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Turbo Speed Sensors on Modular ECUs

December 13, 2017


Increasingly recently, people have started to install turbo speed sensors to monitor the rotor speed of their turbochargers. I’m not sure if the goal here is more data to monitor spool, configure antilag or just to make sure that you’re not overspeeding the turbo, but many people have asked for the ability to measure turbo speed and record it on the ECU, so we’ve added it for some specific types of sensors.

The ECU supports up to 2 turbo speed sensors so that you can measure the turbo speed of two separate turbochargers. If in the future we build the turbo speed into either exhaust back pressure monitoring or part of the boost control algorithm, then turbo 1 will correspond to the odd bank, or the front half of the engine in a twin-turbo inline 6 eg the RB26DETT, and turbo 2 will correspond to the even bank or the rear half of an inline.

The inputs that can be used have to be high speed frequency inputs; so normal digital inputs or analogue inputs are not suitable.

These are:

  • CAS2, if you’re not using it already for part of the engine triggering
  • CAS3, if that’s not being used for the engine trigger or flex fuel
  • CAS 4 or 5, if a Mini RT input module is installed
  • Flex / frequency input on the Mini RT module
  • Any of the 3 VSS inputs on the Mini RT module
  • The main VSS input, if it’s not being used for vehicle speed.

The selection of the source for the input is made on the Turbo speed sensor setup page.

The type of sensor should also be selected. Currently we support the following options:

  • Borg Warner EFR, 67mm compressor (with 12 blades). In this case, the sensor outputs 1 pulse for every 8 blades, which means that the sensor gives out 1.5 pulses per revolution
  • Borg Warner EFR, larger than 67mm compressor (with 14 blades). Again in this case the sensor outputs 1 pulse for every 8 blades, which means 1.75 pulse per revolution
  • Honywell / Garrett with a bar type trigger, ie 2 pulses pre revolution

The above senors all give a digital output, so the ECU must have that input selected as a digital input.

Once the turbo speed input has been selected, it will appear in the main gauge window and of course you can add it to your own gauge page or to the monitor panel on the right hand side, use it as a variable in your built-in scope to watch spool rates and so on.

Thank you and happy learning!