# How your drive by wire ME7 MKIV 1.8T/VR6 Motronic works.



## gdoggmoney (Feb 21, 2004)

http://****************.com/smile/emgift.gif 

This needs to be archived and searchable here. I take no credit for writing this, only credit for posting it here. I did not write this. However I would gladly buy a few beers/high dollar call girls for whoever took the time to put this together and write this article, should they see this post.








This is heavy, put your thinking caps on. 

_Quote, originally posted by *Intelligent Minds* »_The Bosch ME-Motronic system takes a radically different approach to previous engine management systems. While at first it appears little different to any electronic management system - fuel injectors, input sensors, an Electronic Control Unit and so on - the use of accelerator position sensing and an electronic throttle actuator makes this system very different to the average. For example, the relationship between accelerator pedal position and throttle opening is adjustable - not only can this system control injection and ignition, but also the cylinder charge.
Making ME-Motronic even more of a sea change is the underlying operating logic. Unlike older engine management systems, ME-Motronic determines how much engine torque is required in any given situation, and electronically opens the throttle blade sufficiently to allow the engine to develop that much torque. The accelerator pedal travel becomes just the driver's "torque request" input, to be weighed up against other torque requests that may be generated by the traction control system, speed limiter, engine braking torque control, and others. Additionally, at all times the engine management ECU models the engine's instantaneous torque development, adjusting the throttle opening according to the relationship between the requested and developed torque.
A quick example makes this easier to understand. In some situations, the driver may have only depressed the accelerator pedal to the halfway position - but under the bonnet, the throttle blade can have snapped wide open! But in what type of situation could this possibly be advantageous?
In turbocharged cars, the maximum available torque output of the engine can substantially vary across a quite narrow band of engine speed. For example, the current model Audi S4 twin turbo V6 (pictured as the opener to this story) develops a torque maximum of 300Nm at 1400 rpm and 400Nm at 1850 rpm. So, as can be seen in this Audi graph, across just 450 rpm of engine speed, the peak torque output varies by 33 per cent. This characteristic is caused by the two turbos rapidly coming on boost. To a greater or lesser degree, a similar shaped torque curve is associated with all turbocharged engines.
A driver of a turbo car that is equipped with traditional engine management tends to automatically compensate for this steeply varying torque curve. When wishing to accelerate moderately hard, he or she will initially open the throttle a long way, manually backing it off as turbo boost and torque rises. But the driver of an Audi S4 V6 - equipped with Bosch ME 7.1 - doesn't need to do this. When engine response is relatively poor - ie the turbos are yet to generate appreciable boost - the ME-Motronic system can open the throttle far further than the driver directly requests, and then as revs rise, automatically adjust the throttle angle to retain a linear response. In this way, driveability, emissions and fuel consumption can all be improved.
*Inputs and Outputs*








As indicated, at first glance the ME-Motronic system looks very similar to other management systems. This Bosch diagram shows the inputs and outputs of a typical ME-Motronic system. In addition to two-way diagnostics and Controller Area Network buses (the CAN buses communicate with other systems such as the automatic transmission ECU), the inputs comprise:
* Vehicle speed;
* Transmission gear;
* Camshaft position;
* Crankshaft speed and position;
* Dual oxygen sensors (located either side of the catalytic converter - 'V' engines have four sensors);
* Knock sensor;
* Coolant temperature;
* Intake air temperature sensor;
* Battery voltage;
* Intake air mass (plus frequently manifold pressure);
* Throttle position
None of these inputs is unique to this system, but the following one is:
* Accelerator pedal position.
With one exception, the outputs are also very similar to other recent management systems:
* Spark plugs;
* Injectors;
* Instrument panel tachometer;
* Fuel pump relay;
* Oxygen sensor heaters;
* Intake manifold runner control (ie control of the position of valves within dual tuned length manifolds, or the length of infinitely variable intake runners);
* Fuel system evaporative control, secondary air injection and exhaust gas recirculation (all emissions control approaches).
The unique addition is the:
* Electronic throttle control actuator
Given that the additional hardware comprises the accelerator pedal position sensor and electronic throttle control actuator, let's have a look at these two components in more detail.


