NOT Flutter! New V10 REVERSION noise
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NOT Flutter! New V10 REVERSION noise
The new V10 3 valve motor has some notable noises at certain RPMs and loads.
Why don’t we agree that for the 3 valve, V10, we are going to call this new noise REVERSION?
I do not want to call it FLUTTER, that was a term that made sense relative to the funky Y pipe and the necked down, (very small diameter), passenger side tube, that connected at the Y.
This motor has an audible growl and a vibration that you can hear, and feel in your butt and feet!
I have been diagnosing this sound/vibration for a week now, and it is NOT FLUTTER.
I believe it is a circumstantial reversion that is amplified as a harmonic of the fundamental frequency that is not attenuated before the muffler. (OK I test stuff for a living, and have a thing for technical BS type writing).
I have standard diameter tires driven by a 4.30:1 rear through a R5110 TorqueShift automatic transmission. At 40 to 43 MPH, under load (mildly accelerating or moving uphill), and around 1250 RPM (OD), there is a distinct rumble, growl, vibration, that is very sharply defined as RPM related.
If I add a little gas, or let off just a little, it decreases very fast. Under normal acceleration up through this RPM / Gear “zone”, you do not notice it at all. But cruising in stoplight-to-stoplight 40-MPH zones, it is very noticeable.
OK Here is my analysis:
Exhaust has two components, high intensity sound, and hot expanding gasses. The exhaust system has to manage both of these. Typically most owners think that the catalytic converters, any resonator, if equipped, and the muffler, are the system features that deal with the sound pressure, and all the other tubing is just to evacuate the gasses to the rear. Not completely true!
Sound pressure is a physical thing that can be measured. It is also an energy source that can MOVE air. Take three sheets of toilet paper, hold by top edge, and suspend the sheets below your hand right in front of a set of speakers about a foot or two, and increase the volume to prove to yourself that sound does indeed move air. Do the same thing in front of your face and shout at the paper, it will move away from the sound because the sound waves are MOVEING AIR!
Single frequency sounds have very measurable and predictable physical characteristics. However variable frequency, and changing sound pressure levels, are much harder to analyze. The exhaust explosions are related to volume, timing, number of cylinders, manifold and tubing system design, and engine RPM.
As an exhaust valve opens the gases are still expanding AND sound is bouncing all around the cylinder. The escaping gasses to the exhaust manifold, and into the down tube/s direct much of this sound wave downstream. Here is where it gets funky; these sound waves are subject to all the normal laws of wave dynamics, and since they have physical presence, they move away from their source and bounce and reflect off the insides of the tubing. Many times these sound waves are reflected back towards the exhaust valve and this is what we call REVERSION.
Exhaust reversion is sound reflection that has enough power to MOVE, SLOW DOWN, and HINDER the expansion and escape of the exhaust towards the open end. This “backflow” causes some sounds to be amplified and some to attenuate. The design of the exhaust system can dampen or amplify different tones depending on material, length, diameter, angles greater than 45degrees, and a few other variables.
I believe the S curved driver’s side pre-collector pipe sets up an ODD harmonic, off beat note, relative to the short, straight, passenger side pipe. The 2 into 1 collector is about 14 feet in front of the Muffler.
I believe the offbeat; odd harmonics, are reflected back along the 14 feet of pipe from the insides of the muffler and get amplified causing this vibration.
Anyone got ideas on how to prove or disprove my thesis?
Why don’t we agree that for the 3 valve, V10, we are going to call this new noise REVERSION?
I do not want to call it FLUTTER, that was a term that made sense relative to the funky Y pipe and the necked down, (very small diameter), passenger side tube, that connected at the Y.
This motor has an audible growl and a vibration that you can hear, and feel in your butt and feet!
I have been diagnosing this sound/vibration for a week now, and it is NOT FLUTTER.
I believe it is a circumstantial reversion that is amplified as a harmonic of the fundamental frequency that is not attenuated before the muffler. (OK I test stuff for a living, and have a thing for technical BS type writing).
I have standard diameter tires driven by a 4.30:1 rear through a R5110 TorqueShift automatic transmission. At 40 to 43 MPH, under load (mildly accelerating or moving uphill), and around 1250 RPM (OD), there is a distinct rumble, growl, vibration, that is very sharply defined as RPM related.
If I add a little gas, or let off just a little, it decreases very fast. Under normal acceleration up through this RPM / Gear “zone”, you do not notice it at all. But cruising in stoplight-to-stoplight 40-MPH zones, it is very noticeable.
OK Here is my analysis:
Exhaust has two components, high intensity sound, and hot expanding gasses. The exhaust system has to manage both of these. Typically most owners think that the catalytic converters, any resonator, if equipped, and the muffler, are the system features that deal with the sound pressure, and all the other tubing is just to evacuate the gasses to the rear. Not completely true!
Sound pressure is a physical thing that can be measured. It is also an energy source that can MOVE air. Take three sheets of toilet paper, hold by top edge, and suspend the sheets below your hand right in front of a set of speakers about a foot or two, and increase the volume to prove to yourself that sound does indeed move air. Do the same thing in front of your face and shout at the paper, it will move away from the sound because the sound waves are MOVEING AIR!
Single frequency sounds have very measurable and predictable physical characteristics. However variable frequency, and changing sound pressure levels, are much harder to analyze. The exhaust explosions are related to volume, timing, number of cylinders, manifold and tubing system design, and engine RPM.
As an exhaust valve opens the gases are still expanding AND sound is bouncing all around the cylinder. The escaping gasses to the exhaust manifold, and into the down tube/s direct much of this sound wave downstream. Here is where it gets funky; these sound waves are subject to all the normal laws of wave dynamics, and since they have physical presence, they move away from their source and bounce and reflect off the insides of the tubing. Many times these sound waves are reflected back towards the exhaust valve and this is what we call REVERSION.
Exhaust reversion is sound reflection that has enough power to MOVE, SLOW DOWN, and HINDER the expansion and escape of the exhaust towards the open end. This “backflow” causes some sounds to be amplified and some to attenuate. The design of the exhaust system can dampen or amplify different tones depending on material, length, diameter, angles greater than 45degrees, and a few other variables.
I believe the S curved driver’s side pre-collector pipe sets up an ODD harmonic, off beat note, relative to the short, straight, passenger side pipe. The 2 into 1 collector is about 14 feet in front of the Muffler.
I believe the offbeat; odd harmonics, are reflected back along the 14 feet of pipe from the insides of the muffler and get amplified causing this vibration.
Anyone got ideas on how to prove or disprove my thesis?
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