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New Exhaust Droning Bad

Thomas_D

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G'day folks
Car is a VF2.
Have just fitted a full Hurricane system, 1" 3/4 primaries, high flow cats(100cells), 3 inch midpipes,high flow mufflers. Have retained the bi-modal function.
The sound(note) is absolutely phenomenal, however the drone is fierce between 1500 and 2200 rpm or if engine is under some load. It's seriously tinnitus-inducing.
Do these things settle down after a week or so?
What is the biggest contributing factor to drone? Midpipe or mufflers? Using the bi-modal in quiet mode reduces some noise which I appreciate will keep the neighbours happy but the drone is almost as bad. I will contact Hurricane directly and hopefully they can suggest a fix.
Cheers
 

Skylarking

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... Do these things settle down after a week or so?...
Playing a bugle for months won’t change the sounds that come from such a brass wind instrument, notwithstanding the players skill.

Likewise driving for months won’t change the sound that comes from an exhaust... Such is a function of the design of the exhaust and based on tube harmonics ;)

Some imply that a build up of carbon within the exhaust reduces the tinny sound but the notes and drones produced are a function of the harmonics and won’t change with time o_O

You’d have to fiddle with the exhaust harmonics to reduce drone and that implies changes in the pipework :oops:

Well that’s how I understand it anyway :rolleyes:
 

Thomas_D

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Playing a bugle for months won’t change the sounds that come from such a brass wind instrument, notwithstanding the players skill.

Likewise driving for months won’t change the sound that comes from an exhaust... Such is a function of the design of the exhaust and based on tube harmonics ;)

Some imply that a build up of carbon within the exhaust reduces the tinny sound but the notes and drones produced are a function of the harmonics and won’t change with time o_O

You’d have to fiddle with the exhaust harmonics to reduce drone and that implies changes in the pipework :oops:

Well that’s how I understand it anyway :rolleyes:
I heard somewhere mentioned 'Helmholtz' pipes?
 

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I feel my exhaust has changed note considerably since I had it put on. It seems to have mellowed a ton and the droning that I had initially seems to be gone.
Mind you, I have had my car cammed since but its not like the same exhaust sound, with revs and torque. I have pretty ordinary hearing at my age too...who knows but I think it sounds better than it did when new.
 

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I feel my exhaust has changed note considerably since I had it put on. It seems to have mellowed a ton and the droning that I had initially seems to be gone.
Mind you, I have had my car cammed since but its not like the same exhaust sound, with revs and torque. I have pretty ordinary hearing at my age too...who knows but I think it sounds better than it did when new.
There’s no logical reason for an exhaust to change sound without something changing within the pipework or the engine.... if there is I’d love to hear the theories :cool:

But if you’ve noticed a big mellowing change, may be time for a hearing test :p
 

[paradox]

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they do carbon up.. but they dont change too much
 

Not_An_Abba_Fan

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Exhaust note will change due to a few factors, number one being carbon. As the exhaust carbons up it will sound different inside the car. Another is the glass packing inside the mufflers loosens up a bit, also changing the note.

The main thing that contributes to drone is the mismatching of components. Most companies slap a system together based on theory without actual physical real world testing. A few companies will frequency match their mufflers and resonators and also add frequency enhancing/cancelling components like Hemholtz chambers, H pipes and in the case of Manta, they have a different internal in their left and right sides of their front mufflers on the VE/VF systems. There is a lot that goes into a nice sounding exhaust, and while Hurricane do build a nice system (I prefer their extractors and had sold them for 10 years) it doesn't sound very good in my opinion.

If you have the system with the 4 hotdogs in the front, a H pipe fitted in between the two sets of hotdogs may help. I have even added 2 H pipes into a system before and it almost eliminated the drone.

Playing a bugle for months won’t change the sounds that come from such a brass wind instrument, notwithstanding the players skill.

