Wasp Jr. A : compression_ratio : 5.0:1 | Wasp Jr. A : critical_altitude_this_is_the_highest_altitude_at_which_the_engine_can_achieve_its_full_continuous_power_rating._above_this_altitude,_power_falls_off_with_height_as_with_a_naturally_aspirated_engine_._see_supercharger#altitude_effects_for_details. : sea level | Wasp Jr. A : supercharger_gear_ratio : 7:1
When critical altitude is sea level, 5.0:1 is the compression ration and the supercharger gear ratio is 7:1.