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VE Drone

Drizt

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I believe technically yours is not a helmholtz resonantor but a capped quarter-wave resonator. A beer bottle would be an example of a helmholtz resonator.

Quarter-wave resonators are simple to work out but have a narrow bandwidth. It is simply a matter of making a tube of the correct length to match the frequency you want to cancel out.
Helmholtz resonators are more complex but have a wider bandwidth. See here for the forumula -> Helmholtz resonance - Wikipedia, the free encyclopedia
 

PIR4TE

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Haha! Well the two formulae are remarkable fit for the purpose as in their description, the detailed one in the link incorporates ideal gas law including factors such as pressure, volume and temperature which realistically are a given with the basic calculation as a rule of thumb / STP. No need to complicate a toothpick, proven when the basic, simplified calc achieves the purpose of the experiment.
Yes I realise the speed of sound is relative to EGT, a differential of up to 700 feet/sec (which throws things quite a bit), and to be quite exact you need to factor the perceived frequency of sound by the human ear at various pressure / atmospheric conditions above sea level. But having taken into account most variables using a program called PipeMax to calculate exhaust pulse wavelengths within 1/1000th of an inch, breaking the exhaust sound wave into quarter lengths is the most practical to interrupt the phase for this under car application.
But the term quarter wave resonator is not commonly used to describe a car exhaust, the pipes I have are accurately described incorporating the primary principle underpinning its fabrication - Helmholtz pipes.
 

PIR4TE

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An alternative means to cancel the Drone was to use an Xforce VK05 programmable control unit to modulate input to a DSP then amplify that to a 50 watt tactile transducer, strapped to the muffler cans. There are pros and cons to this approach, namely the compact ability to accurately cater for a range of harmonic cancellation (including AFM drone @ 58hz) through reverse phase interruption without a cacophony of plumbed devices affecting performance... and the potential to build on that to generate a synthetic exhaust note similar to that which Lotus has patented.
Ultimately I decided that a length of bent stainless pipe is more reliable, simple, and a little cheaper.
 
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AD07

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F@@@@@@@@rk me.................enough with the drone/synthetic exhaust note /modulate input / pressure, volume and temperature/ reverse phase interruption stuff !!!!!!!!!!!!!
We've ALL had it .......:banstick:
 

Drizt

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Hi anyone who is interested (possibly only Pir4te)....

Here is a sound file I took from my phone. DISCLAIMER: If you play the sound file back loud it will obviously sounds worse than it does in real life.


This is as bad as the drone ever gets... and it has to be in the right conditions e.g. Up a hill, with slight acceleration around 100km/h. 99.9% of the time the car is drone free. So don't think it is like this all the time.

From all the sound files I have taken the drone seems to centre somewhere between 111hz and 130hz depending on speed and engine load. The spike is very high Q (narrow) in all circumstances.

carDrone.jpg
- edit : not sure why the JPG is not showing inline?
JPG spectrum plot : https://www.dropbox.com/s/ofibq5cg1qo40ct/carDrone.jpg

The spike is around 22dB at 125Hz. Again, this is as bad as it gets and it is very rare.


[video]https://www.dropbox.com/s/y2yknfq0s6ne489/Recording005.flac[/video]

I have uploaded the sound file as well.... Tried to post it as a video even though it is FLAC.

https://www.dropbox.com/s/y2yknfq0s6ne489/Recording005.flac
 

PIR4TE

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That massive precipice pinnacle of a spike looks worse than it is then, Haha!
If that's only for a second or two during rev pitch transition or under load that sound is fine, not even spooky in the slightest. I think it would get to be a bother after a constant few days on the open road.
Here's mine in cabin just after the fix:
[video=youtube_share;OuDtjAuZJfM]http://youtu.be/OuDtjAuZJfM[/video]
 
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hanson1128

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Yes, we do a dual 3" system in stainless steel which doesn't drone.
It is $1500 + $140 for freight, or if you are down this way, we would fit it for free for you.
The worst combination for drone is an auto wagon with AFM, which is the vehicle I bought for testing, and it is drone free.
My system isn't overly loud, and if an EPA noise test was done, my cars exhaust is under the 90db legal limit at the 4000rpm rev limit in neutral.
Obviously your cam will make it louder. Your vehicle is a sedan, that drones less, and it is auto but without AFM so it drones even less. I could guarantee no drone, except for the cam, as I don't know whether this increases or reduces drone. All my testing has been done on standard engines.

Many brands claim to be drone free until they have your money.
Even the remote controlled one drones unless it is on quiet - which is dead quiet. Ring them again and say you have an auto wagon with AFM and you want dual 3" straight through with no drone and see what they say. This will show you how drone free they are without mentioning the cam, and will show that ours are more drone free than the others.
All of the "Mass Produced" systems compete against each other, so they are basically the same, and one will not give you $20 more quality than the other, otherwise they lose sales. Our specialty is drone free.
The remote system is good because you can change it from loud to medium to dead quiet, but on the freeway it drones badly, so we have a modification we can do to fix the drone on them.
The dual 3" stainless remote controlled system is $1800 + $140 freight, plus $350 to make it drone free so you can drive on at least medium with no drone and possibly on loud with no drone.
We don't show photos of our complete exhaust systems, otherwise everyone just copies our secrets and ideas.

This is what Sureflo replied me, has anyone knows their system?
 

PIR4TE

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This is what Sureflo replied me, has anyone knows their system?

Mate I like this guy's no BS approach and it appears knows his stuff too, as I mentioned he fits those confounded helmholtz pipes as well!
Sureflo also has a patent on the X-pipe as I understand it, and the videos posted while a bit subtle sound OK (I've no doubt they'd pass the noise tests), next time around I will be speaking to him and NAAF.
Get him to install though, here's what that DIY guy on another forum I mentioned earlier had to say:
(See page 5, 'magnum9')
http://www.clubve.com/forum/viewtopic.php?t=678#p8337
What headers do you have?
What cam?
Current dyno results?
 

Not_An_Abba_Fan

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The patented merge that SureFlow use is more of a "pressure wave termination box" than an X pipe. What it effectively does is dissipate the exhaust waves as they enter from the headers/engine pipes and combine the whole lot before pushing it through the rest of the system. This eliminates the droning as that frequency no longer exists.

The system itself will work very well for top end, but I haven't seen a torque curve from one of their systems compared to others, so I can't really comment on how they perform. I haven't heard anything bad about them though.
 

Not_An_Abba_Fan

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I click on the link and:

You have been permanently banned from this board.

Please contact the Board Administrator for more information.

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May I ask why? lol
 
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