Likewise driving for months won’t change the sound that comes from an exhaust... Such is a function of the design of the exhaust and based on tube harmonics ;)

Some imply that a build up of carbon within the exhaust reduces the tinny sound but the notes and drones produced are a function of the harmonics and won’t change with time o_O

You’d have to fiddle with the exhaust harmonics to reduce drone and that implies changes in the pipework :oops:

Well that’s how I understand it anyway :rolleyes:
If you could somehow paint the inside of that bugle with a 1mm thick layer of carbon it will absolutely change the tone of it.
 

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J-Pipes
 

Thomas_D

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Exhaust note will change due to a few factors, number one being carbon. As the exhaust carbons up it will sound different inside the car. Another is the glass packing inside the mufflers loosens up a bit, also changing the note.

The main thing that contributes to drone is the mismatching of components. Most companies slap a system together based on theory without actual physical real world testing. A few companies will frequency match their mufflers and resonators and also add frequency enhancing/cancelling components like Hemholtz chambers, H pipes and in the case of Manta, they have a different internal in their left and right sides of their front mufflers on the VE/VF systems. There is a lot that goes into a nice sounding exhaust, and while Hurricane do build a nice system (I prefer their extractors and had sold them for 10 years) it doesn't sound very good in my opinion.

If you have the system with the 4 hotdogs in the front, a H pipe fitted in between the two sets of hotdogs may help. I have even added 2 H pipes into a system before and it almost eliminated the drone.



If you could somehow paint the inside of that bugle with a 1mm thick layer of carbon it will absolutely change the tone of it.
Great info, thank you
I'll post back once they've modified it.
 
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Thomas_D

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PS. All else being the same, does the 3inch drone more than the 2.5inch, or is it just louder regardless of drone levels?
 

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When I bought my VE it had a 3" system with the centre muffler removed. My hearing is not that flash but it droned too much for me. I swapped it over for a 2 1/2" system off a GTS, problem solved.
 

Thomas_D

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When I bought my VE it had a 3" system with the centre muffler removed. My hearing is not that flash but it droned too much for me. I swapped it over for a 2 1/2" system off a GTS, problem solved.
Good result!

As NAAF says, I'm sure I could eliminate a fair bit of drone even with my 3inch system providing the parts match up well.
 

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Exhaust note will change due to a few factors, number one being carbon. As the exhaust carbons up it will sound different inside the car. Another is the glass packing inside the mufflers loosens up a bit, also changing the note.
I can see how carbon buildup could act as an insulator of sorts and simply dampen pipe wall vibration, the tinniness sound of the exhaust. But droning is a harmonics issue dependant (I’d think) on gas flow issues and pipework volumes. As such it would requires plumbing changes (as you stated) for any appreciable change in characteristics. However, where droning is caused by something that is close to the limit of not droning, then the small change in pipe area caused by carbon buildup may help though that doesn’t sound like a solution for droning in the majority of cases.

As for glass mat packing, the last time I opened up a car muffler was years ago and there was no packing, just metalwork acting as baffles between chambers and pipework with holes or cutouts in them. May be things have changed o_O

As is, my experience has been the exhaust sound doesn’t appreciably change from new but I’ll defer to what sounds like your years of experience in exhaust work :cool:
If you could somehow paint the inside of that bugle with a 1mm thick layer of carbon it will absolutely change the tone of it.
Not so sure about that as bugles vary in size and they all sound similar... but the analogy was to highlight how plumbing plays a big part in sound....

Hope @Thomas_D solves his issue and let’s us know how it was resolved in the end :)
 

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The way I see it is it could be like people that design opera houses etc. They use sound absorption panels to absorb acoustic sources from the walls. Could it be that the mufflers provide a natural byproduct (like the carbon) to change the note of the exhaust. Rather than bouncing around new shiney mufflers...they carbon up and absorb and regulate the acoustics?
Cant really speak for other people but I feel mine is different (from new) and one of the joys I get out of the car is listening to it. I'm channel LS1 rather than MMM !!!
I've been updating my diary post with the same run up the same part of the street from when I got it stock...I've been meaning to update the post lately as I haven't updated it for a while (had a top end rebuild and have sensitive neighbours). Might be interesting to compare the posts for exhaust noise. Getting the transmission rebuilt atm so hopefully towards the end of the week.

