SI Engine Torque Structure Model
The sparkignition (SI) engine implements a simplified version of the SI engine torque structure calculation used in a Bosch Engine Management System (EMS). For the torque structure estimation calculation, the block requires calibration tables for:
Inner torque — Maximum torque potential of the engine at a given speed and load
Friction torque — Torque losses due to friction
Optimal spark — Spark advance for optimal inner torque
Spark efficiency — Torque loss due to spark retard from optimal
Lambda efficiency — Torque loss due to lambda change from optimal
Pumping torque — Torque loss due to pumping
The tables available with Powertrain Blockset™ were developed with the ModelBased Calibration Toolbox™.
Lookup Table  Used to Determine  Plot 

Inner torque, ${f}_{Tqinr}$ 
$T{q}_{inr}={f}_{Tqinr}(L,N)$ 
The inner torque lookup table, ${f}_{Tqinr}$, is a function of engine speed and engine load, $T{q}_{inr}={f}_{Tqinr}(L,N)$, where:

Friction torque, ${f}_{Tfric}$ 
$${T}_{fric}={f}_{Tfric}\left(L,N\right)$$ 
The friction torque lookup table, ${f}_{Tfric}$, is a function of engine speed and engine load, $${T}_{fric}={f}_{Tfric}\left(L,N\right)$$, where:

Pumping torque, ƒ_{Tpump} 

The pumping work lookup
table, ƒ_{Tpump}, is a function of engine load and engine
speed,

Optimal spark, ${f}_{SAopt}$ 
$S{A}_{opt}={f}_{SAopt}(L,N)$ 
The optimal spark lookup table, ${f}_{SAopt}$, is a function of engine speed and engine load, $S{A}_{opt}={f}_{SAopt}(L,N)$, where:

Spark efficiency, ${f}_{Msa}$ 
$\begin{array}{l}{M}_{sa}={f}_{Msa}(\Delta SA)\\ \Delta SA=S{A}_{opt}SA\end{array}$ 
The spark efficiency lookup table, ${f}_{Msa}$, is a function of the spark retard from optimal $\begin{array}{l}{M}_{sa}={f}_{Msa}(\Delta SA)\\ \Delta SA=S{A}_{opt}SA\end{array}$ where:

Lambda efficiency, ${f}_{M\lambda}$ 
${M}_{\lambda}={f}_{M\lambda}(\lambda )$ 
The lambda efficiency lookup table, ${f}_{M\lambda}$, is a function of lambda, ${M}_{\lambda}={f}_{M\lambda}(\lambda )$, where:

The engine brake torque is a based on inner torque with lambda efficiency, spark retard efficiency multipliers, pumping torque, and a friction torque offset
${T}_{brake}={M}_{\lambda}{M}_{sa}T{q}_{inr}{T}_{fric}{T}_{pump}$
To account for thermal effects, the torque structure model corrects the friction torque calculation as a function of coolant temperature.
$$\begin{array}{l}{T}_{fric}={M}_{fric}{f}_{Tfric}(L,N)\\ {M}_{fric}={f}_{fric,temp}({T}_{coolant})\end{array}$$
The pumping torque is a function of engine speed and engine speed.
$${T}_{pump}={f}_{Tpump}(L,N)$$
$S{A}_{opt}$ 
Optimal spark advance timing for maximum inner torque at stoichiometric airfuel ratio (AFR) 
$\Delta SA$ 
Spark retard timing distance from optimal spark advance 
$SA$ 
Spark advance timing 
$L$ 
Engine load at arbitrary cam phaser angles, corrected for final steadystate cam phaser angles 
N 
Engine speed 
${M}_{\lambda}$ 
Lambda multiplier on inner torque to account for the AFR effect 
$\lambda $ 
Lambda, AFR normalized to stoichiometric fuel AFR 
${M}_{sa}$ 
Spark retard efficiency multiplier 
${f}_{Msa}$ 
Spark efficiency lookup table to account for torque loss due to spark retard from optimal 
${f}_{Tfric}$ 
Friction torque lookup table to account for torque losses due to friction 
${f}_{M\lambda}$ 
Lambda efficiency lookup table to account for torque loss due to lambda change from optimal 
${f}_{SAopt}$ 
Optimal spark lookup table, for maximum inner torque as a function of engine speed and load 
${f}_{Tqinr}$ 
Inner torque lookup table, for maximum torque potential of the engine at a given speed and load 
${T}_{brake}$ 
Engine brake torque after accounting for spark advance, AFR, and friction effects 
${T}_{fric}$ 
Friction torque offset to inner torque 
$T{q}_{inr}$ 
Inner torque based on gross indicated mean effective pressure 
T_{pump} 
Pumping torque 
M_{fric} 
Friction torque modifier 
T_{coolant} 
Coolant temperature 
References
[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.
See Also
SI Controller  SI Core Engine