SLS 88.150 (Secondary Air Control)

From Nefmoto

Jump to: navigation, search

SLS88.150 Function Description

See the funktionsrahmen for the following diagrams:

sls-sls: Function overview

slson: Conditions for switching on secondary air

slsoff: Conditions for switching off secondary air

sls-slp: Conditions for setting the bits of SLP

sls-bmsl: Calculating the secondary air mass

sls-dichte: Calculating the air density correction factor for the secondary air mass

sls-bslpdyn: Description of the dynamic of the secondary air pump

sls-bslsoff: Description of the secondary air dynamic in the exhaust system

sls-bfmlssl: Calculation of enrichment due to secondary air

sls-bkt: Secondary air adaption/short journey

sls-e-slpe E_SLPE: error flag secondary air pump

sls-e-slve E_SLVE: error flag secondary air valve

sls-e-slpanst: Evaluation of the SLP-output stage

sls-slvanst: Evaluation of the SLV-output stage

sls-z-sls: Cycle flag: secondary air control (cylinder bank 1)

sls-z-sls2: Cycle flag: secondary air control (cylinder bank 2)

sls-init: Initialisation

sls-swoff: ECU delay


Function Description

Secondary air control is coordinated by the sub-function BBKHZ in overview module AK 1.10 and consists of the following sub-functions:


Switching Conditions:

The secondary air system is activated (i.e. B_SLS, B_SLV and B_SLP are all equal to 1) when B_kh = 1 and the imlpr-threshold IMLSLMN is crossed when the engine start temperature TMST lies in the window TMSSLU<tmst<TMSSLO and the intake air temperature tans is in the window TASLU<tans<TASLO. This allows the temperature range for switching on the secondary air system with respect to catalyst heating to be restricted, for example, secondary air pumps overheating or switching on to avoid a frozen secondary air system.


By setting bit 0 of the code word CWSLS, secondary air can already be enabled at start in the restricted temperature window TMSSLSTU<tmst<TMSSLST, for example in designs with thermal reactor, the self-ignition already ensured at engine start. However, the pre-condition is that this is voltage-slope compatible, i.e. the battery voltage is greater than UBSLSTMN.


Alternatively, by setting bit 1, the secondary air system can only be activated if the speed threshold VSLS is exceeded. This is common in secondary air designs in which the exothermic reaction is first ignited in the catalytic converter. Control of the secondary air pump relay is achieved by B_slp = 1 with the minimum holding time TSLPMN to prevent opening of the relay during pump starting current. Opening of the secondary air valve (B_slv = 1) can be delayed with respect to the pump by the time TVSLON. The secondary air valve is opened when B_sls = 1. For diagnostic purposes, the secondary air pump and the secondary air valve can be controlled additionally with the flags B_dspe, B_dslfa and B_dslp4.


In twin ECU designs, the secondary air valves or secondary air pumps are activated when it is detected by one of the two ECUs that conditions B_slp or B_slv are met. The two bits B_slp and B_sls are then fed to each ECU over the CAN bus to ensure that the desired effects are initiated on both sides of the same arrangement.


Switch-off/termination Conditions

The secondary air is terminated

· When the threshold IMLSLMX is crossed (B_slpoff = 1)

· Via a debounce time TSLABB after the end of start conditions (B_stend = 1)

· When the maximum air mass threshold MLSLMX is crossed

· When the pressure difference DPSLV is too low to keep the vacuum-actuated secondary air valve open

· When the battery voltage is too low (UBSLMN)

· When there are output stage errors E_slpe, E_slve, or

· When the catalyst-heating termination condition is met (B_khab = 1).


The secondary air is not activated in the first place if:

· the output stage error has already been switched on

· A high electrical system voltage is detected (as UBSLMX) from a boost-start, a twin battery system or battery emergency power.


