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Exhaust hangers and interior noise levels

General engine tech -- Drag Racing to Circle Track

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GARY C
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Re: Exhaust hangers and interior noise levels

Post by GARY C » Wed Mar 27, 2019 6:51 pm

I would change the block style hangers with the rubber strap hangers, at least 2 per side if not 3 so that the weight of the system is equally supported and more able to flex with engine movement.
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Re: Exhaust hangers and interior noise levels

Post by cjperformance » Wed Mar 27, 2019 7:01 pm

RevTheory wrote:
Wed Mar 27, 2019 6:43 pm
cjperformance wrote:
Wed Mar 27, 2019 6:31 pm
Do you also have staggered muffler to collector lengths?
This is straigh up one of the most successful dual exhaust anti drone tricks, i have done this to some really terrible droning systems and only staggering the mufflers has made it completely drone free.
That's pretty interesting. What happens if you have an h-pipe at a Pipemax length recommendation? Does it take enough "anti-drone length stagger" to screw that up enough to notice?
In the case of an H or X that is between the collector and the muffler , just leave the H/X as is and stagger just the muffler. If anything the car psychologically feels faster without the drone!
In any case for a 90% road car i would happily sacrifice a few hp to not have a droning system.
Craig.

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Re: Exhaust hangers and interior noise levels

Post by cjperformance » Wed Mar 27, 2019 7:04 pm

Another trick OEM's use is weights on the pipe. Sometimes just a weight or sometimes a rubber insulated weight, just changing anything that alters a resonant frequency can make some really amazing changes.
This works on dual and single exhausts.
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Re: Exhaust hangers and interior noise levels

Post by NewbVetteGuy » Wed Mar 27, 2019 7:24 pm

pcnsd wrote:
Wed Mar 27, 2019 12:38 am
2000 rpm is in the drone rpm range for V8s assuming your system has a crossover. (100-150 hz) Build and attach one or more suppression resonators.
Drone2000rpm.png
Wow... Nice XLS... Where'd you get that?


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Re: Exhaust hangers and interior noise levels

Post by pcnsd » Thu Mar 28, 2019 11:14 am

NewbVetteGuy wrote:
Wed Mar 27, 2019 7:24 pm
pcnsd wrote:
Wed Mar 27, 2019 12:38 am
2000 rpm is in the drone rpm range for V8s assuming your system has a crossover. (100-150 hz) Build and attach one or more suppression resonators.
Drone2000rpm.png
Wow... Nice XLS... Where'd you get that?


Adam
I am a habitual spreadsheeter with a general interest in NA IC performance and a particular interest in understanding intake and exhaust systems phenomena. PM me a email if you would like a copy of the drone sheet. It is nothing special, mostly based on readily available equations from Wikipedia, the various automotive performance forums and a couple possibly erroneous conclusions of my own regarding the effects of the lower odd harmonics in drone based on reviewing a single spectrum analysis. You should probably note, I have never actually built a drone suppression system.
- Paul

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Re: Exhaust hangers and interior noise levels

Post by F-BIRD'88 » Thu Mar 28, 2019 2:13 pm

As said your tail.pipe exits are too short, behind the bumper. Extend out to a bit beyond the bumper.
The 340 Darts used to have beauti square chrome ex tips. This is why I built my own custom mufflers. (A modified turbo muffler design). You do have room for resonators which would also add tailpipe length as needed. Yup hangers should mount to the frame rails
Not the floor panel. The triflow style "Turbo muffler" is a lot quieter than the straight thru designs like Borla.

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Re: Exhaust hangers and interior noise levels

Post by Belgian1979 » Thu Mar 28, 2019 6:17 pm

cjperformance wrote:
Wed Mar 27, 2019 6:31 pm
Belgian1979 wrote:
Wed Mar 27, 2019 5:48 pm
I have all the tricks mentioned above and the car still drones especially at higher engine speeds (+3000). I have been thinking that the X which is located right under the rear axle has to do something with that + the fact it has a fiberglass body.
Do you also have staggered muffler to collector lengths?
This is straigh up one of the most successful dual exhaust anti drone tricks, i have done this to some really terrible droning systems and only staggering the mufflers has made it completely drone free.
What do you mean with staggering ?

