1 Series E87 116i (N45) 5-door
mapped thermostat.
Knock control
The engine is equipped with a cylinder-selective adaptive knock control.
2 knock sensors detect the combustion knock (cylinders 1 and 2, cylinders 3 and 4). The sensor signals are
evaluated in the DME control unit.
If the engine is operated with combustion knock for longer periods of time, this can cause serious damage.
Knock is encouraged by:
•
Increased compression ratio
•
High cylinder fill levels
•
Inferior fuel grade (RM/MM)
•
High intake-air and engine temperature
The value of the compression ratio can also become too high due to spread due to deposits or the
manufacturing process. For engines without knock control, these unfavourable effects must be taken into
consideration when designing the ignition system by applying a safety margin to the anti-knock limit. This makes
reduced effectiveness in the upper load range unavoidable.
The knock control prevents knock. The firing point of the relevant cylinder (cylinder-selective) is set as far as
possible in the retarded direction only when a knocking risk is present. This means that the ignition control grid
can be designed around ideal consumption values (without having to take the anti-knock limit into account). A
safety margin is no longer necessary.
The knock control performs all the necessary corrections to the firing point due to knock and also makes trouble-
free driving with regular grade petrol (minimum RM 91) possible. The knock control provides:
•
Protection from damage caused by knock (also in unfavourable conditions)
•
Reduced consumption and increased torque throughout the entire upper load range (according to the
quality of fuel used)
•
High economic efficiency through optimum use of the available fuel quality and by taking the specific engine
condition into account
The knock control self-diagnosis performs the following checks:
•
Check for signal interference, e.g. breaks in wiring or defective connector
•
Self-test for evaluating circuit
•
Check of engine noise level recorded by the knock sensor
If a fault is identified during one of these checks, knock control is deactivated. An emergency program assumes
control of the ignition angle. A fault is simultaneously registered in the fault memory. The emergency program
ensures damage-free operation from RM 91 as minimum. The emergency program is dependent on the load,
engine speed and engine temperature.
Tank ventilation
The fuel evaporation control valve controls the regeneration of the activated carbon filter with scavenging air.
Scavenging air drawn through the activated carbon filter is enriched with hydrocarbons (HC) depending on the
loading of the activated carbon. The scavenging air is subsequently fed to the engine for combustion.
The formation of hydrocarbons in the fuel tank is dependent on:
•
Fuel temperature and ambient temperature
•
Air pressure
•
Fill level in the fuel tank
SBT Engine control for N45, N46 E46, E60, E81, E83, E85, E87, E90, E91, E92, E93
BMW AG - TIS
17.01.2013 06:59
Issue status (12/2007) Valid only until next DVD is issued
Copyright
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