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MAP_EFI_V2.1.ino
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// EFI controller based on MAP and Points ONLY, V2
// This version includes a complete AFR mapping table.
// Thresholded rate-of-change-of-MAP is also used to emulate delta-TPS.
// (C) 2021 John Patterson Consulting, LLC
// You are free to modify and redistribute this code without restriction.
// ----------------- Program constants -----------------:
// Pin numbers:
const int pointsPin = 3;
const int MAPPin = 14;
const int injectorPin = 6;
const int LEDPin = 13;
// Timing constants:
const unsigned long injectorUpdateInterval = 30000;
const unsigned long interruptDebounce = 3000;
const unsigned long primeTime = 300;
const unsigned long pumpTime = 0;
const int serialReportModulo = 10;
const int RPMrunningAverageDepth = 5;
const unsigned long blinkTime = 250;
// Engine-related constants:
const int pulsesPerRevolution = 2;
const double displacement_Liters = 1.6;
const double injector_MaxGramsPerMinute = 260.0; // Will depend on your injector and fuel pressure
const double stallRPM = 300.0;
const double Pascals_Per_ADC_Unit = 122.1;
const int vacuum_ADC_value = 102;
const double min_DC = 0.07; // Minimum duty cycle for idling
const double vacuum_ROC_Multiplier = 0.0005; // Add or remove AFR proportional to the rate of change of MAP
const double vacuum_ROC_Cut_In = 51710; // MAP pressure over which vacuum ROC will be applied
//Fuel AFR selector (gas or E51):
//const double fuel_comp = 1.0; // Gas
const double fuel_comp = 0.70; // E51
//// All 14.7:
//// AFR mapping:
//// PSI: 0-1.5 1.5-3 3-4.5 4.5-6 6-7.5 7.5-9 9-10.5 10.5-12 12-13.5 13.5-15
//double AFR_500RPM[10] = {14.700, 14.700, 14.700, 14.700, 14.700, 14.700, 14.700, 14.700, 14.700, 14.700};
//double AFR_1000RPM[10] = {14.700, 14.700, 14.700, 14.700, 14.700, 14.700, 14.700, 14.700, 14.700, 14.700};
//double AFR_1500RPM[10] = {14.700, 14.700, 14.700, 14.700, 14.700, 14.700, 14.700, 14.700, 14.700, 14.700};
//double AFR_2000RPM[10] = {14.700, 14.700, 14.700, 14.700, 14.700, 14.700, 14.700, 14.700, 14.700, 14.700};
//double AFR_2500RPM[10] = {14.700, 14.700, 14.700, 14.700, 14.700, 14.700, 14.700, 14.700, 14.700, 14.700};
//double AFR_3000RPM[10] = {14.700, 14.700, 14.700, 14.700, 14.700, 14.700, 14.700, 14.700, 14.700, 14.700};
//double AFR_3500RPM[10] = {14.700, 14.700, 14.700, 14.700, 14.700, 14.700, 14.700, 14.700, 14.700, 14.700};
//double AFR_4000RPM[10] = {14.700, 14.700, 14.700, 14.700, 14.700, 14.700, 14.700, 14.700, 14.700, 14.700};
//double AFR_4500RPM[10] = {14.700, 14.700, 14.700, 14.700, 14.700, 14.700, 14.700, 14.700, 14.700, 14.700};
//double AFR_5000RPM[10] = {14.700, 14.700, 14.700, 14.700, 14.700, 14.700, 14.700, 14.700, 14.700, 14.700};
//// Richer at high load only:
//// AFR mapping:
//// PSI: 0-1.5 1.5-3 3-4.5 4.5-6 6-7.5 7.5-9 9-10.5 10.5-12 12-13.5 13.5-15
//double AFR_500RPM[10] = {14.500, 14.500, 14.000, 13.700, 13.500, 13.200, 13.000, 12.700, 12.500, 12.000};
//double AFR_1000RPM[10] = {14.500, 14.500, 14.000, 13.700, 13.500, 13.200, 13.000, 12.700, 12.500, 12.000};