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## gdoggmoney (Feb 21, 2004)

_Quote, originally posted by *Intelligent Minds* »_ 
Accelerator Pedal Position Sensor
Two approaches are currently used in the design of this sensor, but they are electrically identical. The throttle pedal assembly from an Audi S4 is shown here. Movement of the accelerator pedal manipulates two rotary potentiometers; unlike some electronic throttle engines, no back-up Bowden cable exists to connect accelerator pedal movement to the throttle blade. Two potentiometers are fitted to the sensor to allow redundancy - if one should fail, the other still lets the system operate








As can be seen here, the outputs of the potentiometers are identical but for an offset. Cars equipped with automatic transmissions do not have an additional kickdown switch in the assembly; instead a 'mechanical pressure point' is used to give the feel of a kickdown switch.








In the event that the accelerator position sensor fails, the lack of any mechanical connection between the accelerator and the throttle blade requires that sophisticated 'limp home' techniques are in place. The Audi S4 uses two techniques:
Emergency running program #1
This occurs when a single accelerator position potentiometer fails.
* Throttle position is limited to a defined value;
* In the case of implausible signals from the two potentiometers, the lower value of the two is used;
* The brake light signal is used to indicate when idling speed should be enacted;
* The fault lamp is illuminated.
Emergency running program #2
This occurs when both accelerator position potentiometers fail.
* The engine runs only at idle speed;
* The fault lamp is illuminated.
Interestingly, if in the Audi the accelerator and brake pedals are depressed together, the throttle valve is automatically closed to a defined small opening. However, if the brake is pressed and depressing of the accelerator then follows this, the torque request is enabled. I assume that the latter provision is solely for those who like to left-foot brake, with applications of power used to balance the car!





_Modified by gdoggmoney at 9:41 PM 6-9-2008_


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## gdoggmoney (Feb 21, 2004)

_Quote, originally posted by *Intelligent Minds* »_
Electronic Throttle Control Actuator








The Audi S4 electronic throttle valve consists of a DC motor, reduction gear drive and dual feedback angle sensors. It is again for reasons of redundancy that two potentiometers are used for angle feedback. However, unlike the accelerator position sensor, these sensors have opposite resistance characteristics to one another, as shown below.








While continuous sensing of throttle blade position does occur, the ECU recognises four key functional positions of the throttle blade:
* Lower mechanical limit stop - the valve is totally shut.
* Lower electrical limit stop - the lower limit used in normal operation. This position does not totally close the valve, thus preventing contact wear of the housing and throttle blade.
* Emergency running position - the position of the valve when it is not energised. This allows sufficient airflow for an idle speed a little higher than standard.
* Upper electrical limit stop - the blade is fully open.
The control system has a self-learning function, whereby the state of the mechanicals within the electronic throttle (eg spring tensions) is determined by the evaluation of the throttle valve's reaction speed.
As with the Accelerator Pedal Position Sensor, sophisticated limp-home techniques are available should the Electronic Throttle Control Actuator develop problems. These include:
Emergency running program #1
This occurs when an angle sensor within the throttle body fails or an implausible signal is received. Required is an intact throttle angle sensor and plausible mass airflow measurement.
* Torque increasing requests from other systems are ignored (eg from the Engine Braking Control);
* The fault lamp is illuminated.
Emergency running program #2
This occurs if the throttle valve drive fails or malfunctions; it requires that both throttle valve potentiometers recognize the Emergency Running Position of the throttle blade.
* The throttle valve drive is switched off so that the valve defaults to the small emergency running opening;
* As far as possible, ignition angle control and turbo boost control(!) are used to execute driver torque demands.
* The fault lamp is illuminated.
Emergency running program #3
This occurs if the throttle valve position is unknown and/or if the throttle valve is not definitely known to be in the Emergency Running Position.
* The throttle valve drive is switched off so that the valve (hopefully!) defaults to the small emergency running opening;
* The engine speed is limited to approximately 1200 rpm by fuel injection control;
* The fault lamp is illuminated.
An Audi schematic diagram showing the operation of the electronic throttle system is shown here.








