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I have a question about interior "drone" noise...
It has been posted on the Zoomers thread (38+ pages of it) that the magnaflow system has a drone to it...
and that is why so many went that route with the zoomers system as it doens't "have" it...
can someone expand on this?
better yet...
does anyone have a magnaflow system that is going to be at the Garden Grove meet next week?
As I know there will be several that have the zoomers system...
Thanks in advance!!!
 

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cbutler32 said:
I have a question about interior "drone" noise...
It has been posted on the Zoomers thread (38+ pages of it) that the magnaflow system has a drone to it...
and that is why so many went that route with the zoomers system as it doens't "have" it...
can someone expand on this?
better yet...
does anyone have a magnaflow system that is going to be at the Garden Grove meet next week?
As I know there will be several that have the zoomers system...
Thanks in advance!!!
Drone is a subjective qualitative characteristic of all exhaust systems. Freuqency and amplitude will vary as design changes. Each persons own "interpretation" of acceptable levels and their own personal auditory capacity wil determine what is appealing to them.

Often times people ASSUME things from previous experience and have not really heard for themselves the actually product in question. Some people assumet that based upon other experiences with products they can make generalizations for all products. Unfortunately that is not goign to lead to valid assumptions.

Example:

F-Body (Camaro / Firebird) Our kit is loud and has some degree of noise both insdie and outside the cabin. This product was designed around a perfromance enthusiast customer ... by definition and market study these people were seeking power as premier and were willing to sacrifice other componets such as drivabilty and comfort. Our cat-back caters to that criteria.

The LX chassis on the other hand is entirely different and our strategy is altered to provide a larger degree of comfort whiel still providing a power enhancing part. These are trade offs but not those made by simple coinsidence.

Our cat-backs are NOT culminations of universal parts and pipes. Pipe diameter, resonator or muffler style, shape, volume and perforation core VARY by application. YES thats right ... putting our universal parts off the shelf together to the same configuration as our cat-back will NOT net the same results. This is why we sell BOTH universal and Cat-back configurations.

Our cat-backs are engineered ... not fitted and replicated. We have a 30,000 sq ft facilty housing two test engineers running two in-ground Mustang and Dynojet dynos, Superflow and Horuba flow benches, 1/3 octave 32 band spectrum analyzers and 4 other engineers designing internals and supporting our Computer Aided Drafting design department. My fabrication and design staff pride themselves in putting out product DESIGNED for its applciation.

It would be interesting to hear some impressions regarding noise / drone / resonance from actual owners ... I know they are out there .... we are still selling over 50 systems a month.

Some threads from owners:
http://www.300cforums.com/forums/showpost.php?p=99462&postcount=1
http://www.300cforums.com/forums/showpost.php?p=94868&postcount=4
http://www.300cforums.com/forums/showpost.php?p=94996&postcount=7
http://www.300cforums.com/forums/showpost.php?p=71057&postcount=1

Searching shows more ... seems to be plenty of info.


Richard
 

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My experience, and I believe that of many others, is that the objectionable drone was a function of the interior tone/resonance change brought about, and emphasized by aftermarket catbacks, by the C going into MDS or 4 cylinder mode. Given that are SRT8s are always firing on 8, I don't envision the drone issue being nearly as prevalent, if at all present.
 

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cbutler32 said:
I have a question about interior "drone" noise...
It has been posted on the Zoomers thread (38+ pages of it) that the magnaflow system has a drone to it...
and that is why so many went that route with the zoomers system as it doens't "have" it...
can someone expand on this?
better yet...
does anyone have a magnaflow system that is going to be at the Garden Grove meet next week?
As I know there will be several that have the zoomers system...
Thanks in advance!!!

What do you mean by drone Chris? When do you get it, at what RPM, etc...?
 

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3SRT4ME said:
My experience, and I believe that of many others, is that the objectionable drone was a function of the interior tone/resonance change brought about by the C going into MDS or 4 cylinder mode. Given that are SRT8s are always firing on 8, I don't envision the drone issue being nearly as prevalent, if at all present.
A dramatic harmonic is introduced when the motor shifts MDS modes. We had to incorporatea completely different design to counter this shift. We started with an external x much like the factory part but when the exhaust pressure was reduced the dampning effect of the x was as well reduced. We had to locate the x all the way inside the first muffler (mid-body) and perforate the x to minimize the MDS "buzz."

Now as far as resonance goes, this noise is function of the noise cancelling capacity of the muffler AND system pipe design. Both noise and harmonics due to exhaust pulse contribute to cab resonance (this is the loud booming in the cab) that typically occurs when the engine is under high load and low throttel position. There are many ways to combat this ranging from harmonic dampners to changing exhaust pulse character through modifying turbulance/laminar flow, speed/heat and balance such as that provided by a cross over tube of sorts.

