Exhaust drone
#1
03-16-2022, 05:08 AM
Exhaust drone
Are there any engineers in the forum who can apply their experience and expertise to the issue?
I’ve just fitted a Milltek exhaust to my V8 defender as detailed in the other thread and the one issue I’d like to resolve is the drone between 1,000 and 1,500 rpm.
i have spoken to Milltek and they acknowledge the issue on both the non res and res version but don’t seem too keen or able to resolve it.
there is always a solution to everything and from my initial reading the issue is to do with densities and weights etc of the exhaust and engine block.
my initial guess is that the lighter and stainless steel exhaust resonates because it is different in that way and from what I’ve read the solution others have found is to add weight to the exhaust to change density and balance out effectively the droning noise.
Can anyone help here?
I’ve just fitted a Milltek exhaust to my V8 defender as detailed in the other thread and the one issue I’d like to resolve is the drone between 1,000 and 1,500 rpm.
i have spoken to Milltek and they acknowledge the issue on both the non res and res version but don’t seem too keen or able to resolve it.
there is always a solution to everything and from my initial reading the issue is to do with densities and weights etc of the exhaust and engine block.
my initial guess is that the lighter and stainless steel exhaust resonates because it is different in that way and from what I’ve read the solution others have found is to add weight to the exhaust to change density and balance out effectively the droning noise.
Can anyone help here?
#2
03-16-2022, 05:58 AM
Pro Wrench
Yes, there is, as evidenced by the fact that never in the history of cars has there been a factory offering with drone. 
The difference is, they keep throwing engineering hours and material at it until they get the sound they want without any drone. The budget is enormous.
Aftermarket exhaust companies? Not so much. Low budget operations by contrast. So they might get the sound you want and it might not drone. Or they might get the sound you want with minor drone. Or they might not get the sound you want and still get the drone.
Unfortunately, the solution might involve a completely different system, or it might be simple. But seems to me that if it was simple, if an engineer on this forum who’s never worked on the Milltec could solve the problem, surely the Milltec engineer(s) could have done so when they heard drone, no?
I spent a lot of money and wasted a lot of time trying to solve this on a 911 Turbo years ago. The factory sound was waaaay quiet, almost whispery. Even at WOT. So unsatisfying, despite brutal performance. This wasn’t my DD so I had no occasion to need it that quiet. So I took it to a Porsche exhaust specialist. They had it for a long time. Fitted two different systems, fiddled with both. Both woke up the exhaust beautifully… with the addition of an ear-splitting drone from 3000-3700 rpm. Just excruciating.
In the end I was glad we hadn’t thrown away the OEM system and I put it back on.
Yet when I bought a later model, after Porsche had decided “always quiet” wasn’t a virtue to most of their customers and offered a controllable valved exhaust, it sounded ferocious in Sport mode, docile in non-Sport mode, and never, not for one second, did it drone.
Same with normally aspirated Porsche GT3s and 4s — pretty loud in Sport mode (moreso than a Turbo), yet not an iota of drone. I even have aftermarket headers on my current one (with stock exhaust) and no drone. And I have friends with full aftermarket exhaust and theirs don’t drone. So it can be done. But if an aftermarket system starts out with drone when you get it, I’ve never found anyone who was able to eliminate it. They can make it louder and quieter by adding or subtracting resonators but the drone is always there, in the same range.
That’s my experience over the years; your mileage may vary, of course, and I hope it does. Please keep us up to date as you try and solve this. But don’t throw the stock system away!
Cheers!
The difference is, they keep throwing engineering hours and material at it until they get the sound they want without any drone. The budget is enormous.
Aftermarket exhaust companies? Not so much. Low budget operations by contrast. So they might get the sound you want and it might not drone. Or they might get the sound you want with minor drone. Or they might not get the sound you want and still get the drone.
Unfortunately, the solution might involve a completely different system, or it might be simple. But seems to me that if it was simple, if an engineer on this forum who’s never worked on the Milltec could solve the problem, surely the Milltec engineer(s) could have done so when they heard drone, no?
I spent a lot of money and wasted a lot of time trying to solve this on a 911 Turbo years ago. The factory sound was waaaay quiet, almost whispery. Even at WOT. So unsatisfying, despite brutal performance. This wasn’t my DD so I had no occasion to need it that quiet. So I took it to a Porsche exhaust specialist. They had it for a long time. Fitted two different systems, fiddled with both. Both woke up the exhaust beautifully… with the addition of an ear-splitting drone from 3000-3700 rpm. Just excruciating.
In the end I was glad we hadn’t thrown away the OEM system and I put it back on.
Yet when I bought a later model, after Porsche had decided “always quiet” wasn’t a virtue to most of their customers and offered a controllable valved exhaust, it sounded ferocious in Sport mode, docile in non-Sport mode, and never, not for one second, did it drone.
