FUEDK 21.90 (Cylinder Charge Control, Calculating Target Throttle Angle)

See the funktionsrahmen for the following diagrams:

fuedk-fuedk FUEDK overview

fuedk-brlpssol BRLPSSOL: target intake manifold pressure

fuedk-umpspi UMPSPI: calculation of reference pressure upstream of the throttle

fuedk-bmldkns BMLDKNS: normalised target air mass flow at throttle

fuedk-bwdksgv BWDKSGV: target throttle angle

fuedk-filter FILTER: median-filter

fuedk-wdksugdt WDKSUGDT: difference of target throttle angle compared to 95% charge (turbocharged engine)

fuedk-wdksugds WDKSUGDS: difference of target throttle angle compared to 95% charge (normally-aspirated engine)

fuedk-wdksgv WDKSGV: throttle angle

fuedk-bde-wdksgv WDKSGV: petrol direct injection throttle angle

fuedk-wdkappl WDKAPPL: calibration interface

fuedk-nachlauf NACHLAUF: calculation of target throttle angle when SKl15 = off

fuedk-init INIT: initialization of function

Function Description

The purpose of this function is to calculate the target throttle plate angles for either a turbocharged or a normally-aspirated engine with an intake manifold (lambda = 1 mode), or direct injection (also lambda > 1). The control is via the system constants SY_TURBO and SY_BDE. The main input variables are the target relative cylinder charge and the required correction from cylinder charge control. Various other signals, such as correction factors for pressure and temperature or information about the fuel tank breather and exhaust gas recirculation are taken from the intake manifold model of cylinder charge detection or the target value for exhaust gas recirculation (in direct injection mode). For these reasons, there is a close connection between calculation of the target throttle plate angle and cylinder charge detection.

Sub-function BRLPSSOL: Calculation of the target intake manifold pressure (pssol_w) and correction of target fresh air charge upstream of the throttle plate (rlfgks_w)

In petrol direct injection engines, the target relative cylinder charge rlsol_w is reduced by the relative air charge from external and internal exhaust gas recirculation. In the case of engines with fuel injection to the intake manifold (lambda = 1) no air is contained in the internally or externally recirculated exhaust gas. The relative residual gas charge = 0 and is therefore not taken into account. A comparison between actual cylinder charge (rl_w) and target cylinder charge (rlsol_w) is made via the variable drlfue from the function FUEREG (cylinder charge control). The variable rlfgks_w represents the proportion of fresh air that flows through the throttle plate or the fuel tank breather to the engine. The target intake manifold pressure for direct injection engines is calculated from the target fresh air charge through the throttle plate and fuel tank breather and the total charge (air and inert gas) from the residual gas (i.e. internal and external exhaust gas recirculation) together. The total charge corresponding to the intake manifold pressure is calculated with the conversion factor fupsrl_w. For engines with fuel injection into the intake manifold, the target relative cylinder charge rlsol_w is increased by the relative charge from the external exhaust gas recirculation feed. The total charge corresponding to the intake manifold pressure is calculated with the conversion factor fupsrl_w. Correcting with the internal exhaust gas recirculation partial pressure (pirg_w) gives the target intake manifold pressure pssol_w. Additionally, in direct injection engines, the correction of the internal residual gases (ofpbrint_w) is still added and then pssol_w is obtained.

Sub-function UMSPI: Calculation of the target reference pressures upstream of the throttle plate for a turbocharged engine (pvdkr_w):

Turbocharged engine:

Target reference pressure pvdkr_w see the following description

Air density correction factor frhodkr_w = ftvdk x pvdkr_w / 1013 mbar.

