Home » Public Forums » GMCnet » Exhaust Systems - Drone at 1400 RPM (Again seeking opinions from the experts...)
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| Re: [GMCnet] Exhaust Systems - Drone at 1400 RPM [message #293383 is a reply to message #293381] |
Sun, 03 January 2016 23:01   |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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Senior Member |
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Steve,
I'm not that well informed on exhaust noise, but sales reps tell us that
larger the volume the muffler has, lower the noise.
I know our kits have the longer mufflers on the duel units and the noise
level is lot lower than the ones with the shorter one.
Flow Master mufflers are louder a they use a sound attenuating against
plates and puts out a pulsing noise, more than the Magnaflow which uses a
perforated pipe core that allows the shock to penetrate through the SS mesh
, then into the fiberglass matting.
I discount that the 3" pipe reduces the sound.
One can shorten or lengthen the pipe to have the sound to have different
level at different RPM as it is a sine function like a trombone.
On Sun, Jan 3, 2016 at 8:34 PM, Steve Weinstock
wrote:
> Greetings -
>
> I've got two mufflers on the coach - pretty large ones - pretty certain
> they're FlowMasters. They're in the original locations. I was surprised to
> discover that the exhaust system is made up of 2.5" diameter piping.
> Headers too.
>
> They've got a real nice low rumble sound...but may be a bit too loud for
> my liking. The most offending issue is a pretty load drone at 1400 RPM or
> so...
>
> I rode in a friends coach today and was pleasantly surprised at how much
> quieter it was... smaller mufflers underneath and 3" pipes. And a nice
> insulated aluminum engine cover vs my original wooden deck.
>
> So here's the questions:
>
> Are mufflers the major component of any noise generation ?? Especially
> that drone...
>
> Is 3" exhaust piping a major noise reducer ??
>
> Might that insulated aluminum engine hatch be introducing significant
> noise reduction ?
>
> Any trickery for eliminating the drone noise ?
>
> Might a single muffler system be a solution ??
>
> As always, THANK YOU for all of the advice offered here. It's been a
> tremendous help and inspiration for me during the "modernization" of my 23
> footer.
>
>
>
> http://www.gmcmhphotos.com/photos/data/6900/IMG_4297.PNG
>
> Steve W
> 1973 23'
> Southern California
>
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
Jim Kanomata
Applied/GMC, Fremont,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
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1-800-752-7502
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| Re: Exhaust Systems - Drone at 1400 RPM [message #293385 is a reply to message #293381] |
Sun, 03 January 2016 23:46 |
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SteveW
Messages: 538
Registered: June 2005
Location: Southern California - Ora...
Karma: 1
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Senior Member |
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Thank you Jim !!
Your "trombone" analogy made me realize that there's some resonance at issue here...
With some help from our friends at Google and the modern marvel of the interwebs - I found this:
Quote:
The concept behind drone is pretty simple; nearly everything has a resonant frequency...exhaust systems, electronic RLC circuits, even gravitation has resonance. At peak resonance, the amplitude of the wave at the resonant frequency shoots up to many times higher than normal amplitude. With sound resonance, it pops up when a certain frequency emitted from the engine resonates with the exhaust system and muffler to create that nasty in-cab drone. Unfortunately this resonance often has its peak right in the area where you want to cruise, between 55-75mph.
The solution is a 1/4 wave resonator tube. Simply put, it is a small piece of exhaust pipe with a flat capped end welded nearly perpendicular to the exhaust flow post-muffler that serves to take some of the resonant amplitude and shoot it back into the exhaust pipe out of phase with the resonant frequency to bring down the amplitude. If you've ever taken a physics class, this is in the 'standing wave dynamics' chapter. Mufflers are designed to bring down the amplitude or volume of the exhaust note at all RPMs, but they typically can't do anything about resonance. Corsa mufflers have a built-in resonator that works decent, but only with the entire exhaust kit. Sometimes you'll run across a setup that drones at an RPM the Corsa muffler and exhaust wasn't designed to combat, so theres a chance the internal resonator will do little to no good.
