Spica Air Box

[Loyd.Heimbruch@xxxxxxxxxxx (Loyd Heimbruch)]

Scott Johnson posted:

My own personal opinion, from reading extensively and looking at my own car
and others, is that the SPICA intake box is a carefully thought out piece
of work. It has a cold air intake that *may* have some ram effect, has four
tuned-length air horns inside, and overall is almost as large as the head
itself. Even though the intake opening may look smallish, it should be
remembered that while the engine is running only one horn is drawing air at
any one time (in a 4 anyway), and the main opening is much larger than any
single horn.

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While the engine is running *at optimum rpm*, all of the air horns are drawing
air at the same time.  Without air horns, the opening and closing of the intake
valve causes a pulsating effect at the intake opening.  When the valve closes,
air bounces back.  The tuned length air horns change the pulsing to a constant
airflow at the opening of the horn and a positive pressure at the valve for
increased air intake upon opening of the valve.  The length of the air horn is
selected for the best air flow for the engine within a certain rpm range.  At
very low rpm it is quite likely that only one horn is drawing are at any one
time, but at optimum rpm all air horns are operating simultaneously.  The Spica
intake air box is an engineering work of art.

I am not sure of the diameters of the air horns or the air box opening, but the
formula for areas of circles is such that if a circle has twice the diameter of
another it will have exactly four times the area.

Loyd Heimbruch
Stella del Nord Chapter (Minnesota), AROC 
78 Niki Spider

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