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| Exhaust Drone..? https://www.ausmini.com/forums/viewtopic.php?f=23&t=53622 |
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| Author: | Mini Mad [ Tue May 26, 2009 12:18 pm ] |
| Post subject: | Exhaust Drone..? |
What exhaust systems are people with 4EFTE's running? Mine has a noticeable drone at freeway speeds 100km/h+ kind of like a hmm hmm hmm hmm hmm hmm and gets annoying after 20-30min. It's fine around town and even at freeway speeds if you are accelerating it goes away, it's just under slight load with i'm guessing back pressure. My system is just a straight through 2.5in system with a cat. Should i look at putting a silencer in? I dont want to sacrifice huge amounts of power but if there is nothing in it i would rather sort it out. |
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| Author: | Mick [ Tue May 26, 2009 1:11 pm ] |
| Post subject: | |
There's nothing specific about the drone peculiar to the car and engine you have...so I might throw something in. It's often a harmonic that is set up in the silencer or the body panels around it. You might try dampening it by putting in sound deadening into the floor space above or below the panel. Sticking it on will dampen the noise and reduce the vibration, just having it there will only dampen the noise a little. |
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| Author: | Gordo [ Tue May 26, 2009 1:19 pm ] |
| Post subject: | |
As said the drone may be harmonic... Try and get rid of it. Harmonics can make even the strongest things crack at the right frequencies... |
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| Author: | Mearcat [ Tue May 26, 2009 3:45 pm ] |
| Post subject: | |
I had this issue in my old car (not a Mini btw) and was fixed by adding a Hotdog (resonator) in between the cat & muffler and the drone dropped right away. The drone was still audible but the headaches I'd get cruising down the freeway were gone 
Ironically, my last Mini only had a single Hotdog in the entire exhaust - no actual muffler was ever installed. |
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| Author: | Archangel007 [ Tue May 26, 2009 7:29 pm ] |
| Post subject: | |
Josh, Definitely sounds like harmonic resonance to me. Try interrupting the flow, or make the pipework either shorter ot longer. Some 4x4's have a rubber damper welded onto the piepwork to cancel this out, that may help as well. Cheers, Tricky |
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| Author: | 92 [ Tue May 26, 2009 8:24 pm ] |
| Post subject: | |
I have a slight drone with mine aswell but not enough to cause any trouble. I have a hotdog then a straight through muffer and my system is only 2 1/4" |
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| Author: | 74snail [ Tue May 26, 2009 10:06 pm ] |
| Post subject: | |
Also where exactly does your tip finish, if its well under your beaver panel it can set up a harmonic vibration through the boot space, if its just past the lip of the beaver panel the harmonics have a much better chance of dissipating sideways, also check your exhaust mounts , if their hard mounted to the body it might be worth seeing if you can fit one or two rubber washers. |
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| Author: | '77 clubby van [ Thu May 28, 2009 6:35 pm ] |
| Post subject: | |
Just turn up the tunes man!!! 
Nah seriously, I've got 2.5" - High flow cat - almost straight through (with a bend) muffler and side exit tail pipe and mines pretty quiet really. I do have an extra foot of exhaust length though! I drove From Kal to Perth and back and didn't really notice any droning and I have hardly any sound proofing in the van. 
As said above: Try changing the resonance frequency of the exhaust or surrounding body work. Probably the easiest way would be to try a different muffler. Can be straight through still, but maybe longer or shorter, or use one a straight through muffler with an internal kink. Lukey make some real good ones. 
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