Things you need to know to build the resonator:
-RPM that drone occurs at
-Number of cylinders (engines with simultaneous firing cylinders like the SRT-10 truck will divide this number by two)
You will also need to know the speed of sound. It varies with temperature, but is generally accepted to be 343m/s.
Say your V8 truck resonates at 2000rpms, right at cruising speed. You'll need to find the frequency of the drone. Units here are pulses per second, or Hertz.
f = RPM * pulses/rev * (1/60)
f = 2000 rev/min * 4 pulses/rev * (1/60)
f = 133.34 pulses/second = 133.34Hz
At 2000rpms, your V8 fires 4 times per revolution. RPM is in minutes, so divide by 60 to reduce to seconds. Now you need to find the length of the wave at the frequency you just calculated. Wavelength is denoted by lambda (λ), units are meters.
λ = v/f = speed of sound / frequency
λ = (343m/s)/(133.34Hz)
λ = 2.572 meters
This gives you the length of a full sound wave. The idea here is to reintroduce a sound wave into the exhaust that is 180° out of phase with your drone frequency. To do this, you build your resonator tube at exactly one-fourth the length of the resonant wave. By the time the sound wave enters the resonator tube, bounces off the end and re-enters the exhaust stream, the amplitude is exactly opposite of the drone frequency and will lower or eliminate the volume of the drone.
Dividing the wavelength by 4 gives you 0.643m, or about 2.1 feet. Its long and kind of awkward, but someone who has had to deal with a droning truck on a road trip will likely sacrifice the space to make it fit
The diameter of the tube you'd need is debatable, as I haven't tried different sizes of tubing. When I built mine, I took a shot in the dark and went with 2" pipe on my 3" exhaust. It gives about half the surface area at the end of the tube to bounce off of. I assume a larger resonator tube would allow more sound to bounce back and cancel more of the drone noise. However, space is somewhat limited when you are sending an exhaust pipe off of your existing pipe at some odd angle. You can bend the resonator tube to some extent, but it needs to be mandrel bent, not more than one bend or more than ~30°. If the bend is too sharp, the sound will bounce back too early and the resonator will work poorly or won't work at all.
The reason for this is simply the fact that sound waves do not necessarily 'flow' with whatever medium they are travelling in. Sound is a pressure wave, and any obstacle (bends) will return the wave prematurely. To minimize 'obstables' in the resonator tube, the straighter it is, the better it will work. The intent is not to randomly scatter the sound wave as a radius will tend to do, but to send it back to the exhaust precisely when it is needed.
So, you just need to mock up your resonator tube in a place that it will fit, cut a hole into the exhaust pipe and weld the tube to it and enjoy a drone-free ride.
End Quote.
Source:
http://www.performancetrucks.net/forums/gm-engine-exhaust-performance-21/how-build-exhaust-resonator-tube-eliminate-drone-489463/
My calculations suggest that I need a resonator tube at .46m (18")
I might just try it !
Steve W
1973 23'
Southern California
Steve W
1973 : 23'
Southern California
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| Re: Exhaust Systems - Drone at 1400 RPM [message #293387 is a reply to message #293381] |
Mon, 04 January 2016 00:20 |
djeffers
Messages: 219
Registered: June 2004
Karma: 2
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Senior Member |
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Too bad. We like a quiet coach too.
Your drone is a resonance within the exhaust system and perhaps bouncing off the bottom of the floor as well.
Several questions, in no particular order of importance:
1. What year is your coach? Does it have the underfloor foam insulation with the thin aluminum sheet to protect the foam? These coaches with the underfloor insulation also have, I believe, 1/4 inch thicker plywood floors. Someone can correct me if wrong.
2. The underfloor insulation sags down away from the plywood in heat areas; above the mufflers and down the exhaust pipe in the frame rail. Ours had sagged all the way down onto the mufflers. I found a way to correct this with 3/4 inch aluminum angle from Ace Hardware. Contact me if interested.
3. Are your exhaust pipes connected to or hung from the frame or body in any way? Hangers should be minimal and made with rubber straps.
4. The factory hanger at the end of the Y-Pipe is a heavy rubber strap. Is it intact? No exhaust pipes should be attached directly to the frame or body.
5. The stock exhaust pipe going down the frame rail rides in two do-nuts, each in a crossmember bracket. Are both your do-nuts intact? Jim K sells new ones, I believe.
