The first Sabre engines were ready for testing in January 1938, although they were limited to 1,350 hp (1,000 kW). By March, they were passing tests at 2,050 hp (1,500 kW) and by June 1940, when the Sabre passed the Air Ministry's 100-hour test, the first production versions were delivering 2,200 hp (1,640 kW) from their 2,238 cubic inch (37 litre) displacements. By the end of the year, they were producing 2,400 hp (1,800 kW). The contemporary 1940 Rolls-Royce Merlin II was generating just over 1,000 hp (750 kW) from a 1,647 cubic inch (27 litre) displacement.