Harmonic pulsation / Vibration?????????

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shadango said:
Am I missing something? I have read that link a few times and can find no reference to feeling physical vibrations due to exhaust...they talk about vibration, but in a sound-related sense. ????
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The bussing at 2000 RPM I mentioned is mostly heard and not felt like in the butt with a bad U joint. I'm sure if I were to put my hand on the exhaust (not a good idea) I would feel it also.

The problem Shadango is that the word vibration is kind of generic. Is the vibration (mostly felt) being caused by an inbalance in a power train component like the converter, crank, or driveshaft in which case it usually gets worse as the RPM gets greater. Or is the vibration, heard and sometimes felt, being caused because a component such as the exhaust system is having its "natural frequency" or harmonic being excited at a certain RPM. The swaying and later collapse of a bridge in San Francisco, years and years ago, is a perfect example of this. The wind got to swaying the bridge at just the right condition that the natural frequency was excited and she got worse and came apart. Everything out there in the entire world has a natural frequency that if the conditions are perfect it will be excited and start moving around or simply bussing. I used to see and feel it alot when starting steam turbines. In this case the operation RPM range was 4000 to 5000 RPM. Problem was they all had a natural frequency at 2000 RPM that you had to get through quickly as you were speeding the unit up. Even though you went through the speed in 3 seconds you could still feel and hear the vibration in the piping and base but since you never ran at 2000 RPM for any amount of time the designers left it alone.
 
mopar340dave said:
Terry, have you read what Spintech says about this and if so, what do ya think?

http://www.spintechmufflers.com/index.php?_a=viewDoc&docId=1
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Dave I looked at their site and figure that the main jist of their mufflers is very little back pressure, like a straight pipe, but still good sound muffling. Their mufflers will still have a natural frequency but who's to say at what RPM the exitation will happen at. Spintech could test them and find out what that frequency is but it would be a waste of time since as soon as you start connecting pipe and installing hangers that frequency/RPM that the exitation occurs will change either up or down.

I do have a problem with the term "sound vibration energy". I think what they are trying to say (in all the gooblygoop) is that the sound you hear is caused largely by the molecules of the exhaust gases bouncing into each other in the piping and the muffler components and at the same time making heat (the heat part makes sense). They then incorporate space age technology that converts the sound of molecules smacking around into more heat which ultimately muffles the sound. I'm getting a head ache thinking about this. Either way their mufflers do nothing to help harmonics from rearing their ugly heads that I can see.
 
This is the link I should have posted:
http://www.4secondsflat.com/SpinTech.html

"Traditional muffler designs remove sound in two ways: friction and absorption. Friction mufflers (stock type, turbo type, chambered) have high back pressure and can cause extreme high resonance and noise inside the vehicle at certain engine speeds (2000 to 3000) RPM."


"Our XL Sportsman series will give you the ultimate sound without the obnoxious drone of the competitions Tin Performance Mufflers."
 
Keep in mind that i have already tried, checked and replaced every other aspect of my exhaust...which led me to believe that it is the flowmasters. The vibes were the same with a boneyard 318 from an 85 new yorker or my built 340 w/solid cam.

An exhaust resonator may also help at the expense of more back pressure...so I'm told. My Chrysler's exhaust is downright complex and it's quiet as a church mouse with zero drone, ever....
 
I still dont think that any exhaust system will cause a physical vibration or harmonic. (understanding that "harmonic" can apply to a sound wave or a physical vibration wave)

Yes, I have a "drone" at certain rpms.......in fact I have that in my durango with an aftermarket exhaust too to some degree.

But actual physical vibration I think has to be a mechanical concern.....engine or drivetrain, wheels, etc.

i am still searching for a cause for my harmonic vibration (mechanical shake)...starts at about 40 mph and is gone by 50. I feel it in the whole car including the steering wheel....front end was rebuilt and the convertor is correct, new balancer, etc.

i would love to believe its "just" my exhaust, but I really dont think it is. If it were the exhaust, the vibration would be felt at rest at the same rpm........and I have an exhaust that is pretty popular on e-bodies (magnaflow, x pipe) and I have not seen anyone else with the same exhaust on an ebody complain of the vibration....there are so many of these exhausts out there, I doubt highly that a vibration like mine would go unaddressed by the buying public and magnaflow if it were in fact the exhaust causing it.

