Ardamir: Full ignition model of SIMK43

2026-09-16T17:54:46Z

Full ignition model of SIMK43

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This document describes the ignition-angle and ignition-torque model implemented in the '''Siemens SIMK43 ca663056''' calibration.

It documents how the ECU calculates its Reference and Basic ignition angles, applies operating-condition corrections, represents ignition retard as a torque-efficiency quantity, converts torque requests into ignition-angle requests, incorporates knock control, applies the minimum allowable ignition angle, and determines the final spark angle independently for each cylinder.

== Index ==

__TOC__

== General Architecture ==

SIMK43 does not use a simple strategy consisting of one main ignition map followed by a small number of corrections.

Ignition timing is integrated directly into the engine torque model.

The ECU maintains two principal ignition-angle references:

* '''Reference ignition angle'''
* '''Basic ignition angle'''

The Reference angle represents the ignition timing used by the torque model as its reference point.

The Basic angle represents the normal operating ignition-angle path.

These two paths are corrected independently before entering the torque and final-spark calculations.

The overall structure is:

<pre>
ENGINE OPERATING POINT
RPM / Load / Temperature / Lambda / VVT
|
+-----------+-----------+
| |
v v
IGA_REF map IGA_BAS map
0x15CA5 0x158ED
| |
v v
Reference corrections Basic corrections
| |
v v
IGA_REF_COR IGA_BAS_COR
| |
| +-------+-------+
| | |
| v v
| Average knock Per-cylinder
| correction knock correction
| |
| v
| Basic + Avg Knock
| |
+-------+-------+
|
v
Ignition efficiency model
|
v
Torque coordinator
|
v
Requested ignition angle
|
+-------------------+
|
Basic + cylinder knock ------------------+
|
Minimum allowable ignition -------------+
|
v
FINAL PER-CYLINDER SPARK
|
v
Final average ignition
|
v
Ignition efficiency
|
v
Torque model feedback
</pre>

The important point is that ignition timing serves two purposes simultaneously:

* It determines the actual combustion phasing of the engine.
* It acts as a fast torque-control actuator.

The ignition model therefore has to describe both the physical spark angle and the amount of torque that is expected from that spark angle.

== Ignition-Angle Conventions ==

Ignition angle is expressed in crankshaft degrees.

Throughout this document:

'''IGA'''

means ignition angle.

'''degCRK'''

means crankshaft degrees.

A more advanced spark angle is numerically further toward the advanced direction.

A retarded angle is later relative to the Reference ignition angle.

SIMK43 commonly represents ignition torque loss using a positive '''retard difference''' from the Reference angle.

The fundamental relationship is:

<pre>
IGA_DIF = IGA_REF_COR - IGA
</pre>

Therefore:

<pre>
IGA_DIF = 0 deg
</pre>

means that the current ignition angle is equal to the corrected Reference angle.

A larger positive IGA_DIF means that spark has been moved further away from Reference in the retard direction.

Conceptually:

<pre>
IGA_REF_COR
|
| 0 deg retard
v
Reference spark
|
| Increasing IGA_DIF
v
More retarded spark
|
v
Lower ignition torque efficiency
</pre>

== Engine Operating Point ==

The principal ignition maps operate primarily as functions of:

* engine speed
* cylinder air charge

Cylinder air charge is expressed in:

<pre>
mg/stk
</pre>

The load quantity is therefore the same cylinder-charge state produced by the [[SIMK43 Airflow and Load Model|SIMK43 airflow/load model]].

The basic relationship is:

<pre>
Engine speed
+
Cylinder air charge
|
v
Ignition base maps
</pre>

Additional operating conditions modify the resulting ignition angles.

These include functions related to:

* intake-air temperature
* coolant temperature
* lambda
* ambient pressure
* valve timing
* transient operation
* knock control
* exhaust temperature protection

== Reference Ignition Angle ==

The principal Reference ignition-angle map is:

'''IGA_REF'''

Address:

<pre>
0x15CA5
</pre>

It is a 16 x 12 map indexed by:

* engine speed
* cylinder air charge

Its output is:

<pre>
degCRK
</pre>

Functionally:

<pre>
IGA_REF = f(RPM, MAF_CYL)
</pre>

The Reference ignition angle is not simply another normal operating spark map.

