashlight and pick your poison.

      Many mufflers have smaller outlets because as the exhaust gases cool off, they take up less space and therefore you can get away with a smaller diameter pipe at the back of the car.

      Got any pics of your car (especially under the hood)?
      - Ryan

    3. #3
      Join Date
      Sep 2010
      Location
      Martinez, CA
      Posts
      142
      Country Flag: United States
      Thanks. I never really thought about the internal dimensions, just the connection points. More homework to do.
      Heres a pic of my engine compartment with the V6.

      Attached Images Attached Images  
      1966 Chevelle, 3.6L/217 CI, 4 cam direct injected V6, 6 speed auto, full Hotchkis suspension, 4 wheel Wilwood discs, white w/red interior, cowl hood. 3260 lbs w/full tank. Built for 35 mpg. So far 32.


    4. #4
      Join Date
      Aug 2004
      Location
      Red Deer, Alberta, Canada
      Posts
      1,309
      Country Flag: Canada
      I need to know more on this engine. pics, videos. Something different, I like it.

      The 50 series I have never liked. Its a chambered tin can.

      I feel you would greatly enjoy a magnaflow or borla muffler. To quiet down from there Id put resonators on each bank.

      On a more budget friendly, a turbo muffler like mentioned above will take a bunch of noise away. Kind of a guessing game not knowing your pain tolerance hah
      Matt
      72 Chevelle 370ci LS Turbo. Speedtech equipped.
      Instagram: Cst_koon

    5. #5
      Join Date
      Sep 2010
      Location
      Martinez, CA
      Posts
      142
      Country Flag: United States
      Quote Originally Posted by protour_chevelle View Post
      I need to know more on this engine. pics, videos. Something different, I like it.

      The 50 series I have never liked. Its a chambered tin can.

      I feel you would greatly enjoy a magnaflow or borla muffler. To quiet down from there Id put resonators on each bank.
      I put this together for mpg. Its a 325 hp V6 from a 2013 Camaro. Its connected to the stock 6 speed double OD auto. I lifted the body off to make the frame mods for the engine and at the same time added a full Hotchkis suspension and Wilwood 4 wheel discs.
      It runs great, averages about 32 mpg and Ive had a high mpg of 39.9 when I drove it like there was an egg under my foot.
      Its really light at 3260 with a full tank of gas and handles/stops great. Im currently working on NVH, ie, chasing down the last squeaks and groans, a pretty loud howl from the rear end and these ridicules mufflers.Name:  E094EAB5-D367-4184-A30F-0E71CE67DC8B.jpg
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      1966 Chevelle, 3.6L/217 CI, 4 cam direct injected V6, 6 speed auto, full Hotchkis suspension, 4 wheel Wilwood discs, white w/red interior, cowl hood. 3260 lbs w/full tank. Built for 35 mpg. So far 32.

    6. #6
      Join Date
      Apr 2009
      Location
      Michigan
      Posts
      265
      Country Flag: United States
      Very cool! Looks like a well thought out build, and I bet it's plenty quick being that light.
      - Ryan

    7. #7
      Join Date
      Oct 2004
      Posts
      2,438
      Country Flag: United States
      Slightly downsizing the tailpipes compared to mid-pipes typically give a lower tone (which can be more pleasing to the ear even at the same dB), as well as reduce overall sound level; without penalty to peak power (as mentioned earlier). While your replacing the mufflers it'd probably be a good idea to downsize the tailpipes too.

      Love the dare-to-be-different theme to your build.
      Red Forman: "The Mustang's front end is problematic; get yourself a Firebird."

    8. #8
      Join Date
      Aug 2004
      Location
      Ontario, Canada
      Posts
      2,310
      Country Flag: Canada
      I would start by replacing the Flowmasters with a pair of DynoMax Super Turbos. I have a pair in a 2 1/2" system with a H-pipe, all behind a SBC 400 with good results. I have a bit of resonance around 1500 - 1800 but it is tolerable.
      Depending on the routing of your tail pipes you could also use a glass pack style muffler as a resonator.

