NefMoto

Bit of a guide I did for a forum from various Bosch guides on here and other places;

MOTRONIC 2 TO ME7 EVOLUTION – A BRIEF OVERVIEW:

Ignition – Motronic:
Takes approx. 2ms (0.002s) from start of mixture ignition to complete combustion.
Time remains constant for all engine speeds, time “available” for process to occur lessens as revs rise, therefore the spark must be generated sooner, this process is called ignition advance.
At idle spark occurs near top of compression stoke, higher revs spark must be generated sooner so maximum cylinder pressure occurs on power stroke.

Emissions system:
Throttle positioners and dashpots
EGR
Oxidation Cat
02
Secondary air system
Intake air pre-heating
Evaporative emissions (fuel tank)
Crankcase emissions

Leak Detection Pump (LDP) – pressurize evap system for emissions

Component control via ECU:

Example: Temp sensor receives constant 5V signal, also ground for accurate signal. As temp changes, resistance changes and results in variable voltage drop. ECU watches for a valid signal, which varies by component but will not be 0 or 5V. If battery+ Ground or 5V reference is seen by ecu, a DTC (Diagnostic Trouble Code) is seen.

Short circuit to Ground the same way – abnormal condition – DTC's, same applies for open circuit – i.e. no signal from loom/sensor etc – 0V – DTC.
 
ETC/DTC – Diagnostic/error trouble codes


Motronic 2.3.2 Basics:

ECU load and speed dependent.
SENSORS:
Crank speed signal – secondary signal for crank position also
Hall sender in Dizzy provides camshaft position info to identify cylinder 1, allowing sequential injection and valve open time.
Engine load from MAF.
02 sensor to check exhaust gasses/emissions/content – determines whether the injector open time needs to be lengthened or shortened for lambda=1 -  “Adaption”.
Values obtained from engine operating conditions are stored and used on next start up. These values can constantly change and the ecu learns from them - “adaptive learning”.

As well as mixture adaption, idle speed and ignition timing also adapt based on operating conditions.

MOTRONIC SYSTEMS OVERVIEW – 2.3.2.

Sequential fuel injection:
Fuel injection via map control
Starting enrichment
Ignition control
After-start enrichment
Acceleration enrichment
Fuel deceleration shut-off
Max engine speed
02 sensor control
Vehicle speed limits

Ignition timing control:
Dwell angle map control
starting control
Temp corrections
Digital Idle stabilization
Selective cylinder knock control

Idle air control (IAC):
Idle air volume via map control
Start control
Correction for A/C on
Correction for transmission in gear

Exhaust Gas Recirculation Control:
EGR via map control
OBD Diagnostics (later models/legislative requirements at time)

Fuel tank ventilation:
FTV via map control


ADAPTION:

Adaption split into 2 areas – coarse and fine – the latter giving tighter control.
Coarse control range is known as long term adaption – a learned value.
Fine control range is known as short term adaption.
Fuel adaption is for part throttle and idle conditions.

Idle adaption = additive
Part throttle adaption = multiplicative

CAT/LAMBDA:
The period when the 02 sensor is not up to temp, therefore not used, is “open loop” operation, once a signal is used it becomes “closed loop”. As a result of the signal the ecu either lengthens the injector duration to richen the mixture or shortens it to lean it out.
If sensor malfunctions, no signal and no substitute for it either, then ecu will revert to basic injection times so engine can run.
OBD MIL – No 02 signal within 5 minutes after engine start with coolant over 40C – also recognizes open and short circuits.

ENGINE COOLANT TEMPERATURE (ECT):
Placed in coolant stream, as coolant temp changes, resistance does and gives ecu guide to temperature.
USED FOR:
Correction factor for ignition timing, injector duration and idle speed stabilizing.
OTHER SYSTEMS THAT USE IT FOR CALCS:
Knock sensor function
Idle speed adaption
02 sensor operation
Fuel tank ventilation

Substitute function:
If broke, ecu uses 80C temp. as substitute.
Set to 20C at engine start, 10C increases per minute until 80-85C limit reached under malfunction.

INTAKE AIR TEMP SENSOR:
Placed in air stream in inlet manifold, resistance changes when air passes over it. Increased air temp = increased resistance, colder air temp = decreased resistance.