After switching off the secondary air pump, the secondary air valve can be closed after the time delay TVSLOFF. This is possibly required for engine designs in which the secondary air effects an improvement in fuel atomization in the combustion chamber. Closing the secondary air valve later can dampen the load-diminishing effect due to run-down of the secondary air pump. Caution: For designs with a valve check function for the secondary air diagnosis, a delayed switch-off of the secondary air valve is not acceptable, since the pump must work against the closed secondary air valve. After the power is switched off, the function to reinitialize secondary-air (C_ini) is blocked.


Description of the Secondary Air Mass

The secondary air mass msl is dependent on the electrical system voltage which is predetermined by the characteristic MSLUB and is corrected depending on the operating point from the map KFFMSML and the ambient air density (characteristic FMSRHOL). When the engine is hot, especially during adaptations- additional diagnostic phase, the secondary air mass can still be corrected depending on tmot by the characteristic FMSTMOT. The pump will run up and down described by the dynamic factor fslpdyn.


In twin cylinder bank designs (SY_STERVK) as well as twin-ECU designs (SY_2SG) with an exhaust bank per ECU (not SY_STERVK) and a single SLP (SY_SLPANZ = 1) and one exhaust bank each, the secondary air system can be split in half and corrected on a bank-specific basis (FMSL, -2).


With bit 6 from the code word CWSLS (= B_slsadap), a secondary air adaptation factor fmsla(2) can be included as determined from the secondary air diagnosis. Finally, the secondary air dilution factor flamsl is calculated for the mixture control from the secondary air mass msl. After opening or closing the secondary air-valve, the dynamics of the secondary air flow into the exhaust are described by factor fmsldyn with the time constants ZKSLON and ZKSLOFF, after the air masses IMLSLSA, IMLSLSE were incorporated. The secondary air wash after closing the valve is indicated by B_slsoff.


Calculation of Enrichment due to Secondary Air

Bit 3 of the code word CWSLS determines whether there is lambda-engine set point during secondary air injection via map KFLMSKH from function LAKH (flmssl = 0) or whether there is lambda-exhaust set-point, including secondary air via map KFLASKH from function LAKH (flmssl = 1) from an automatic calculation of the required lambda-engine ​​with consideration of the secondary air dilution factor flamsl. Designs with lambda-exhaust set point can also be dependent on bit 4 realized after leaving the debounced idle or inputting the driving phase (bit 5) of the transition to lambda-engine through a filter with time constants ZFLMSSL. Via bit 2 of the codeword CWSLS, one can select whether with transition from B_slsoff or B_sls flmssl from the PT1-filter output is switched hard to 0.


Secondary Air Adaption/Short Journey

The secondary air adaption via B_dslfa is requested from the secondary air diagnosis and switches on the secondary air for the time TDDSLA (B_sldsl4). It occurs in conjunction with the specification for lambda catalyst-heating then the secondary air mass adaptation or diagnosis in diagnostic phases 4, 5 (see also the description of the secondary air diagnosis in DSLSLR or DLSLRS).


The short journey is requested via B_fa and B_fasls when tmot > TMFASLMN and secondary air is activated for the time TDSLKT (B_slkt) when indicated by B_dslfa from module DSLSLR(S) via the diagnostics readiness. If catalyst heating is active, it remains so for the short test until the time TFALAMN and after that is disabled (since passive diagnostics are already running). Additionally, idle speed and torque reserve can be specified to set a diagnostics-capable engine operating point. This is especially necessary in conjunction with the diagnostic function DSLSLR for the two-point lambda control, by holding the engine under lambda = 1-control while the secondary air is not to operate at the rich limit.


It can be determined via CWFASL bit 2 whether the repeated incentives of short trips in a driving cycle is possible.


Application Notes

Suggested initial programming

Overview of the coding variants of code word CWSLS:

Bit 0 = 0: secondary air with B_kh

Bit 0 = 1: secondary air at start already in engine temperature window

Bit 1 = 0: secondary air with B_kh

Bit 1 = 1: no secondary air until vehicle speed >= VSLS threshold

Bit 2 = 0: select lambda-engine with B_sls TRUE.