I am wondering if my driveshaft needs balanced.

Or it could simply be that my engine has this "quirk" as someone else put it due to someone rebuilding it etc....I dont know the history of my engine other than it has had a cam, heads, intake and carb replaced.....
 
then you have not looked!

[ame="http://www.google.com/search?q=magnaflow+exhaust+drone+&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:eek:fficial&client=firefox-a"]magnaflow exhaust drone - Google Search[/ame]

you are segregating the words vibration and harmonic....same same in this app.
 
what's really interesting about the exhaust pipe welded on idea is that my Chrysler's intake has a similar device on it. A plenum that goes nowhere between the air filter box and the throttle body....
 
I'm eager to hear more about this. I have a vibration in my 64 Dart that only comes in when in motion at about 30 mph and 60 mph. all other speeds its smooth. It feels almost like the car is rolling over rumble strips on the highway. I can feel it in the steering wheel. Front wheels were recently balanced with new tires put on, driveshaft was professionally shortened and balanced with new U-joints installed about two years ago. This vibration has been there all along. I'm thinking I need to adjust my pinion angle as the car is raised a bit in the rear with air shocks for tire clearence.
 
mopar340dave said:
what's really interesting about the exhaust pipe welded on idea is that my Chrysler's intake has a similar device on it. A plenum that goes nowhere between the air filter box and the throttle body....
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yeah, i read on those posts that its a factory deal on some cars.
alot of that reading was mumbo jumbo to me since i'm not a mr. science type, but the main jist of it seems to be sound cancellation which to me makes perfect sense. i'm not smart enough to measure sound dB's and then calculate how long the pipes should be based on that data, but i'm willing to take a ballpark shot at it based on gut feeling.
 
Optik said:
I'm eager to hear more about this. I have a vibration in my 64 Dart that only comes in when in motion at about 30 mph and 60 mph. all other speeds its smooth. It feels almost like the car is rolling over rumble strips on the highway. I can feel it in the steering wheel. Front wheels were recently balanced with new tires put on, driveshaft was professionally shortened and balanced with new U-joints installed about two years ago. This vibration has been there all along. I'm thinking I need to adjust my pinion angle as the car is raised a bit in the rear with air shocks for tire clearence.
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i've had the same problem for years. finally have started to attack it incrementally. i just changed to a poly rear tranny mount and will check driveline balance next. after that i'll check pinion angle.
something i didn't know before researching was that the tranny yoke and the pinion yoke must be clocked differently, something i make sure of now when re-installing the shaft.
 
"Exhaust System

DMA (digital model assembly) found room for added muffler volume, a major factor in reducing exhaust noise. Conventional rolled construction further reduces noise because the outer shell has less tendency to resonate than did the previous stamped construction. To prevent exhaust noise from being transferred to the passenger compartment, hangers that support the muffler attach to the rubber isolated rear suspension cross member, providing a second level of isolation compared to the previous body mounts in these location. Hangers have improved isolation characteristics.

Two resonators are used with all power trains. A computer program was used to design the muffler and resonators silencing systems and position them at their most effective locations. One resonator is located under the floor and the other just forward of the tailpipe outlet. The muffler
is placed transversely beneath the rear suspension cross member-a location proven to be highly effective for noise reduction. The exhaust system for each engine is also individually tuned for quietness while providing a pleasantly perceptible sound under medium to hard acceleration."
http://www.allpar.com/model/lh2/conc_noise.html
 
mopar340dave said:
then you have not looked!

magnaflow exhaust drone - Google Search

you are segregating the words vibration and harmonic....same same in this app.
Click to expand...

No, I looked.....I didnt see anyone posting ny posts saying "I have a vibration that shakes the car/steering wheel/seat and when I changed my exhaust it went away !"

"Drones" went away or were changed.

I see lots of people talking about an audible drone or "resonance"....every time I have ever seen or heard the word "drone" it is referring to an AUDIBLE sound/noise/vibration (the "one constant note" defintion in wikipedia)...not a PHYSICAL vibration felt in the steering wheel etc.

I am segregating the two words because they are separate in how I am using them.

Can "vibration" be used to describe a sound? Yes.