USED FOR: Idle stabilization and ignition timing.
Substitute function: ECU uses 20C value from memory.


BAROMETRIC SENSOR:
Used for atmospheric pressure sensing – from 14.7psi at sea level to around 12.5 high altitudes.
Located in E-Box in passenger footwell.

Used to control turbo boost pressure at high altitudes to stop turbo overspeeding. Signal also used for A/F ratio adjustment at engine start up in high altitude regions.

MANIFOLD ABSOLUTE PRESSURE SENSOR (MAP):
Vaccum line attached to manifold and instead of measuring ambient pressure, provides ecu with boost pressure for regulation.

EGR TEMP SENSOR:
Takes a small amount of non combustible exhaust gas and vents it back to intake. Increased temp changes resistance and tells ecu EGR working for better Nox emissions and reduced combustion temps.

OTHER SIGNALS USED IN MOTRONIC:
Battery voltage. Injectors cycle faster (decreased dead times) at higher voltages and other parts that change speeds with voltage need the ecu to make adjustments accordingly.
Air conditioner/anciliiaries – the systems which can drain the amount of torque due to being attached to pulley system and clutched ON must be factored into in tuning i.e. revs rising at idle due to A/C being on.
Vehicle speed sensor – max limit's, plus more modern systems electronically controlled driver aids like ESP etc.
Automatic Gear related functions – smoother transitions etc

MOTRONIC 5:

Later Motronic systems added component and system monitors which enabled the ecu to check the plausibility of signals it receives by looking at various related components., for example engine coolant temp with IAT then if the signal/values are too out of sync after a period of time (learning routines), it delivers a DTC.

Emissions control also became more stringent towards the late 90's, as such, more control over such systems evolved, for example additional sensors pre/post Cat.
Evolution also came from things like; heated windscreens, better/more complex instrument clusters and so on as well as the development of electronic driver aids. The dreaded MIL light being something you'll be well aware of and had a new operating mode for the new OBD2 procedures.

The Hot Film Mass airflow sensor (HFM) were evolved into a heated metallic film on a ceramic substrate compared with earlier wire versions, thus negating the need for a “burn-off” period cleaning the sensor after the engine is switched off.
Throttle position sensor used as substitute if broken.

It was also around this time when dizzy systems were replaced with coilpacks/single coils as the ignition control became more advanced and controllable.

Variable length inlet manifold tracts came into play around this time too and the change over barrel functions needed to be integrated into the ecu as well as any other sub systems.

There were also evolutions of things like the fuel pumps and evap cannisters/control depending on M5 system ages and vehicle dependent.

At this time (mid/late 90's) on the M5.9 systems the throttle valve control was new and had 3 input sensors and 1 actuator, replacing the earlier TPS and IAT sensors, which were housed on the side of the throttle body unit, or, to be more technical, the “Throttle Control Module” (TCM).

There was a new on/off switch relating to a Closed Throttle Position (CTP). This was used for idling purposes and switches to a common ground signal once the throttle valve moves.

The ecu recognizes circuit malfunctions now referred to as low and high inputs for OBD compliance and also uses the Mass Air Flow sensor (MAF) to check for a plausible throttle position signal. The sensor was also upgraded over earlier items and housed in a glass membrane so as to stop turbulent and reverse flow giving the ecu incorrect readings.

Various other components also evolved due to design and manufacturing evolutions such as above.

Variable camshaft geometry also evolved at this time, first with the inlet cam and later with both inlet and exhaust camshafts. Such cam controls required additional sensory inputs and outputs and again, can be related to other systems that the ecu looks at within it's logic.

ME7:

So, as the Motronic systems evolved, the ME7 as found on your V6 4motion and R32 vehicles were the next major development from Bosch and those we will look at in greater detail later on.
Where these systems differ to earlier Motronic systems is that they use a centralised processor that houses all sub-systems required for engine operation, whereas earlier systems used a number of processing points.

The previous way of looking at the inputs and outputs was done away with and the system became a torque based system.

This system is continually monitoring and looks at both external inputs like driver demand, as well as internal like idle speed. The ecu interprets them as “torque demands” and controls the actuators to produce the required torque as requested.