The target reference pressure for the pressure upstream of the throttle plate (pvdkr_w) for a turbocharged engine is formed from the maximum range of ambient pressure (pu_w) and the target boost pressure (plsol_w) or the actual pressure upstream of the throttle plate (pvdk_w). The target boost pressure is given by pssol_w / vpsspls_w, whereby vpsspls_w is the required pressure ratio from the boost pressure control. When vpsspls_w > 0.95, the throttle plate is linearly actuated, with boost pressure regulation active, in order to minimise the pressure drop at the throttle plate (see sub-function WDKSUGDT). The air mass dependent characteristic KLDPDK takes the pressure drop across the throttle plate into account. In so doing, this gives a larger value for the target boost pressure than the actual boost pressure being implemented in the boost pressure control. The actual pressure can be ramped up towards the target pressure via the characteristic FUEPMLD. When the predicated boost pressure difference pdpld exceeds the threshold DPUPS, then a switch is made to the actual pressure pvdk_w, because this condition represents a boost pressure error (B_ldrugd = false). In the transition from ambient pressure to dev basic boost pressure, the actual boost pressure is filtered with the low-pass filter, because pressure pulsations will be experienced in this range because of non-clean waste-gate closure.

Sub-function BMLDKNS: Calculation of the normalised target air mass flows through the throttle plate (msndkoos_w)

The target air mass flow mlsol_w is calculated by multiplying the corrected target cylinder charge rlfgks_w by umsrln_w. Since the engine cylinder charge at start is obtained from the intake manifold, initially, no throttle opening would be required (umsrln_w = KUMSRL x nmot = 0). A minimum air flow through the throttle is predetermined by the threshold KUMSRL x NRLMN so that the throttle does not close at the start and then open when the engine picks up speed. The threshold NRLMN is set to 400 rpm since that is assumed to be the engine speed at start. The threshold NRLMNLLR is disabled so that the throttle will be closed during a speed drop, for instance when starting up.

The target air mass flow is reduced by the air mass flow which is directed into the intake manifold through the fuel tank breather (mste) since this amount must be made up via the throttle. The normalized air mass flow through the throttle (msndks_w) is calculated by dividing the target air mass flow through the throttle (msdks_w) by the corrected density, KLAF. The throttle valve actuator air bleed (msndko_w) will still be subtracted from this air mass flow via an adaptation in the function BGMSZS to obtain the normalized air mass that will flow through the throttle (msndkoos_w).

The discharge characteristic, KLAF, is addressed with the target pressure ratio psspvdkb_w. This target pressure ratio comprises the minimum of psspvdk_w = pssol_w / pvdkr_w (turbo) or psspvdk_w = pssol_w / pvdk_w (normally-aspirated engine) and PSPVDKUG together. This means that the target throttle angle only up to the unrestricted range, psspvdkb_w = 0.95 = PSPVDKUG, is calculated via KLAF. The remaining 5% is calculated in the sub-function WDKSUGDS for a normally-aspirated engine and in the sub-function WDKSUGDT for a turbocharged engine. If psspvdk_w > PSPVDKUG, condition flag B_klafbg will be set indicating that the characteristic KLAF is limited.

Sub-function BWDKSGV: Target throttle angle (wdksgv_w)

In this sub-function, the target angle (wdksgv_w) for controlling the throttle plate is calculated from the normalized target air mass (msndkoos_w). Up to the throttle angle for unrestricted operation wdkugd_w (output from the speed dependent characteristic WDKUGDN from the function %BGMSZS) the target angle is determined via the map KFWDKMSN. This is the inverse map of KFMSNWDK (from the function %BGMSZS) and is calibrated to the built-in throttle actuator. If the calculated value of the normalized target air mass flow from KFWDKMSN is greater than the angle wdkugd_w, then the condition for unrestricted operating B_ugds = true.

If the target pressure ratio is greater than 0.95, the numeric basic stability of the normalized air mass flow and thus the target throttle angle can no longer be determined via the discharge characteristic KLAF. For the rest of the target throttle angle range beyond wdkugd_w to 100% for both a normally-aspirated and turbocharged engine, a different residual angle dwdksus_w or dwdksut_w is implemented. This residual value in the unrestricted range (naturally-aspirated: B_dwdksus = true and turbocharged: B_fkmsdks = true) is added to wdkugd_w. If applicable, the target throttle angle is limited by the maximum allowable target throttle angle KFWDKSMX and made available as wdksgv_w. This can be used for power reduction or attenuation of induction noise. To extend the life of the throttle-adjustment actuator, the normalized air mass flow (msndkoos_w) is smoothed via a median filter with small changes in rlsol_w in the sub-function FILTER. If the delta rlsol (drlsolmf = abs (rlsol_w - rlsol (t - 40 ms)) is less than the threshold DRLSOLMF, which means very small changes in the target torque, the filter is active (B_mfact = true). The actual value of msndkoos_w is cached in a five-value capacity input filter buffer. The values are stored in decreasing values in a five-value capacity output filter buffer. If the old filter value mlwdknf_w is not within the maximum and minimum value of the output filter buffers, it will be centered on the mean value of these buffers. Otherwise, mlwdknf_w is not changed. If the threshold drlsolmf_w > DRLSOLMF, then the filter output value mlwdknf_w is set directly to the filter input value msndkoos_w. In addition, the filter input value is transferred to the filter input buffer.

