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HOWTO: Flat shifting/fuel cut on gear shift in manuals


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As part of our workshop edition we have a custom operating system which has several features available, one of which can be selected as part of the 5 credit "Standard Custom OS".

One of these features is the "Flat Shift control using throttle" which performs a cylinder cut when the following conditions are met:

  • TPS > TPS Threshold (typically set at 95% throttle)
  • Clutch Is depressed
  • RPM > RPM Setpoint (typically set at 3500 rpm)
  • Speed is less than speed setpoint (typically set out of range unless you are using this for launch control)

Here is a video of a Bremer shifter and the flat shifting patch in action 


To enable the flat shifting patch first open the custom operating system wizard and select "Standard Custom OS"


Press Next

You will then see a "Custom OS Options" page. Select "TPS Override for flat shifting" from the "Flat Shift control using throttle" drop down menu.

This will automatically set all scalars for launch control and flat shifting along with adding the new TPS enable condition.

Press "Check License and Proceed" This will charge you 5 credits total for the vehicle (2 extra on top of the existing 3 credits). 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). Leave these as the standard values.


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

Now navigate to "Custom Operating System Configuration" within the navigator and locate "TPS Threshold for the car to use when Flat Shifting".


Now set "TPS Threshold" to roughly 420 which should be approximately 90% throttle (experimentation will be required as some throttle bodies vary).


This will enable the car to flat shift on full throttle if the following  conditions are met.

RPM > auF2035 (Fuel cut RPM for launch)

Clutch has been depressed

TPS > auF100016 (420 is roughly 80% throttle).

This means you can drive the car around town normally above 2500 with no fuel cut, however if you use full throttle you will get a fuel cut.

If you have enabled a multi tune you can add auF2035 to different tunes and set it out of range. This allows you to make flat shifting only enabled in specific tunes.

It is recommended to bend the clutch switch bracket so that he clutch switch is not activated until the pedal is at least halfway pressed in. Otherwise there will be a lag between the clutch engaging and the injectors reactivating.

Please warn customers that flat shifting is hard on the drive line and can break diff mounts, engine mounts, tailshafts and axles. It is recommended to run upgraded diff bushes and a diff hat you can quickly destroy the stock bushings.

Independent Motor Sports make a great diff hat replacement.


For some more background reading on how the flat shifting torque requestors read you can read this thread.


OId Manual Method (no TPS activation setpoint and no Custom OS required)

Now to enable flat shifting we utilise the launch control whilst the car is moving. To do this we set the launch control rpm to something reasonably high but is still above the lowest rpm you will be shifting at. Eg 3500 rpm should be a good point.

Next set auF11836 (Minimum vehicle speed (mph) for manual vehicles to limit launch rpm to a high number like 200mph. Note that this parameter is only available in the workshop version of the software.


Now when you shift gears and are above 3500 rpm there will be an aggressive fuel cylinder cut above 3500 rpm once the clutch switch is activated. This means you can hold the throttle flat during shifts.

Once you have the clutch switch adjusted you can play with the rpm setpoint so that you can still daily drive the car without a fuel cut occuring.

On the drag strip this will mean you retain close to full boost on gear shifts. Eg in testing (using a WOT box so not 100% the same system) we have seen a car running 20psi only drop to 16 psi on a gear shift. In contrast if you close the throttle you lose all boost, this will make a big difference on the drag strip.


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