( I originally posted this in the automotive section, but i think this forum is more appropriate. please see thread71-166172 )
Ive just been reading a few articles, in particular:
Wave reflections from duct terminations
A. Selamet and Z. L. Ji
and
The acoustics of racing engine intake systems
M.F. Harrison,*, A. Dunkley
now ive typically designed my intake runners to terminate (either within an airbox, or atmosphere) with a (relatively) small radiused bellmouth (r/D=0.25 or greater) - for the obvious reason that the loss coefficient of the bellmouth provides better net flow capability.
however, reading about the acoustic boundary of a bellmouth (being possibly the worst re: low reflection coefficient) im concerned that by and large an effective bellmouth cacels out any acoustic tuning advantage i design into my intake runners.
harrisions article suggests that acoustic tuning is reasonably weak and contributes only in the lower rpm band, ineria ram being responsible for the majority of higher engine VE increases.
have i just dudded myself out of all the hours i spend calculating harmonic intake lengths??
an example of my bellmouths can be seen below:
comparison with other performance engines is varied. some go large 180deg mod large radius bellmouth, other go for small radius
given the drop in reflection coefficient, would this bellmouth see losses in tuned performance, have a significantly louder intake noise, both?
ALSO - what would the introduction of pulse plates be over a bellmouth such as the image i liked above? can anyone provide a good reference for pulse plate function and design - specific application wrt IC engine intakes would be a bonus!
cheers
ed
Ive just been reading a few articles, in particular:
Wave reflections from duct terminations
A. Selamet and Z. L. Ji
and
The acoustics of racing engine intake systems
M.F. Harrison,*, A. Dunkley
now ive typically designed my intake runners to terminate (either within an airbox, or atmosphere) with a (relatively) small radiused bellmouth (r/D=0.25 or greater) - for the obvious reason that the loss coefficient of the bellmouth provides better net flow capability.
however, reading about the acoustic boundary of a bellmouth (being possibly the worst re: low reflection coefficient) im concerned that by and large an effective bellmouth cacels out any acoustic tuning advantage i design into my intake runners.
harrisions article suggests that acoustic tuning is reasonably weak and contributes only in the lower rpm band, ineria ram being responsible for the majority of higher engine VE increases.
have i just dudded myself out of all the hours i spend calculating harmonic intake lengths??
an example of my bellmouths can be seen below:
comparison with other performance engines is varied. some go large 180deg mod large radius bellmouth, other go for small radius
given the drop in reflection coefficient, would this bellmouth see losses in tuned performance, have a significantly louder intake noise, both?
ALSO - what would the introduction of pulse plates be over a bellmouth such as the image i liked above? can anyone provide a good reference for pulse plate function and design - specific application wrt IC engine intakes would be a bonus!
cheers
ed
