Racing in 1913 had helped to prove the design, and encouraged a 10 mm increase in bore to 90 mm, the stroke remaining at 150 mm. Its rated output was 225 bhp (168 kW) at 2,000 rpm. Named the ‘Mohawk', the engine was the most powerful available to British aviation at the outbreak of World War I. During the war further enlargement to 100 x 150 mm created the 240 bhp (180 kW) 'Gurkha'.[2]