For an automotive spark-ignition engine, the combustion duration (from time of ignition through completion) is approximately one-sixth of a crankshaft revolution. This corresponds to a time of approximately 17 ms at an engine speed of 600 rev/min. To maintain the same combustion duration of one-sixth of a crankshaft revolution at 3,000 rev/min, turbulence must increase the mass rate of conversion of reactants to products by a factor of _________ compared the rate of conversion at 600 rev/min.