Bit 2 = 1: select lambda-engine with B_slsoff TRUE

Bit 3 = 0: select lambda-engine

Bit 3 = 1: select lambda-exhaust (= secondary air enrichment)

Bit 4 = 0: lambda-set point the same as idle/part-load.

Bit 4 = 1: transition to lambda-engine in part load

Bit 5 = 0: lambda-set point the same as o/m drive.

Bit 5 = 1: transition to lambda-engine with driving phase

Bit 6 = 0. without secondary air adaptation

Bit 6 = 1: with secondary air adaptation

Bit 7 = 0: KFLASKH-set point with B_atmtpl (B_atmtpl enable secondary air enrichment)

Bit 7 = 1: KFLASKH-set point without B_atmtpl, B_atmtpl is meaningless. (WARNING: only set for application phase!)


Secondary Air Concept with Thermal Reaction in the Exhaust Manifold

CWSLS.0 = true. Secondary air already in the start in FTP-tmst region for quick start of post-reaction, Attention: On-board system load!

CWSLS.3 = true. Lambda exhaust set point --> automatic calculation of lambda-engine from secondary air dilution flamsl_w

CWSLS.4 = true. Transition to lambda-engine when leaving idle, because post-reaction stops anyway

CWSLS.5 = true. Transition to lambda-engine when loading the driving phase, because post-reaction stops anyway

CWSLS.6 = false. No secondary air adaptation

CWSLS.7 = false. KFLASKH set point only when B_atmtpl = true


Secondary Air Design with Further Reaction in the Catalyst

CWSLS.0 = false: no secondary air in the start

CWSLS.1 = true/false depending on the start of partial light-offs in the catalyst (cat-position)

CWSLS.3 = false: lambda engine set point during secondary air injection

CWSLS.6 = false: no secondary air adaptation


Overview of the coding variants of code word CWFASL:

Bit 0: 0: Short test termination if B_fs, vfzg> 0 or B_brems / B_kuppl (see bit 1). 1: no short test termination via B_fs, or vfzg B_brems/B_kuppl possible.

Bit 1: 0: Short test termination if B_brems or B_kuppl. 1: brake and clutch have to be actuated for a short test.

Bit 2: 0: short test can be induced only once in the driving cycle. 1: Short test times can be induced (see bit 3).

Bit 3: 0: Short test only possible after deleting previous fault memory. 1: short test possible without deleting error memory.

WARNING: When bit 3 is set, there is a risk that the catalyst is superheated by repeatedly carrying out short tests.


SLS parameters:

IMLSLMN

0

Secondary air at the same time as B_kh

IMLSLMX

0.9961

Secondary air during entire catalyst heating

TMSSLSTU

15°C

Secondary air from tmst > 15°C is already at the start CWSLS.0 = true

TMSSLSTO

35°C

Secondary air from tmst < 35°C

TMSSLU

15°C

Secondary air with B_kh when tmst > 15°C

TMSSLO

35°C

Secondary air with B_kh when tmst < 35°C

TASLSU

15°C

Secondary air with B_kh when tans > 15°C

TASLSO

35°C

Secondary air with B_kh when tans < 35°C

VSLS

10 km/h

Secondary air only when vehicle speed > 10 km/h when CWSLS.1 = true

MLSLMX

200 kg/h

Termination threshold when ml > 200 kg/h

DPSLV

0 mbar

Termination threshold pressure difference to open the secondary air valve

UBSLMN

9 V

Minimum battery voltage for sufficient secondary air mass

TSLABB

1 sec

Debounce time for secondary air termination after engine start (B_stend)

UBSLMX

16 V

Fan protection during boost start

UBSLSTMN

8 V

B_sls at start when battery voltage > 8 V

TSLUBST

2 sec

Debounce time for battery voltage at start


Secondary air pump parameters

TVSLVON

0.1 sec

Secondary air valve opened at the same time as secondary air pump control

TVSLVOFF

0 sec

Secondary air valve closes at the same time as secondary air pump control

TVDSLOFF

2 sec

Secondary air valve closes 2 seconds after short journey/adaptation

TSLPMN

500 ms

Minimum dwell time of the secondary air pump-relay to the relay protection

TVSLP2

2 sec

Delay time for triggering a second secondary air pump


BMSL parameters:

MSLUB =

Function of battery voltage. Obtained from laboratory measurements of the fan at 100 mbar back pressure, check the details required in the vehicle!