As far as your question "Are mufflers the major component of any noise generation ??" The answer is no. Coming out or the exhaust port the exhaust "cracks" when the valve opens. Out of the down pipe from the manifold the exhaust "barks".
At roughly the location of the mufflers is a sweet spot where much of the pressure wave tends to collapse. This length changes with engine speed and intensity with engine load. But that general area is where the mufflers are placed to provide an expansion volume to absorb the crack and bark. Leaks or breaks in the system will let some of the noise out.
The resonance you refer to may actually be an excited mechanical resonance of a length of the pipe system transmitted to the frame and body, in additional to an acoustical resonance within the pipes. Check the complete system as above.
Our coach is very, very quiet. Conversations at highway speeds are easy.
Following are some of the features of our exhaust system:
1. Cad 500 engine into cast iron exhaust manifolds. Cad or Olds, shouldn't make any difference, but cast iron manifolds are quieter.
2. Rubber insulator straps on the down pipes.
3. Dumping into 36" body length, 2 1/4 inch pipe diameter, heavy duty glass pack mufflers from some truck company in Wisconsin; don't remember the company name. I had to do some modification to the stock Y-Pipe to get the long 36"-body mufflers into the space.
The glass packs are not rackety loud; they have a low throaty sound barely discernible in the coach and have been in there for 45,000 miles. At the Bonneville Salt Flats we got compliments on the exhaust note ... "Sounds good".
Personally, I don't like baffled mufflers. Quality straight-through seamless, bullet shaped, glass packs can be pleasant and last several years. Steel-packs are even longer lasting if you can find them. Many baffled mufflers rust out from the condensation in the chambers and seams.
4. We still have the original 2 1/2 inch exhaust pipe that our coach left the factory with in 1978.
5. Our wooden engine hatch has 3/4 inch of durable, heavy, flexible, black sound insulating foam on top and the carpet drops down over it from the front. We also have non-flexible foam on the bottom of the hatch, sculpted out to clear the throttle body hat and hose from the fresh air intake system.
6. And not related to the exhaust, but a noise source is the radiator fan. The viscous fan drive needs to be working well. We have no fan noise in our coach. We drove about 25 coaches when we were looking for a coach and a lot of coaches had fans that roared.
7. The only noise we have is intake roar at high altitude (8-10 thousand feet) and full throttle going up the mountains. It sounds like the engine is straining its guts out, but it's not. We get a high altitude, full throttle intake resonance in our home-made fresh air intake system with no baffles and a K&N air filter on the end. I bought a factory GMC Suburban air cleaner box with factory paper filter and a resonance chamber hanging off the side, but have not yet installed it; just one of a large number of projects still to go.
Hope this helps in some way.
Don and Susan Jeffers
78 Eleganza II Cad 500 EFI
[Updated on: Mon, 04 January 2016 02:11] Report message to a moderator |
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| Re: Exhaust Systems - Drone at 1400 RPM [message #293389 is a reply to message #293381] |
Mon, 04 January 2016 02:07 |
Bill Van Vlack
Messages: 419
Registered: September 2015
Location: Guemes Island, Washington
Karma: 14
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Senior Member |
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I had terrible drone on a 5L V8 (not a GMC) and cured it by changing the exhaust from an 'X' pipe with twin cats and Magnaflows..... to the 'X', then a 'Y' pipe into a single 3" exhaust with a Flowmaster. I also added a 1/4 wave resonance tube with an adjustable end. The Mustang folks have had success with the Hemholtz resonance tubes as well.
I'm pretty sure that if you were to apply Steve's equations above, you'd have to assume 2 pulses per revolution, given that each half of the engine has a separate exhaust system. (4 cylinders firing once every two revolutions). Also note that the section of the exhaust system creating the resonance is limited to the odd harmonics (1,3,5,etc times wavelength of the drone). At 1400 RPM, the 1/4 wavelength is about six feet, assuming 200 deg F exhaust temp. Using 500 deg exhaust would give a 1/4 wavelength of about 8 ft.
However you approach it, it will be an experiment. I think I'd try some different or additional mufflers first. It seems like the dual 2.5" exhaust arrangement is plenty big enough to add a little back pressure.