The ME7 designates signals and co-ordinates torque demand along 2 pathways;
CHARGE AIR PATH – All charge influencing components such as throttle angle or wastegate actuation.
CRANKSHAFT SYNCHRONOUS PATH – Controls all operations occurring in line with the operating cycle of the engine, such as ignition and injector opening and duration.

The engine based path is suited to meeting short term torque demands whereas the air path is good for long term demands. The former usually has a torque reduction effect whereas the latter is primarily required for required torque increases.

The throttle (abbr. DK -drosselklappen in tuning you'll come across), was the new “fly by wire” which receives it's sensory inputs from the pedal box – ergo, “driver demand”electronically rather than directly via a cable.

Evolutionary changes:

Electronically controlled throttle
Cruise control – no longer vacuum but ecu integrated/controlled
Upgraded/evolved sensors including integrating BARO into ECU.
Re-circulation valve

ME7 NOTES:
Charge Air Pressure Sensor:
Earlier Motronic (M5.9) controlled charge pressure via a map which used engine speed, throttle angle and MAF (load).
ME7 housed this in the intake tract between charge cooler and throttle module and operates via a 5V reference with the resistance variations referencing the Manifold Absolute Pressure (MAP).
Atmospheric pressure gives a signal of approx 2.5V and works from 0.14-4.88V to give a plausible signal.

If this sensor fails then the charge air pressure is controlled by a map defined by engine speed and load – power however, is reduced.

Recirc valve N249:
Older M systems was operated by inlet manifold vacuum with fully closed throttle to give full engine vacuum to operate the valve.
With the new electronic control, the valve may be held partially open for emissions purposes and is used to provide vacuum to the re-circ valve from a reservoir under the front wheel housing liner which in turn allows the ecu to better control the valve under throttle transitions. If it fails, then the operation is done by manifold vacuum.

EPC – Electronic Power Control light was also added as a seperate indicator light and engine load signals/sensors use this light.

Further sensor and monitoring evolutions also followed for the ever tightening emissions controls.

ME7 SYSTEM OVERVIEW

Due to the system’s modularity, very different system configurations can be realized. For example systems with different sensors for cylinder charge determination (air mass or speed density), naturally aspirated or turbocharged engines, engines with or without EGR and engines with variable camshaft actuation are possible.

 The main system features are as follows:

• The engine torque management which controls all torque influencing actuators
• A/F ratio control with a central A/F manager, λ-pilot control, λ-closed loop control, or alternatively with a Nernst or universal λ-sensor and trim control
• Sequential, cylinder individual fuel injection.
• Ignition timing, including control of dwell angle and ignition angle.
• Cylinder individual knock control.
• Emission control functions for optimized emissions during cranking, start and after start which enable the realization of different catalyst warm-up strategies, using a lean mixture or a rich mixture including exhaust gas recirculation (EGR) and secondary air injection (SAI) control if necessary
• Canister purge control based on canister charge.
• Idle speed control.
• Diagnostic and monitoring functions:
• The system is comprised of the complete OBD II functionality to meet both MY ‘98 and future EOBD requirements. A torque-based monitoring systems supervises the throttle control under all operating conditions and reacts with the appropriate limphome functionality in case of a failure.
• To communicate with external systems, such as a transmission control system or a vehicle dynamic control system, torque demands can be received via a torque interface, realized via CAN. Therefore the EMS is able to process external torque demands within the torque manager.
• Conventional or continuous camshaft control.
• Resonance flap actuation.
• Engine fan control.
• Control of air-conditioner (A/C).
• Cruise control.
• The system contains the necessary interfaces to application tools, end of line programming tools, service and SCAN-tools.
• Immobilizer.
• Additional customer defined functions as required.

In principal, the comprehensive dependency of internal torque on cylinder charge, engine speed, Lambda, ignition timing and cylinder individual fuel cut-off could be described in a five dimension map.

The decisive step to simplify this dependency is the introduction of two central reference values:
• the optimal spark advance “sa_opt“ and
• the corresponding optimal internal torque “tqi_opt“, which reaches it’s maximum value at optimal spark advance.
In some operating points the optimal spark advance is a theoretical value, because of the engine knock limit.


