Better exhaust flow idea

[MaxRothery]

Right, I was watching a /Drive video recently about exhausts and how to make more power with them and the guy on it mentioned that one type of silencer which used a surrounding packing to muffle sound at low speeds but could out flow a straight pipe due to resistance of the pipe sides, it's rather hard do describe if you haven't watched it, but it got me thinking. Could you get better flow from an exhaust if you drilled holes in the pipe that will make up the correct size exhaust and then placed a thin wall pipe around it?

[PaulKemp]

I really have no idea what your trying to describe without seeing the video
However straight through silencers use a perforated tube the same diameter as the exhaust pipe, this perf pipe is inside the silencer can which is much bigger and the space is filled with heat resist and sound absorbing packing.
The gasses go straight through with little resistance while the sound waves go into the packing.
Normal car silencers route the gasses round the can changing direction with angled plates that reflect the sound waves back on themselves cancelling the sound out so the theory goes

[MaxRothery]

PaulKemp said:

I really have no idea what your trying to describe without seeing the video
However straight through silencers use a perforated tube the same diameter as the exhaust pipe, this perf pipe is inside the silencer can which is much bigger and the space is filled with heat resist and sound absorbing packing.
The gasses go straight through with little resistance while the sound waves go into the packing.
Normal car silencers route the gasses round the can changing direction with angled plates that reflect the sound waves back on themselves cancelling the sound out so the theory goes

The theory behind this idea, is that because the exhaust gasses fill the side chamber at high rpm, there is a slight pressure inside the chamber which is pushed out and reduces the air friction, therefore flowing better

[PaulKemp]

So you push gas into a space until it's slightly over pressure and then it pushes out thus reducing the pressure which then is filled again increasing the pressure?!?
Sounds like fluid dynamics, could be like the dead zone around a bath plug where you get rapid moving fluid next to almost stationary.
Most exhausts are not very efficient so to add this on its own would give no benefit
Please post a link to the video or do some reaserch and post a (much) better explanation

[MaxRothery]

PaulKemp said:

So you push gas into a space until it's slightly over pressure and then it pushes out thus reducing the pressure which then is filled again increasing the pressure?!?
Sounds like fluid dynamics, could be like the dead zone around a bath plug where you get rapid moving fluid next to almost stationary.
Most exhausts are not very efficient so to add this on its own would give no benefit
Please post a link to the video or do some reaserch and post a (much) better explanation

https://m.youtube.com/watch?v=RWTARjxiqlo

Basially, for an active exhaust, the moving exhaust gasses move along the inner pipe until it gets to the silencer chamber, some of it then moves into the surrounding chamber and the rest move on, going through holes further down which fill the silencer chamber. air moving down a pipe has a slight pressure acting outwards, so when the moving air passes through the pipe inside the chamber, it pushes air into the already full chamber, which in turn tries to push out. In turn this creates a layer of air for the air to flow along, rather than the rough pipe wall which creates a resistance.

My idea would be to create a chamber around the whole length of the exhaust so it always has an air flow to run along, rather than the pipe wall