maf_airmass.cpp

Go to the documentation of this file.

#include "pch.h"
 
#include "maf_airmass.h"
#include "maf.h"
#include "fuel_math.h"
 
float MafAirmass::getMaf() const {
    auto maf = Sensor::get(SensorType::Maf);
 
    if (Sensor::hasSensor(SensorType::Maf2)) {
        auto maf2 = Sensor::get(SensorType::Maf2);
 
        if (maf && maf2) {
            // Both MAFs work, return the sum
            return maf.Value + maf2.Value;
        } else if (maf) {
            // MAF 1 works, but not MAF 2, so double the value from #1
            return 2 * maf.Value;
        } else if (maf2) {
            // MAF 2 works, but not MAF 1, so double the value from #2
            return 2 * maf2.Value;
        } else {
            // Both MAFs are broken, give up.
            return 0;
        }
    } else {
        return maf.value_or(0);
    }
}
 
AirmassResult MafAirmass::getAirmass(float rpm, bool postState) {
    float maf = getMaf();
 
    return getAirmassImpl(maf, rpm, postState);
}
 
/**
 * Function block now works to create a standardised load from the cylinder filling as well as tune fuel via VE table. 
 * @return total duration of fuel injection per engine cycle, in milliseconds
 */
AirmassResult MafAirmass::getAirmassImpl(float massAirFlow, float rpm, bool postState) const {
    // If the engine is stopped, MAF is meaningless
    if (rpm == 0) {
        return {};
    }
 
    // kg/hr -> g/s
    float gramPerSecond = massAirFlow * 1000 / 3600;
 
    // 1/min -> 1/s
    float revsPerSecond = rpm / 60.0f;
    mass_t airPerRevolution = gramPerSecond / revsPerSecond;
 
    // Now we have to divide among cylinders - on a 4 stroke, half of the cylinders happen every revolution
    // This math is floating point to work properly on engines with odd cylinder count
    float halfCylCount = engineConfiguration->cylindersCount / 2.0f;
 
    mass_t cylinderAirmass = airPerRevolution / halfCylCount;
 
    //Create % load for fuel table using relative naturally aspirated cylinder filling
    float airChargeLoad = 100 * cylinderAirmass / getStandardAirCharge();
    
    //Correct air mass by VE table
    mass_t correctedAirmass = cylinderAirmass * getVe(rpm, airChargeLoad, postState);
 
    return {
        correctedAirmass,
        airChargeLoad, // AFR/VE/ignition table Y axis
    };
}