Can "vibration" be used to describe a physical feeling? Yes.

Can it be both? Yes

In my case, I have the physical vibration but no sound. To get a vibration as big as I am feeling, there should be major sound if they are married together.

Can "drone" be used to describe a physical feeling? No where I have looked....many definitions of drone, but "a physical feeling or physical vibration" isnt one of them.

Harmonic can be used to describe either a sound or a physical vibration as well....the word refers more to "a wave" than "a sound" or "a feeling". A sound wave can be felt and heard, true.

But can a series of sound waves be "bad" enough to cause the whole chassis of a car to shake/shimmy?

I still say no.

Is there a "drone" ? Yes. An audio drone. Audio is vibration, true. But in a different definition than we are using to describe the symptoms.

Trust me, I would love to believe my issue is "just" the exhaust.

But I dont think that my vibration nor the OP's vibration as he described it is caused by this.

An easy test I guess would be to unbolt the exhaust, put a short length of pipe and muffler on each side and go for a ride.....any harmonics would then change.
 
pauly v.100 said:
i've had the same problem for years. finally have started to attack it incrementally. i just changed to a poly rear tranny mount and will check driveline balance next. after that i'll check pinion angle.
something i didn't know before researching was that the tranny yoke and the pinion yoke must be clocked differently, something i make sure of now when re-installing the shaft.
Click to expand...

How does one check the "clocking" ? That has promise. But I thought there was really only two ways to put each yoke on and that it made no diff. ??

I was looking at the "rotor phasing" post again and still cant figure that out.....the line on the rotor as viewed thru a hole in the cap would just show the timing of the rotor going past the wire tower and when it fires...which is what you re adjusting when you adjust timing. How is this different from "clocking" the rotor?
 
shadango said:
How does one check the "clocking" ? That has promise. But I thought there was really only two ways to put each yoke on and that it made no diff. ??

I was looking at the "rotor phasing" post again and still cant figure that out.....the line on the rotor as viewed thru a hole in the cap would just show the timing of the rotor going past the wire tower and when it fires...which is what you re adjusting when you adjust timing. How is this different from "clocking" the rotor?
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maybe "clocking" was the wrong term.
 
Sound IS vibration. While we think of sound as things we hear, sound waves go far above and below what we can hear.
When you are driving on the highway and you get that rhythmic vibe that seems to oscillate at different speeds as you are cruising depending on throttle position....I can't really explain it any better....

Shadango, if you really don't think it's your exhaust then what else is it? I've been through my entire drivetrain with a change to ss springs, spring seat relocation....no change...


Do you think oem manufacturers are just doing all this trick exhaust work for their health? They would not do it if it didn't work and it sure works on my Chrysler.
 
shadango said:
How does one check the "clocking" ? That has promise. But I thought there was really only two ways to put each yoke on and that it made no diff. ??

I was looking at the "rotor phasing" post again and still cant figure that out.....the line on the rotor as viewed thru a hole in the cap would just show the timing of the rotor going past the wire tower and when it fires...which is what you re adjusting when you adjust timing. How is this different from "clocking" the rotor?
Click to expand...

From what I have read and learned ( not an expert) when you phase the rotor, you are aiming for the rotor to be aligned or very close to aligned with the cap tip whenever it fires, when timing is not advanced, it will be at one position and when it is fully advanced, it will be at a different position.
You want those 2 points to be equally close to the cap tip( probably will be on either side..

When I made a reluctor position change, I had made it worse, the rotor was well beyond the tip when it fired, at all advance positions. So it was out of phase. Now it fires right around the tip which I believe is the proper phasing.


340 dave... I am changing my exhaust... over the next week or so, trying different mufflers, and will let you know if it makes any difference.


Ignition wise, I also found I may have had a weak alternator and changed that at the same time as replacing and re wiring my voltage regulator to properly use "remote sensing".
Before my voltage guage was almost always showing 14.5 or so volts , but a fast flickering of the needle and the lights flickered quickly.

With the regulator and alt change.. NO MORE FLickering!!

The vehicle also seems to run much strong ( seat of the pants feel). Gotta test it some more but I think the pulsation I have been feeling is reduced/or gone.

Not sure but perhaps week alt / poor regulator might have affected the ignition??