Bill Van Vlack
'76 Royale; Guemes Island, Washington; Twin bed, full (DS) side bath, Brazilian Redwood counter and settee tops,455, 6KW generator; new owner a/o mid November 2015.
[Updated on: Mon, 04 January 2016 14:04] Report message to a moderator |
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| Re: Exhaust Systems - Drone at 1400 RPM [message #293398 is a reply to message #293381] |
Mon, 04 January 2016 08:22 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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Simply, your muffler body length and thereby the internal path length is probably too short to cancel the resonance. Are you sure your resonance is at 1400? That seems a little lower than normal. In the example 2.1' is 2000RPM. At 1400 the path would need to be longer. How long are your mufflers? Going to larger diameter head pipes almost ALWAYS causes a loss of low end torque and the pulses become diluted and scavaging effect is lost. 2.5 is plenty big up front condidering the factory tailpipe was 2.5 for the summed L and R banks.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] Exhaust Systems - Drone at 1400 RPM [message #293413 is a reply to message #293383] |
Mon, 04 January 2016 12:48 |
<rallymaster
Messages: 361
Registered: May 2014
Karma: 2
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Senior Member |
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Hi, Guys & Gals
Don'f forget that if your drone weighs more than 1/2 pound and you fly it
outdoors, you have to register it. (snicker, snicker, chuckle, snort)
Sorry 'bout that, I couldn't resist. Brother-in-law's drone is stuck in
a tall tree, and he's complaining about having to register it anyway.
Three windstorms, and it's still in that fershlugginer tree.
RonC
On Sun, 03 Jan 2016 22:46:39 -0700 Steve Weinstock
writes:
> Thank you Jim !!
>
> Your "trombone" analogy made me realize that there's some resonance
> at issue here...
>
> With some help from our friends at Google and the modern marvel of
> the interwebs - I found this:
>
> Quote:
> The concept behind drone is pretty simple; nearly everything has a
> resonant frequency...exhaust systems, electronic RLC circuits, even
> gravitation has
> resonance. At peak resonance, the amplitude of the wave at the
> resonant frequency shoots up to many times higher than normal
> amplitude. With sound
> resonance, it pops up when a certain frequency emitted from the
> engine resonates with the exhaust system and muffler to create that
> nasty in-cab
> drone. Unfortunately this resonance often has its peak right in the
> area where you want to cruise, between 55-75mph.
>
> The solution is a 1/4 wave resonator tube. Simply put, it is a small
> piece of exhaust pipe with a flat capped end welded nearly
> perpendicular to the
> exhaust flow post-muffler that serves to take some of the resonant
> amplitude and shoot it back into the exhaust pipe out of phase with
> the resonant
> frequency to bring down the amplitude. If you've ever taken a
> physics class, this is in the 'standing wave dynamics' chapter.
> Mufflers are designed
> to bring down the amplitude or volume of the exhaust note at all
> RPMs, but they typically can't do anything about resonance. Corsa
> mufflers have a
> built-in resonator that works decent, but only with the entire
> exhaust kit. Sometimes you'll run across a setup that drones at an
> RPM the Corsa
> muffler and exhaust wasn't designed to combat, so theres a chance
> the internal resonator will do little to no good.
>
> Things you need to know to build the resonator:
>
> -RPM that drone occurs at
> -Number of cylinders (engines with simultaneous firing cylinders
> like the SRT-10 truck will divide this number by two)
>
> You will also need to know the speed of sound. It varies with
> temperature, but is generally accepted to be 343m/s.
>
> Say your V8 truck resonates at 2000rpms, right at cruising speed.
> You'll need to find the frequency of the drone. Units here are
> pulses per second, or
> Hertz.
>
> f = RPM * pulses/rev * (1/60)
>
> f = 2000 rev/min * 4 pulses/rev * (1/60)
>
> f = 133.34 pulses/second = 133.34Hz
>
> At 2000rpms, your V8 fires 4 times per revolution. RPM is in
> minutes, so divide by 60 to reduce to seconds. Now you need to find
> the length of the
> wave at the frequency you just calculated. Wavelength is denoted by
> lambda (?), units are meters.