      Ken
      If there is a hard way to do something, I'll find it!
      My other car is a Vega.

    9. #9
      Join Date
      Apr 2001
      Location
      The City of Fountains
      Posts
      15,638
      Country Flag: United States
      I really like the 19" case Borla XS Pro muffler that I had recently installed on my Cougar.

      Andrew
      1970 GTO Version 2.0
      1967 Cougar build
      GM High-Tech Performance feature
      My YouTube Channel Please Subscribe!
      Instagram @projectgattago
      Dr. EFI
      I deliver what EFI promises.
      Remote Holley EFI tuning.
      Please get in touch if I can be of service.

      "You were the gun, your voice was the trigger, your bravery was the barrel, your eyes were the bullets." ~ Her

    10. #10
      Join Date
      Sep 2010
      Location
      Martinez, CA
      Posts
      142
      Country Flag: United States
      Quote Originally Posted by 68Formula View Post
      Slightly downsizing the tailpipes compared to mid-pipes typically give a lower tone (which can be more pleasing to the ear even at the same dB), as well as reduce overall sound level; without penalty to peak power (as mentioned earlier). While your replacing the mufflers it'd probably be a good idea to downsize the tailpipes too.

      Love the dare-to-be-different theme to your build.
      Thanks.
      Im trying desperately not to change my tail pipes. They are SS and mandrel bent, ie, not cheap. Its bad enough I have to buy more mufflers. Although as a side note all soon have some slightly used 50 series Flowmasters for sale.

      I wonder if putting some form of a reducer in the end of the tail pipe would have the same affect?
      1966 Chevelle, 3.6L/217 CI, 4 cam direct injected V6, 6 speed auto, full Hotchkis suspension, 4 wheel Wilwood discs, white w/red interior, cowl hood. 3260 lbs w/full tank. Built for 35 mpg. So far 32.

    11. #11
      Join Date
      Apr 2001
      Location
      The City of Fountains
      Posts
      15,638
      Country Flag: United States
      You should look into adding a J pipe
      1970 GTO Version 2.0
      1967 Cougar build
      GM High-Tech Performance feature
      My YouTube Channel Please Subscribe!
      Instagram @projectgattago
      Dr. EFI
      I deliver what EFI promises.
      Remote Holley EFI tuning.
      Please get in touch if I can be of service.

      "You were the gun, your voice was the trigger, your bravery was the barrel, your eyes were the bullets." ~ Her

    12. #12
      Join Date
      Aug 2004
      Location
      Red Deer, Alberta, Canada
      Posts
      1,309
      Country Flag: Canada
      Quote Originally Posted by andrewb70 View Post
      You should look into adding a J pipe
      Are you talking about a helmholtz resonator? A friend and I did one. Worked great. Make it adjustable(slip) so you can lengthen and shorten to erase the resonance where you want(rpm)
      Matt
      72 Chevelle 370ci LS Turbo. Speedtech equipped.
      Instagram: Cst_koon

    13. #13
      Join Date
      Aug 2008
      Location
      jacksonville,fl
      Posts
      964
      Country Flag: United States
      I agree, look into J-pipes if drone is your main complaint. They are just a tuned length of hollow capped off pipe that cancels certain tones, no hp loss. Many factory mufflers have em internally. Search it on the camaro 5 forums.

    14. #14
      Join Date
      Apr 2001
      Location
      The City of Fountains
      Posts
      15,638
      Country Flag: United States
      Quote Originally Posted by protour_chevelle View Post
      Are you talking about a helmholtz resonator? A friend and I did one. Worked great. Make it adjustable(slip) so you can lengthen and shorten to erase the resonance where you want(rpm)
      Yes. We have a big thread about it here on this forum. I can't seem to find it right now, but hopefully someone else will post a link.

