STP Technical Class - Map Switching
Posted on March 28 2019
Enjoy this article as Pavlotech goes in-depth about Map Switching. Check out his full blog HERE
STP Technical Class - Map Switching
A frequent (and sometimes controversial) question comes up a lot since vehicle electrical systems continue to evolve. What is map switching? The short answer is the ability to change the ECU lookup table reference points. While that sounds complicated, this can be a very simple concept.
A good example would be a car with electronic throttle control that has a “sport” switch that changes the sensitivity. The ECU would have multiple lookup tables for throttle targets which are then dependent on a switch (or something else) to actively change it. Attached are examples of two electronic throttle target tables. The axis for the lookup tables is configured to follow RPM and pedal position.
You can see the relationship between the pedal and target throttle position is not linear in either map. This is normally contrary to popular belief (especially if the application uses a very large throttle body or individual throttles), but regardless of that, each map has a different pedal to throttle curve which is what changes the throttle sensitivity.
With modern electronics, map switching can be configured too much more than simply change the throttle sensitivity of the engine. While the examples I am showing you are utilizing the @emtron #emtune calibration software, some (if not many) of these functions can be configured in a modern factory ECU as well.
Attached is an example of the CAL (calibration) slot control page in Emtune. You can see there are 4 CAL slots on the top which correspond to multiple tables for various functions of the ECU. You can change every important lookup table of the calibration based on the position of the CAL slots at the top. To add flexibility, Emtune lets you define however you want to control the slot change as well. You can have a multi-position switch telling the ECU what slot you want to be in, change slots based on an analog voltage, change slots based on speed, or change slots based on temperature. The configuration is totally open so you can do almost anything you want. They even give you a 3D table to configure this based on multiple axes.
Emtune also has some advanced features that allow you to “blend” tables automatically in addition to the above mentioned CAL slot control. This is called their Z-Axis function. In one of the attachments, the configuration is shown where, based on vehicle speed, a boost target table (in KPA) is automatically switched (and blended automatically when in between). Z-Axis is available for almost any important map within the Emtron ECU systems.
In addition to some of the reasons why map switching can be useful above, here is a quick list of common examples:
Drive by wire target
Fuel mixture table
Boost target switch
Launch mode enable
Ground speed limit enable
Torque limit switch
Map switching can be very useful in race series that base car classification on power to weight. The car can be set up to run in a number of classes by changing parts, installing a restrictor plate (to limit engine power), or switching the calibration.
Hopefully, after reading all of this you can see how being able to switch calibrations could be useful in this instance. Especially if the car has electronic throttle!
While this subject can be highly controversial (due to making it easy to cheat), if used LEGITIMATELY it can yield impressive results further justifying investing in the proper electronics solutions.
Attached is a dyno plot using running two different calibrations so the same car can be used in two separate racing classes that are based on the power to weight. The max power and detuned run were NOT back to back here (you can see the detune was several runs after the max run), so there was some heat soak. Even still, the detuned plot shows essentially maximum torque available until the peak HP is “clamped” at roughly 6000rpm.
This was done properly with a number of calibration changes that included throttle target tables, proper fueling changes, ignition correction, cam position, Emtune torque limiting tables, and more. Rather than simply installing a restrictor plate which usually relies on an automatic function to compensate for reduced airflow, each calibration slot is customized, consistent, and therefore reliable.
Interested in learning more? Feel free to contact @pavlotech to discuss the options!