It establishes the ignition angle that the ECU uses as the reference point for ignition-related torque calculations.

Conceptually:

<pre>
RPM
+
Cylinder load
|
v
IGA_REF
0x15CA5
|
v
Reference ignition angle
</pre>

The Reference angle represents the theoretical or reference torque-producing spark angle used by the ECU's ignition-efficiency model.

It therefore acts as the '''zero-retard reference''' for the torque calculation.

=== Reference Ignition Corrections ===

The Reference ignition path contains additional corrections that modify the base Reference map before it is used by the torque model.

Identified ca663056 calibrations include:

'''IP_IGA_REF_TEMP'''

Address:

<pre>
0x15D6D
</pre>

This provides a temperature-related correction to the Reference ignition path.

Another identified correction is:

'''IP_IGA_REF_OFS_IVVT'''

Address:

<pre>
0x1942C
</pre>

This provides a VVT-related Reference ignition offset as a function of engine speed and cylinder load.

The functional structure is therefore:

<pre>
IGA_REF
|
+---- Temperature influence
|
+---- IVVT influence
|
+---- Other operating-state corrections
|
v
IGA_REF_COR
</pre>

The corrected Reference angle becomes the zero point used by the ignition-efficiency calculations.

== Basic Ignition Angle ==

The principal Basic ignition-angle map is:

'''IGA_BAS'''

Address:

<pre>
0x158ED
</pre>

It is also a 16 x 12 map indexed by:

* engine speed
* cylinder air charge

Its output is:

<pre>
degCRK
</pre>

Functionally:

<pre>
IGA_BAS = f(RPM, MAF_CYL)
</pre>

The Basic ignition angle represents the normal operating ignition path.

Conceptually:

<pre>
RPM
+
Cylinder load
|
v
IGA_BAS
0x158ED
|
v
Basic operating ignition angle
</pre>

The Basic map does not have to be identical to the Reference map.

In many operating regions, Basic can be intentionally more retarded than Reference.

The difference between them forms part of the ECU's available ignition torque reserve.

=== Basic Ignition Corrections ===

The Basic ignition path contains a larger set of operating-condition corrections.

Identified calibrations include:

'''IP_IGA_BAS_OFS_IVVT'''

Address:

<pre>
0x193EC
</pre>

This provides a VVT-dependent offset to Basic ignition timing.

'''IP_IGA_BAS_TEMP'''

Address:

<pre>
0x15A95
</pre>

This provides a temperature-related Basic ignition correction.

'''IP_IGA_BAS_TEMP_FAC'''

Address:

<pre>
0x15AD5
</pre>

This provides an additional temperature-dependent correction factor.

'''IP_IGA_BAS_AMP_COR'''

Address:

<pre>
0x159AD
</pre>

This provides an ambient-pressure-related Basic ignition correction.

'''IP_IGA_BAS_LAMB'''

Address:

<pre>
0x159CD
</pre>

This provides an additive ignition correction associated with lambda setpoint.

The functional Basic path can therefore be represented as:

<pre>
IGA_BAS
|
+---- IVVT correction
|
+---- Temperature correction
|
+---- Ambient-pressure correction
|
+---- Lambda correction
|
+---- Transient / operating-state corrections
|
v
IGA_BAS_COR
</pre>

The resulting corrected Basic angle is the normal ignition candidate before torque intervention and per-cylinder knock correction are applied.

== Ignition Torque Reserve ==

The corrected Reference and Basic ignition angles define an important torque-control quantity.

Conceptually:

<pre>
Ignition torque reserve = IGA_REF_COR - IGA_BAS_COR
</pre>

If Basic is more retarded than Reference, the ECU has the ability to increase engine torque rapidly by advancing ignition timing toward Reference.

Example:

<pre>
IGA_REF_COR = 30 deg
IGA_BAS_COR = 24 deg

Reserve = 6 deg
</pre>

The Basic engine operating point is therefore 6 degrees behind the Reference angle.

