Lambda drivers (LAMFAW)

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:

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

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