KFFMSML =

Function of engine speed and relative load

FMSRHOL

overall factor = 1, approximate without air density correction

FMSTMOT =

Function of engine temperature overall = 1, approximate without correction

FMSL,-2

1 no single bank correction


BSLPDYN parameters:

ZKSLPON

1s

Fan run-up

ZKSLPOFF

1s

Fan run-down


BSLSOFF parameters

IMLSLA

3.5 g

IMLSLSE

3.0 g

Implementing air mass to clean out the secondary air system


Dynamic SLP:

Dependent on ml:

20

40

60

100

kg/h

ZKSLSONML 0.5 s

1.5 s

1.0 s

0.5 s

0.2 s

Project specific

ZKSLSOFML 0.5 s

1.5 s

1.0 s

0.5 s

0.2 s

Project specific


BFMLSSL parameters

TLMSSLMX 60 s Termination of the thermal reaction (lambda-exhaust set point) after 60 s at idle

TLMSSLAB 1s Debounce time for detection of exit from idle

ZFLMSSL 1s Time constant for transition from lambda-exhaust --> lambda-engine


BKT parameters:

CWFASL s. o

TMFASLMN: 60°C

TFASLAMN: 60 sec

TDDSLA: 25 s

TDSLKT: 10 s


Abbreviations

Parameter

Description

CONT

CWFASL

Code word: calibrator intervention for secondary air diagnostics

CWSLS

Code word for secondary air system

DPSLV

Minimum pressure difference across the secondary air valve

FMSL

Factor for correcting secondary air mass, cylinder bank 1

FMSL2

Factor for correcting secondary air mass, cylinder bank 2

FMSLOFF

Clearing threshold of the secondary air terminated

FMSRHOL

Air density correction of the secondary air mass

FMSTMOT

Engine speed correction of the secondary air mass

IMLSLMN

Minimum ratio factor psum_w/mlsu for switching on SLS

IMLSLMX

Maximum ratio factor psum_w/mlsu for switching on SLS

IMLSLSA

Air mass integral threshold for initiation of secondary air in exhaust

IMLSLSE

Air mass integral threshold for termination of secondary air in exhaust

KFFMSML

Exhaust back-pressure corrections of the secondary air mass

MLSLMX

Maximum engine-air mass for secondary air injection

MSLUB

Secondary air mass dependent on the battery voltage

SY_BATTSG

System constant: twin battery design

SY_SGANZ

System constant: number of ECUs

SY_SLPANST

System constant: activation of the secondary air pump with twin-ECU, 0 = master, 1 = slave, 2 = master & slave. Seperate

SY SLPANZ

System constant for the number of secondary air pumps

SY_SLVANST

System constant: activation of the secondary air valve with twin-ECU, 0 = master, 1 = slave, 2 = master & slave. Seperate

