The overall effect is {HEAD ~ the use} of {TAIL ~ the negative pressure wave} advantageously during high and intermittent engine r.p.ms rather than at substantially a single engine speed 
of
The overall effect is { HEAD ~ the use } of { TAIL ~ the negative pressure wave } advantageously during high and intermittent engine r.p.ms rather than at substantially a single engine speed
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH