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Why is there a "MAP vs RPM" and a "TPS vs RPM" fuel map?

kento_ftecukento_ftecu Posts: 776Staff User
in ECU Maps

Most fuel-injected bikes utilize what is called a "speed density" system that estimates the amount of air flowing into the engine to determine the amount of fuel the engine needs based upon the rpm, ambient temp, the engine's load (the MAP or manifold absolute pressure sensor), and the throttle position (the TPS or throttle position sensor). The TPS x RPM map handles the baseline fuel delivery for a particular rpm, while the MAP vs RPM map handles fine tuning of that fueling.

Comments

  • leonwelle@gmail.comleonwelle@gmail.com Posts: 5Verified User

    Can you explain why the Flash Tune PCV import only affects the TPS x RPM map and not the MAP vs RPM map?

  • jason@ftecu.comjason@ftecu.com Posts: 1,071Staff User

    Hi,


    Because a Power Commander cannot access your MAP sensor. Their fueling maps only go off of TPS vs RPM because that’s all they can tune for fuel.


    Thanks,


    Jason A.

  • leonwelle@gmail.comleonwelle@gmail.com Posts: 5Verified User
    edited July 2019

    This means that after importing the PCV map into FT-ECU, only one map is affected, while the other map (MAP vs. RPM) is untouched. When the bike switches from the TPS to the MAP mapping, it's falling back to original (unrestricted) fuel injection settings. If this is the case, it's not possible to delete the power commander after flashing the PCV map into the ECU, or am I missing something?

  • chrisgardellchrisgardell Posts: 48Staff User
    edited July 2019

    Using PCV import is not recommended for just that reason.. it has always meant to be a coarse import to help people get closer when moving away from an older piggy-back style tuner.

    By the way, that same issue impacts the normal operation of a piggy-back tuner as in their normal operation they dont know if the ecu is using MAP or TPS and they simply always apply a % based on TPS.

    You're best bet for correctly tuning MAP and TPS simultaneously is ActiveTune.

  • edge540rc@yahoo.comedge540rc@yahoo.com Posts: 3Verified User

    So, my assumption has always been that the MAP sensors would provide a percentage change to the base map (TPS vs RPM) and I was not aware of a separate speed density map that overrides the tps based map. Do the two maps work together, or are you saying that the TPS/RPM map can be totally ignored? If that is the case, what situation would cause this to happen? What would be the benefit to throwing the PCV in the trash can? At this point, you would HAVE to run Active Tune to tune correctly, albeit more accurately that a PCV I assume? Hypothetically, if I loaded a PCV map and removed the Power Commander, how close would that bike run if the PCV map was previously spot on?

  • edge540rc@yahoo.comedge540rc@yahoo.com Posts: 3Verified User

    Is the Fuel MAP vs RPM table adjusting the fuel compensation factor based on atmospheric conditions? In other words, if I tune here in Texas in August, and re-dyno in January and see that I am overly lean, would I hypothetically lower the values in the Fuel MAP vs RPM in the affected areas to compensate, or is it more complicated than that?

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