Formulas and Calculations

CONVERSIONS FACTORS

• Fuel Demand % to Lambda = 1 / (1 + (x * 0.01))
• lambda to Fuel Demand % = ((1/x) - 1)*100

PHYSICAL DIMENSIONS

• Engine Displacement (cc)

BASE SENSORS

• IAT (˚C)
• ECT (˚C)
• BARO (kPa)
• MAP (kPa)
• MAF (g/s)
• CKP (rpm)
• VCT

CALCULATED INPUTS

• RPM = 120,000,000 / CKP Delta

AIR DENSITY

• Air Density (g/cc) = (353 * BARO) / (101320 * (((ECT - IAT) * 0.1992 + IAT) + 273))

LOAD

• Load Base (% cylinder fill) = (120 * MAF) / (engine displacement * air density * RPM)
• Load Scaling = corrects load base for VE changes (includes VCT)
• Load Limit = maximum cylinder efficiency across rpm range
• Load A = min (load base * load scaling, load limit)
• Load B = min (load base with idle correction * load scaling, load limit)
• Load Corrected = air density * load A / 0.0012
• Load Corrected w/ Idle (Absolute) = air density * load B / 0.0012

MAF CORRECTED

• MAF corrected = (load B * engine displacement * air density * RPM) / 120
  • used for MAF breakpoints
  • used for STFT coefficients
  • determines transition to CL delay
  • impacts fuel scaling due to control module fault
  • impacts throttle compensation (the one that closes throttle slightly at WOT)
  • impacts R02S correction

INJECTOR PULSE WIDTH

• IPW = Base IPW * MAP Scaling (%) * Load_Fuel (%) * Fuel Demand Change (%) * Global Constant (%)
  • Base IPW = calculated injector pulse width required to maintain stoich AFR
  • MAP Scaling = scaling required to maintain stoich AFR across manifold pressures
  • Global Constant = 1.065 (2L), 1.079 (1.8L), still trying to understand if it serves any function outside of being a global scaler.
  • Fuel Demand Change (%) = all fuel request that demand IPW outside base (stoich)

FUEL CLOSED LOOP

• CL Fuel Demand = (100 / (EqRatioDsd + P0133 Monitor Add + STFT) - 100) + Trans to CL Comp
  • EQ RATIO DESIRED = (CL Target + ((100 / (RO2S Based Trims + 100)) - 1) + ((100 / (P0421 Warm-Up Cat Monitor / 2) + 100) -1)
    • RO2S Based Trims
      • Decel Recovery Comp
      • P0133/P0421 Monitor
      • Rear O2S Trim
      • P0140 Rear O2S No Activity Monitor