>
> ? = v/f = speed of sound / frequency
>
> ? = (343m/s)/(133.34Hz)
>
> ? = 2.572 meters
>
> This gives you the length of a full sound wave. The idea here is to
> reintroduce a sound wave into the exhaust that is 180° out of phase
> with your
> drone frequency. To do this, you build your resonator tube at
> exactly one-fourth the length of the resonant wave. By the time the
> sound wave enters
> the resonator tube, bounces off the end and re-enters the exhaust
> stream, the amplitude is exactly opposite of the drone frequency and
> will lower or
> eliminate the volume of the drone.
>
> Dividing the wavelength by 4 gives you 0.643m, or about 2.1 feet.
> Its long and kind of awkward, but someone who has had to deal with a
> droning truck
> on a road trip will likely sacrifice the space to make it fit
>
> The diameter of the tube you'd need is debatable, as I haven't tried
> different sizes of tubing. When I built mine, I took a shot in the
> dark and went
> with 2" pipe on my 3" exhaust. It gives about half the surface area
> at the end of the tube to bounce off of. I assume a larger resonator
> tube would
> allow more sound to bounce back and cancel more of the drone noise.
> However, space is somewhat limited when you are sending an exhaust
> pipe off of
> your existing pipe at some odd angle. You can bend the resonator
> tube to some extent, but it needs to be mandrel bent, not more than
> one bend or more
> than ~30°. If the bend is too sharp, the sound will bounce back too
> early and the resonator will work poorly or won't work at all.
>
> The reason for this is simply the fact that sound waves do not
> necessarily 'flow' with whatever medium they are travelling in.
> Sound is a pressure
> wave, and any obstacle (bends) will return the wave prematurely. To
> minimize 'obstables' in the resonator tube, the straighter it is,
> the better it
> will work. The intent is not to randomly scatter the sound wave as a
> radius will tend to do, but to send it back to the exhaust precisely
> when it is
> needed.
>
> So, you just need to mock up your resonator tube in a place that it
> will fit, cut a hole into the exhaust pipe and weld the tube to it
> and enjoy a
> drone-free ride.
> End Quote.
>
> Source:
>
http://www.performancetrucks.net/forums/gm-engine-exhaust-performance-21/
how-build-exhaust-resonator-tube-eliminate-drone-489463/
>
> My calculations suggest that I need a resonator tube at .46m (18")
>
> I might just try it !
>
>
> Steve W
> 1973 23'
> Southern California
>
>
>
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
Ron & Linda Clark
North Plains, ORYGUN
78 Eleganza II
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| Re: [GMCnet] Exhaust Systems - Drone at 1400 RPM [message #293420 is a reply to message #293416] |
Mon, 04 January 2016 15:12 |
sgltrac
Messages: 2797
Registered: April 2011
Karma: 1
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Senior Member |
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Or the exhaust could be rubbing against the frame where it passes through.
Another possibility is that the exhaust is rigid mounted somewhere along
its length. The exhaust should be isolated from the chassis with rubber
hangers or the like.
Sully
77 royale
Seattle
On Monday, January 4, 2016, Carl Stouffer wrote:
> I have Jim K's 3" dual muffler exhaust system on our coach. It uses
> Magnaflow SS mufflers and I don't hear any exhaust noise or resonance in the
> coach at all. Maybe you just need a new set of the right mufflers.
> --
> Carl Stouffer
> '75 ex Palm Beach
> Tucson, AZ.
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
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Sully
77 Royale basket case.
Future motorhome land speed record holder(bucket list)
Seattle, Wa.
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| Re: [GMCnet] Exhaust Systems - Drone at 1400 RPM [message #293421 is a reply to message #293417] |
Mon, 04 January 2016 15:37 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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Being a subscriber to the "loud pipes save lives" school of thought,
exhaust notes from a common exhaust center port engines like the Oldsmobile
or Ford flatheads, make a pleasing exhaust note to me. But, anything over
about 90db in volume is not pleasant. There are many ways to tune an
exhaust to lessen the volume. Short resonators, called "racket busters" can
help a great deal. There are also some tail pipe extensions that do much
the same thing, but if you tow, be careful of anything below the rear
bumper.
