i have been doing an extensive researches on how air behaves in motion for my intake and exhaust design and came across Radial Momentum theory which basically says air that flow in conical shaped tube where the radius increases from inlet to outlet will have gradual pressure drop
this is in contrast with bernoulli's where when gas expands due to increased radius, pressure will increase. please take some time to read the link below, it really helps understanding how air works if u are designing ur intake or exhaust
www.radialmomentum.com
if i interpret this correctly, we can apply this to intake and exhaust operation:
intake:
conical filter (pipercross venom / k&n apollo) tend to cause pressure drop across intake so a cylindrical airbox like BMC CDA /kracing carbon filter is preferable. however these 2 is still inferior to a geometry designed airbox (i.e. comptech icebox) in terms of retaining positive pressure before throttle body which is favourable
exhaust:
i have experienced where i removed centre bullet and replaced it with straight pipe gives much less power than when it was installed
i was confused with this phenomenon as by bernoulli's, putting bullet will make the exhaust expand thus slowing down flow and increase pressure. by replacing it with pipe, exhaust should be gaining velocity faster as there is no expansion.
with radial momentum theory, it makes sense why putting centre bullet is better than just replacing it with a straight pipe. gas particle expands in bullet causing less densities per volume thus pressure dropped. this pressure drop will create bigger pressure difference between bullet and header, so gas will be forced to travel to the bullet, this also reduce exhaust reversion achieving higher exhaust velocity faster, making exhaust system more effective
well this is just a thought, but it really helps me to determine my exhaust design and spec
p/s: airbox is an important stuff we enthusiast always take granted for, using straight pipe and pod only does no good on effective hp on street driven cars. you might get the psychological power due to the addictive sound it makes but the fact is restrictive stock airbox is better than none at all. Even F1 cars use airbox and they take it seriously in terms of the airbox design and size
this is in contrast with bernoulli's where when gas expands due to increased radius, pressure will increase. please take some time to read the link below, it really helps understanding how air works if u are designing ur intake or exhaust
www.radialmomentum.com
if i interpret this correctly, we can apply this to intake and exhaust operation:
intake:
conical filter (pipercross venom / k&n apollo) tend to cause pressure drop across intake so a cylindrical airbox like BMC CDA /kracing carbon filter is preferable. however these 2 is still inferior to a geometry designed airbox (i.e. comptech icebox) in terms of retaining positive pressure before throttle body which is favourable
exhaust:
i have experienced where i removed centre bullet and replaced it with straight pipe gives much less power than when it was installed
i was confused with this phenomenon as by bernoulli's, putting bullet will make the exhaust expand thus slowing down flow and increase pressure. by replacing it with pipe, exhaust should be gaining velocity faster as there is no expansion.
with radial momentum theory, it makes sense why putting centre bullet is better than just replacing it with a straight pipe. gas particle expands in bullet causing less densities per volume thus pressure dropped. this pressure drop will create bigger pressure difference between bullet and header, so gas will be forced to travel to the bullet, this also reduce exhaust reversion achieving higher exhaust velocity faster, making exhaust system more effective
well this is just a thought, but it really helps me to determine my exhaust design and spec
p/s: airbox is an important stuff we enthusiast always take granted for, using straight pipe and pod only does no good on effective hp on street driven cars. you might get the psychological power due to the addictive sound it makes but the fact is restrictive stock airbox is better than none at all. Even F1 cars use airbox and they take it seriously in terms of the airbox design and size
