Overview
This document contains information on:
General
Function requirements
Function
General
The ignition system initiates the ignition of the fuel/air mixture in spark-ignition engines through a high-voltage ignition spark. With this, it contributes substantially to the generation of the specific engine output and influences the combustion emissions as well as engine torque and the exhaust gas temperature.
Function requirements
Engine management ON (circuit 87M)
Engine configuration and ignition firing order |
1 | Cylinder 1 |
2 | Cylinder 2 |
3 | Cylinder 3 |
4 | Cylinder 4 |
P07.10-2041-71
Function
Single spark ignition
Ignition coils are charged once per ignition process and an ignition spark is generated. Single-spark ignition is characterized by a long charging time for the ignition coils.
Multi-spark ignition
To ignite the fuel/air mixture optimally, even under critical conditions (e.g. high flow rates), the multi-spark ignition is used.
After the compression of the fuel/air mixture and supercharging by the respective ignition coil, a spark plug generates up to four ignition sparks at distances defined at time intervals for multi-spark ignition. As a result, efficient combustion of the fuel/air mixture is achieved, the fuel consumption is reduced correspondingly and an optimized output of the combustion engine is generated. Between the ignition sparks, the ignition coils do not discharge completely. When the charging current is interrupted at the firing point, an ignition spark is produced. In order to reduce the charging time until the next spark, energy is stored for the next ignition spark through intermediate charging.
Ideal development of the primary and secondary current for a multi-spark ignition |
A | Dwell time |
B | Spark duration |
C | Recharging threshold |
D | Discharging threshold |
E | Ignition timing |
V | Supply voltage |
i1 | Primary current |
i2 | Secondary current |
P15.10-2401-76
Function schematics | |||
Function schematic for ignition system | Engine 282 in model 118, 177, 247 | ||
Engine 260 in model 118, 177, 247Engine 264 in model 167 | |||
Engine 254, 264 in model 213, 238, 257 as of model year 2021Engine 256 in model 167Engine 256 in model 213, 238 as of model year 2021 | |||
Engine 176, 177 in model 167 | |||
Engine 139 in model 118, 177 | |||
Additional basic functions | |||
Ignition angle setting, basic function | Engine 139, 176, 177, 254, 256, 260, 264, 282 | ||
Components | |||
Ignition coils, basic function | Engine 139, 176, 177, 254, 256, 260, 264, 282 |