The ECU can move toward the Reference angle without waiting for a large air-path change.

Conceptually:

<pre>
More retarded More advanced

IGA_BAS_COR -----------------------------> IGA_REF_COR
| |
Normal operating Reference torque
spark spark
| |
+------------ Torque reserve --------------+
</pre>

Ignition therefore provides a very fast torque-control mechanism.

== Knock-Control Integration ==

Knock control operates in parallel with the normal Basic ignition path.

SIMK43 maintains both:

* an average knock correction
* individual per-cylinder knock corrections

These have different roles in the ignition model.

The '''average knock correction''' is used when calculating the torque efficiency associated with the Basic ignition path.

The '''individual cylinder corrections''' are applied later when determining the actual final ignition angle of each cylinder.

The structure is therefore:

<pre>
IGA_BAS_COR
|
+-----------+-----------+
| |
v v
Average knock Per-cylinder knock
correction corrections
| |
v |
Basic torque-efficiency |
calculation |
v
Final cylinder spark
</pre>

This separation allows the torque model to account for the overall torque loss caused by knock retard while still applying the necessary protection independently to each cylinder.

=== Basic Ignition Angle with Average Knock ===

For the torque model, the corrected Basic angle is combined with the average knock correction.

Conceptually:

<pre>
IGA_BAS_KNK = IGA_BAS_COR + IGA_KNK_AVG
</pre>

A knock correction in the retard direction moves the effective Basic angle later.

The ECU then calculates the retard difference between Reference and the knock-corrected Basic angle:

<pre>
IGA_DIF_BAS = IGA_REF_COR - IGA_BAS_KNK
</pre>

Negative retard differences are not physically required for the normal efficiency calculation, so the effective difference is constrained to the valid retard region.

Conceptually:

<pre>
IGA_DIF_BAS =
max(
IGA_REF_COR - IGA_BAS_KNK,
0
)
</pre>

This difference is then converted into Basic ignition torque efficiency.

== Ignition Efficiency Model ==

SIMK43 represents the effect of spark retard on torque using an ignition-efficiency model.

The principal calibration is:

'''IPM_EFF_IGA'''

Address:

<pre>
0x14FD4
</pre>

Definition:

<pre>
EFF_IGA = f(IGA_DIF)
</pre>

where:

'''IGA_DIF'''

is spark retard relative to corrected Reference ignition.

The fundamental calculation is:

<pre>
IGA_DIF = IGA_REF_COR - IGA
</pre>

followed by:

<pre>
EFF_IGA = IPM_EFF_IGA(IGA_DIF)
</pre>

Conceptually:

<pre>
Current ignition angle
|
v
Reference - Current
|
v
Ignition retard
[degCRK]
|
v
IPM_EFF_IGA
0x14FD4
|
v
Ignition torque efficiency
</pre>

When:

<pre>
IGA = IGA_REF_COR
</pre>

then:

<pre>
IGA_DIF = 0
</pre>

and ignition efficiency is approximately unity.

As ignition is retarded further from Reference, ignition efficiency decreases.

=== Meaning of Ignition Efficiency ===

Ignition efficiency represents the fraction of Reference torque that the ECU expects to remain after ignition retard.

Conceptually:

<pre>
EFF_IGA = 1.0
</pre>

means approximately full Reference ignition torque.

A lower value means the ECU expects less torque because combustion has been deliberately phased later.

For example, conceptually:

<pre>
Reference spark
IGA_DIF = 0
EFF_IGA approximately 1.0

|
v

Small retard
IGA_DIF increases
EFF_IGA decreases

|
v

Large retard
IGA_DIF increases further
EFF_IGA decreases further
</pre>

The efficiency model therefore converts an ignition-angle difference into a torque-domain quantity.

=== Basic Ignition Torque Efficiency ===

The Basic ignition path is converted into a torque-efficiency value using the average knock-corrected Basic angle.

