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Old Tue, Oct-30-2012, 12:14:40 PM   #136
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Default Re: Comprehensive MSS54/MSS54HP DME Information

Here's some info on some of the different DME adaptations:

Adaptations and equipment variations
The adaptation makes it possible that the engine control unit can learn certain values of components and thus compensate for certain component tolerances.
When used for the first time, the engine management system also learns equipment variations that are fitted.
The service function ”Reset adaptation values” can be used to reset the adaptation values and equipment variations to their default settings; thereafter, they have to be relearned. Longer operation between idle speed and partial load is necessary, for example, in order to learn the mixture adaptation values.
• Deleting adaptations after repairs:
In general, the adaptations should not be deleted after a repair (part replacement). On replacement of the throttle valve, the MDK adaptations are to be deleted to avoid a fault code memory entry.
• Deleting equipment variations and adaptations after a conversion or vehicle upgrades:
After a vehicle conversion, e.g. from manual to automatic gearbox, or vehicle upgrade, e.g. retrofitting a trailer module or a multifunction steering wheel, the equipment variations and adaptations must be deleted and relearned.

Examples of various adaptations

Fuel mixture adaptation
The mixture formed in the intake area requires some time before it reaches the oxygen sensor as exhaust emissions. This time decreases as load and engine speed increase. For this reason, the response time of the oxygen-sensor control system is also dependent on load and engine speed. Fuel-air mixture deviations detected by the oxygen sensor result in adaptation values (learned correction values) being stored. By way of the adaptations, the injection can be brought close to the nominal value in advance. A reduction in the response time is achieved in this way.
For example, if the basic fuel injection values of the engine control unit characteristic map are too low at idle speed to maintain the ideal fuel-air mixture, the oxygen-sensor control would have to continuously increase the fuel injection period. In this case, an adaptation value is learnt which corrects the basic injection value. The oxygen-sensor control then only needs to undertake the fine adjustment.

Idle mixture adaptation (additive)
If idling is detected in the off-load phase of the tank ventilation due to the throttle-valve position, an idling fuel mixture adaptation is made at certain intervals. As the idling and part-load fuel mixture adaptations mutually influence one another, complete adaptation requires a number of switches between idling and part-load.

Partial load mixture adaptation (multiplicative)
Also in the part-load range, a fuel mixture adaptation is carried out at regular intervals. The determined adaptation value is taken into consideration in all partial load ranges.

Tank venting adaptation
When the tank ventilation valve is open, an additional combustible mixture is supplied from the carbon canister to the engine. The shift in mixture detected by the oxygen sensor is completely corrected out by means of the tank ventilation adaptation value.

Idle speed adaptation
The idle speed adaptation is handled by the idle actuator. It uses the air volume to ensure a constant idle speed.

Sensor adaptation
Misfiring causes irregularities in the rotational speed of the crankshaft. These irregularities can be detected by way if changes in the segment time.
The crankshaft sensor continuously determines segment times (time in which a certain number of teeth of the increment gear run past the sensor). These segment times are constantly checked during engine operation. In the event of a fault, a corresponding fault code is stored in the fault code memory and the fuel injection is deactivated at the corresponding cylinder. Refer to misfiring detection.

To prevent incorrect evaluations, a sensor adaptation must be run after replacement of the DME control unit or crankshaft sensor.
If the increment gear is replaced, the sensor adaptation must be deleted both before and after replacement.
The sensor wheel adaptation determines the irregularity of the increment wheel and takes it into consideration when evaluating the segment times. The sensor adaptation is run automatically as soon as the engine is overrun for at least 10 seconds.
Explaining additive and multiplicative adaptations:
Engine Adaptation Values
Additive mixture adaptations: This adaptation is referred to as “short term fuel trim”. This value is measured in milliseconds and can occur in positive or negative values. These adaptations are made to the engine while at idle.
Excessively positive Additive values indicate a lean condition. Some common causes are:
• Unmetered air leaks, torn intake boot, leaking intake manifold gaskets
• Crankcase vent system fault, system valve stuck open
• Low fuel pressure, pressure regulator malfunction
• MAF malfunction, sending incorrect signal information
Excessively negative Additive values indicate a rich condition. Some common causes are:
• A restriction at engine intake, such as clogged air filter blocking air intake into engine
• Crankcase vent valve stuck closed or blocked
• High fuel pressure, caused by pressure regulator or restricted fuel return line
• MAF malfunction, sending incorrect signal information to ECM

Multiplicative mixture adaptation: This adaptation is referred to as “long term fuel trim”. This value is measured in percentages and can occur in the positive or negative values. This adaptation occurs during part-load driving conditions.
Excessively positive multiplicative adaptation values indicate lean condition. Some common causes are:
• MAF malfunction, incorrect signal information sent to the ECM
• Low fuel pressure, faulty fuel pump
• Unmetered air leak, such as torn intake boot, etc
• Pressure regulator malfunction
Excessively negative multiplicative adaptation values indicate rich condition. Some common causes are:
• Sensor failure that could result in erroneous information to falsely enrich mixture, such as engine coolant temperature sensor or intake air temperature sensor
• High fuel pressure, restriction in return line or fault with fuel pressure regulator
• MAF malfunction, incorrect signal information being sent to the ECM
• Restriction at air intake blocking airflow into engine, such as a clogged air filter
Hint: To determine if the MAF is sending incorrect information to the ECM, check the additive and multiplicative mixture adaptations. When the mixture adaptations are contradicting each other, this indicates that the MAF is faulty and sending incorrect signal information.

///M3 '06 Carbon Black

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- Fuel adaptations explained

- Checksum Verification

Last edited by SliM3; Tue, Oct-30-2012 at 12:17:49 PM.
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