Both reference values refer to Lambda equal to 1.0 („sa_opt_l1“ and „tqi_opt_l1“) and are defined by 2- dimensional look-up tables:
sa_opt_l1 = fn. (rc, n_eng) (1)
tqi_opt_l1 = fn. (rc, n_eng) (2)

Relative cylinder air charge “rl/rc“ refers to a 100% value defined by the displacement per cylinder and the standard air density. The second influencing variable is the engine speed “n_eng“.

The actual torque value “tqi“ is the result of a multiplication with Lambda- and spark advance efficiencies
eff_lam = fn. (lam) (3)
eff_sa = fn. (d_sa) (4)

(fn. Function of, depending on)

and the reduction factor “eff_red“ caused by a cylinder individual fuel cut-off:
tqi = tqi_opt_l1 * eff_lam * eff_red * eff_sa (5)

(In equations 3 through 5 “lam“ represents Lambda)

For simplification of the basic equation (equation 5), spark advance efficiency is defined depending on the difference between actual spark advance “sa“ and the optimal spark advance:
d_sa = sa_opt – sa

Calculation of the desired values
As previously mentioned, the torque model is not only used to determine the actual value of the internal torque.
The basic equation (equation 5) can also deliver the desired values of the controller outputs:
tqi_tar = tqi_opt_l1 (rc_tar, n_eng)
* eff_lam_tar
* eff_red_tar

The target torque value “tqi_tar“ is calculated by multiplication of the optimal torque at lamba = 1.0 and optimal spark advance by the efficiencies. Solving equation (6) for “rc_tar“, “eff_lam_tar“, “eff_red_tar“ or “eff_sa_tar“ delivers the target values for the controller outputs which influence torque

ABBREVIATIONS
d_sa = sa_opt - sa
eff_lam Lambda efficiency
eff_lam_act Actual Lambda efficiency
eff_red Reduction factor
eff_red_act Actual reduction factor
eff_sa Spark advance efficiency
eff_..._tar Target efficiency values
lam Lambda
lam_bas Lambda of basic calibration
n_eng Engine speed
rc Relative cylinder charge
rc_act Actual relative cylinder charge
rc_tar Target value rc
sa Ignition angle reffering to TDC
sa_bas Spark advance of basic calibration
sa_opt Optimal spark advance
sa_opt_l1 Optimal sa at lamda 1.0
tq_i Internal torque, generated by combustion
tqi_bas tqi at sa_bas and lam_bas
tqi_opt, Optimal internal torque
tqi_opt_l1 Optimal tq_i at Lambda 1.0
tqi_tar Target value t_qi

Calculating cylinder charge
The air mass within the cylinder following closure of the intake valve is the air charge.

There is also a “relative (air/luft in German to get used to acronyms) charge” (rl/rc) which is independent of piston displacement. It is defined as the ratio of the current charge to a charge obtained under specified standard conditions: (p0 =1,013 hPa, T0 = 273 K) and used to calculate fuel quantity.

It is also the primary parameter that influences the engine output, used as a simulation model as there is no way to directly monitor the charge density.

The requirements for the charge model are:
– Precise determination of charge density under all operating conditions
– Accurate response to exhaust-gas components in systems with variable rate EGR (controlled external or internal EGR),
– Calculation of the control command parameter for “throttle-valve aperture” corresponding to any given charge density requirement.


Inlet manifold simulation model:

The actual mass of the air within the cylinder is relevant for fuel metering and torque calculations and it is calculated using an inlet manifold simulation model due again, to the fact that there is no direct way to monitor charge and therefore requires modelling/simulation.

The inlet mani model can either be monitored directly or simulated depending on MAF/HFM or MAP sensor’s being used by that particular model (HFM/Air mass obviously for the NA VR engines).

The HFM led cars can calculate charge density directly from the induction air mass during static engine operation, but when the throttle is opened there can be a lag due to the manifold plenum having to be filled with air before entering the cylinder. There is a disparity between the air entering the cylinder and what is being measured and it is not until pressure levels rise that the measured air and cylinder air start to be measured more accurately as they equal out.

