smart51
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| posted on 13/9/06 at 11:15 AM |
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airbox design info needed
does anyone have any good info or a link to a good site about airbox design? I want to make an airbox to reduce intake noise at 8500 - 9000 RPM.
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smart51
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| posted on 14/9/06 at 10:05 AM |
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I've looked up bits on airbox design and they talk about helmholtz resonators. The box is tuned for a particular frequency (or engine speed)
and is used to fill in flat spots and such. They are restrictive at other speeds. I don't want this, I just want to contain, reduce or
redirect intake noise.
What can I use to smooth the airflow into an airbox, other than an exhaust like silencer?
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smart51
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| posted on 14/9/06 at 02:29 PM |
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What do you think of this reasoning?
I've been trying to think the whole airbox thing through. If I have an airbox that is 100 times the volume of the cylinder (ie 25 litres) then
the pressure in the box would drop by 1% when the inlet valve opens, at full throttle. The pressure in the carb's venturi tube would drop quite
a lot at first. The air next to this would rush in leaving a meduim sized pressure drop. As the pressure wave expands across the box, the pressure
drop would dimish to very little. The small pressure drop would draw air into the box through a hole the size of the carb inlet more slowly than the
carb drew the air in.
A long tube could be connected to this hole. It could be run to the front of the car where the cold air comes in. Would the pressure waves dissipate
in the tube or would they be propogate along it?
The tube could be connected to a trumpet at the inlet to dissipate any remnant of the pressure wave a bit more.
What do you think? Would it work or is it nonsense.
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TangoMan
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| posted on 15/9/06 at 10:13 PM |
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I think that if the box is too big then any pressure waves will be lost. I thought a lot about this before I built mine.
How big should the airbox be and How big should the intake pipe be.
I decided to go for a box that was a small as possible without unduly shrouding the filter. I couldn't see any benefit in having it larger than
required as too big may allow turbulance. For the intake I thought about having it about the same bore as the carbs (slightly larger) to create a ram
effect from the constant draw of air by each cylinder at differing times.. I think this may work but decided against it in the end as it will
probably cause a restriction at high revs. In the end I decided to go for 3 inch bore to ensure sufficient air capacity.
Summer's here!!!!
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