Exhaust/Cabin Drone Problems

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Exactmax

Active member
After having my quad system fitted at the weekend I no experience alot of cabin drone when cruising on the motorway around the 70mph mark. Is there something that can be done to distribute the resonance?

I have read that some people have added weights to the pipes to help distribute the sound? I did notice that when you open the window then the cabin drone almost disappears.... I ran the garage where I had the exhaust done and they said that could fit a silencer to one of the pipes (this might help). Will it make a big difference if only one silencer is fitted to the left side of the pipes and not the right?

Max
 
What you've done is what happens when you take a system set up for a particular car and just have a garage bolt on a random pair of back boxes. You can add bigger back boxes, put the resonator back into the system, add crossover pipes, etc, but it's largely trial and error.

I don't believe adding to one side of the system is sensible as it will off balance the flow from cylinders 1-3 Vs 4-6 unless you have some sort of crossover before the added box.

One thing to check before oyu start is that the mounts are correct and nothing is touching the body and there is free movement of the system on all the hangers.
 
When the garage mentioned adding a silencer to just one side it made me worry that it would have an adverse effect!!! Do all of the mounting brackets of the exhaust need to be mounted on rubber dampers?

I've since read that people have added sound proofing to the boot to help reduce the noise, add weights to the exhaust pipes or just adding a resonator back into the system.

It was strange that the noise disappeared when I opened the windows though.... :(
 
The noise was most likely simply 'lost' due to the massive increase in noise with the window open.

All the mounting brackets need to be on flexibles else any vibration is transmitted direct into the bodywork.

Of course if you add soundproofing you simply mask it, but fix the problem not hide it

Weights may alter the noise by changing the frequency at which the system vibrates.

Frankly take it back and ask them to fix it....
 
I'll check tomorrow about the mounting problems. Any idea if adding metal weights might help distribute the vibrations?
 
As cj suggests check for any fouling on the underneath and make sure there are rubber mountings on all fixings and thay are very sturdy ones ,sound deadening will help but as stated will only mask the drown i would suggest the garage should fit two small silencers, 4" or 5" by 12" round ones .
 
This is what happens when you mess with a perfectly good car for no other reason that to make it "look better".
 
Well the drone was a bit better this morning for some reason - I will check the exhaust for all the rubber dampers and maybe buy some metal weights to help disperse the vibrations from the exhaust. Just clamping a U-Clamp to the pipe with some weight might help...
 
Exactmax said:
Well the drone was a bit better this morning for some reason - I will check the exhaust for all the rubber dampers and maybe buy some metal weights to help disperse the vibrations from the exhaust. Just clamping a U-Clamp to the pipe with some weight might help...
Click to expand...

You're probably just getting used to it, unless some bracket/bush has settled and stopped touching the body

As for weights I really think you are just messing around and not addressing the base issues
 
After reading Some more into the droning issue, I read that possible adding more supports to the exhaust might help reduce the droning. Also some mentioned that if the brackets are over tightened then this can cause vibrations to run through the car?

Anyone experienced this?
 
Adding an extra support will change the frequency at which the system resonates and may alleviate the issue.

Overtight clamps or too rigid a rubber transmits vibration direct to the body.
My system is on very soft mounts for this reason.

To your earlier point about weights the z4 auto has a single weight as some sort of vibration suppressor, so it might help if you can get the exact right area.
 
You can see here the stock weight that is added to the car - I think it might need something similar on each tail pipe to make a good start on distributing the vibrations:-

IMG_1234-Copy2.jpg


Any ideas where I can get something similar?
 
This is what I'm needing to place on each exhaust to see if it makes a difference - any idea where I can get one from? I've tried Google and its a pretty rare thing to find :(

ExhaustMassDamper2-Small.jpg


???
 
Exactmax said:
This is what I'm needing to place on each exhaust to see if it makes a difference - any idea where I can get one from? I've tried Google and its a pretty rare thing to find :(

ExhaustMassDamper2-Small.jpg


???
Click to expand...

If it's rare to find it tells me it's not a good solution to the problem.
Drop into a custom exhaust shop and ask them if they keep them, or what solution they would propose.
mjperformance.com of Walsall would be a good start point - they did the tube work on mine and know what they are talking about
 
In terms of cabin drone noises am I right in thinking that if you can hear the alternator belt (or that sounds like a belt) turning I have to change it soon? Or is this a normal noise due to the lack of sound proofing in the engine bay?
 
Just a quick update - I have had the exhausted fitted for about a month now and the droning has almost gone (maybe I've got used to it or it has settled down a bit). It sounds fantastic - I really should record a little clip of it so people can see it...
 
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