The functional sequence is:

<pre>
IGA_BAS_COR
|
v
Add average knock correction
|
v
IGA_BAS_KNK
|
v
IGA_REF_COR - IGA_BAS_KNK
|
v
IGA_DIF_BAS
|
v
IPM_EFF_IGA
0x14FD4
|
v
EFF_IGA_BAS
</pre>

Mathematically:

<pre>
IGA_BAS_KNK = IGA_BAS_COR + IGA_KNK_AVG
</pre>

<pre>
IGA_DIF_BAS =
max(
IGA_REF_COR - IGA_BAS_KNK,
0
)
</pre>

<pre>
EFF_IGA_BAS = IPM_EFF_IGA(IGA_DIF_BAS)
</pre>

This means knock retard is fed back into the torque model.

If knock control retards ignition, the ECU does not continue assuming that the engine is producing the same torque.

The reduced spark efficiency is reflected in the calculated torque state.

=== Torque Coordinator and Requested Ignition Efficiency ===

The torque coordinator does not have to request a particular spark angle directly.

Instead, it can express the required ignition intervention as a requested ignition efficiency.

Conceptually:

<pre>
Requested engine torque
|
v
Torque coordination
|
v
Requested ignition efficiency
|
v
EFF_IGA_SP
</pre>

A requested efficiency near unity requires ignition close to the Reference angle.

A lower requested efficiency requires additional spark retard.

This creates a clean relationship between the torque-control system and the ignition system:

<pre>
Torque request
|
v
Required torque fraction
|
v
Requested ignition efficiency
|
v
Required spark retard
</pre>

=== Inverse Ignition-Efficiency Model ===

The ECU contains an inverse calibration that converts requested ignition efficiency back into the spark retard required to produce that efficiency.

The calibration is:

'''IP_IGA_DIF_SP'''

Address:

<pre>
0x15BED
</pre>

Its functional relationship is:

<pre>
IGA_DIF_TQ_REQ = IP_IGA_DIF_SP(EFF_IGA_SP)
</pre>

The structure is:

<pre>
Requested ignition efficiency
|
v
IP_IGA_DIF_SP
0x15BED
|
v
Required retard from Reference
|
v
IGA_DIF_TQ_REQ
</pre>

This is effectively the inverse of the forward ignition-efficiency model.

Forward:

<pre>
Ignition retard
|
v
IPM_EFF_IGA
|
v
Ignition efficiency
</pre>

Inverse:

<pre>
Requested ignition efficiency
|
v
IP_IGA_DIF_SP
|
v
Required ignition retard
</pre>

== Torque-Requested Ignition Angle ==

Once the required retard from Reference has been calculated, the ECU converts it back into an absolute ignition angle.

The relationship is:

<pre>
IGA_TQ_REQ = IGA_REF_COR - IGA_DIF_TQ_REQ
</pre>

The complete torque-request path therefore becomes:

<pre>
Torque request
|
v
Requested ignition efficiency
|
v
IP_IGA_DIF_SP
0x15BED
|
v
Required retard from Reference
|
v
IGA_REF_COR - retard
|
v
IGA_TQ_REQ
</pre>

This ignition angle represents the spark timing required by the torque coordinator.

=== Relationship Between Basic and Torque-Requested Spark ===

At this stage the ECU has at least two important ignition candidates.

The first is the normal operating path:

<pre>
IGA_BAS_COR
+ cylinder knock correction
+ additional cylinder-specific corrections
</pre>

The second is the torque-control path:

<pre>
IGA_TQ_REQ
</pre>

The torque coordinator must be able to reduce torque relative to the Basic path.

Therefore, under normal torque-reduction operation, the more retarded of the two candidates is selected.

Conceptually:

<pre>
Basic / knock candidate -----+
|
v
Select later
spark angle
^
|
Torque-request candidate ----+
</pre>

This allows torque intervention to retard spark below the normal Basic ignition request.

If no additional torque reduction is required, the Basic path remains dominant.

=== Ignition Torque Feedback Loop ===

The complete ignition-torque relationship therefore forms a closed loop.

