3. Determine the total induction length, from the point of intake entry of the tract to the head of the inlet valve, to optimize the wave ram effect at the following engine speeds: 2000, 3000 and 4000 rev/min. The crank-angle for the pressure-wave to travel through the tract from end to end and back again is at. Assuming an average value for & to be 85 and the velocity of sound in air to be C = 330 m/s. Plot tract length (mm) versus engine speed from 1000 to 8000 rev/min. This plot enables a rough approximation of the tuned pipe length for any engine speed to be picked off directly from the graph.