For special cases, for example start and warm-up conditions, it is necessary to predefine a torque calculation independently of the throttle angle. For this purpose, the input wdksom_w is used when B_wdksom is active. With the switch B_tfwdksom, the filter time constant tfwdksom can be switched on. The low pass filter is required during the transition from "start angle" to "torque-based" operation. For engines with fuel injection to the intake manifold, the filter can also be switched on during the operation via the code word CWFUEDK (6 bits) with the variable time constant tfwdks_w. If the condition B_fkmsdks (B_ugds or B_klafbg for normally-aspirated engine and B_fkmsdks for a turbocharged enginer) is set, the charge control is disabled (see Section %FUEREG) and the alignment between MAF meter and throttle-based charge detection (fkmsdk) in the function BGMSZS%.

Turbocharged Engine: Sub-function WDKSUGDT

Because cylinder charge in the unrestricted region for a turbocharged engine is achieved via the boost pressure control, the throttle should be completely open in this region to avoid throttling losses. For this purpose, in the boost pressure control, the pressure ratio vpsspls_w is defined as target manifold pressure / ambient pressure. If vpsspls_w > 0.95, i.e. vpsspls_w > PSPVDKUG, so begins the unrestricted area. The throttle plate residual value dwdksumx_w = difference between the unrestricted target angle wdkugd_w and 100% which is linearly scaled by the ratio (1 - vpsspls_w) / (1 - PSPVDKUG). The value for PSPVDKUG is 0.95 (see function BGMSZS). If the throttle angle is controlled by the actual manifold pressure (CWFUEDK Bit 7 = true), the upper value is enabled only when the calculated target throttle angle from the torque structure is greater than the unrestricted angle. The angle can be unrestricted through tolerances of the MAF meter and pressure sensors, even if a demand of vpsspls_w = 1 is still greater than wdksbugd_w. Therefore, this tolerance can be applied in DWDKUGD. Then the upper value is enabled via a pressure ratio vpsspls_w > VPSSPLSWDK already at wdksbugd (angle calculated from the torque structure) > wdkugd minus DWDKUGD.

With active throttle plate residual value, the bit B_fkmsdks is set, which is either when B_klafbg is set or vpsspls_w >= PSPVDKUG or when CWFUEDK bit 7 = true only dependent on B_klafbg.

Normally-Aspirated Engine: Sub-function WDKSUGDS

Here a so-called pedal-crossover is introduced: Bit 4 of CWFUEDK = false: If the target pressure ratio psspvdk_w > PSPVDKUG (i.e. B_klafbg = true) or if B_ugds = true, then the pedal-crossover begins (B_dwdksus = true). mrfa_w is frozen at the beginning of the crossovers in mrfabug_w.

The throttle plate residual value dwdksumx_w (= difference between the unrestricted target angle wdkugd_w and the maximum permissible target angle from the map KFWDKSMN) is linearly scaled through the ratio for the pedal crossover between mrfabugd_w and mrfamx_w thus:

[mrfa_w - min(100%, mrfabugd)] / [mrfamx_w - min(100%, mrfabugd)]

whenever B_dwdksus = true.

The value dwdksus_w is added to wdkugd_w and as the target angle wdksvin_w provided. wdksgv_w can be maximum WDKSMX. The end of the pedal-crossovers is reached when, for example, mrfa_w is once more smaller then mrfabugd_w or [milsol_w < FMIUGDS x mifafu_w] (0.95 x mifafu_w) or, for vehicles with continuously-variable transmissions (CVT), when B_mgbget = true.

