|
Re: Reduce exhaust drone
[Re: 70GranCoupe]
#2991399
12/02/21 09:15 PM
12/02/21 09:15 PM
|
Joined: Feb 2003
Posts: 16,128
Mesa, Arizona
dart4forte
I Live Here
|
I Live Here
Joined: Feb 2003
Posts: 16,128
Mesa, Arizona
|
Try the Hemi resonators? Another muffler is the Magnafow. Nice rumble at idle and fairly quiet while cruising. No drone. I think TTI uses them in their exhaust sets.
“So if it’s on the internet it must be true”
Abe Lincoln
|
|
|
Re: Reduce exhaust drone
[Re: dart4forte]
#2991527
12/03/21 09:18 AM
12/03/21 09:18 AM
|
Joined: Jun 2004
Posts: 3,372
St. Charles, MO
wingman
Uncreative Title
|
Uncreative Title
Joined: Jun 2004
Posts: 3,372
St. Charles, MO
|
IMO every car is a little different. A combo that drones on one car may not drone on another car. And what fixes drone on one car may not fix it on another. That said....my 70 RR with a 440 and flowmasters droned like crazy. I made a switch from an "H" crossover to an X pipe and the drone disappeared--no other changes.  Some guys I hang out with also used glasspacks as resonators near the tailpipe for this purpose with mixed results.
Last edited by wingman; 12/03/21 09:20 AM.
1969 Dodge Coronet Super Bee 383 A4
1970 Plymouth Road Runner 440 FC7 (sold)
|
|
|
Re: Reduce exhaust drone
[Re: 70GranCoupe]
#2991543
12/03/21 10:07 AM
12/03/21 10:07 AM
|
Joined: Jan 2003
Posts: 11,996
Benton, IL.
DaveRS23
Special needs idiot
|
Special needs idiot
Joined: Jan 2003
Posts: 11,996
Benton, IL.
|
I basically have your same car with the same exhaust. On this one and all my other Mopars, I have killed the drone by putting glass packs (bullets) beside the gas tank in the tail pipes. Any cheap ones will work, no need to spend any big bucks.
Master, again and still
|
|
|
Re: Reduce exhaust drone
[Re: DaveRS23]
#2991672
12/03/21 02:19 PM
12/03/21 02:19 PM
|
Joined: Sep 2003
Posts: 19,310
north of coder
moparx
"Butt Crack Bob"
|
"Butt Crack Bob"
Joined: Sep 2003
Posts: 19,310
north of coder
|
I basically have your same car with the same exhaust. On this one and all my other Mopars, I have killed the drone by putting glass packs (bullets) beside the gas tank in the tail pipes. Any cheap ones will work, no need to spend any big bucks. this ^^^^^^  however, you might have to experiment with the length of the glass packs [or race bullets] to get the results you need or want. it is best to put the glass packs just past where the pipe comes over the housing and starts rearward by the gas tank, so you have room for the tip or turn down of your choice. another way would be to get your tip/turn down in the position you want, then measure what length of glass pack will work, attaching to your tip and the tail pipe coming rearward. 
|
|
|
Re: Reduce exhaust drone
[Re: moparx]
#2991727
12/03/21 04:51 PM
12/03/21 04:51 PM
|
Joined: Jan 2008
Posts: 553
DE
Ply72rr
mopar
|
mopar
Joined: Jan 2008
Posts: 553
DE
|
|
|
|
Re: Reduce exhaust drone
[Re: 70GranCoupe]
#2991850
12/03/21 10:53 PM
12/03/21 10:53 PM
|
Joined: Jan 2003
Posts: 5,443
Indiana
YO7_A66
master
|
master
Joined: Jan 2003
Posts: 5,443
Indiana
|
Classic Chambered Exhaust made me a set for my 70 Challenger. They mount beside the gas tank and he is a member here. I took a few dimensions and emailed him and he told me what he could make. They fit perfect beside the tank and fit well with the aftermarket exhaust tips.
