The following reading was taken during the test of four - stroke single cylinder petrol engine : load on the brake drum = 50 kg , diameter of brake drum = 1250 mm , spring balance reading = 7 kg ,...

The following reading was taken during the test of four - stroke single cylinder petrol engine : load on the brake drum = 50 kg , diameter of brake drum = 1250 mm , spring balance reading = 7 kg , engine speed = 450 rpm , fuel consumption = 4 kg / hr calorific value of the fuel - 43000 kj / kg . = Calculate ( a ) Indicated thermal efficiency ( b ) Brake thermal efficiency . Assume mechanical efficiency as 70 % .