SY_SLWG

System constant condition flag: secondary air/turbo wastegate present

SY_STERVK

System constant condition flag: stereo lambda control before catalytic converter

TASLSO

Upper air intake temperature threshold for secondary air system

TASLSU

Under air intake temperature threshold for secondary air system

TDDSLA

Continuous secondary air injection for adaptation phase

TDSLKT

Continuous short test secondary air diagnose for mass measurement

TFASLAMN

Minimum catalyst heating time for test requirement in secondary air diagnostics

TLMSSLAB

Debounce time for terminating secondary air enrichment

TLMSSLMX

Maximum time for secondary air enrichment during idle

TMFASLMN

Engine temperature threshold test requirement for secondary air diagnostics

TMSSLO

Upper start temperature threshold for secondary air

TMSSLSTO

Upper temperature threshold for secondary air at start

TMSSLSTU

Lower temperature threshold for secondary air at start

TMSSLU

Lower start temperature threshold for secondary air

TSLABB

Delay time for secondary air – termination condition

TSLPMN

Minimum duty cycle of the secondary air pump

TSLUBST

Debounce time for secondary air on at start by UBSLSTMN

TVDSLOFF

Time delay for closing secondary air valve for adaptation/short journey

TVSLP2

Time delay for control of the no. 2 secondary air pump

TVSLVOFF

Time delay on closing the secondary air valve

TVSLVON

Time delay on opening the secondary air valve

UBSLMN

Minimum voltage for secondary air on

UBSLMX

Maximum voltage for secondary air on

UBSLSTMN

Minimum voltage for secondary air on at start

VSLS

Vehicle speed threshold for secondary air control on

ZFLMSSL

Time constant: mixture part secondary air

ZKSLPOFF

Time constant: secondary air fan off/low flow

ZKSLPON

Time constant: secondary air fan on/run-up

ZKSLSOFML

Time constant: evacuation of the secondary air after valve shut

ZKSLSONML

Time constant: introduction of secondary air after valve open

Variable

Description

B_ATMTPL

Condition flag: dew point after catalyst exceeded (last journey)

B_BATNOT

Condition flag: battery emergency start with twin battery design

B_BREMS

Condition flag: brake operated

B_DSLFA

Condition flag: secondary air system requirement for short test

B_DSLRESET

Condition flag: reset secondary air adaptation/short test

B_DSLSET

Condition flag: set secondary air adaption/short test

B_DSLSP4

Condition flag: secondary air system requirement for secondary air adaption/additional diagnostics

B_DSPE

Condition flag: diagnostic secondary air on

B_DWG

Condition flag: wastegate diagnostics

B_ESLPE_C

Condition flag: error secondary air pump (output stage) sent via CAN

B_ESLVE_C

Condition flag: error secondary air valve (output stage) sent via CAN

B_FA

Condition flag: general functional requirement

B_FASLA

Condition flag: external request to activate secondary air system

B_FASLS

Condition flag: function requirement secondary air system

B_FS

Condition flag: driving phase

B_KH

Condition flag: catalyst heating

B_KHA

Condition flag: catalyst-heating requirement

B_KHAB

Condition flag: catalyst-heating terminated

B_KUPPL

Condition flag: clutch actuated

B_LL

Condition flag: idle

B_LMSSLOF

Condition flag: lambda-engine-set point-secondary air part, off

B_MASTERHW

Condition flag: master-ECU in accordance coding pins (plausibility check)

B_MSLMN

Condition flag: insufficient secondary air mass

B_MSLOFF

Condition flag: secondary air mass ausgeräumt after secondary air phase

B_MSLON

Condition flag: steady-state secondary air mass after start of the secondary air

B_NMOT

Condition flag: engine speed > NMIN

B_SLDSL4

Condition flag: enabling secondary air for diagnostics phase 4

B_SLKHOF

Condition flag: switching off the secondary air pump via imlpr-threshold

B_SLKT

Condition flag: enabling secondary air for short test

B_SLP

Condition flag: secondary air pump No. 1

B_SLP2

Condition flag: secondary air pump No. 2

B_SLPANST

Condition flag: for evaluation of the output stage error in secondary air control function

