Several velocities, time, and length scales are useful in understanding what goes on inside engines. Make estimates of the following quantities for a 1.6-liter displacement fourcylinder spark-ignition engine, operating at wide-open throttle at 2500 rev/min. Assume that the port (for both intake and exhaust) area is about 20 percent of the piston area. (a) The mean piston speed and the maximum piston speed. (b) The maximum charge velocity in the intake port. (c) The time occupied by one engine operating cycle, the intake process, the compression process, the combustion process, the expansion process, and the exhaust process. (Note: The word process is used here not the word stroke.) (d) The average velocity with which the flame travels across the combustion chamber. (e) The length of the intake system (the intake port, the manifold runner, etc.) which is filled by one cylinder charge just before the intake valve opens and this charge enters the cylinder (i. e., how far back from the intak