Each application changes how effective a certain approach will be at reducing noise. There is NO one best way. I does infact take time and testing.

Richard
 

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I had the zoomers on for about a day. I had to take that thing out.. The tone was never constant. What I mean is that the sound of the exhuast was never the same. When you are cruzin it sounds ok but once you ease off the gas then give it some it sounds horrible inside the cabin. For example if you are out on the streets and come to a red light. Once you give just a bit of gas it would make this ugly knocking noise. The guys around here all told me it because there is no backpressure and the hemi does require some bp. The weird thing is that you can only here the knocking noise from the inside of the car. From the outside it sounds nice. Go figure..

Rmedina
 

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rmedina said:
I had the zoomers on for about a day. I had to take that thing out.. The tone was never constant. What I mean is that the sound of the exhuast was never the same. When you are cruzin it sounds ok but once you ease off the gas then give it some it sounds horrible inside the cabin. For example if you are out on the streets and come to a red light. Once you give just a bit of gas it would make this ugly knocking noise. The guys around here all told me it because there is no backpressure and the hemi does require some bp. The weird thing is that you can only here the knocking noise from the inside of the car. From the outside it sounds nice. Go figure..

Rmedina

I've had Zoomers for a couple of months and I've never heard a horrible "ugly knocking noise" from the inside (or outside). Is there any other way to describe this noise? You said yours made this noise both when you gave it a bit of gas as as well when you eased off the gas? :confused:


Audrey
Hers: '05 'nilla C....fully loaded except engine block heater, volant cai, zoomers, tint, painted engine shroud w/ss trim kit

His: New arrival: '05 1500 Dodge Ram P/U Quad Cab w/hemi (of coarse)
 

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Kewl 'Nilla Hemi said:
I've had Zoomers for a couple of months and I've never heard a horrible "ugly knocking noise" from the inside (or outside). Is there any other way to describe this noise? You said yours made this noise both when you gave it a bit of gas as as well when you eased off the gas? :confused:


Audrey
Hers: '05 'nilla C....fully loaded except engine block heater, volant cai, zoomers, tint, painted engine shroud w/ss trim kit

His: New arrival: '05 1500 Dodge Ram P/U Quad Cab w/hemi (of coarse)
Not when I ease off the gas, just when I gave it just a little. For example when you are out looking for a parking space at a grocery store. Stop and go driving.. The noise was similar to a dump trunk. As soon I as gave it more gas it would go away..
 

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rmedina said:
I had the zoomers on for about a day. I had to take that thing out.. The tone was never constant. What I mean is that the sound of the exhuast was never the same. When you are cruzin it sounds ok but once you ease off the gas then give it some it sounds horrible inside the cabin. For example if you are out on the streets and come to a red light. Once you give just a bit of gas it would make this ugly knocking noise. The guys around here all told me it because there is no backpressure and the hemi does require some bp. The weird thing is that you can only here the knocking noise from the inside of the car. From the outside it sounds nice. Go figure..

Rmedina
One day? I've never heard any one complain about any type of drone or resonance at any speed. Was it knocking like "pinging" cylinder detonation? Did you check for any leaks? Was the system clamped and welded? Sorry to hear of your problem, before you took them off perhaps we could have discussed a possible solution. I guess everyone’s ear is different and tolerant to different sounds. Our patented tip design does a good job canceling out the exhaust pluses that cause drone or cabin resonance. We developed the venturi tip for just this purpose to cancel out the noise with out loss of performance.
 

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You hear drone in a car when the sound coming out both pipes resonates harmonically and creates an abnormally loud sound. If you think back to high school physics you may remember the experiments where you move back and forth between two identical sound sources and the sound will get louder and softer as you move. In a car with dual exhaust, you will hear a similar warble as you accellerate. It will get louder and softer as it goes up through the RPM range. If you happen to be cruising with the engine in the right RPM range, you will be stuck listening to the loud droning noise.

Solutions include changing speed, changing engine speed by shifting gears, having single exhaust, or the magical approach used by car manufacturers: the mufflers are slightly different left-to-right so the sound sources are not identical and will not resonate.
 

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Dutch said:
You hear drone in a car when the sound coming out both pipes resonates harmonically and creates an abnormally loud sound. If you think back to high school physics you may remember the experiments where you move back and forth between two identical sound sources and the sound will get louder and softer as you move. In a car with dual exhaust, you will hear a similar warble as you accellerate. It will get louder and softer as it goes up through the RPM range. If you happen to be cruising with the engine in the right RPM range, you will be stuck listening to the loud droning noise.

