Jump to content

HOWTO: Custom OS - Window Switch Output Trigger (Fuel pump, water meth, nitrous etc)


Recommended Posts

Problem: You have 2 fuel pumps for your large power goal which causes high pressure fuel spikes at low load/idle due to over supply.

Problem 2:  You want to control a water meth injection system based off rpm / load however traditional window switches cannot easily access load/map pressure.

Solution: Utilise our custom operating system IMRC/IMCC output re-configuration which allows the IMRC/IMCC output to be used as an external trigger based off an RPM window and a Load (MAP Pressure) setpoint. As the turbo vehicles do not use the IMRC runners this output driver exists on the PCM and the plug can be re-pinned to re-utilise this output.

To enable this feature you require the workshop edition and a 5 credit "Standard Custom OS". This is an extra 2 credits on top of a standard license.

First open the custom operating system wizard, select "Standard Custom OS" and press Next.


You will then see a "Custom OS Options" page. Leave these options standard.


Press "Check License and Proceed" which will then ask you to license the file, this will charge you an extra 2 credits (total of 5 for the vehicle). This will only be charged once.

You will now see a second set of Custom OS options (these can be changed later by relaunching the custom os wizard). Select "IMCC Controlled via MAP pressure" from the IMCC Configuration dropdown.


Press Next then "Finish" and the file will automatically save and re-open.

Next navigate to "Minimum MAP reading to activate the IMCC"


If you are staging a fuel pump, calculate the kPa that you wish the fuel pump to turn on at and enter this value. Remember that 101 kPa is atmospheric eg 1.0 load and 0 psi. In this example we have entered 150 kPa which is approximately 7 psi. If you were using the output for water meth injection you might enter a lower value of 101 kPa (eg 0 psi)


Next Navigate to IMCC - Scalars


The following settings will turn the IMCC on (eg it will output 5V) at 3000rpm, it will then remain on until the rpm drops below 2950 rpm (eg a 50 rpm deadband). The 8000 and 8050 rpm are set out of range.


If you wanted to turn the output between 3000 RPM and 4000 RPM you could use the following values. Eg the IMCC will output 5v when the RPM hits 3000 RPM, then it will turn off at 4050 RPM. When the RPM is falling, the IMCC will output 5v at 4000 RPM, and then turn off again at 2950 RPM.


Depending on your relay setup, you can invert the behaviour by swapping the RPM setpoints to make the output be inverted.

This setup can also be used for nitrous injection with feedback to adjust fueling and spark. It could also be used with a low level/flow switch for your water meth injection to trigger a fail safe map where less spark timing is used if the water meth tank ran low.


For wiring up the IMCC runner output you can repin the B03 pin on the PCM plug. This is as the IMCC was never installed on turbo vehicles so you can either harvest another unused pin or purchase one from here. If the pin is wired up already the loom wire colour should be light green, however always check this as it may not be true for all models.


To read about some more advanced scenarios where this can be used see this guide.


  • Like 1
Link to comment
Share on other sites

  • 10 months later...
  • 1 month later...
On 8/26/2022 at 1:00 PM, Roland@pcmtec said:

If anyone has recently done this with the MAP setpoint could you please let us know what your use case was and if it all worked correctly? We are trying to determine if anyone is actually using this feature and if it should remain in the software.

I used it for the W2A pump on our development BA. Worked fine 🙂  will be using it to stage fuel pumps in the next few weeks.

  • Like 1
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Unfortunately, your content contains terms that we do not allow. Please edit your content to remove the highlighted words below.
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...