But your probably right Skylarking, Its probably an internal issue between the ears and brain. Wouldn't be the first time my missus has accused me of it lol
 

Thomas_D

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Quote : Chuckmeister......and one of the joys I get out of the car is listening to it. I'm channel LS1 rather than MMM !!!
Indeed, when I had my VY with Pacemaker system the driving pleasure never got old, even until the final day of ownership. It sounded superb and droned minimally (to my ears).
I'm hoping to replicate the same driving please with this one as it sounds even better.
Hopefully once it's modified it will retain the awesome sound/note, but with acceptable drone(to my ears).
There is a scientific explanation as to why the V8 engine sounds so good to the human ear... I'll see if I can find the link
 

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... Its probably an internal issue between the ears and brain. Wouldn't be the first time my missus has accused me of it lol
You made me LOL :cool:
... There is a scientific explanation as to why the V8 engine sounds so good to the human ear... I'll see if I can find the link
Here is one simple explanation :cool:

I do suspect that part of the allure of the sound of a V8 is the familiarity created via the millions spent on advertising to spruik motor racing. That coupled with people’s desire to mimic their racing hero’s makes for a strong desire to create a distinctive noise. Not surprisingly, that was one of the complaints of F1 during their quiet car period of a few years ago, the race cars weren’t noisy enough for fans...

Me, personally, I’d rather a car made no noise at all so if i decided to open it up a little, there would not be a huge sound to attract attention from the constabulary ;)
 

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Without multi quoting and filling my reply with endless words...

I stated that carbon build up alters the note, not drone. Droning is a manufacturing issue, if a system drones on a car it's either not a quality system or it's not the right one for the car IE twin 3" with no resonators on a V6.

The characteristics of the exhaust will affect drone rather than size. People can also confuse drone for noise, if a system is too loud it can be incorrectly labelled as droning when it's actually not, it's just loud. A 3" will be louder than 2 1/2" of the same design. Droning is caused by the existence of certain frequencies that the ear doesn't like, these are built in to the system because a) the builder has no idea, b) the builder is working to a budget or c) the wrong components are put together (see a).

It depends on manufacturer regarding glass packing. Some mufflers don't have it and rely on internal baffles and tubing to reduce noise, I was referring to sports/performance systems, most, if not all, have glass packing to absorb frequencies that harm baby dolphins so that they can retain flow and reduce noise without being restrictive. Some are successful, some not so much.

Regarding the bugle, if you were to have the same person play the same series of notes on the same bugle clean and then with a layer of carbon internally then absolutely it will sound different. That was my point. It alters the tone, not the drone.

If you have ever heard a flat plane V8 or a set of cross over headers then you will know why the V8 sounds like it does. It's the difference between say a HQ 308 and an F1 race car. Cross plane V8's fire 2 cylinders on the same bank in each full cycle (LRLLRLRR) where flat planes fire alternatively (LRLRLRLR).
 

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Yes, and hence why there's no doubt mine is loud at 2500rpm and above it doesn't drone at those rpms.

I suspect the shop (Hurricane) will swap the 3inch with a 2.5 in order to reduce the volume(but as NAAF explained does not address the real issue)
I hope they put some thought into it, I've spoken to the owner and he seemed very genuine about finding a solution for me.

NAAF, if I was a more informed/educated customer, could I make a suggestion to them? Surely there is a fix for this whilst retaining the current brand?
 
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Not_An_Abba_Fan

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If you have the system with the 4 hotdogs in the front, a H pipe fitted in between the two sets of hotdogs may help. I have even added 2 H pipes into a system before and it almost eliminated the drone.
 
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