MAP sensor cars make the manifold pressure a primary factor as the relative charge and manifold pressure can be portrayed using a linear equation.
The linear equation’s offset is defined by the partial pressure emanating from internal residual gases, making it a function of valve overlap, rpm and ambient barometric pressure, while the gradient is determined by engine speed, valve overlap and combustion-chamber temperature.

Other flow into the manifold
Any additional air that isn't entering through the throttle valve (DK), results from activation of such
systems as the evaporative-emissions control. The regeneration flow required by this system can be varied with the aid of a tank vent valve (purge valve). With manifold pressure as a known quantity, it is possible to calculate the regeneration flow for use in the intake-manifold model
simulation process.


Monitoring charge density with the HFM

When the HFM measures the incoming air, it multiplys the mean mass air flow monitored during an intake stroke (segment) by the intake strokes duration for conversion into a relative charge density.
Other aspects of the inlet mani model simulation (such as intake-air temperature) are either monitored directly or calculated in the modelling process (in this case intake-manifold pressure, but also secondary parameters such as combustion- chamber temperature).


Monitoring charge density with a manifold-pressure sensor

Manifold pressure can be monitored directly with MAP systems by calculating the mass of the air entering the inlet manifold based on manifold pressure.

Cylinder charge control

The model for the inlet manifold also controls the density of the charge air entering the cylinder due to the air flow flowing through an orifice/valve (like the throttle plate) , being able to be formulated into an equation.

Main factors calculated within model:
Pressure prior to valve
Pressure drop
Temperature
Orifice size

Other parameters relevant for specific throttle valves (such as friction losses in the air current) must
be quantified using test-stand measurements.

Once this has been done the manifold model can now be “turned around” to calculate the throttle valve aperture from the desired cylinder charge density (which has been calculated by the torque-led control of the ME system). This aperture is transmitted to the throttle-valve actuator’s position controller as a command value.


Calculating injection timing & Calculating injection duration

The cylinder-charge density can be used as the basis for calculating the fuel mass required to obtain a stoichiometric air/fuel ratio. The injector constant (krkte), which varies according to injector design, can then be incorporated into the calculations to produce the injection duration.

Injection duration is also affected by the differential between the fuel’s supply pressure and injection counter-pressure. The standard fuel supply pressure is generally 300 kPa (3 bar). This pressure can be maintained using any of a variety of reference sources.

Fuel-supply systems with return lines maintain constant supply pressures relative to manifold pressure. This strategy ensures that the pressure differential across the injectors remains constant in the face of changing manifold pressures, so that roughly consistent flow rates result.

Returnless fuel systems rely on a different concept, maintaining their 300 kPa supply pressure relative to ambient pressure. Fluctuations in the pressure within the intake manifold produce variations in the differential between its own pressure and that of the fuel supply. A compensation function corrects this potential error source.
As the injectors open and close they induce pressure waves in the fuel-supply system. This leads to flow-rate inconsistencies when the injector is opened. An adaptation factor correlated with engine speed and injection duration is used to compensate.

The opening duration calculated up to this point will be valid if we assume that the injector has already opened and is discharging fuel at a constant flow rate, but the injector’s opening time must also be considered in real-world operation.
This opening duration displays significant variations depending on the voltage being supplied by the battery. There may be substantial lag before the valve opens completely, especially in the starting phase or when the battery is partially discharged. A supplementary injection duration based on battery voltage is added to the base duration to compensate for this effect.

Excessively short injection durations would lend disproportionate influence to the valve opening and closing times. This is why a minimum injection duration is defined to guarantee precise fuel
metering. This minimal duration is less than the injection period required for minimum potential cylinder charging.



Injection timing
Optimal combustion depends on correct injection timing as well as precise metering. The fuel is usually injected into the intake manifold while the intake valve is still closed. Termination of the injection period is defined by something known as the injection advance, which is indicated in crankshaft degrees, and uses intake valve closure as a reference. The injection duration can then be correlated with engine speed to obtain a point for initiating injection defined as an angle.
Current operating conditions are also reflected in the calculations to define the injection advance angle.

ME-Motronic triggers an individual injector for each cylinder, making it possible to preposition a separate fuel charge for each cylinder (sequential injection). This option is not available with
systems that rely on only one injection valve (single-point injection) or simultaneous activation of several injectors at once (group injection).

As below.

File Attached