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LH 2.4 Lambda



Lambda Overview


General behavior

During idle, cruise, and most low-load conditions the lambda sensor is used to maintain an approximately stoich (14.7) AFR. Once Fuel Load goes beyond a certain value, or other conditions are met, the ECU goes into open loop operation.

Three (or more) values direct open loop selection.
As one can see the two constants are set so high by Volvo that they do not have any influence during normal driving.

1.If load at a determined rpm is over the value in the "Lambda cutoff upper threshold" map then open loop are selected.
These values can be lowered if it is desired that the LH leaves closed loop at a lower load.

cutoff threshold



2.If rpm is higher than what is set in the universal "lambda cutoff threshold" rpm constant.

Lambda rpm const


3.If load is higher than what is set in the universal "lambda cutoff threshold" load constant.

Lambda Load const


'Learning'

During normal operation, the ECU notes the adjustment necessary for stoich operation. These adjustments are saved into a region of CPU memory that is not lost when the key is removed. Because the learned values are stored in RAM and not in ROM, the Ostrich cannot be used to change these values. The only way to erase the learned values is to briefly remove power from the ECU. About 10 seconds is necessary for the memory to reset.

Target AFR

In LH2.4, the narrowband lambda sensor's signal is further simplified electrically before it's information is delivered to the CPU. It is only possible for the CPU to know whether it is lean, rich, or stoich. There is NO way to change the target AFR for lambda in the LH Software.

However, if you have a wideband with narrowband emulation capability, you can use the narrowband output to 'fool' LH into maintaining a different AFR. The long term interaction of this and LH's learned adjustments are unknown however.

Parameters in the 950 BIN (B204FT)


The following are screenshots and details from the 950 BIN software.

Table 1

lambda_1_950.PNG
Data type: 8-bit integer
Range: 0-255
Structure: 5x5 table w/axis, RPM vs. Load
Comments: Lambda related. Unknown.

Table 2

lambda_2_950.PNG
Data type: 8-bit integer
Range: 0-255
Structure: 5x5 table w/axis, RPM vs. Load
Comments: Higher values cause the AFR to oscillate more rapidly.

Table 3

lambda_3_950.PNG
Data type: 8-bit integer
Range: 0-255
Structure: 5x5 table w/axis, RPM vs. Load
Comments: High values cause greater fueling adjustment. At 255, AFRs swing approx. 6 points. At 1, lambda responds VERY slowly.



Table 4

lambda_4_950.PNG
Data type: 8-bit integer
Range: 0-255
Structure: 5x5 table w/axis, RPM vs. Load
Comments: Higher values cause lambda to swing richer.
This table is chosen by the coding plug.
If coding plug is grounded (default Volvo on this engine) then this table will be used out of the last three.

Table 5

lambda_5_950.PNG
Data type: 8-bit integer
Range: 0-255
Structure: 5x5 table w/axis, RPM vs. Load
Comments: Appears unused.
This table is selected by the coding plug.
If coding plug is connected with an inline resistor to get the voltage at appx 3 volts then this table will be used out of the last three.
Probably an alternate lambda table used for other versions/markets.

Table 6

950 Lambda 6
Data type: 8-bit integer
Range: 0-255
Structure: 5x5 table w/axis, RPM vs. Load
Comments: Appears unused.
This table is selected by the coding plug.
If coding plug is left unconnected (floating) then this table will be used out of the last three.
Probably an alternate lambda table used for other versions/markets.


Parameters in the 937 BIN (B230FT)


The following are screenshots and details from the 937 BIN software.

Table 1

lambda_1_937.PNG
Data type: 8-bit integer
Range: 0-255
Structure: 5x5 table w/axis, RPM vs. Load
Comments: Lambda related. Unknown.

Table 2

lambda_2_937.PNG
Data type: 8-bit integer
Range: 0-255
Structure: 5x5 table w/axis, RPM vs. Load
Comments: Higher values cause the AFR to oscillate more rapidly.

Table 3

lambda_3_937.PNG
Data type: 8-bit integer
Range: 0-255
Structure: 5x5 table w/axis, RPM vs. Load
Comments: Higher values cause lambda to compensate more for a lean condition.

Table 4

lambda_4_937.PNG
Data type: 8-bit integer
Range: 0-255
Structure: 5x5 table w/axis, RPM vs. Load
Comments: Similar to Lambda #3
This table is chosen by the coding plug.
If coding plug is grounded (default Volvo on this engine) then this table will be used out of the last three.

Table 5

lambda_5_937.PNG
Data type: 8-bit integer
Range: 0-255
Structure: 5x5 table w/axis, RPM vs. Load
Comments: Appears unused.
This table is selected by the coding plug.
If coding plug is connected with an inline resistor to get the voltage at appx 3 volts then this table will be used out of the last three.
Probably an alternate lambda table used for other versions/markets.


Table 6

937 Lambda 6
Data type: 8-bit integer
Range: 0-255
Structure: 5x5 table w/axis, RPM vs. Load
Comments: Appears unused.
This table is selected by the coding plug.
If coding plug is left unconnected (floating) then this table will be used out of the last three.
Probably an alternate lambda table used for other versions/markets.



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