Same with normally aspirated Porsche GT3s and 4s — pretty loud in Sport mode (moreso than a Turbo), yet not an iota of drone. I even have aftermarket headers on my current one (with stock exhaust) and no drone. And I have friends with full aftermarket exhaust and theirs don’t drone. So it can be done. But if an aftermarket system starts out with drone when you get it, I’ve never found anyone who was able to eliminate it. They can make it louder and quieter by adding or subtracting resonators but the drone is always there, in the same range.
That’s my experience over the years; your mileage may vary, of course, and I hope it does. Please keep us up to date as you try and solve this. But don’t throw the stock system away!
Cheers!
The following 2 users liked this post by NoGaBiker:
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#3
03-16-2022, 06:16 AM
Recovery Vehicle
Over the years so many LR3 and LR4 owners tried the Milltek exhaust system because they thought the V8 was just too quiet. Then they couldn't live with the low rpm drone on the highway and put the OEM exhaust back on. Sorry to hear you are dealing with the same issue. But as NoGaBiker noted, save your OEM exhaust for when you get tired of the drone.
#4
03-16-2022, 06:43 AM
Yes, there is, as evidenced by the fact that never in the history of cars has there been a factory offering with drone.
The difference is, they keep throwing engineering hours and material at it until they get the sound they want without any drone. The budget is enormous.
Aftermarket exhaust companies? Not so much. Low budget operations by contrast. So they might get the sound you want and it might not drone. Or they might get the sound you want with minor drone. Or they might not get the sound you want and still get the drone.
Unfortunately, the solution might involve a completely different system, or it might be simple. But seems to me that if it was simple, if an engineer on this forum who’s never worked on the Milltec could solve the problem, surely the Milltec engineer(s) could have done so when they heard drone, no?
I spent a lot of money and wasted a lot of time trying to solve this on a 911 Turbo years ago. The factory sound was waaaay quiet, almost whispery. Even at WOT. So unsatisfying, despite brutal performance. This wasn’t my DD so I had no occasion to need it that quiet. So I took it to a Porsche exhaust specialist. They had it for a long time. Fitted two different systems, fiddled with both. Both woke up the exhaust beautifully… with the addition of an ear-splitting drone from 3000-3700 rpm. Just excruciating.
In the end I was glad we hadn’t thrown away the OEM system and I put it back on.
Yet when I bought a later model, after Porsche had decided “always quiet” wasn’t a virtue to most of their customers and offered a controllable valved exhaust, it sounded ferocious in Sport mode, docile in non-Sport mode, and never, not for one second, did it drone.
Same with normally aspirated Porsche GT3s and 4s — pretty loud in Sport mode (moreso than a Turbo), yet not an iota of drone. I even have aftermarket headers on my current one (with stock exhaust) and no drone. And I have friends with full aftermarket exhaust and theirs don’t drone. So it can be done. But if an aftermarket system starts out with drone when you get it, I’ve never found anyone who was able to eliminate it. They can make it louder and quieter by adding or subtracting resonators but the drone is always there, in the same range.
That’s my experience over the years; your mileage may vary, of course, and I hope it does. Please keep us up to date as you try and solve this. But don’t throw the stock system away!
Cheers!
The difference is, they keep throwing engineering hours and material at it until they get the sound they want without any drone. The budget is enormous.
Aftermarket exhaust companies? Not so much. Low budget operations by contrast. So they might get the sound you want and it might not drone. Or they might get the sound you want with minor drone. Or they might not get the sound you want and still get the drone.
Unfortunately, the solution might involve a completely different system, or it might be simple. But seems to me that if it was simple, if an engineer on this forum who’s never worked on the Milltec could solve the problem, surely the Milltec engineer(s) could have done so when they heard drone, no?
I spent a lot of money and wasted a lot of time trying to solve this on a 911 Turbo years ago. The factory sound was waaaay quiet, almost whispery. Even at WOT. So unsatisfying, despite brutal performance. This wasn’t my DD so I had no occasion to need it that quiet. So I took it to a Porsche exhaust specialist. They had it for a long time. Fitted two different systems, fiddled with both. Both woke up the exhaust beautifully… with the addition of an ear-splitting drone from 3000-3700 rpm. Just excruciating.
In the end I was glad we hadn’t thrown away the OEM system and I put it back on.
Yet when I bought a later model, after Porsche had decided “always quiet” wasn’t a virtue to most of their customers and offered a controllable valved exhaust, it sounded ferocious in Sport mode, docile in non-Sport mode, and never, not for one second, did it drone.