//double AFR_1500RPM[10] = {14.500, 14.500, 14.000, 13.700, 13.500, 13.200, 13.000, 12.700, 12.500, 12.000};
//double AFR_2000RPM[10] = {14.500, 14.500, 14.000, 13.700, 13.500, 13.200, 13.000, 12.700, 12.500, 12.000};
//double AFR_2500RPM[10] = {14.500, 14.500, 14.000, 13.700, 13.500, 13.200, 13.000, 12.700, 12.500, 12.000};
//double AFR_3000RPM[10] = {14.500, 14.500, 14.000, 13.700, 13.500, 13.200, 13.000, 12.700, 12.500, 12.000};
//double AFR_3500RPM[10] = {14.500, 14.500, 14.000, 13.700, 13.500, 13.200, 13.000, 12.700, 12.500, 12.000};
//double AFR_4000RPM[10] = {14.500, 14.500, 14.000, 13.700, 13.500, 13.200, 13.000, 12.700, 12.500, 12.000};
//double AFR_4500RPM[10] = {14.500, 14.500, 14.000, 13.700, 13.500, 13.200, 13.000, 12.700, 12.500, 12.000};
//double AFR_5000RPM[10] = {14.500, 14.500, 14.000, 13.700, 13.500, 13.200, 13.000, 12.700, 12.500, 12.000};
//// Richer at high load only with rich idle:
//// AFR mapping:
//// PSI: 0-1.5 1.5-3 3-4.5 4.5-6 6-7.5 7.5-9 9-10.5 10.5-12 12-13.5 13.5-15
//double AFR_500RPM[10] = {13.500, 13.500, 13.000, 13.500, 13.500, 13.200, 13.000, 12.700, 12.500, 12.000};
//double AFR_1000RPM[10] = {13.500, 13.500, 14.000, 13.700, 13.500, 13.200, 13.000, 12.700, 12.500, 12.000};
//double AFR_1500RPM[10] = {14.500, 14.500, 14.000, 13.700, 13.500, 13.200, 13.000, 12.700, 12.500, 12.000};
//double AFR_2000RPM[10] = {14.500, 14.500, 14.000, 13.700, 13.500, 13.200, 13.000, 12.700, 12.500, 12.000};
//double AFR_2500RPM[10] = {14.500, 14.500, 14.000, 13.700, 13.500, 13.200, 13.000, 12.700, 12.500, 12.000};
//double AFR_3000RPM[10] = {14.500, 14.500, 14.000, 13.700, 13.500, 13.200, 13.000, 12.700, 12.500, 12.000};
//double AFR_3500RPM[10] = {14.500, 14.500, 14.000, 13.700, 13.500, 13.200, 13.000, 12.700, 12.500, 12.000};
//double AFR_4000RPM[10] = {14.500, 14.500, 14.000, 13.700, 13.500, 13.200, 13.000, 12.700, 12.500, 12.000};
//double AFR_4500RPM[10] = {14.500, 14.500, 14.000, 13.700, 13.500, 13.200, 13.000, 12.700, 12.500, 12.000};
//double AFR_5000RPM[10] = {14.500, 14.500, 14.000, 13.700, 13.500, 13.200, 13.000, 12.700, 12.500, 12.000};
// Richer at idle only:
// AFR mapping:
// PSI: 0-1.5 1.5-3 3-4.5 4.5-6 6-7.5 7.5-9 9-10.5 10.5-12 12-13.5 13.5-15
double AFR_500RPM[10] = {12.000, 12.000, 12.000, 12.000, 12.000, 12.000, 12.000, 12.000, 12.000, 12.000};
double AFR_1000RPM[10] = {13.500, 13.500, 13.500, 13.500, 13.500, 13.200, 13.000, 12.500, 12.500, 12.000};
double AFR_1500RPM[10] = {14.000, 14.000, 14.000, 14.000, 14.000, 14.000, 14.000, 13.500, 13.500, 13.000};
double AFR_2000RPM[10] = {14.000, 14.000, 14.000, 14.000, 14.000, 14.000, 14.000, 14.000, 13.500, 13.500};
double AFR_2500RPM[10] = {14.000, 14.000, 14.000, 14.000, 14.000, 14.000, 14.000, 14.000, 14.000, 14.000};
double AFR_3000RPM[10] = {14.000, 14.000, 14.000, 14.000, 14.000, 14.000, 14.000, 14.000, 14.000, 14.000};
double AFR_3500RPM[10] = {14.000, 14.000, 14.000, 14.000, 14.000, 14.000, 14.000, 14.000, 14.000, 14.000};
double AFR_4000RPM[10] = {14.000, 14.000, 14.000, 14.000, 14.000, 14.000, 14.000, 14.000, 14.000, 14.000};
double AFR_4500RPM[10] = {14.000, 14.000, 14.000, 14.000, 14.000, 14.000, 14.000, 14.000, 14.000, 14.000};