As you can see, Bosch engineers have been very careful to ensure that a failure of the electronic throttle system will not cause the car to suddenly have full power - or a stalled engine.


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## gdoggmoney (Feb 21, 2004)

_Quote, originally posted by *Intelligent Minds* »_As discussed last week, the Bosch ME-Motronic engine management system is a radical departure from previous electronic engine management. The relationship between the accelerator pedal position and the opening angle of the throttle valve is no longer fixed; instead the Electronic Control Unit (ECU) determines how much torque the engine is required to produce and then opens the throttle valve to the appropriate angle. The chosen throttle opening is based on complex software that models the engine's instantaneous torque output and compares this with the required torque output, as requested not only by the driver but also by in-car systems.
The Audi twin turbo V6 (pictured above) is an example of an engine equipped with ME-Motronic management.
Torque Control Logic








The ME-Motronic system prioritises and coordinates torque demands in order that it can implement an overall torque control strategy. As this Audi diagram shows, torque requests are categorised as 'Internal' or 'External'. External torque requests include those made by the driver, cruise control system and driving dynamics systems like Automatic Stability Control. Internal torque requests are those made by the internal programming of the ECU - factors such as engine governing and idle speed control. The total requested torque is then modified by strategies such as those which take into account catalytic converter temperature or driving smoothness.
n older engine management systems, the driver - via the mechanical alteration of the throttle blade angle - exercised direct control over the mass of cylinder charge, while the management system was limited to torque reduction strategies (eg by fuel cuts) or minor torque increases through manipulation of the mass of air bypassing the throttle. However, this approach does not cope very well with competing and contrary torque demands that may well occur simultaneously. This Audi diagram shows some of the required torque variations found in current cars, excluding those requested by the driver.








The ME-Motronic system internally models the net torque development of the engine. This model takes into account losses through internal friction, pumping losses, and parasitic loads such as that of the power steering and water pumps. Internal mapping within the ECU allows optimal specifications for charge density, injection duration and ignition timing for any desired net torque value, taking into account the often conflicting requirements of best fuel economy and emissions. These requirements dictate that the system must perform well in transients (ie sudden changes in torque), as well as when being subjected to steady-state loads. To allow good performance in both constant and transient load conditions, two different control approaches are taken.
The first control strategy is termed by Bosch the Charge Path. 'Charge' in this context refers to the mass density of air trapped in the cylinder. At a given air/fuel ratio and ignition advance, the mass of this air is directly proportional to the force generated during the combustion process. The Charge Path, controlled by the opening angle of the throttle blade (and boost pressure in a forced induction car), is used to control engine torque output in static operations. The ability of this control system to change quickly is limited by the regulating speed of the throttle actuator and the time constant of the intake manifold, which can be as high as several hundred milliseconds at low engine speeds.
The other technique used to control torque output is termed, somewhat oddly, the Crankshaft Synchronous Path. This refers to torque variations able to be rapidly created by changes in ignition timing and injection operation, with the latter used to effect the air/fuel ratio. Examples of when this approach is employed include torque reduction during automatic transmission gear changes and when Vehicle Stability Systems are operating.


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## gdoggmoney (Feb 21, 2004)

Here comes the awesome meat:

_Quote, originally posted by *Intelligent Minds* »_
Getting confused? This Bosch diagram puts it all together.