Last edited by YO7_A66; 12/03/21 11:00 PM.
1970 YO7 A66 [Canadian Export] F8 Challenger
340 (Currently in shop for stroker assy.)
|
|
|
Re: Reduce exhaust drone
[Re: YO7_A66]
#2991855
12/03/21 11:08 PM
12/03/21 11:08 PM
|
Joined: May 2019
Posts: 710
Lake Villa Il
INTMD8
super stock
|
super stock
Joined: May 2019
Posts: 710
Lake Villa Il
|
Fwiw, I would just change the mufflers. I like pypes race pro. They are straight through but one of the quieter mufflers out there. (more so than magnaflow or dynomax ultra flo) I have zero drone with h-pipe and dual 3".
Friend of mine has a roadrunner with dual 2.5" and x-pipe with the same mufflers and sounds great as well.
69 Charger. 438ci Gen2 hemi. Flex fuel. Holley HP efi. 650rwhp @7250 510rwtq @5700
|
|
|
Re: Reduce exhaust drone
[Re: second 70]
#2994016
12/10/21 12:37 PM
12/10/21 12:37 PM
|
Joined: Feb 2010
Posts: 270
Mountain View, CA
68rrunner
enthusiast
|
enthusiast
Joined: Feb 2010
Posts: 270
Mountain View, CA
|
Helmholtz Resonance-
the concept of this resonator is quite complicated when trying to understand how sound and frequency works, but the steps involved are fairly simple. here's how:
1. you will need two variables: the drone RPM, and # of cylinders your engine has.
2. divide the RPM by 60 to get the RPS, or revolutions per second.
3. divide the # of cylinders by 2 to get # fired per revolution.
4. multiply RPS by # fired per rev to get the drone frequency in Hz.
5. divide the speed of sound by the Hz. the speed of sound is a constant 1,260 ft/s. the number is funky because sound travels faster in warm air, and the air coming from an exhaust is very hot.
6. take the result from #5 and divide by 4.
7. take the result from #6 and multiply by 12 to get the resonator length in inches needed to cancel the drone at that RPM.
here's an example:
1. my car drones the worst at 3,300 RPM and has 4 cylinders.
2. 3,300 / 60 = 55.0 RPS
3. 4 / 2 = 2
4. 55.0 * 2 = 110 Hz
5. 1,260 / 110 = 11.45
6. 11.45 / 4 = 2.86
7. 2.86 * 12 = 34.36 inches
from the result shown, my car needs a resonator of approximately 34.4 inches to add a damper that is tuned for my drone.
Hope this helps.
|
|
|
Re: Reduce exhaust drone
[Re: second 70]
#2994237
12/10/21 11:57 PM
12/10/21 11:57 PM
|
Joined: Jan 2003
Posts: 8,392
Highland, MI.
Sunroofcuda
master
|
master
Joined: Jan 2003
Posts: 8,392
Highland, MI.
|
I have full 3 " with Flowmaster super 40's and have no drone. That's a first!
No Man With A Good Car Needs To Be Justified
|
|
|
Re: Reduce exhaust drone
[Re: 68rrunner]
#2994238
12/10/21 11:58 PM
12/10/21 11:58 PM
|
Joined: Jan 2003
Posts: 8,392
Highland, MI.
Sunroofcuda
master
|
master
Joined: Jan 2003
Posts: 8,392
Highland, MI.
|
Helmholtz Resonance-
the concept of this resonator is quite complicated when trying to understand how sound and frequency works, but the steps involved are fairly simple. here's how:
1. you will need two variables: the drone RPM, and # of cylinders your engine has.
2. divide the RPM by 60 to get the RPS, or revolutions per second.
3. divide the # of cylinders by 2 to get # fired per revolution.
4. multiply RPS by # fired per rev to get the drone frequency in Hz.
