VT-VZ Exhaust What's Responsible For Drone

[Mohit]

Which mufflers on a VT-VZ LS1 exhaust are responsible for drone, the 2 centre mufflers or the rear muffler?

[ittwgn]

isn't it just as much about the diameter of the pipes like running dual 3 inch when dual2 1/2 inch is all that's needed for the amount of airflow !!?? like when your getting more drone when just cruising but in upper rpm more airflow less drone !!?? cheers

[bozodos]

I believe the rear muffler is the one that relates most to drone or lack thereof.

[surfwagon]

Pipe size has more to with drone than the mufflers.
Deleting mufflers besides making an exhaust louder is usually responsible for drone or more drone into a system.

[bigfoot]

I have found that fitting headers and hi flow cats as well often helps getting rid of drone that you often get by just fitting a cat back system.

[bozodos]

the droniest system I've ever heard was Tri Ys, stock cats and Redback twin 2.5 with rear resonator delete, had to drive around with the blasted thing in power mode because the droning at 60km/h was insufferable!

[macca_779]

Deleting the rear resonator is the primary culprit to drone. Been there, done that, learnt my lesson.

[whitels1ss]

Deleting the rear resonator is the primary culprit to drone. Been there, done that, learnt my lesson.

Yeah very true.....

Just looked up the word "Resonator" on an online dictionary.

It came up with this in the results.....

"An instrument for detecting the presence of a particular frequency by means of resonance"

I think the word "detecting" might be a typo and should read "deleting"

[BLACK 346]

Here is another, this one specifically explains what the resonator's purpose is in life.

Waves canceling inside a simplified muffler

In reality, the sound coming from the engine is a mixture of many different frequencies of sound, and since many of those frequencies depend on the engine speed, the sound is almost never at exactly the right frequency for this to happen. The resonator is designed to work best in the frequency range where the engine makes the most noise; but even if the frequency is not exactly what the resonator was tuned for, it will still produce some destructive interference.

Some cars, especially luxury cars where quiet operation is a key feature, have another component in the exhaust that looks like a muffler, but is called a resonator. This device works just like the resonator chamber in the muffler -- the dimensions are calculated so that the waves reflected by the resonator help cancel out certain frequencies of sound in the exhaust.

There are other features inside this muffler that help it reduce the sound level in different ways. The body of the muffler is constructed in three layers: Two thin layers of metal with a thicker, slightly insulated layer between them. This allows the body of the muffler to absorb some of the pressure pulses. Also, the inlet and outlet pipes going into the main chamber are perforated with holes. This allows thousands of tiny pressure pulses to bounce around in the main chamber, canceling each other out to some extent in addition to being absorbed by the muffler's housing.

[Drewie]

In my case definetlely the rear muffler, I had a HM stainless steel cat back on my VX SS, was supposed to be stainless but the inside of the rear muffler must have been mild steel, it rusted out internally and the fibreglass filling started to come out, the outer case was fine but the inner tube rusted out, anyway the more fibreglass that came out the more the drone increased it got to the stage I ripped it off and put the stock system back on, never really noticed any difference in performance but on a long trip it is now a pleasure to travel in. I will probably get around to getting a new catback but I will thoroughly research drone before laying down my dollars.

[Mohit]

The reason I asked the original question is because I recently got a Supercat cat back exhaust for my VYII Calais.

The first couple of days I didn't really notice it but the exhaust seems to drone a lot more than I remember.

I had the exact same cat back on my VYII SS three years ago and I don't remember it droning like it does now. Not sure if I'm just older now and more annoyed by certain noises but it seems like it drones and sounds boomy under acceleration and when sitting at certain speeds like on the freeway.

What would happen if I replaced the centre mufflers section with a standard VYII SS item (twin instead of single pipework) and only left the rear Supercat muffler on (effectively a diff back exhaust). Would this have any affect on reducing drone while still retaining a bit of an exhaust note?

[LS1VYSS03]

Could be multiple things,

Resonators caused drone on my F150 with 1 3/4 Longtubes, magnaflow X-pipe, dynomax bullets and 4" tips
Went to magnaflow high flow cats...zero drone, deeper done, not as loud but passed emissions

Resonators, straight pipes, mufflers size, shape, brand - not everyone is the same, cylinder deactivation also plays a role

[VY Sleeper]

I have found that fitting headers and hi flow cats as well often helps getting rid of drone that you often get by just fitting a cat back system.

I had no drone with my cat-back system, recently I had ceramic coated pacey's and 100 cel cats fitted. After I was over the initial excitement of the new sound I quickly realized there is an annoying drone between 1500 & 2000rpm! Which is were it sits most of the time, aaahhhhhhhhh!!!

[bigfoot]

I had no drone with my cat-back system, recently I had ceramic coated pacey's and 100 cel cats fitted. After I was over the initial excitement of the new sound I quickly realized there is an annoying drone between 1500 & 2000rpm! Which is were it sits most of the time, aaahhhhhhhhh!!!

Yeah, fair enough, can see where you are coming from with a 6 speed manual but I was talking
more about with an auto as far as for the hi flow cats and headers being a help.

[Phillshz]

Here is another, this one specifically explains what the resonator's purpose is in life.

Waves canceling inside a simplified muffler

In reality, the sound coming from the engine is a mixture of many different frequencies of sound, and since many of those frequencies depend on the engine speed, the sound is almost never at exactly the right frequency for this to happen. The resonator is designed to work best in the frequency range where the engine makes the most noise; but even if the frequency is not exactly what the resonator was tuned for, it will still produce some destructive interference.

Some cars, especially luxury cars where quiet operation is a key feature, have another component in the exhaust that looks like a muffler, but is called a resonator. This device works just like the resonator chamber in the muffler -- the dimensions are calculated so that the waves reflected by the resonator help cancel out certain frequencies of sound in the exhaust.

There are other features inside this muffler that help it reduce the sound level in different ways. The body of the muffler is constructed in three layers: Two thin layers of metal with a thicker, slightly insulated layer between them. This allows the body of the muffler to absorb some of the pressure pulses. Also, the inlet and outlet pipes going into the main chamber are perforated with holes. This allows thousands of tiny pressure pulses to bounce around in the main chamber, canceling each other out to some extent in addition to being absorbed by the muffler's housing.

MY06 VZ`s with the L76/L98 engine, have a small resonator on the drivers side bank after the cat. Must be there to quiet them down for the Euro 3/ADR/MY06 drive by noise regs that came in on jan 06.

Cheers Phill