For positive load changes corresponding to fast throttle-opening, a large increase of torque via the air path (mifal) is predetermined by the driver’s requested torque calculation function. This large increase is also conveyed to the throttle-side so that the unrestricted range is reached via the pressure ratio psspvdk. If the corresponding driver’s requested torque were to be saved, then this torque would be too small because it contains this large increase. Therefore, the saving is prevented via B_lsd until this dynamic action is once again reduced.

The map MRFARUGDN (reset threshold for linear pedal travel in the unrestricted throttle region) prevents the value 0 being stored in mrfabugd_w during startup when mrfa_w and psspvdk_w = 0 and > 0.95. This prevents pedal crossover that is activated when wped is in the region of 0.

Bit 4 CWFUEDK = true:

The pedal crossover does not depend on mrfabugd_w calculation but depends on the characteristic MRFARUGDN. Whether the pedal crossover is switched on or off depends on the same conditions as in bit 4 of CWFUEDK = false.

Sub-function WDKAPPL: Applications interface

If the applications interface is enabled, normal calculation of target throttle angles (which is the function of the torque interface) is disabled (via constant CWMDAPP). Instead, the target throttle angle depends only on the pedal value, or is even set to be constant. When the engine speed = 0 rpm, the target throttle angle depends directly on the pedal position (wped). Thus, for example in the workshop, a movement of the throttle valve actuator can be achieved via the throttle pedal. Via the system constant SY_TWDKS, a sub-program can be incorporated, which enables the tester to control the throttle by a predetermined angle cvwdk. In so doing, the tester must assign the target angle cvwdk and set the bit in B_cwdk.

When using this feature you must ensure that no acceleration of the vehicle takes place, e.g. through examination of brake switch, clutch switch, etc. Ensure that engine and vehicle speed = 0!

When the map FPWDKAPP is switched on, then when evtmod < EVTMODKMNDK an offset WDKSOFS is added to the curve. This prevents the wrong throttle learning, for example by freezing. With nmot_w = 0 and ignition on, the target value of the throttle angle should correspond to the emergency air point.

Subfunction NACHLAUF: Calculation of the target throttle angles for delayed accessory power only when SY_UBR = 1 (main relay installed) included.

For delayed accessory power, a throttle angle is determined independently of the torque structure. This angle wdksom_w is defined in the function WDKSOM. For systems with a built-in main relay, the throttle actuator also supplies the ECU-delayed accessory power with power and therefore this angle is set by the throttle actuator. This ensures a quieter engine output.

Application Notes

Normally-aspirated and Turbocharged engines:

KLAF: see cylinder charge detection

KFWDKMSN: the inverse of KFMSNWDK

KUMSRL: see cylinder charge detection

CWFUEDK bit allocation:

Bit 0: normally-aspirated engine, fkmsdk-correction via pedal upper travel

Bit 1: not used in this FDEF.

Bit 2: for start packet: if throttle angle from the torque structure > throttle angle from start packet, there is no filtering of tfwdksom

IT IS RECOMMENDED TO SET THIS BIT TO FALSE!

Bit 3: not used in this FDEF.

Bit 4: normally-aspirated engine, via pedal upper travel dwdksus_w is calculated via mrfabugd_w or mrfaugd:

IT IS RECOMMENDED TO SET THIS BIT TO FALSE!

Bit 5: B_ldrugd can only be set independently of B_llrein with a turbocharged engine

Bit 6: only for non-direct injection engine: low-pass filter before wdksgv_w is enabled either just at start or always

Bit 7: KLAF is calculated by filtered actual intake manifold pressure (for turbo) / target intake manifold pressure (for normally-aspirated engine)

CWFUEDK=64 Bit 0 = false: functionality as per %FUEDK 18.20

Bit 2 = false: functionality as per %FUEDK 21.50

Bit 4 = false: functionality as per %FUEDK 18.20

Bit 5 = false: functionality as per %FUEDK 18.20

Bit 6 = true: as per %FUEDK 18.20, when Bit 6 = false ® run time reduction

Bit 7 = true: for turbo: calculation from KLAF with filtered actual intake manifold pressure

Bit 7 = false: for normally-aspirated engines: calculation from KLAF with target intake manifold pressure as previously

CWRLAPPL: only for dynamometer (switching from pssol_w with and without influence from charge control)

EVTMODMNDK = 5°C

WDKSOFS = 5% (Emergency air point minus one value of KLFPWDKAPP) thus throttle target value when lambda = 1 and engine speed = 0 corresponds to the emergency air point.

