New Gen4 Snorkel

Thanks for the offer Roger, very kind. I will keep you in mind, but will see if I can find any locally.

I will have a measure up at what diameter pipe is needed and see if I can come up with something.

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How thick is the wall section of the flexible pipe? I know it's supposed to be flexible by nature but it looks like it would begin to resonate with the intake without too much effort. I might suggest looking at a suitable diameter piece of twin wall conduit as it will take a fairly tight bend but it's smooth inside and quite rigid for what it is.

Not sure how thick it is tbh, didn't pay too much attention to the thickness. Maybe as a cheap try out i could try wrapping the pipe and adding some securing points to rule out the pipe itself resonating?

A quick point on fitment and 300bhpton's door rubbing. Looking back through this thread I noticed the difference in the holes we had to drill for the riv-nut.

You can see on this one how close it is to the existing square hole.
 

Where mine is further towards the front.
 

This is something out of our control as it is determined buy the fitting of a bolt in rear most existing wing bolt hole and using the snorkel as a template.

Harmonics is is some kind of (black) magic. If what you describe is the result of a standing wave then spoiling it might help. One easy way might be to put a rectangular baffle into the vertical part of the snorkel that sits axial, just jams a little, and can withstand the air flow. This would be easily removable and will change the harmonics of the long circular pipe.

My first suggestion would be to ask the manufacturer/supplier if this is a known problem?

I might have missed something but does 300BHP have the same snorkel and his doesn’t vibrate? If so check to see what is different.

As RainerK says, it’s a black art, think of an acoustic guitar, it’s the string that vibrates when plucked, but it is the wooden body that we hear the sound from. The snorkel it’s self is probably just amplifying the sound rather than generating it.

In your case there isn’t a pluck but a series of small vibrations which when the structure hits resonance can be heard and felt.

The small vibrations might come from the air moving through the system, it is taken in pulses or might just be from the engine. If it’s from the air, the air box and filter should dampen them, so it might be from the engine.

You could try re-routing the flexi pipe, possibly rubber mount it and put more fixing points, anything to change the resonant frequency.

Robin

DrRobin, 300bhpton did report the same issue, only I think his could be worse than mine going off his description? I also think he did contact Bravo, which I should do, just being lazy at the moment. I'll put it on my to do list
 

I did look at the "empty box" and think it must be something like that. But trying to fit that withing the flexi-pipe and getting a good seal will be nigh impposible. If the pipe can be replaced with something solid, the you will have a much better chance.

Just writing an email to Bravo now.

Just catching up on this thread, sadly have been ill since Christmas Eve...

I did try reversing the head on my snorkel, as you can see you can't quite fully reverse it, but it does work fine like this.

It has no impact to the resonation noise being made, however if you open the window and induce the noise you can clearly hear it is induction noise, with the window up it does however sound far more fog horn and intense like.





In terms of the cause. I suspect this engine must have a harmonic trait as the factory ducting contains a baffle/resonator box (as Martin lists above). The tube also has some hole in it too, which must be there for harmonic tuning.




A test I'd like to run is to have no ducting to the airbox at and see what results.


My hunch however, the flexible ducting on the Bravo snorkel is not the issue or source. I suspect it must fully be the internal chamber of the snorkel, which is either amplifying an existing noise or more than likely producing the noise and amplifying it. I will await Bravo's reply before attempting any real fix. As I do not see how it cannot be an issue on every single snorkel they have sold for the Gen 4 Jimny.

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Those holes are the water drains according to the Brazilian snorkel instructions. The Brazilian snorkel kit provides a blanking plate for those holes and a duck billed drain valve so that the entire tube is sealed

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Interesting, although I'd suggest that maybe they are multifunctional. But I can't see their prime function being water drain holes, as they'd need to be on the lowest point or in some kind of vee. Under moving airflow water would be unlikely to collect or drip out of the holes as air will be being sucked in through them.

As they are located next to a tuning baffle/resonator, I'd guess they are very much part of the harmonic tuning. Bit like the finger holes on a recorder or Irish whistle.