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Re: Exhaust hangers and interior noise levels

Post by cjperformance » Thu Mar 28, 2019 6:19 pm

20190329_084250-800x450.jpg
I dont agree with the 'must have the tailpipe out past the bumper and not pointing/turning down thing' , i have no problems making a system that has no drone, sounds great, makes power and ends before the bumper and turns down so that the pipes are unseen unless you are crouching down and looking right up behind the bumper.
You do not have the required permissions to view the files attached to this post.
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Re: Exhaust hangers and interior noise levels

Post by cjperformance » Thu Mar 28, 2019 6:21 pm

Belgian1979 wrote:
Thu Mar 28, 2019 6:17 pm
cjperformance wrote:
Wed Mar 27, 2019 6:31 pm
Belgian1979 wrote:
Wed Mar 27, 2019 5:48 pm
I have all the tricks mentioned above and the car still drones especially at higher engine speeds (+3000). I have been thinking that the X which is located right under the rear axle has to do something with that + the fact it has a fiberglass body.
Do you also have staggered muffler to collector lengths?
This is straigh up one of the most successful dual exhaust anti drone tricks, i have done this to some really terrible droning systems and only staggering the mufflers has made it completely drone free.
What do you mean with staggering ?
Having a slightly different length (dual system with or without x or h ) from the collector end the the muffler inlet. Most bodies i deal with I can get these lengths from 3 to 6 inches different, even 2 inches makes a difference on a really bad droning system.
Craig.

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Re: Exhaust hangers and interior noise levels

Post by BigBlockMopar » Thu Mar 28, 2019 6:52 pm

F-Bird, I'm not looking to turn the car into a wheelbarrow ;) but the end-tips are just about where a factory exhaust would've ended.

I'm wondering if a baloney cut on the exhaust ends will do anything for sound, perhaps make it less 'pop' when the (muffled) soundwaves exit into the open air.

Paul,
I think there's an error in the Imperial values at the helmholtz chamber resonance part of the sheet.
The metric and Imperial-value don't match up at the Resonator pipe length.

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Re: Exhaust hangers and interior noise levels

Post by cjperformance » Thu Mar 28, 2019 7:16 pm

bigblockmopar wrote:
Thu Mar 28, 2019 6:52 pm
F-Bird, I'm not looking to turn the car into a wheelbarrow ;) .
:lol: =D>
Thats now my favorite exhaust description/saying ,, cant wait till next time someone asks for chrome exhaust tips!!
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Re: Exhaust hangers and interior noise levels

Post by F-BIRD'88 » Thu Mar 28, 2019 7:51 pm

You can be all attitude or you can spend 20 minutes testing some extenstions on the end of your pipes.
Your choice...... :-)

Exhaust that exits say 1-2" from the bumper will not make it a wheelbarrow.
You could (while you're there) test resonators on the ends of the pipes and or uneven lengths, etc.

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Re: Exhaust hangers and interior noise levels

Post by BigBlockMopar » Thu Mar 28, 2019 8:06 pm

No attitude, just some bad memories of what I've seen done around here at times. ;)
I've had the engine on a teststand before and played around checking difference in engine sound between no mufflers and a pair of large case Walker Dynomax mufflers on the ends. Didn't try the Borla's at the time as they already were on the car.
But I think I'm pretty sure the loudness comes from the mufflers, or that area at least (the hangers).
I'll start by unbolting the hangers from the car first and let the exhaust rest on a jackstand for instance, tomsee how much of a change this makes just revving the engine a bit or loading it up against the convertor.

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Re: Exhaust hangers and interior noise levels

Post by GARY C » Thu Mar 28, 2019 8:23 pm

F-BIRD'88 wrote:
Thu Mar 28, 2019 7:51 pm
You can be all attitude or you can spend 20 minutes testing some extenstions on the end of your pipes.
Your choice...... :-)

Exhaust that exits say 1-2" from the bumper will not make it a wheelbarrow.
You could (while you're there) test resonators on the ends of the pipes and or uneven lengths, etc.
Why?
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Re: Exhaust hangers and interior noise levels

Post by pcnsd » Thu Mar 28, 2019 11:08 pm

bigblockmopar wrote:
Thu Mar 28, 2019 6:52 pm

Paul,
I think there's an error in the Imperial values at the helmholtz chamber resonance part of the sheet.
The metric and Imperial-value don't match up at the Resonator pipe length.
Nah, two different system definitions with about the same suppression frequency.
The metric converted:
2.4" x 10.63"+ 250cc chamber
The imperial:
1.9" x 2.93" + 446.34cc/27.24CI chamber
- Paul

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