FPWDKAPP

WDKSAPP 2%

TWDKSV:

NMOTCVWDK = 2000 rpm

NRLMN: 400 rpm (defined via umsrln_w, the throttle opening in start). The throttle opening is limited by wdkugd_w.

NRLMNLLR: 100 rpm below idle speed (700 rpm)

ZKPSFIL = 0.02 s

KFWDKSMX: Engine speed sample points are selected as per WDKUGDN. It is important to note that for the throttle angle limit to reduce power, the sample points in the reduction range may be more closely distributed.

Upper sample point: the uppermost sample point for the altitude is selected so that it corresponds to the altitude at which the power reduction occurs. In the ​​power reduction region, KFWDKSMX is less than 100% such that the desired maximum engine performance is thereby made through the restriction.

The lowest sample point is selected so that it corresponds to the altitude at which the lowest air density yields the natural power reduction to the desired performance standard. As a reference point, it is assumed that an altitude gain of 1000 m brings about a 10% power reduction (delta fho_w = -0.1). This sample point is recorded over the entire speed range KFWDKSMX = 100%.

Engine speed: 240, 760, 1000, 1520, 2000, 2520, 3000, 3520, 4000, 6000 rpm

fho_w: 0.8, 0.9, 1.0

Values: KFWDKSMX = 100% ® angle limit is not active.

Determination of the activation threshold for the median filter:

1) Median-Filter switch-off: DRLSOLMF = 0;

Let the vehicle roll at idle to determine the maximum occurring drlsolmf_w. This is value 1.

Slowly pay out idling gas (low dynamics). The drlsolmf_w which occurs in this case determines value 2.

At idle, rotate the power steering to its end stop, The drlsolmf_w which occurs in this case detemines value 3.

Increase vehicle speed (accelerate under load with greater dynamics). The drlsolmf_w which occurs in this case determines value 4.

The threshold value DRLSOLMF is determined from the maximum of values 1 and 2 and the minimum of values 3 and 4.

It will lie in the mostly in value 4.

DRLSOLMF default value is: 2%

For the charge detection application on the engine dynamometer, speed or load sample points shall be reached automatically. The target specification in the function %MDFUE is achieved by specifying a constant rlsol or a target throttle pedal value. Thus, the predetermined rlsol will be implemented in a real rl with the same value, the charge control is used with a changed parameter set to balance rl - rlsol. This functionality is only effective if the system constant SY_RLAPP in the function PROKON is set to a value > 0. With bit 0 of CWRLAPPL, the functionality is then activated final. The link with the driving speed ensures that the balancing function can be activated only when the vehicle is stationary, or on the engine dynamometer.

Normally aspirated engine only:

MRFABUMX = 100%

MRFARUGDN (SNM12FEUB)

nmot_w

Values all at 80%

FMIUGDS: 0.95

Turbocharged engine only:

FUEPMLD

ZPVDKR

DPUPS: ³ 250 mbar

DWDKUGD = 2% tolerance of wdkugd

KLDPDK: 0 mbar at all sample points

Application: to measure the pressure drop across the throttle plate, especially the magnitude of the air mass flow rate. From these 16 sample points, mlkge_w is determined and the associated pressure drop applied in the characteristic.

PLSOLAP: 0 mbar. In the applications phase, if a target boost pressure is predetermined, B_plsolap = Bit 5 of CWMDAPP is set to be true and the desired boost pressure is specified via PLSOLAP.

PSPVDKUG see function BGMSZS

When CWFUEDK Bit 7 = true:

TFWDKSOF = 0.1275 s

VPSSPLSWDK = 0.995 From this pressure ratio, the throttle should be opened to wdkugd, when the throttle angle from the torque structure is equal to wdkugd - DWDKUGD (tolerance)

WDKSHYS = 2%