Mr. WW and those that like to follow this kind of stuff,

In the formula you listed that is used in my book,

*Engine Airflow*, there is indeed a wispy old imaginary number which is the sq rt of -1. Z denotes the impedance.

Probably not a "do it this way" application that fits all.

What Engleman was trying to produce there is an acknowledgement of the oscillation of a wave that simulates an Alternating Current wave of electricity. The impedance of a circuit is simply its ratio of resistance to the capacitance oscillation. He had likened the intake system to that of a resistor and a capacitor where a circuit will oscillate as in DC circuits.

One can also look at the intake manifold (including any plenum) as a Helmholtz resonator and the ratio of the inflow resistance to the outflow that can be damped by using a plenum volume (perhaps variable) giving a boost in intake supercharging across a wider range of rpm than the normal approach of a fixed length inlet path.

Remember that intake oscillations are more pronounced with fewer cylinders than greater. That is another way of stating the pulsations on the intake of a single cylinder are greater than the pulses on a group of cylinders joined by a plenum. Plenum volume typically damps those pulses.

You two stroke guys probably remember the "boost bottle" approaches from years ago. The same kind of application can be done for a 4 stroke.

Bo, I will send you a PM to perhaps sort out the process which I hope will be of some benefit.

Regards to All,

HB2