Same with normally aspirated Porsche GT3s and 4s — pretty loud in Sport mode (moreso than a Turbo), yet not an iota of drone. I even have aftermarket headers on my current one (with stock exhaust) and no drone. And I have friends with full aftermarket exhaust and theirs don’t drone. So it can be done. But if an aftermarket system starts out with drone when you get it, I’ve never found anyone who was able to eliminate it. They can make it louder and quieter by adding or subtracting resonators but the drone is always there, in the same range.
That’s my experience over the years; your mileage may vary, of course, and I hope it does. Please keep us up to date as you try and solve this. But don’t throw the stock system away!
Cheers!
however, I think it’s also a little down to laziness on the part of players like Milltek and also a missed opportunity. I told them today in a direct way that they would hugely benefit from developing a drone free or less drone system. I realise it’s different for every engine so a biggish task but worth it for them.
i also think that if an engineer can explain the exact cause it should be solveable with some trial and error of attaching weights etc and adding some further mount insulations etc.
for sure I’ll look for the solutions one way or another so I can have my non res exhaust drone free.
I won’t keep the stock exhaust however as the difference in power and response is hugely improved without it.
#5
03-16-2022, 09:50 AM
Are there any engineers in the forum who can apply their experience and expertise to the issue?
I’ve just fitted a Milltek exhaust to my V8 defender as detailed in the other thread and the one issue I’d like to resolve is the drone between 1,000 and 1,500 rpm.
i have spoken to Milltek and they acknowledge the issue on both the non res and res version but don’t seem too keen or able to resolve it.
there is always a solution to everything and from my initial reading the issue is to do with densities and weights etc of the exhaust and engine block.
my initial guess is that the lighter and stainless steel exhaust resonates because it is different in that way and from what I’ve read the solution others have found is to add weight to the exhaust to change density and balance out effectively the droning noise.
Can anyone help here?
I’ve just fitted a Milltek exhaust to my V8 defender as detailed in the other thread and the one issue I’d like to resolve is the drone between 1,000 and 1,500 rpm.
i have spoken to Milltek and they acknowledge the issue on both the non res and res version but don’t seem too keen or able to resolve it.
there is always a solution to everything and from my initial reading the issue is to do with densities and weights etc of the exhaust and engine block.
my initial guess is that the lighter and stainless steel exhaust resonates because it is different in that way and from what I’ve read the solution others have found is to add weight to the exhaust to change density and balance out effectively the droning noise.
Can anyone help here?
#6
03-16-2022, 01:59 PM
i am surprised that you have so much drone compared to mine. The exhaust layout is a little different with opf filters but i would imagine that would reduce noise and drone
are you getting the drone at highway cruising speeds? of course that’s the worst drone you can have.
i get something very similar but just at very slow speeds and low gears and it goes away very quickly. I can’t stand drone and i would try to figure out a solution but it’s not even what i would consider drone. my wife would be the first to nag me about it and she hasn’t mentioned anything
mot sure how much you want to get into modifying the system but a different resonator could help the problem.
i added a vibrant ultra quiet resonator on my milltek p400 defender system. take in mind it had no resonator but after adding it removed all drone.
that might be a consideration. but a larger resonator means a more overall quiet exhaust
QUOTE=TheEscapist;818061]I agree.
however, I think it’s also a little down to laziness on the part of players like Milltek and also a missed opportunity. I told them today in a direct way that they would hugely benefit from developing a drone free or less drone system. I realise it’s different for every engine so a biggish task but worth it for them.
i also think that if an engineer can explain the exact cause it should be solveable with some trial and error of attaching weights etc and adding some further mount insulations etc.
for sure I’ll look for the solutions one way or another so I can have my non res exhaust drone free.
I won’t keep the stock exhaust however as the difference in power and response is hugely improved without it.[/QUOTE]
are you getting the drone at highway cruising speeds? of course that’s the worst drone you can have.
i get something very similar but just at very slow speeds and low gears and it goes away very quickly. I can’t stand drone and i would try to figure out a solution but it’s not even what i would consider drone. my wife would be the first to nag me about it and she hasn’t mentioned anything
mot sure how much you want to get into modifying the system but a different resonator could help the problem.
i added a vibrant ultra quiet resonator on my milltek p400 defender system. take in mind it had no resonator but after adding it removed all drone.
that might be a consideration. but a larger resonator means a more overall quiet exhaust
QUOTE=TheEscapist;818061]I agree.
however, I think it’s also a little down to laziness on the part of players like Milltek and also a missed opportunity. I told them today in a direct way that they would hugely benefit from developing a drone free or less drone system. I realise it’s different for every engine so a biggish task but worth it for them.
i also think that if an engineer can explain the exact cause it should be solveable with some trial and error of attaching weights etc and adding some further mount insulations etc.
for sure I’ll look for the solutions one way or another so I can have my non res exhaust drone free.
I won’t keep the stock exhaust however as the difference in power and response is hugely improved without it.[/QUOTE]
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