Jim Hupy
Salem, Or.
78 GMC ROYALE 403
On Jan 4, 2016 1:22 PM, "Wally Anderson" wrote:
> SteveW wrote on Sun, 03 January 2016 22:34
>> Greetings -
>>
>> I've got two mufflers on the coach - pretty large ones - pretty certain
> they're FlowMasters. They're in the original locations. I was surprised
>> to discover that the exhaust system is made up of 2.5" diameter piping.
> Headers too.
>>
>> They've got a real nice low rumble sound...but may be a bit too loud for
> my liking. The most offending issue is a pretty load drone at 1400 RPM
>> or so...
>>
>> I rode in a friends coach today and was pleasantly surprised at how much
> quieter it was... smaller mufflers underneath and 3" pipes. And a nice
>> insulated aluminum engine cover vs my original wooden deck.
>>
>> So here's the questions:
>>
>> Are mufflers the major component of any noise generation ?? Especially
> that drone...
>>
>> Is 3" exhaust piping a major noise reducer ??
>>
>> Might that insulated aluminum engine hatch be introducing significant
> noise reduction ?
>>
>> Any trickery for eliminating the drone noise ?
>>
>> Might a single muffler system be a solution ??
>>
>> As always, THANK YOU for all of the advice offered here. It's been a
> tremendous help and inspiration for me during the "modernization" of my 23
>> footer.
>>
>>
>> Steve W
>> 1973 23'
>> Southern California
>
> I hear you on the drone. Reminds me of how school bus's used to sound with
> that long tailpipe. Think the effect in seen on our fuel map too. Thought
> of a stub resonator like some of the hot rod guys use would help but I've
> not seen any GMCers try it. NASA's predecessor studied this way back on page
> 22 of report 1192.
>
> http://www.performancetrucks.net/forums/gm-engine-exhaust-performance-21/how-build-exhaust-resonator-tube-eliminate-drone-489463/
> http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930092208.pdf
>
> http://www.enoisecontrol.com/wp-content/uploads/2014/12/engine_exhaust_sound_control_barrier_wall.pdf
>
> --
> Wally Anderson
> 1975 Glenbrook
> Megasquirt 455 port injection science project
> Omaha Nebraska
> Bob Stone hydroBOOOOST
> Greater Midwest Classics
> GMCES
> http://wallyandsue.blogspot.com/
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
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| Re: Exhaust Systems - Drone at 1400 RPM [message #293422 is a reply to message #293381] |
Mon, 04 January 2016 16:13 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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You might try a short exhaust tip. Just clamp it on and try it. I installed one years ago and it took care of the resonance. I later went to Emery's rear muffler design but reused the tail pipe with the tip welded on. So it is also installed on the newer single rear muffler system.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: Exhaust Systems - Drone at 1400 RPM [message #293434 is a reply to message #293381] |
Tue, 05 January 2016 09:45 |
TR 1
Messages: 348
Registered: August 2015
Location: DFW
Karma: -7
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Senior Member |
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The above replies will more than likely stop your drone issue, but if you are already welding on the system, and you don't already have one, it's not a bad idea to instal a flex coupling:
These are mostly used to decouple engine movements from being transferred to the exhaust system, but I've noticed they can help with drone in some applications as well...
IMO, Worth it to install one (or 2 depending on your system) just for the decoupling of engine movement, even if it doesn't do anything for the drone...
Mark S. '73 Painted Desert,
Manny 1 Ton Front End,
Howell Injection,
Leigh Harrison 4bag and Rear Brakes,
Fort Worth, TX
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| Re: Exhaust Systems - Drone at 1400 RPM [message #293460 is a reply to message #293381] |
Wed, 06 January 2016 09:17 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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That makes good sense to make the muffler also the Y. GM did that in the mid 90s Tahoe Suburban trucks ftom the factory. I would like to see the internal flow path on the Spintech. The stock 2 mufflers into a Y has the drawback in that if the mufflers are not balanced, the difference trys to flow through the intake crossover. And if running restrictors, blockoffs or not, none of the scenarios is good.
John Lebetski
Woodstock, IL
77 Eleganza II
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