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

[bozodos]

I had read that it was there to induce a pulse in the exhaust system due to them being so quiet stock. I could be wrong though.

[paok_18]

I think it is a few things. How ever a major part is the quality of mufflers..
Ie: Xforce cat-back with the rear twin in/twin out muffler-resi drones.. How ever the same setup in DiFilippo does not drone..

[munz]

I think it is a few things. How ever a major part is the quality of mufflers..
Ie: Xforce cat-back with the rear twin in/twin out muffler-resi drones.. How ever the same setup in DiFilippo does not drone..

It might have something to do with length of the reso's, I measured my Diflippo (2.5in) and Manta (3in) reso's and both were 14in long.

Wouldn't mind knowing the length of other dual rear resonated systems that have drone or not, if any of you care to share?

[Mohit]

Will check the length of my Supercat rear resonator on the weekend.
So would the first thing to do is try a bigger (longer) rear resonator to reduce drone?
What about the two centre mufflers do they play a role in the drone caused?

[munz]

could possibly be the length,


but it probably will come down to the material and how good the glass is packed in the muffler

[IJ.]

It all plays a part, diameter/length/position in the pipe work, some cars run a Helmholtz style resonator (muffler looking thing T'd into the main pipe) to kill certain frequencies of noise, I built my own system for the Tonner out of Difilipo parts supplied by Darren to my sizes, I lucked out and must have gotten it just right as there is no Drone at all and it's easily within legal limits sound wise.

It consists of Difilipo 1.75" long tube headers 2x3" Hi flow Cats, small balance pipe just before the 2x long VE type HotDogs into 2x 3"in/out Offset Mufflers then 2x 3" in 2" dual outlet rear mufflers, I've been spoiled over the years playing with Turbo Cars that are easily quietened down by comparison.

[Angeldust]

my VR SS i used to have droned really bad. Was very annoying as it was in the 1500-2500 rpm range.

Every lsx car i've owned since (VX, VY II and now VZ) has had no drone problems. All had modified exhasuts/pacey's etc. Unfortunately
i've bought them all with modified exhausts already fitted so had no idea what was in it.

Actually, how do i tell what exhaust is on my car at the moment? is there anything to look for that will identify what brand/type all the bits are?

[Mohit]

So looks like I wasn't imagining the extra drone from when I last had the Supercat cat back on my previous LS1 car.
Spoke to the exhaust shop and he said there are 2 versions of the rear muffler, a quiet and a loud.
Most people ask for a loud system so they fit the loud rear muffler.
They are ordering the quiet rear muffler for me and will swap it over.
Let's hope it's as good as I remember from last time.

[wally01]

So looks like I wasn't imagining the extra drone from when I last had the Supercat cat back on my previous LS1 car.
Spoke to the exhaust shop and he said there are 2 versions of the rear muffler, a quiet and a loud.
Most people ask for a loud system so they fit the loud rear muffler.
They are ordering the quiet rear muffler for me and will swap it over.
Let's hope it's as good as I remember from last time.
I have a supercat cat back on my SS no drone at all sometimes makes you wonder if it is a V8 until you get up it not loud really not to me it sounds just nice ,but in saying that my kids hear me leaving home in the morning for work 7.30 am they like how it sounds so all good here ..

[BLACK 346]

I have a supercat cat back on my SS no drone at all sometimes makes you wonder if it is a V8 until you get up it not loud really not to me it sounds just nice ,but in saying that my kids hear me leaving home in the morning for work 7.30 am they like how it sounds so all good here ..

Some people seem to get quality of note mixed up with volume of noise. I like a good loud V8 like anyone, but would not trade loudness for a good quality deep note. How your car sounds outside compared to what you hear in the cabin is also a factor.

[Wonky]

Some people seem to get quality of note mixed up with volume of noise. I like a good loud V8 like anyone, but would not trade loudness for a good quality deep note. How your car sounds outside compared to what you hear in the cabin is also a factor.

Precisely! Plenty of loud exhausts around which sound shit! Raspy and barky. Plenty of volume but absolutely no quality. People stick their fingers down their throat after they've passed.

[bozodos]

I was thinking that was a little bit more to do with the inherent way LS motors sound; that said some of the US made GTO catbacks are the worst exhausts I have ever heard (XForce haters take note!)


The deepest I've heard IRL was another VZ L76 with a custom twin 3", wish I knew what mufflers were used in it.

[BLACK 346]

I was thinking that was a little bit more to do with the inherent way LS motors sound; that said some of the US made GTO catbacks are the worst exhausts I have ever heard (XForce haters take note!)


The deepest I've heard IRL was another VZ L76 with a custom twin 3", wish I knew what mufflers were used in it.

Doesn't the LS motors firing order make it sound unique as well?

[IJ.]

I was thinking that was a little bit more to do with the inherent way LS motors sound; that said some of the US made GTO catbacks are the worst exhausts I have ever heard (XForce haters take note!)