5. divide the speed of sound by the Hz. the speed of sound is a constant 1,260 ft/s. the number is funky because sound travels faster in warm air, and the air coming from an exhaust is very hot.
6. take the result from #5 and divide by 4.
7. take the result from #6 and multiply by 12 to get the resonator length in inches needed to cancel the drone at that RPM.
here's an example:
1. my car drones the worst at 3,300 RPM and has 4 cylinders.
2. 3,300 / 60 = 55.0 RPS
3. 4 / 2 = 2
4. 55.0 * 2 = 110 Hz
5. 1,260 / 110 = 11.45
6. 11.45 / 4 = 2.86
7. 2.86 * 12 = 34.36 inches
from the result shown, my car needs a resonator of approximately 34.4 inches to add a damper that is tuned for my drone.
Hope this helps.
WAAAAAAY too technical!
No Man With A Good Car Needs To Be Justified
|
|
|
Re: Reduce exhaust drone
[Re: 68rrunner]
#2994278
12/11/21 09:58 AM
12/11/21 09:58 AM
|
Joined: Jan 2006
Posts: 8,162
USA
360view
Moparts resident spammer
|
Moparts resident spammer
Joined: Jan 2006
Posts: 8,162
USA
|
Helmholtz Resonance-
the concept of this resonator is quite complicated when trying to understand how sound and frequency works, but the steps involved are fairly simple. here's how:
1. you will need two variables: the drone RPM, and # of cylinders your engine has.
2. divide the RPM by 60 to get the RPS, or revolutions per second.
3. divide the # of cylinders by 2 to get # fired per revolution.
4. multiply RPS by # fired per rev to get the drone frequency in Hz.
5. divide the speed of sound by the Hz. the speed of sound is a constant 1,260 ft/s. the number is funky because sound travels faster in warm air, and the air coming from an exhaust is very hot.
6. take the result from #5 and divide by 4.
7. take the result from #6 and multiply by 12 to get the resonator length in inches needed to cancel the drone at that RPM.
here's an example:
1. my car drones the worst at 3,300 RPM and has 4 cylinders.
2. 3,300 / 60 = 55.0 RPS
3. 4 / 2 = 2
4. 55.0 * 2 = 110 Hz
5. 1,260 / 110 = 11.45
6. 11.45 / 4 = 2.86
7. 2.86 * 12 = 34.36 inches
from the result shown, my car needs a resonator of approximately 34.4 inches to add a damper that is tuned for my drone.
Hope this helps.
Interesting. In step #5 above a questionable assumption is made to ignore how the speed of sound in a gas varies with temperature, pressure, and what the gas is a mixture of ( various percents of nitrogen, carbon dioxide, water vapor, oxygen) Maybe 1,260 feet per second is “close enough.” In past Moparts posts on “Drone” we have discussed “stubs” for reduction instead of resonators. Another post above points out that whether the air/fuel mixture is rich or lean affects Drone. This is also saying: rich or lean affects the speed of sound of exhaust gas. Drone will change if you climb a steep hill at constant speed. (pressure of exhaust gas goes up) Drone will change if you vice grip a large socket into your exhaust pipe tip. (pressure again)
|
|
|
Re: Reduce exhaust drone
[Re: INTMD8]
#3017562
02/21/22 11:53 PM
02/21/22 11:53 PM
|
Joined: Sep 2003
Posts: 286
Marysville, OH
mrploww
enthusiast
|
enthusiast
Joined: Sep 2003
Posts: 286
Marysville, OH
|
Fwiw, I would just change the mufflers. I like pypes race pro. They are straight through but one of the quieter mufflers out there. (more so than magnaflow or dynomax ultra flo) I have zero drone with h-pipe and dual 3".
Friend of mine has a roadrunner with dual 2.5" and x-pipe with the same mufflers and sounds great as well. Do you have any videos with the Pypes Race Pro?
'64 Plymouth Belvedere 9 passenger surf wagon
|
|
|
|
|
