The extra supercharger boost, which increased engine output by nearly , gave the Hurricane an approximate increase in speed of , under altitude and greatly increased the aircraft's climb rate. "Overboost" or "pulling the plug", a form of war emergency power as it was called in later Second World War aircraft, was an important wartime modification that allowed the Hurricane to be more competitive against the Bf 109E and to increase its margin of superiority over the Bf 110C, especially at low altitude. With the + "emergency boost", the Merlin III was able to generate at .