Sparkignition engine from intake to exhaust port
Powertrain Blockset / Propulsion / Combustion Engine Components / Core Engine
The SI Core Engine block implements a sparkignition (SI) engine from intake to exhaust port. You can use the block in larger vehicle models, hardwareintheloop (HIL) engine control design, or vehiclelevel fuel economy and performance simulations.
The SI Core Engine block calculates:
Brake torque
Fuel flow
Port gas mass flow, including exhaust gas recirculation (EGR)
Airfuel ratio (AFR)
Exhaust temperature and exhaust mass flow rate
Engineout (EO) exhaust emissions
Hydrocarbon (HC)
Carbon monoxide (CO)
Nitric oxide and nitrogen dioxide (NOx)
Carbon dioxide (CO_{2})
Particulate matter (PM)
To calculate engine air mass flow, configure the SI engine to use either of these air mass flow models.
Air Mass Flow Model  Description 

SI Engine SpeedDensity Air Mass Flow Model 
Uses the speeddensity equation to calculate the engine air mass flow, relating the engine air mass flow to the intake manifold pressure and engine speed. Consider using this air mass flow model in engines with fixed valvetrain designs. 
SI Engine DualIndependent Cam Phaser Air Mass Flow Model 
To calculate the engine air mass flow, the dualindependent cam phaser model uses:
In contrast to typical embedded air mass flow calculations based on direct air mass flow measurement with an air mass flow (MAF) sensor, this air mass flow model offers:

To calculate the brake torque, configure the SI engine to use either of these torque models.
Brake Torque Model  Description 

SI Engine Torque Structure Model 
For the structured brake torque calculation, the SI engine uses tables for the inner torque, friction torque, optimal spark, spark efficiency, and lambda efficiency. 
SI Engine Simple Torque Model 
For the simple brake torque calculation, the SI engine block uses a torque lookup table map that is a function of engine speed and load. 
To calculate the fuel flow, the SI Core Engine block uses fuel injector characteristics and fuel injector pulsewidth.
${\dot{m}}_{fuel}=\frac{N{S}_{inj}P{w}_{inj}{N}_{cyl}}{Cps\left(\frac{60s}{\mathrm{min}}\right)\left(\frac{1000mg}{g}\right)}$
To calculate the fuel economy for highfidelity models, the block uses the volumetric fuel flow.
$${Q}_{fuel}=\frac{{\dot{m}}_{fuel}}{\left(\frac{1000kg}{{m}^{3}}\right)S{g}_{fuel}}$$
The equation uses these variables.
${\dot{m}}_{fuel}$  Fuel mass flow, g/s 
$\omega $  Engine rotational speed, rad/s 
$$Cps$$  Crankshaft revolutions per power stroke, rev/stroke 
${S}_{inj}$  Fuel injector slope, mg/ms 
$P{w}_{inj}$  Fuel injector pulsewidth, ms 
${N}_{cyl}$  Number of engine cylinders 
N  Engine speed, rpm 
Sg_{fuel}  Specific gravity of fuel 
Q_{fuel}  Volumetric fuel flow 
To calculate the airfuel (AFR) ratio, the CI Core Engine and SI Core Engine blocks implement this equation.
$AFR=\frac{{\dot{m}}_{air}}{{\dot{m}}_{fuel}}$
The CI Core Engine uses this equation to calculate the relative AFR.
$\lambda =\frac{AFR}{AF{R}_{s}}$
To calculate the exhaust gas recirculation (EGR), the blocks implement this equation. The calculation expresses the EGR as a percent of the total intake port flow.
$$EG{R}_{pct}=100\frac{{\dot{m}}_{intk,b}}{{\dot{m}}_{intk}}=100{y}_{intk,b}$$
The equations use these variables.
$AFR$  Airfuel ratio 
AFR_{s}  Stoichiometric airfuel ratio 
${\dot{m}}_{intk}$  Engine air mass flow 
${\dot{m}}_{fuel}$  Fuel mass flow 
λ  Relative AFR 
y_{intk,b}  Intake burned mass fraction 
EGR_{pct}  EGR percent 
${\dot{m}}_{intk,b}$  Recirculated burned gas mass flow rate 
The block calculates the:
Exhaust gas temperature
Exhaust gasspecific enthalpy
Exhaust gas mass flow rate
Engineout (EO) exhaust emissions:
Hydrocarbon (HC)
Carbon monoxide (CO)
Nitric oxide and nitrogen dioxide (NOx)
Carbon dioxide (CO_{2})
Particulate matter (PM)
The exhaust temperature determines the specific enthalpy.
${h}_{exh}=C{p}_{exh}{T}_{exh}$
The exhaust mass flow rate is the sum of the intake port air mass flow and the fuel mass flow.
${\dot{m}}_{exh}={\dot{m}}_{intake}+{\dot{m}}_{fuel}$
To calculate the exhaust emissions, the block multiplies the emission mass fraction by the exhaust mass flow rate. To determine the emission mass fractions, the block uses lookup tables that are functions of the engine torque and speed.
$$\begin{array}{l}{y}_{exh,i}={f}_{i\_frac}({T}_{brake},N)\\ {\dot{m}}_{exh,i}={\dot{m}}_{exh}{y}_{exh,i}\end{array}$$
The fraction of air and fuel entering the intake port, injected fuel, and stoichiometric AFR determine the air mass fraction that exits the exhaust.
$${y}_{exh,air}=\mathrm{max}\left[{y}_{in,air}\frac{{\dot{m}}_{fuel}+{y}_{in,fuel}{\dot{m}}_{intake}}{{\dot{m}}_{fuel}+{\dot{m}}_{intake}}AF{R}_{s}\right]$$
If the engine is operating at the stoichiometric or fuel rich AFR, no air exits the exhaust. Unburned hydrocarbons and burned gas comprise the remainder of the exhaust gas. This equation determines the exhaust burned gas mass fraction.
$${y}_{exh,b}=\mathrm{max}\left[(1{y}_{exh,air}{y}_{exh,HC}),0\right]$$
The equations use these variables.
${T}_{exh}$  Engine exhaust temperature 
${h}_{exh}$  Exhaust manifold inletspecific enthalpy 
$C{p}_{exh}$  Exhaust gas specific heat 
${\dot{m}}_{intk}$  Intake port air mass flow rate 
${\dot{m}}_{fuel}$  Fuel mass flow rate 
$${\dot{m}}_{exh}$$  Exhaust mass flow rate 
$${y}_{in,fuel}$$  Intake fuel mass fraction 
y_{exh,i}  Exhaust mass fraction for i = CO_{2}, CO, HC, NOx, air, burned gas, and PM 
$${\dot{m}}_{exh,i}$$  Exhaust mass flow rate for i = CO_{2}, CO, HC, NOx, air, burned gas, and PM 
T_{brake}  Engine brake torque 
N  Engine speed 
y_{exh,air}  Exhaust air mass fraction 
y_{exh,b}  Exhaust air burned mass fraction 
For the power accounting, the block implements equations that depend on Torque model.
When you set Torque model to Simple Torque Lookup
, the block implements these equations.
Bus Signal  Description  Equations  



