LAMFAW 7.100 (Driver's Requested Lambda)

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See the funktionsrahmen for the following diagrams:

lamfaw-lamfaw

lamfaw-lamkr

lamfaw-lamwl

lamfaw-lamfadisable

lamfaw-lamrlmin

lamfaw-initialise


Function Description

The function LAMFAW brings about an enrichment of the fuel-air mixture via lamfa_w when the driver demands maximum torque via mrfa_w. This then corresponds to the full-load enrichment. The intervention to the mixture via lamfa_w can be delayed via the delay time TLAFA. During turbocharger overboost, an additional enrichment is applied by a delta-lambda from the characteristic DLAMOB.


For the time TLAMFAS, an enrichment via the driver’s request as a function of altitude (LAMFAS) can be prevented (see sub-function LAMFADISABLE). Triggering of this time will be initiated if B_kh = true, LAMFA <1.0 and the altitude at which the function is disabled (as defined in LAMFAS) has been reached.


In this way, a reproducible driving cycle can also be achieved at higher altitudes.

During a torque reduction, e.g. traction control intervention, engine speed limiter, etc. the enrichment via the map LAMFAW can be disabled by setting CWMFAW Bit 1 = true.


In the sub-function LAMKR, an enrichment can be implemented during ignition angle intervention.

The sub-function LAMWL can be used for the enrichment during warm-up. If this procedure is used, tank-venting via the function LAMKO is not switched off.


In the sub-function LAMRLMIN, an enrichment via LAMRLMN is active for low loads (rl). This improves the combustion efficiency at low loads. If CWLAMFAW bit 2 is set, then the emergency fuel tank breather is disabled during lamrlmn-intervention.


Application Notes

A delay time TLAFA > 0 can only be applied when the mixture intervention via lamfa_w should be delayed.


Map LAMFA:


Engine speed sample points: 1000, 1400, 1800, 2200, 2600, 3000, 3400, 3800, 4200, 4600, 5000, 5400, 5800, 6200, 6600, 7000 rpm

mrfa_w sample points: 70, 80, 90, 100, 110, 120 %

Map values of 1.0


DLAMOB comprises the delta-lambda, so that an additional mixture enrichment is implemented in overboost mode.

Sample points for engine speed: implemented as a group characteristic SNM06GKUB

Neutralization of the function by data:

LAMFA = 1.0 and DLAMOB = 0.0 ---> lamfa_w is then 1.0

The time TLAMFAS must be selected so that no large gradients are caused in the driver’s requested enrichment (typically 240 s).


The characteristic LAMFAS contains values ​​from 0 to 1. If the value is 0, enrichment via the altitude effect is active. Values ​​other than 0 deactivate enrichment via LAMFA, if B_kh = true and LAMFA values ​​are < 1.0.


The characteristic LAMFAS is not interpolated, which means that the characteristic initial value remains constant until a node is crossed.


For the fho-sample points of the characteristic LAMFAS, the following relationship applies: fho = 1 – altitude [m]/10,000 m


Since the variable fho has a quantization of 4/256 = 0.015625, this resolution must be considered when determining the switch-off. Similarly, there is a potential altitude deviation of ± 250 m because of the sensor tolerance.


For the calculation of the lower or upper threshold of fho, the following relationship applies for a nominal altitude cut-off threshold:


Lower altitude cut-off threshold:

fho [phys] = 1 – ((nominal altitude [m] – 250 m ) /10,000)

---> fho[Ink] = Integer (fho[phys]/0.015625) + 1Ink

---> fho upper limit [phys] = (1 – fho[Ink] x 0.015625)

---> Altitude upper limit = (1 – fho upper limit [phys]) x 10,000


Upper altitude cut-off threshold:

fho [phys] = 1 – ((nominal altitude [m] + 250 m)/10,000)

---> fho[Ink] = Integer (fho[phys]/0.015625)

---> fho lower limit [phys] = fho[Ink] x 0.015625

---> Altitude lower limit = (1 – fho lower limit [phys]) x 10,000


This produces the following values:

Nominal altitude

2,200 m

1,600 m

Altitude upper limit

2,500 m

1,875 m

The altitude upper limit is the fho lower limit!

fho lower limit

0.75

0.8125

Altitude lower limit

1,875 m

1,250 m

fho upper limit

0.8125

0.875


Thus, the characteristic LAMFAS is parameterized as follows for the nominal altitude of 2,200 m:


fho

0.734375

0.7500

0.8125

Value

0

1

0

Enrichment active

Enrichment inactive

Enrichment active


Switching off the altitude-dependent enrichment suppression: LAMFAS = 0, TLAMFAS = 0


Values for lambda intervention lamfawkr_w during ignition angle retardation:


ZKLAMFAW: 2 s

ZKWLAFWL: 2 s

DLAMFAW: 0.01

KFLAMKR: Engine speed sample points: Group characteristic SNM06GKUB

rl sample points: Group characteristic SRL06GKUB

Map values: All are 1.0 ---> no weighting active


KFLAMKRL: dzlamfaw sample points: Group characteristic SDZ0 6GKUB

rl sample points: Group characteristic SRL06GKUB

Map values: All are 1.0 ---> lambda intervention not active


DLAMTANS: Ambient temperature sample points: 50.25, 60, 70.5, 80.25 °C

Map values: All are 0 ---> lambda intervention not active


KFLAFWL: Engine speed sample points: Group characteristic SNM06GKUB

rl sample points: Group characteristic SRL06GKUB

Map values: All are 0 ---> lambda intervention not active

In the map, delta values are entered, –0.1 ---> lamfwl_w = 0.9!