      Andrew
      1970 GTO Version 2.0
      1967 Cougar build
      GM High-Tech Performance feature
      My YouTube Channel Please Subscribe!
      Instagram @projectgattago
      Dr. EFI
      I deliver what EFI promises.
      Remote Holley EFI tuning.
      Please get in touch if I can be of service.

      "You were the gun, your voice was the trigger, your bravery was the barrel, your eyes were the bullets." ~ Her

    15. #15
      Join Date
      Feb 2018
      Location
      Southern IN
      Posts
      136
      Country Flag: United States
      Nice looking ride and I like the red interior!
      Shane
      #theanchorholds
      68 Camaro build thread:
      http://lateral-g.net/forums/showthread.php?t=56387

    16. #16
      Join Date
      Apr 2009
      Location
      Michigan
      Posts
      265
      Country Flag: United States
      Going back to the turbo muffler idea, Engine Masters did a nice comparison in Episode 49. The engine was a 600 hp 408 ci SBF, and all the mufflers they tested were 2.5" duals. If you're looking for quiet, the Cherry Bomb Turbo or Hush Thrush would be fine at your power level. Going off memory, these were the ones with the smaller internals, resulting in less noise but some power loss on the 600 hp motor.

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      - Ryan

    17. #17
      Join Date
      Apr 2001
      Location
      The City of Fountains
      Posts
      15,638
      Country Flag: United States
      Here is the thread I was referring to:

      https://www.pro-touring.com/threads/...ight=helmholtz

      Andrew
      1970 GTO Version 2.0
      1967 Cougar build
      GM High-Tech Performance feature
      My YouTube Channel Please Subscribe!
      Instagram @projectgattago
      Dr. EFI
      I deliver what EFI promises.
      Remote Holley EFI tuning.
      Please get in touch if I can be of service.

      "You were the gun, your voice was the trigger, your bravery was the barrel, your eyes were the bullets." ~ Her

    18. #18
      Join Date
      Sep 2010
      Location
      Martinez, CA
      Posts
      142
      Country Flag: United States
      Quote Originally Posted by Gmachine1911 View Post
      Nice looking ride and I like the red interior!
      Thanks. It was black when I bought the car but I love the bright colored interiors. My 67 conv was bright blue.
      I had to make my own console because I had to raise the trans and driveshaft tunnel all the way back to the rearend. Nothing fancy, kinda stock looking.
      Did you notice the tach on the console? It actually my fuel gauge. The only gauge in the car.

      - - - Updated - - -

      I may look into a j pipe but I still think I want to bring the volume down too.
      1966 Chevelle, 3.6L/217 CI, 4 cam direct injected V6, 6 speed auto, full Hotchkis suspension, 4 wheel Wilwood discs, white w/red interior, cowl hood. 3260 lbs w/full tank. Built for 35 mpg. So far 32.

    19. #19
      Join Date
      Oct 2004
      Posts
      2,438
      Country Flag: United States
      Quote Originally Posted by andrewb70 View Post
      You should look into adding a J pipe
      We're still talking exhaust, right? j/k
      Red Forman: "The Mustang's front end is problematic; get yourself a Firebird."

    20. #20
      Join Date
      Sep 2010
      Location
      Martinez, CA
      Posts
      142
      Country Flag: United States
      Quote Originally Posted by 68Formula View Post
      We're still talking exhaust, right? j/k
      Yup. My bad for going off track.
      I did get something back from Walker Exhaust (Walker, Dynomax, Thrush) and they suggested a Super Turbo number 17748 or a Quiet-Flow number 21856. Both the same size and similar in size to the Flowmasters I have now.
      The Quiet-Flow 21856 is used in 70s Cadillacs with 7.7 liter (500 ci) engines with single exhaust.
      With two of them being fed from my 217 ci engine it may suck noise out of the car next to me!
      1966 Chevelle, 3.6L/217 CI, 4 cam direct injected V6, 6 speed auto, full Hotchkis suspension, 4 wheel Wilwood discs, white w/red interior, cowl hood. 3260 lbs w/full tank. Built for 35 mpg. So far 32.

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