The forward physical model is:

<pre>
Actual spark retard
|
v
IPM_EFF_IGA
|
v
Actual ignition efficiency
|
v
Calculated engine torque
</pre>

The inverse control model is:

<pre>
Requested torque
|
v
Requested ignition efficiency
|
v
IP_IGA_DIF_SP
|
v
Required spark retard
|
v
Requested ignition angle
</pre>

The final spark calculation then determines what angle is actually used.

That result is converted back into ignition efficiency and returned to the torque model.

Conceptually:

<pre>
Torque request
|
v
Requested efficiency
|
v
Required retard
|
v
Requested spark
|
v
Final arbitration
|
v
Actual spark
|
v
Actual efficiency
|
v
Torque model
</pre>

Ignition timing is therefore both an actuator and a feedback quantity within the torque-control system.

== Minimum Ignition Angle ==

SIMK43 also calculates a minimum permissible ignition angle.

The main ca663056 calibration involved in this path is:

'''Base Minimum Ignition Angle Difference'''

Address:

<pre>
0x15B1D
</pre>

It is a 16 x 12 map indexed by:

* engine speed
* cylinder air charge

This calibration participates in the calculation of the minimum ignition-angle limit.

The XDF identifies it as a '''minimum ignition angle difference''' rather than simply a direct final spark-angle table.

The disassembly shows that this map is processed through additional scaling and correction logic before the final minimum ignition angle is obtained.

The functional path is therefore better represented as:

<pre>
RPM
+
Cylinder load
|
v
Minimum-angle base map
0x15B1D
|
v
Scaling / corrections
|
v
Minimum allowable ignition angle
IGA_MIN
</pre>

The minimum-angle system prevents normal torque-control retard from moving spark beyond the allowed combustion-stability or protection boundary.

=== Minimum-Angle Temperature Protection ===

The minimum-angle system also contains an exhaust-temperature-related calibration:

'''IP_IGA_DIF_MIN_TEG'''

Address:

<pre>
0x15BDD
</pre>

This calibration modifies the permitted minimum ignition behaviour according to dynamic exhaust-gas temperature.

Functionally:

<pre>
Dynamic exhaust temperature
|
v
IP_IGA_DIF_MIN_TEG
0x15BDD
|
v
Minimum-angle correction
</pre>

The minimum ignition angle is therefore not simply a fixed RPM/load boundary.

It can be modified by engine thermal conditions and other operating-state corrections.

=== Interaction Between Minimum Angle and Knock Control ===

The normal minimum-angle limiter prevents torque control from requesting excessive retard.

Knock control, however, has a different priority.

If additional retard is required to protect an individual cylinder from knock, the normal torque-control minimum-angle restriction must not prevent the required protective retard.

The logic therefore distinguishes between:

* retard requested for torque control
* retard required for knock protection

Conceptually:

<pre>
Torque-control retard
|
v
Limited by normal IGA_MIN

Knock-required retard
|
v
Special protection authority
|
v
Can override normal retard restriction
</pre>

This prevents the torque-control minimum-angle system from interfering with knock protection.

== Per-Cylinder Ignition Path ==

Final spark timing is calculated individually for each cylinder.

Each cylinder receives its own knock correction.

Conceptually:

<pre>
IGA_BAS_COR
|
+--------------+--------------+
| | |
v v v
Cylinder 1 Cylinder 2 ...
knock correction knock correction
| |
v v
Basic + knock Basic + knock
candidate candidate
</pre>

The torque-request angle is common to the torque-control system, while knock correction can differ from cylinder to cylinder.

The final arbitration is therefore repeated independently for all four cylinders.

== Final Ignition Arbitration ==

The normal final per-cylinder ignition logic can be represented approximately as:

<pre>
IGA_FINAL_CYL =
max(
IGA_MIN,
min(
IGA_TQ_REQ,
IGA_BAS_COR
+ IGA_KNK_CYL
+ other cylinder corrections
)
)
</pre>

The inner selection:

<pre>
min(
IGA_TQ_REQ,
Basic + Knock
)
</pre>

selects the more retarded of the normal Basic/knock path and the torque-request path.