DLAMOB: Engine speed sample points: Group characteristic SNM06GKUB

Map values: All are 0 ---> no additional enrichment during overboost

In the map, delta values are entered + 0.1 ---> lamfa = lamfaw – 0.1!


RLLAMMN: Engine speed sample points: Group characteristic SNM06GKUB

Map values: 0% ---> enrichment via LAMRLMN not active


LAMRLMN: Engine speed sample points: Group characteristic SNM06GKUB

Map values: 1.0 ---> lambda = 1.0 (no enrichment)


CWLAMFAW Bit 0: 0: dzwlamfaw = min (0, dzwwl)

1: dzwlamfaw = min (0, (dzwwl + wkrma)). Default value = 0.


CWLAMFAW Bit 1: 0: LAMFAW also during torque reduction, e.g. via traction control, engine speed limiter, etc. active

1: no enrichment via LAMFAW during torque reduction (milsol < mifa)


CWLAMFAW Bit 2: 0: B_ldeffw is always false ---> emergency fuel tank breather also during lamrlmn_w-intervention active

1: B_ldeffw dependent on lamrlmn_w-activation, when B_ldeffw = true, emergency fuel tank breather disabled, i.e. fuel tank breather valve shuts.


CWLAMFAW Bit 3: 0: Disable driver’s requested lambda activation through catalyst heating enabled

1: Disable driver’s requested lambda activation through catalyst heating not possible


CWLAMFAW Bit 4: 0: lamfwl_w dependent on B_stend and VZ1-term

1: lamfwl_w not dependent on B_stend and VZ1-term


Group characteristic for engine speed sample points: SNM06GKUB: 760, 1520, 2560, 3520, 4560, 5520 rpm

Group characteristic for relative load sample points: SRL06GKUB: 20, 40, 60, 80, 90 %

Group characteristic for engine temperature sample points: STM0 8GKUB: –15, 0, 20, 40.5, 60, 75, 85.5, 105 °C

Group characteristic for dzwlamfaw sample points: SDZ06GKUB: –30, –20, –15, –10, –5, 0 degrees

Parameter

Description

CWLAMFAW

Codeword LAMFAW

DLAMFAW

Threshold value for activating enrichment via driver’s request

DLAMOB

Delta lambda during overboost

DLAMTANS

Air temperature-dependent enrichment

GANGFAW

Gear threshold for deactivating driver’s request at altitude

KFLAFWL

Offset engine target lambda

KFLAMKR

Weighting factor for enrichment during ignition angle retardation

KFLAMKRL

Enrichment during ignition angle retardation

LAMFA

Driver’s requested lambda

LAMFAS

Disable driver’s requested lambda

LAMRLMN

Lambda control when rl < RLLAMMN to improve the combustion efficiency

RLLAMMN

Minimum requested load threshold for enrichment due to combustion efficiency

SDZ06GKUB

Sample point distribution for KFLAMKRL

SNM06GKUB

Sample point distribution for KFLAMKR, DLAMOB

SRL06GKUB

Sample point distribution for KFLAMKRL, KFLAFWL, KFLAMKR

STM08GKUB

8 engine temperature sample point distribution for KFLAFWL

SY TURBO

System constant: turbocharger

TLAFA

Delay time with driver’s requested lambda active

TLAMFAS

Delay time with driver’s requested lambda at altitude active

TMSTFWMN

Minimum engine start temperature for deactivating driver’s request at altitude

TMSTFWMX

Maximum engine start temperature for deactivating driver’s request at altitude

TNSTFWMN

Minimum time after start for deactivating driver’s request at altitude

TNSTFWMX

Maximum time after start for deactivating driver’s request at altitude

ZKLAMFAW

Time constant filtering enrichment via driver’s request

ZKWLAFWL

Time constant weighting offset engine target lambda

Variable

Description

B_KH

Condition flag: catalyst heating

B_LAMFAS

Condition flag: disable driver’s requested lambda

B_LAMFASA

Condition flag: altitude-dependent disabling time for driver’s requested lambda is required

B_LAMFASH

Condition flag: altitude-dependent disabling time for driver’s requested lambda is active

B_LDEFFW

Condition flag: defined target lambda (cylinder bank 1) via driver’s request

B_LDOB

Condition flag: overboost active

B_SAB

Condition flag: overrun fuel cut-off readiness

B_STEND

Condition flag: end of start conditions reached

DZWLAMFAW

Delta ignition angle during knock control intervention or warm-up for enrichment via lambda

DZWWL

Delta ignition angle during warm-up

FHO

Altitude correction factor

GANGI

Actual gear

LAMFAWKR_W

Driver’s requested target lambda during ignition angle retardation (knock control), WL

LAMFAWS W

Driver’s requested target lambda steady-state part

LAMFAW_W

Driver’s requested target lambda part from map LAMFA

LAMFA_W

Driver’s requested target lambda (word)

LAMFWL_W

Offset engine target lambda during warm-up

LAMRLMN_W

Target lambda control to improve the combustion efficiency at lower relative loads

MIFA_W

Indexed driver’s requested engine torque

MILSOL_W

Driver’s requested torque for cylinder charge path

MRFA_W

Relative driver’s requested torque from cruise control and throttle pedal

NMOT

Engine speed

RL

Relative cylinder charge

TANS

Ambient air temperature

TMOT

Engine temperature

TMST

Engine start temperature

TNST_W

Time after end of start conditions

WKRMA

Average value of the individual cylinder ignition angle retardation (knock control), general (in emergency mode with safety margin)

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