The deepest I've heard IRL was another VZ L76 with a custom twin 3", wish I knew what mufflers were used in it.
Mine is very "deep" rumbles at idle and matches the resonant frequency of the big Shed ;)
(vibrates the tin sheeting)

[Wonky]

Doesn't the LS motors firing order make it sound unique as well?

Yep. Firing order is different to the old 5 litre motors which is why they don't have the same sound.

[Mohit]

I have a supercat cat back on my SS no drone at all sometimes makes you wonder if it is a V8 until you get up it not loud really not to me it sounds just nice ,but in saying that my kids hear me leaving home in the morning for work 7.30 am they like how it sounds so all good here ..
Exactly how the Supercat used to sound like on my VYII SS, which is why I was surprised with the drone on my VYII Calais when another Supercat was fitted to it.
I'm sure once the quieter rear muffler is put on by the shop it should be all good again, like this:


http://www.youtube.com/watch?v=Tzff6qmHMD8

[wally01]

Mine is louder than that now has 35 k on it still sounds good though ,and your SS with that cat back was the reason i bought one it was just what i was looking for ..

[wally01]

Some people seem to get quality of note mixed up with volume of noise. I like a good loud V8 like anyone, but would not trade loudness for a good quality deep note. How your car sounds outside compared to what you hear in the cabin is also a factor.

Alot of people that have heard mine have said it sounds very nice ,quiet at first get into it and it and it stands out ..

[Mohit]

So looks like I wasn't imagining the extra drone from when I last had the Supercat cat back on my previous LS1 car.
Spoke to the exhaust shop and he said there are 2 versions of the rear muffler, a quiet and a loud.
Most people ask for a loud system so they fit the loud rear muffler.
They are ordering the quiet rear muffler for me and will swap it over.
Let's hope it's as good as I remember from last time.
Problem solved.
The exhaust shop put on the quieter (much larger) rear muffler and the drone is now gone.
Part number for the quieter/larger rear Supercat muffler is SCMS 5001.

[VL Executive]

The key to the drone problem on VT - VZ exhaust systems is definantly in the rear muffler/s. I have a VY SS Ute, and went from a stock system to a Manta twin 2.5" with centre mufflers and rear hotdogs, and the drone is bad at highway speeds 100 km/h in 6th gear or around 1500 -200 rpm. Got the full mufflers from Manta and put those on in place of the hotdogs and drone problem gone. Only trade off is it took away abit of the nice deep note and loudness it had with hotdogs.

[QldKev]

The key to the drone problem on VT - VZ exhaust systems is definantly in the rear muffler/s. I have a VY SS Ute, and went from a stock system to a Manta twin 2.5" with centre mufflers and rear hotdogs, and the drone is bad at highway speeds 100 km/h in 6th gear or around 1500 -200 rpm. Got the full mufflers from Manta and put those on in place of the hotdogs and drone problem gone. Only trade off is it took away abit of the nice deep note and loudness it had with hotdogs.


Did you try hotdogs in the center and keep the rear resonators/mufflers?
Hotdogs up front for mufflers won't muffle the sound as much hence will allow a deeper / louder sound
A decent resonator at the back will then help get rid of the resonating frequencies that cause drone.

[macca_779]

Did you try hotdogs in the center and keep the rear resonators/mufflers?
Hotdogs up front for mufflers won't muffle the sound as much hence will allow a deeper / louder sound
A decent resonator at the back will then help get rid of the resonating frequencies that cause drone.

Bingo. My car is pretty loud with that config and doesn't drone

[white lie]

The closer you can get that back muffler to the end of the system, the less drone you're going to have. This is a no brainer and applies to all exhaust systems.

Otherwise the sound is just going to echo and resonate in the metal pipe all the way to the end. If you break the sound waves up right before they hit the end of the pipe then there's no chance of that happening.
So either keep/install a decent resonator at the back of the car or dump the system right behind the middle mufflers

[VL Executive]

Did you try hotdogs in the center and keep the rear resonators/mufflers?
Hotdogs up front for mufflers won't muffle the sound as much hence will allow a deeper / louder sound
A decent resonator at the back will then help get rid of the resonating frequencies that cause drone.


Bingo. My car is pretty loud with that config and doesn't drone

I was originally ment to get the Centre hotdogs and rear mufflers configuration. But Manta buggered up the order and ended up with Centre 'muffs and rear 'dogs. The reverse of what I wanted. :( So as a quick fix, I got the rear muffs / ressies from them. When I want quiet highway running, I change to the muffs and when I want the louder better sound around town short runs I put the hotdogs on. Takes about 10 mins to swap 'em over.

[kewgi]

I'm running a X-force cat back with a rear resonator on my wagon and I can hardly stand the drone. Originally it had a straight through rear section and it was terrible. I had hoped the resonator would have fixed it.

[Wonky]

Sounds like you need a bigger rear muffler kewgi to reduce/eliminate drone. However, it will probably also reduce how loud it is which you probably don't want.

[QldKev]

Change your diff ratio to a shorter ratio to free up the load on the engine, it helps reduce drone, and the extra off line performance is a win win.