double AFR_5000RPM[10] = {14.000, 14.000, 14.000, 14.000, 14.000, 14.000, 14.000, 14.000, 14.000, 14.000};
// Lean coasting:
//// AFR mapping:
//// PSI: 0-1.5 1.5-3 3-4.5 4.5-6 6-7.5 7.5-9 9-10.5 10.5-12 12-13.5 13.5-15
//double AFR_500RPM[10] = {13.500, 13.500, 13.500, 13.500, 13.500, 13.200, 13.000, 12.700, 12.500, 12.000};
//double AFR_1000RPM[10] = {13.500, 13.500, 13.500, 13.500, 13.500, 13.200, 13.000, 12.700, 12.500, 12.000};
//double AFR_1500RPM[10] = {14.000, 14.000, 14.000, 14.000, 13.500, 13.200, 13.000, 12.700, 12.500, 12.000};
//double AFR_2000RPM[10] = {14.000, 14.000, 14.000, 14.000, 13.500, 13.200, 13.000, 12.700, 12.500, 12.000};
//double AFR_2500RPM[10] = {15.000, 14.000, 14.000, 14.000, 13.700, 13.200, 13.000, 12.700, 12.500, 12.000};
//double AFR_3000RPM[10] = {16.500, 15.500, 14.000, 14.000, 14.000, 13.200, 13.000, 12.700, 12.500, 12.000};
//double AFR_3500RPM[10] = {17.000, 16.500, 15.000, 14.000, 14.000, 13.200, 13.000, 12.700, 12.500, 12.000};
//double AFR_4000RPM[10] = {18.000, 17.500, 16.000, 15.000, 14.000, 13.200, 13.000, 12.700, 12.500, 12.000};
//double AFR_4500RPM[10] = {19.000, 18.500, 17.000, 16.000, 15.000, 13.200, 13.000, 12.700, 12.500, 12.000};
//double AFR_5000RPM[10] = {19.500, 18.500, 17.000, 16.000, 15.000, 13.200, 13.000, 12.700, 12.500, 12.000};
// Physical parameters:
const double airTempKelvin = 298;
const double airMolarMass = 28.9;
const double R_Liter_Pascal_Kelvin = 8314.0;
// ----------------- Global Variables -----------------:
unsigned long updateLastMicros = 0;
unsigned long pointsLastMicros = 0;
unsigned long pointsDiff = 100000000;
bool stalled = 0;
int serialReportCount = 0;
double RPMrunningAverage[RPMrunningAverageDepth];
int RPMrunningAverageIndex = 0;
unsigned long blinkLastMillis = 0;
bool blinkState = 0;
unsigned long lastMAP = 0;
// ----------------- Functions -----------------:
// ISR triggered when the points open:
void points()
{
//Determine if interrupt is valid based on time since last interrupt:
if((micros() - pointsLastMicros) > interruptDebounce)
{
// Compute difference in time from last points opening:
pointsDiff = micros() - pointsLastMicros;
// Reset points timer:
pointsLastMicros = micros();
}
}
// Function to obtain AFR target:
double AFR(double speedRPM, double pressurePa)
{
// Determine index of MAP pressure in AFR table to use:
int MAP_index = 0;
if(pressurePa < 10342.1)
{
MAP_index = 0;
}
else if(pressurePa < 20684.3)
{
MAP_index = 1;
}
else if(pressurePa < 31026.4)
{
MAP_index = 2;
}
else if(pressurePa < 41368.5)
{
MAP_index = 3;
}
else if(pressurePa < 51710.7)
{
MAP_index = 4;
}
else if(pressurePa < 62052.8)
{
MAP_index = 5;
}
else if(pressurePa < 72394.95)
{
MAP_index = 6;
}
else if(pressurePa < 82737.1)
{
MAP_index = 7;
}
else if(pressurePa < 93079.22)
{
MAP_index = 8;
}
else
{
MAP_index = 9;
}
// Determine RPM range to use and return relevant AFR:
if(speedRPM < 500)
{
return AFR_500RPM[MAP_index];
}
else if(speedRPM < 1000)
{
return AFR_1000RPM[MAP_index];
}
else if(speedRPM < 1500)
{
return AFR_1500RPM[MAP_index];
}
else if(speedRPM < 2000)
{
return AFR_2000RPM[MAP_index];
}
else if(speedRPM < 2500)
{
return AFR_2500RPM[MAP_index];
}
else if(speedRPM < 3000)
