Borg Warner Speed Sensor RPM sensor for the compressor wheel on Borg Warner SX-E, EFR and Airwerks turbochargers Pin 1: 0-5V square wave / Digital Pin 2: Ground Pin 3: +5V supply (Pin 1 is on the left when the connector is facing you and the locking tab is pointing upward) The sensors output square wave switches at 5V and has a 50% duty cycle. The frequency depends on the wheel speed. Each blade on the wheel generates a pulse, and depending on the number of blades the turbo has, different frequencies are produced for different turbochargers. EFR units have 14 blades except for the 67mm variants which have 12 blades. The sensor divides this value by 8. Example: 100,000 rpm * 14 pulses/blades per revolution = 1.4 million blades passing per minute. 1.4 million / 60 seconds = 23,333 blades passing per second (Hz) 23,333 / 8 = 2,917 Hz So the sensor output is 2.917 Hz at 100,000 rpm on a 14-blade compressor wheel. A matching connector is linked.