On the far left is the driver, who (at least on the diagram!) is still given pride of place. The driver request for torque is prioritised and processed in terms of driveability functions. These include filtering and slope-limiting, dashpot (to ensure that torque changes do not occur too quickly) and anti-jerking. These functions can be calibrated to suit a wide range of applications - for example a high level of anti-jerk to suit a luxury car, or very quick throttle response to suit a sports car.
In addition to the driver's torque request, other torque variations (for example, an increase in torque to operate the air conditioner compressor, or a reduction in torque required by the load change damping system) are processed, with the final request then fed into the 'Torque to charge density conversion' box. When a torque request is made, the ECU must calculate how much fresh air mass is required to be inhaled by the engine to meet this demand. The actual mass of air that is needed will be dependent on ignition timing (eg if the engine is running relatively retarded ignition to decrease oxides of nitrogen emissions, more air will be needed because efficiency will be lower), internal engine friction, the instantaneous air/fuel ratio and other factors.
Once a mass airflow that will meet the requirements is quantified, a throttle valve opening angle is calculated. However, in all engines, the required angle will be dependent on the manifold pressure, and in forced aspirated engines, manifold pressure will be quite critical to the mass of air actually inhaled. Thus, in these engines the turbocharger boost pressure and throttle valve opening are both specified such that the appropriate charge density required for the prescribed torque output is reached.
Calculating Cylinder Charge
As can be seen from the above, the accurate calculation of cylinder charge is vital if the torque modelling strategy is to be effective, and if appropriate amounts of fuel are to be accurately added to this air. Traditionally, a mass airflow meter positioned between the airfilter box and the throttle body has been used to measure intake airflow. However, the mechanical design of engines is now taking advantage of techniques that maximise cylinder charge in a way in which an averaged mass airflow measurement may not be able to accurately sense.
In the ME-Motronic system the available sensors are used as inputs to a charge air model, rather than being evaluated directly. The requirements for such a charge air model are:
* Accurate mass charge air determination in engines using resonant tuned and/or variable length intake manifolds, and engines using variable valve timing;
* Accurate response to Exhaust Gas Recirculation conditions;
* Calculation of required throttle valve aperture (and required turbo boost in forced induction engines).
While the engine is subjected to a constant load, mass airflow measurement is relatively accurate: ie if Xkg of air per second is passing through the airflow meter, it can be assumed that all of it is ending up in the cylinders! However, during transients, the situation is much more complex. For example, if the throttle blade is abruptly opened, the intake plenum chamber will rapidly fill with air. For an instant this will give an inaccurately high reading from the airflow meter - the meter will indicate a higher cylinder charge than has actually had time to occur. It is only when intake manifold pressure has risen that the flow will commence into the cylinders.
As a result of this characteristic, the ME-Motronic system generally uses both manifold absolute pressure (MAP) and hot wire airflow meter (HFM) inputs. (In some cases the MAP sensor is not fitted; further software modelling duplicates its function.) The HFM is a further development of the design used by Bosch and other management systems for about 15 years. Its improvements result in better accuracy; for example, it is capable of differentiating reverse flow pulses from airflow passing into the engine.


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## stjacket (Apr 26, 2007)

*Re: (gdoggmoney)*

good post


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## Issam Abed (Feb 12, 2004)

*Re: How your drive by wire ME7 MKIV 1.8T/VR6 Motronic works. (gdoggmoney)*

Excellent post! Thanks for shairing!


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## 03redgti (Feb 18, 2006)

*Re: How your drive by wire ME7 MKIV 1.8T/VR6 Motronic works. (Wizard-of-OD)*

oh crap..this is the exact problem im having.. accelerator position sensor code from vag..it comes on after i clear even before i start the car..i'm thinking its a bad wire going to the ECU..but i doubt that the sensor itself just went out after swapping ECU's and after the BT install.. heres the exact code im getting 18047 P1639 Accelera.Pedal Pos.Sensor 1+2 Range/Performance and the car won't boost at all..EPC light is on..and it wont rev past about 3.5krpm..and if it does it revs really slow.. any idea's??


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## MILESisBROKE (Dec 28, 2009)

Ok since looking over this I have a question. My car will not rev over 2500rpm's. And when I shut the car down I hear a vibrating/ whining coming from what I think is the accelerator pedal potentiometer, this is on a VR6 AFP by the way. What are the chances that the potentiometer is my problem here? Would this make my car only rev out to 2500rpms then cut off? Sometimes it won't even rev out past 1000 rpms. Please help.


gdoggmoney said:


> _Quote, originally posted by *Intelligent Minds* »_
> Accelerator Pedal Position Sensor
> Two approaches are currently used in the design of this sensor, but they are electrically identical. The throttle pedal assembly from an Audi S4 is shown here. Movement of the accelerator pedal manipulates two rotary potentiometers; unlike some electronic throttle engines, no back-up Bowden cable exists to connect accelerator pedal movement to the throttle blade. Two potentiometers are fitted to the sensor to allow redundancy - if one should fail, the other still lets the system operate
> 
> ...