{
return AFR_3000RPM[MAP_index];
}
else if(speedRPM < 3500)
{
return AFR_3500RPM[MAP_index];
}
else if(speedRPM < 4000)
{
return AFR_4000RPM[MAP_index];
}
else if(speedRPM < 4500)
{
return AFR_4500RPM[MAP_index];
}
else
{
return AFR_5000RPM[MAP_index];
}
}
// Function to compute RPM based on time since last points opening:
double RPM()
{
// If pointsDiff is longer than the time since points() was last called,
// just use pointsDiff to compute the RPM:
if(pointsDiff > (micros() - pointsLastMicros))
{
// RPM = (Pulses/sec)/(Pulses/Revolution)*(60 sec/min)
RPMrunningAverage[RPMrunningAverageIndex] = (1000000.0/pointsDiff)/pulsesPerRevolution*60.0;
}
// If it has been longer than pointsDiff since points() was last called,
// use the elapsed time to compute the RPM:
else
{
// RPM = (Pulses/sec)/(Pulses/Revolution)*(60 sec/min)
RPMrunningAverage[RPMrunningAverageIndex] = (1000000.0/(micros() - pointsLastMicros))/pulsesPerRevolution*60.0;
}
//Increment running average index, reset if needed:
RPMrunningAverageIndex++;
if(RPMrunningAverageIndex >= RPMrunningAverageDepth)
{
RPMrunningAverageIndex = 0;
}
// Compute running average sum:
double sum = 0;
for(int i = 0; i < RPMrunningAverageDepth; i++)
{
sum = sum + RPMrunningAverage[i];
}
// Return running average of RPM:
return sum/RPMrunningAverageDepth;
}
// Function to measure the Manifold Absolute Pressure (MAP):
double MAP()
{
double estimatedMAP = (analogRead(MAPPin) - vacuum_ADC_value)*Pascals_Per_ADC_Unit;
// Ensure only positive MAP values are returned:
if(estimatedMAP < 0)
{
estimatedMAP = 0;
}
return estimatedMAP;
}
// Function to report human-readable stats to the serial port:
void reportStats(double RPM_report, double MAP_report, double DC_report)
{
// Report engine RPM:
Serial.print("Engine RPM: ");
Serial.println(RPM_report);
Serial.print("Manifold Absolute Pressure: ");
Serial.print("kPa: ");
Serial.print(MAP_report/1000.0);
Serial.print(" PSI: ");
Serial.println(MAP_report/6894.76);
Serial.print("Injector Duty Cycle: ");
Serial.print(DC_report*100.0);
Serial.println("%");
Serial.println(" ");
}
// Function to compute the required fuel injector duty cycle:
double getInjectorDC()
{
//Get measurements:
double RPM_value = RPM();
double MAP_value = MAP();
// Compute the volume flow rate of air (L/min) into the engine
// (Otto cycle with 2 revolutions per intake stroke assumed):
double volFlowRate = displacement_Liters*RPM_value/2.0;
// Compute the density of air (g/L) using the Ideal Gas Law (PV=nRT):
// Density = mass/volume = n(airMolarMass)/V = P(airMolarMass)/(RT)
double airDensity = MAP_value*airMolarMass/(R_Liter_Pascal_Kelvin*airTempKelvin);
// Compute the mass air flow rate into the engine:
double massAirFlow = volFlowRate*airDensity;
// Get AFR:
// Adjust the AFR based on the rate of change of the MAP level:
double vacROC = (double)MAP_value - (double)lastMAP;
lastMAP = MAP_value;
// Look up AFR in table:
double AFR_target = AFR(RPM_value,MAP_value);
// If MAP is above threshold, apply rate-of-change factor:
if(MAP_value > vacuum_ROC_Cut_In)
{
AFR_target = AFR_target - vacuum_ROC_Multiplier*vacROC;
}
// Otherwise, just use AFR from the table directly.