The outer selection:

<pre>
max(
IGA_MIN,
selected angle
)
</pre>

prevents the normal torque-control result from moving beyond the minimum allowable ignition angle.

The functional sequence is:

<pre>
Basic + cylinder knock
|
+----------------+
|
v
Torque-request angle -> Select more retarded angle
|
v
Apply minimum-angle limit
|
v
Final cylinder ignition
</pre>

Knock-protection authority modifies this normal limitation when additional knock retard is required.

=== Final Spark for Each Cylinder ===

The final result of the arbitration is four independent ignition angles:

<pre>
IGA_FINAL_CYL1

IGA_FINAL_CYL2

IGA_FINAL_CYL3

IGA_FINAL_CYL4
</pre>

These represent the actual spark-angle commands after:

* Basic ignition calculation
* Reference-based torque control
* knock correction
* minimum-angle limitation
* cylinder-specific corrections

The structure is:

<pre>
Final arbitration
|
+----------------+----------------+
| | |
v v v
Cylinder 1 Cylinder 2 Cylinder 3
final IGA final IGA final IGA
|
+---- Cylinder 4
final IGA
</pre>

=== Final Average Ignition Angle ===

The four final cylinder ignition angles are also combined into an average final ignition angle.

Conceptually:

<pre>
IGA_FINAL_CYL1
+
IGA_FINAL_CYL2
+
IGA_FINAL_CYL3
+
IGA_FINAL_CYL4
|
v
Average
|
v
IGA_FINAL_AVG
</pre>

The average angle is required because the torque model describes the overall engine rather than one individual cylinder.

=== Final Ignition Efficiency ===

Once the final average ignition angle is known, the ECU calculates ignition efficiency again.

First:

<pre>
IGA_DIF_FINAL = IGA_REF_COR - IGA_FINAL_AVG
</pre>

Then:

<pre>
EFF_IGA_FINAL = IPM_EFF_IGA(IGA_DIF_FINAL)
</pre>

The complete feedback path is:

<pre>
Final cylinder ignition angles
|
v
Average final ignition
|
v
IGA_REF_COR - IGA_FINAL_AVG
|
v
Final ignition retard
|
v
IPM_EFF_IGA
0x14FD4
|
v
Final ignition efficiency
|
v
Torque model feedback
</pre>

This is an important part of the SIMK43 torque architecture.

The torque model does not only calculate what ignition timing should be commanded.

It also recalculates the torque effect of the spark angle that actually survived final arbitration.

=== Final Spark Output and Event Scheduling ===

After the final spark angle has been calculated for each cylinder, the result is transferred to the low-level ignition event scheduler.

The ca663056 disassembly traces the ignition path all the way from the high-level ignition calculations to the crank-synchronous spark scheduling mechanism.

Functionally:

<pre>
Final per-cylinder ignition angle
|
v
Ignition output conversion
|
v
Crank-synchronous scheduler
|
v
Physical ignition event
</pre>

The scheduler converts the requested crankshaft angle into the timing required for the actual ignition event.

This is the final stage between the torque/ignition model and the ignition hardware.

== Complete Functional Sequence ==

The complete ignition path can be represented as:

<pre>
ENGINE OPERATING POINT
RPM / Load / Temp / Lambda / VVT
|
+-----------+-----------+
| |
v v
IGA_REF IGA_BAS
0x15CA5 0x158ED
| |
v v
Reference corrections Basic corrections
| |
v v
IGA_REF_COR IGA_BAS_COR
| |
| Average knock
| |
| v
| Basic + Avg Knock
| |
| v
| REF - BASIC
| |
| v
| IPM_EFF_IGA
| 0x14FD4
| |
| v
| EFF_IGA_BAS
|
|
TORQUE COORDINATOR
|
v
Torque request
|
v
EFF_IGA_SP
|
v
IP_IGA_DIF_SP
0x15BED
|
v
IGA_DIF_TQ_REQ
|
v
IGA_REF_COR - IGA_DIF_TQ_REQ
|
v
IGA_TQ_REQ
|
+--------------------------+
|
v
Basic + per-cylinder knock ------------ Final arbitration
^
|
Minimum ignition angle ---------------------+
|
v
Final cylinder ignition
|
v
Average final ignition
|
v
IGA_REF_COR - IGA_FINAL_AVG
|
v
IPM_EFF_IGA
0x14FD4
|
v
EFF_IGA_FINAL
|
v
Torque model feedback
|
v
Crank-synchronous scheduler
</pre>