Solutions include changing speed, changing engine speed by shifting gears, having single exhaust, or the magical approach used by car manufacturers: the mufflers are slightly different left-to-right so the sound sources are not identical and will not resonate.
Not necessarily the case ...

Drone or resonance is a function of harmonics created directly by the firing pulse and how it is expelled and how these sound pressure waves are either altered by mass and lack of dampning or how they are reflected through or on other adjascent surfaces. Finding the resonant frequency of a particular motor or vehicle is a matter of considering motor dynamics ... compression / firing order / volume of exhaust gas expelled / manifold design. Then Combine that with the dynamics of the silencer system ... exhaust system mass / hanger locations / routing / dampening method / tubing diameter. Together you will have introduced some 30-40 variables. NOT an easy computation.

In the case of the MDS 5.7L Hemi, Damlier-Chrysler went through some 200 computer generated model iterations before they came actaully building a sample prototype. The LX exhaust system was engineered using just about ALL the technologies available to minimize noise. Careful examination of the OEM system reveals the use of a crossover/balance tube, packed/perforation core based silencer, chambered silencer, helmholtz resonator and usual pipe/tube size alterations to control heat and gas velocity. The MDS component proves to be a large challenge as it introduces a 4 cylinder (V4 pattern) leading to very long pulse widths and dramatic changes in the pressure of the exhaust system between pulses. You have heard the distinct exhasut note of a boxer type motor (porshce/subaru.) Fortunately, you are only trying to control this exhaust pulse under low throttle position. All in all one can see where the OEM exhaust systems gets its nearly $900 price tag.

But back to resonance ...

Changing speed or shift gears is nto really a solution as it doesnt change the problem but only avoids a symptom.

Having a single or dual exhaust will NOT make a system any less resonant by design alone.

If simply changing a system's left and right banks would reduce drone/resonance why is the stock system entirely symetrical? Symetry alone cannot control resonance ... remember that exhaust gas will travel the path of least resistance (resistance in terms of pressure/heat)

One of the single largest overlooked part of controlling resonance is understanding how mass and system suspension effect harmonics. Look at your exhaust system as a large tuning fork ... this opens a whole new discussion. Just as a brief example: In designing our GTO system we PURPOSELY ommited OEM hangers in 3 locations utiliznig only 3 of 6 hangers due to the change in mass from the OEM to our system. Allowing the system the same degree of movement after having lightened the system kept the sytem from being overly rigid which woudl in turn INCREASE its ability to transmit harmonics through adjascent componets ...

Just something to think about ... BTW this is what happens @ 4am when you can't sleep due the FLU!!! :eek:uch:
 

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btlfed1500 said:
Not necessarily the case ...Just something to think about ... BTW this is what happens @ 4am when you can't sleep due the FLU!!! :eek:uch:
Darned informative btlfed! If you have the time between fevers... :wink1: I'm interested in putting headers and a catback on my 300C, but I don't want it to be real loud or vibrate a lot at idle or cruising speeds. I've read & heard a lot of different things, some of which directly conflict. Some say the headers will create a cabin drone or vibration regardless of the make/type of header or the exhaust you pick. Others have indicated that headers themselves will not make that much noise or vibration? From what I've been able to dig up it appears that the mopar or borla 140112 type catback (funtionally identical?) is the least noisy of the catbacks. Would you agree or disagree with that?

I've ridden in a truck with dynaflow headers and magnaflow exhaust and it was extremely loud. Way too loud! Since you obviously know a lot about the subject I'd be interested in what combinations of header/catback you (or others who have experience) think would be the least noisy when the throttle is at idle or cruise. I'm looking for efficient engine operation without obnoxious noise, as opposed to just raw HP. :confused:
 

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I put on the magnaflow system this weekend. Just a few miles so far, but it's definitely louder than stock. There's is a little drone or resonance at about 1700 rpm. When the MDS kicks in, you can definitely hear it. The pitch of the exhaust seems to get lower, a growl so to speak. When you punch the trottle, the exhaust roars. The 300C with magnaflows seem to attract all the "I wanna hot car like yours" crowd with all the resultant motor revving. Don't know if it's added any extra horses. The tires ain't spinning out, but I haven't used autostick yet. It does seem to throw you back into the seat a bit more, but then it may be the exhaust noise making you think there's a bit more g's. I'll see how things work out when I get some more miles in it. I kept the stock exhaust in case this experiment in a performance exhaust wears a bit thin for my ears.
 
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