// Apply fuel compensator (for E51, E85, etc.)
AFR_target = fuel_comp*AFR_target;
// Compute the required mass fuel flow rate into the engine:
double massFuelFlow = massAirFlow/AFR_target;
// Compute the duty cycle for the fuel injector
// (based on the maximum fuel delivery rate):
double estimated_DC = massFuelFlow/injector_MaxGramsPerMinute;
// Ensure that the duty cycle does not exceed 1 or fall below the minimum duty cycle value:
if(estimated_DC > 1.0)
{
estimated_DC = 1.0;
}
if(estimated_DC < min_DC)
{
estimated_DC = min_DC;
}
// Report human-readable stats every serialReportModulo iterations:
if(serialReportCount < serialReportModulo)
{
serialReportCount++;
}
else
{
serialReportCount = 0;
reportStats(RPM_value, MAP_value, estimated_DC);
}
return estimated_DC;
}
// ----------------- Main Program -----------------:
void setup() {
// Set pin modes:
pinMode(injectorPin, OUTPUT);
pinMode(pointsPin, INPUT);
pinMode(LEDPin, OUTPUT);
// Attach interrupt for detecting points pulses:
attachInterrupt(digitalPinToInterrupt(pointsPin), points, RISING);
//Start Serial port:
Serial.begin(115200);
Serial.println("EFI controller based on MAP and Points ONLY");
Serial.println("(C) 2020 John Patterson Consulting, LLC");
Serial.println(" ");
//Wait for fuel pump to build pressure:
Serial.println("Waiting for fuel pump...");
delay(pumpTime);
Serial.println(" ");
// Prime engine with some fuel before starting:
Serial.println("Priming intake...");
digitalWrite(injectorPin, HIGH);
delay(primeTime);
digitalWrite(injectorPin, LOW);
Serial.println("Priming complete. Ready to crank!");
Serial.println(" ");
}
void loop() {
//Determine if the engine is currently stalled:
stalled = (RPM() < stallRPM);
// If engine is running, keep LED on and steady:
if(!stalled)
{
digitalWrite(LEDPin, HIGH);
}
// If engine is stalled, blink LED:
else if(millis() - blinkLastMillis > blinkTime)
{
blinkLastMillis = millis();
blinkState = !blinkState;
digitalWrite(LEDPin, blinkState);
}
// Pulse the injector if it is time to do so:
if((micros() - updateLastMicros) > injectorUpdateInterval)
{
// Reset injector update timer:
updateLastMicros = micros();
// Compute fuel injector duty cycle:
double computed_DC = getInjectorDC();
// Only dispense fuel if engine is running:
if(!stalled)
{
// Open injector for amount of time specified by duty cycle:
unsigned long injectorMicros = micros();
while((micros() - injectorMicros) < (unsigned long)(injectorUpdateInterval*computed_DC))
{
digitalWrite(injectorPin, HIGH);
}
//Close injector:
digitalWrite(injectorPin, LOW);
}
}
}