B_SLPENA

Condition flag: switching on the secondary air pump

B_SLPMN

Condition flag: minimum operating time of the secondary air pump

B_SLPOFF

Condition flag: secondary air pump switched off

B_SLPOFST

Condition flag for setting flip-flop B_slpoff

B_SLPT

Condition flag for secondary air pump, temporary intermediate size

B_SLP_C

Condition flag for secondary air pump, sent via CAN

B_SLS

Condition flag: secondary air active

B_SLSADAP

Condition flag: secondary air mass adaptation

B_SLSDIS

Condition flag for switching off the secondary air pump

B_SLSERR

Condition flag for blocking activation of the secondary air pump

B_SLSFZ

Condition flag: secondary air system installed in the vehicle

B_SLSINHI

Condition flag: blocked by setting bit B_sls

B_SLSOAB

Condition flag: secondary air system without implementing the termination criterion

B_SLSOFF

Condition flag: secondary air injection terminated after elimination of the secondary air

B_SLST

Condition flag: secondary air active, temporary intermediate size

B_SLS_C

Condition flag: secondary air active sent via CAN

B_SLV

Condition flag for secondary air valve

B_SLVANST

Condition flag for determining the output stage error in the secondary air control module

B_ST

Condition flag: start

B_STEND

Condition flag: end of start conditions reached

DFP_SLPE

Internal error path number: secondary air pump output stage

DFP_SLS

Internal error path number: secondary air system (cylinder bank 1)

DFP_SLS2

Internal error path number: secondary air system (cylinder bank 2)

DFP SLVE

Internal error path number: secondary air valve output stage

E_SLPE

Error flag: secondary air pump (output stage)

E_SLVE

Error flag: secondary air valve (output stage)

FLAMSL_W

Factor for lambda adjustment through secondary air (cylinder bank 1)

FLAMSL2_W

Factor for lambda adjustment through secondary air, (cylinder bank 2)

FLMSSL

Factor lambda-engine-set point secondary air part

FMSAGD

Exhaust gas back-pressure correction factor for the secondary air mass

FMSLA

Correction factor secondary air mass adaptive (cylinder bank 1)

FMSLA2

Correction factor secondary air mass adaptive (cylinder bank 2)

FMSLDYN

Factor for dynamic specification of secondary air

FMSLKOR

Factor to correct the secondary air mass

FMSLRHO

Air density correction of the secondary air mass

FMSLTM

Engine temperature correction of the secondary air mass

FRHOKOR_W

Factor to address the air density correction of the secondary air

FSLPDYN

Factor for dynamic specification of the secondary air pump

IMLPR

Relative air mass integral during catalyst heating

IMLSLA_W

Air mass integral for introducing the secondary air

IMLSLE_W

Air mass integral for end of secondary air in exhaust

MLBB_W

Air mass flow filtered (word), cylinder bank 1

MLBB2_W

Air mass flow filtered (word), cylinder bank 2

ML_W

Air mass flow filtered (word)

MSL

Secondary air mass flow (cylinder bank 1)

MSL2

Secondary air mass (cylinder bank 2)

MSL2_W

Secondary air mass (cylinder bank 2) 16-Bit value

MSLKORR_W

Corrected secondary air mass flow with consideration of pump dynamics (bank 1)

MSLPUB_W

Secondary air mass flow (battery voltage dependent) 16-Bit

MSLSTAT

Static secondary air mass flow

MSLSTAT_W

Static secondary air mass flow, 16-Bit

MSL_W

Secondary air mass flow 16-Bit value

NMOT

Engine speed

PS_W

Intake absolute pressure (word)

PU

Ambient pressure

RL

Relative air charge

TANS

Ambient air temperature

TMOT

Engine temperature

TMST

Engine start temperature

TNST_W

Time after end of start

UBSQF_W

System voltage, converted into standard quantization and filtered

VERHMSB_W

Number of the cylinder-specific mass flow distribution factor for cylinder bank 1

VERHMSB2_W

Number of the cylinder-specific mass flow distribution factor for cylinder bank 2

VFZG

Vehicle speed

Z_SLS

Cycle flag: secondary air-system (cylinder bank 1)

Z_SLS2

Cycle flag: secondary air-system (cylinder bank 2)

Personal tools