I run HEi Module and msd blaster 2 with full voltage(no resistor)

I also used to get an intermittent stutter at idle.. and that also appears to be gone.. I think MY old Alternator was going--lots of volts, but perhaps not enough amps..

Sorry for the long one, but thought I would update on some of the items I have changed and am working on
 
mopar340dave said:
Sound IS vibration. While we think of sound as things we hear, sound waves go far above and below what we can hear.
When you are driving on the highway and you get that rhythmic vibe that seems to oscillate at different speeds as you are cruising depending on throttle position....I can't really explain it any better....

Shadango, if you really don't think it's your exhaust then what else is it? I've been through my entire drivetrain with a change to ss springs, spring seat relocation....no change...


Do you think oem manufacturers are just doing all this trick exhaust work for their health? They would not do it if it didn't work and it sure works on my Chrysler.
Click to expand...

Yes, sound is created by way of vibration. Keep in mind that sound is the RESULT of vibration at a certain frequency. And not all vibration results in a sound, at least not one that is audible to humans.

Vibration can also be caused by numerous other mechanical issues.

Droning is a term used to describe a certain , steady and annoying vibration resulting in a soundwave that repeats over and over and over (resonates) to a point where , for human hearing, its annoying. The interior of a car tends to exacerbate this resonance, as it acts like a big speaker cabinet and gives the soundwaves somewhere to "gather" and makes the resultant resonance worse.

Soundwaves range from extremely high to extremely low.....an example of low would be a sub woofer....boom boom boom....a subwoofer needs an enclosure of some type to work the best, and the soundwaves are non-directional.

Hogher soundwaves (in the human range of hearing) are directional and need less of an enclosure to work.

The mufflers could very well be producing a "vibration"...in fact they are, since sound is vibration and the mufflers are acting like speaker cabinets to the exhaust pulses (small explosions), with the outlet of the muffler being kind of like a speaker.

But I still think we are talking about our cars having two different manifestations of vibration.
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From wikie:
Free vibration occurs when a mechanical system is set off with an initial input and then allowed to vibrate freely. Examples of this type of vibration are pulling a child back on a swing and then letting go or hitting a tuning fork and letting it ring. The mechanical system will then vibrate at one or more of its "natural frequencies" and damp down to zero.
Forced vibration is when an alternating force or motion is applied to a mechanical system. Examples of this type of vibration include a shaking washing machine due to an imbalance, transportation vibration (caused by truck engine, springs, road, etc), or the vibration of a building during an earthquake. In forced vibration the frequency of the vibration is the frequency of the force or motion applied, with order of magnitude being dependent on the actual mechanical system.
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I think exhaust induced vibration is the "free vibration" type whereas what I am talking about is more the "forced" type.

While I dont disagree that an exhaust can cause "vibration", I think the mainfestation of vibration it can induce is very different from the type of vibration I and the OP are experiencing.

Maybe your vibration IS caused by the exhaust. You should, then, swap the exhaust immediately to ANY other exhaust and your vibration should be gone or significantly changed. Let us know how that turns out. But suggesting that one particular brand is the cure for "vibration" is, I think, far too general of a statement. They may well have "droning" under control, but I siggest that droning is not the type of vibration we are talking about here.

Me, I have my doubts. Like I said, I have a major brand exhaust kit on my car....one that has been used by many people.....if this kit were to induce a chassis shaking vibration I am pretty sure that there are a lot of smarter people than you and I out there who would have called this to the attention of everyone by now and made a major fuss about it.

And that is just one brand (magnaflow).

what about the people who have other brands/configurations and still have vibration? So are ALL exhausts (besides spintech of course) faulty? LOL

In my 25 years or so of driving, I have never seen a vehicle have a vibration like I am talking about caused by an exhaust...and I have had a ton of different exhausts. It has always been caused by a mechanical issue.....out of balance wheel, bad tire, driveshaft out of balance, front end issues, engine, etc. I have checked for most of these issues and not found my issue....Like I said...would love to think mine was caused by muffler design.....I am frustrated...but I frankly feel that blaming my particular vibration on the mufflers or exhaust would be like blaming it on the type of seat belt I am running.

I am pretty sure that my vibration, and that of the OP , is a mechanical imbalance of some part(s)....just gotta figure out which.
 
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