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## gdoggmoney (Feb 21, 2004)

Scan it! That is the next step. But yes that sounds probable. I've yet to experience that in a DBW car.


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## woodrowstar (Jun 17, 2005)

Throttle body on its way out?


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## Zweibb (Jun 6, 2006)

*'01 1.8T Hot Start Problem*

Appreciate the post on the Bosch ME-Motronic System....having issues with what appears to be a "hot start" symptom. Problem is associated to hot day (outside temperatures 85°F and higher) and actual driving time of 15 minutes or longer. Initially vehicle starts and operates great, problem occurs when I attempts to restart within a few minutes (15 minutes approx.) vehicle will not start after 5+ seconds of cranking. But, will start/fire after the initial attempt with the "EPC" illuminated, vehicle will operate but reduced power. But, if I immediate turn-off and restart "EPC" does not come on and vehicle operation fine. Your thoughts please.

Thank You


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## ps2375 (Aug 13, 2003)

Zweibb said:


> Appreciate the post on the Bosch ME-Motronic System....having issues with what appears to be a "hot start" symptom. Problem is associated to hot day (outside temperatures 85°F and higher) and actual driving time of 15 minutes or longer. Initially vehicle starts and operates great, problem occurs when I attempts to restart within a few minutes (15 minutes approx.) vehicle will not start after 5+ seconds of cranking. But, will start/fire after the initial attempt with the "EPC" illuminated, vehicle will operate but reduced power. But, if I immediate turn-off and restart "EPC" does not come on and vehicle operation fine. Your thoughts please.
> 
> Thank You


scan it.


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## gdoggmoney (Feb 21, 2004)

Check all your throttle body and pedal harness connections.


I had my throttle body harness pop off and leave me semi stranded. I thought I blew the car up, it was pulling 5" of vacuum and would barely idle.



Hot can cause expansion, and resistance or break contacts enough or just a little....


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## Zweibb (Jun 6, 2006)

Appreciate the info, will check out after the evening commute. Thank you


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## gdoggmoney (Feb 21, 2004)

Here is the ME7 functions. Yes it is in German. Thank Tony and the nefmoto boys for their work and sharing this even though it is more common on the web now.


http://nefariousmotorsports.com/forum/index.php?action=dlattach;topic=400.0;attach=359


http://www.nefariousmotorsports.com/wiki/index.php/Funktionsrahmen


Some of the functions have been translated.


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## Zweibb (Jun 6, 2006)

Still having problems, connections on throttle valve control unit and accelerator pedal position sensors appear to tight. Brief description what happen today, pulled vehicle out of garage turned off and restarted within 3 minutes. Drove for 15-20 minutes, turn-off & re-started within 2-3 minutes. Started OK but required longer start time (3-4 seconds), ran car for less than 1 minute turned-off and re-started after 10-15 minutes. Again longer start time (3-4 sec) ran for less than 1 minute and turned-off. Re-started after 15-20 minutes, normal start time (1-2 seconds). Drove vehicle 10-15 minutes, turned-off and sat for 15-20 minutes. Would not start after 5+ plus seconds, tried 3 times but would not fire, 4th time pushed accelerator pedal to floor after turning on ignition, engine immediately fires but "EPC" turned on. Knowing the driviablity of an "EPC" situation immediately turned off and immediately re-started the vehicle. Fired up within the normal 1-2 second and no "EPC". Vehicle ran for 25 minutes approx., turned off vehicle and allowed to sit for 5 minutes and re-started/fired after 3-4 seconds. Allowed unit to sit for additional 20-25 minutes and it fired immediately. What is going on.


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