== Complete Mathematical Model ==

=== Corrected Reference Angle ===

<pre>
IGA_REF_COR = IGA_REF + Reference corrections
</pre>

=== Corrected Basic Angle ===

<pre>
IGA_BAS_COR = IGA_BAS + Basic corrections
</pre>

=== Ignition Torque Reserve ===

<pre>
IGA_RESERVE = IGA_REF_COR - IGA_BAS_COR
</pre>

=== Basic Angle Including Average Knock ===

<pre>
IGA_BAS_KNK = IGA_BAS_COR + IGA_KNK_AVG
</pre>

=== Basic Retard from Reference ===

<pre>
IGA_DIF_BAS =
max(
IGA_REF_COR - IGA_BAS_KNK,
0
)
</pre>

=== Basic Ignition Efficiency ===

<pre>
EFF_IGA_BAS = IPM_EFF_IGA(IGA_DIF_BAS)
</pre>

=== Torque-Requested Retard ===

<pre>
IGA_DIF_TQ_REQ = IP_IGA_DIF_SP(EFF_IGA_SP)
</pre>

=== Torque-Requested Ignition Angle ===

<pre>
IGA_TQ_REQ = IGA_REF_COR - IGA_DIF_TQ_REQ
</pre>

=== Normal Final Per-Cylinder Spark ===

<pre>
IGA_FINAL_CYL =
max(
IGA_MIN,
min(
IGA_TQ_REQ,
IGA_BAS_COR
+ IGA_KNK_CYL
+ cylinder corrections
)
)
</pre>

Knock-protection logic can modify the normal minimum-angle restriction when further protective retard is required.

=== Final Average Ignition Angle ===

<pre>
IGA_FINAL_AVG =
Average(
IGA_FINAL_CYL1,
IGA_FINAL_CYL2,
IGA_FINAL_CYL3,
IGA_FINAL_CYL4
)
</pre>

=== Final Retard from Reference ===

<pre>
IGA_DIF_FINAL = IGA_REF_COR - IGA_FINAL_AVG
</pre>

=== Final Ignition Efficiency ===

<pre>
EFF_IGA_FINAL = IPM_EFF_IGA(IGA_DIF_FINAL)
</pre>

== Functional Interpretation ==

The SIMK43 ignition system can be divided into five principal functional layers.

'''1. Reference Spark Model'''

The ECU calculates the corrected Reference ignition angle representing the zero-retard point used by the ignition torque model.

'''2. Basic Spark Model'''

The ECU calculates the corrected Basic ignition angle representing the normal operating spark path.

'''3. Ignition Torque Model'''

The difference between Reference and actual spark is converted into ignition torque efficiency.

'''4. Torque Intervention'''

Requested torque is converted into requested ignition efficiency, then into required spark retard and finally into a requested ignition angle.

'''5. Final Spark Arbitration'''

Torque-request spark, Basic spark, knock correction and minimum-angle protection are combined separately for each cylinder before the final ignition event is scheduled.

Ignition timing is therefore simultaneously a combustion parameter, a knock-control mechanism, and one of the ECU's fastest torque-control actuators.

← Older revision		Revision as of 07:49, 17 September 2026
Line 1,459:		Line 1,459:

	Ignition timing is therefore simultaneously a combustion parameter, a knock-control mechanism, and one of the ECU's fastest torque-control actuators.		Ignition timing is therefore simultaneously a combustion parameter, a knock-control mechanism, and one of the ECU's fastest torque-control actuators.

			__INDEX__
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			[[Category:Siemens L4 2.0L]]
			[[Category:Documentation]]

SIMK43 Ignition Strategy - Revision history

Ardamir: Added new category

Ardamir: Full ignition model of SIMK43