The Otto-cycle engine in a Mercedes-Benz SLK230 has a compression ratio of 8.8. (a) What is the ideal efficiency of the engine? Use ? = 1.40. (b) The engine in a Dodge Viper GT2 has a slightly higher compression ratio of 9.6. How much increase in the ideal efficiency results from this increase in the compression ratio?

Solution 7E Problem (a) Step 1: Compression ratio r = 8.8 Ratio of heat capacity = 1.40 To find Ideal efficiency of the engine Step 2: e = 1 1 r e = 1 1 8.8.401 1 e = 1 0.40 8.8 e = 0.581 or 58.1% The theoretical efficiency of the otto-cycle engine is 58.1% Problem (b) Step 1: The engine in a Dodge Viper GT2 has a slightly higher compression ratio of 9.6 To find the increase in the ideal efficiency Take the values Compression ratio r = 9.6 Ratio of heat capacity = 1.40 Step 2: e = 1 r1 e = 1 1 9.6.401 1 e = 1 9.6.40 e = 0.595 or 59.5%