 Intake heat flow  ${\dot{m}}_{intk}{h}_{intk}$ 
PwrExhHeatFlw  Exhaust heat flow  ${\dot{m}}_{exh}{h}_{exh}$  
PwrCrkshft  Crankshaft power  ${T}_{brake}\omega $  
 PwrFuel  Fuel input power  ${\dot{m}}_{fuel}LHV$  
PwrLoss  All losses  ${T}_{brake}\omega {\dot{m}}_{fuel}LHV{\dot{m}}_{intk}{h}_{intk}+{\dot{m}}_{exh}{h}_{exh}$  
 Not used 
When you set Torque model to Torque Structure
, the block implements these equations.
Bus Signal  Description  Equations  



 Intake heat flow  ${\dot{m}}_{intk}{h}_{intk}$ 
PwrExhHeatFlw  Exhaust heat flow  ${\dot{m}}_{exh}{h}_{exh}$  
PwrCrkshft  Crankshaft power  ${T}_{brake}\omega $  
 PwrFuel  Fuel input power  ${\dot{m}}_{fuel}LHV$  
PwrFricLoss  Friction loss  ${T}_{fric}\omega $  
PwrPumpLoss  Pumping loss  ${T}_{pump}\omega $  
PwrHeatTrnsfrLoss  Heat transfer loss  ${T}_{brake}\omega {\dot{m}}_{fuel}LHV{\dot{m}}_{intk}{h}_{intk}+{\dot{m}}_{exh}{h}_{exh}+{T}_{fric}\omega +{T}_{pump}\omega $  
 Not used 
h_{exh}  Exhaust manifold inletspecific enthalpy 
h_{intk}  Intake port specific enthalpy 
${\dot{m}}_{intk}$  Intake port air mass flow rate 
${\dot{m}}_{fuel}$  Fuel mass flow rate 
$${\dot{m}}_{exh}$$  Exhaust mass flow rate 
ω  Engine speed 
T_{brake}  Brake torque 
T_{pump}  Engine pumping torque offset to inner torque 
T_{fric}  Engine friction torque 
LHV  Fuel lower heating value 
[1] Gerhardt, J., Hönninger, H., and Bischof, H., A New Approach to Functional and Software Structure for Engine Management Systems — BOSCH ME7. SAE Technical Paper 980801, 1998.
[2] Heywood, John B. Internal Combustion Engine Fundamentals. New York: McGrawHill, 1988.