What is Simos 19?
Simos 19 is a family of petrol engine management systems used in Volkswagen Group applications. Volkswagen's self-study programme 822223 identifies Simos 19.6 on the EA888 Evo4 2.0-litre engine in its documented GTI, Atlas, Arteon and Golf R examples. EcuTek also identifies Simos 19.3 and 19.6 in its Mk8 EA888 Evo4 tool scope. These examples do not mean that every vehicle with the same engine family uses the same ECU, hardware or calibration.
The explanation below uses the documented EA888 Evo4 as an orientation. It is a simplified account of torque and air control, not a verified function diagram for every Simos 19 variant. Individual maps, units, signals and operating modes depend on the exact software and application.
From a request to engine output
- Request: Accelerator position and operating conditions contribute to the driver's torque request. Other vehicle functions, including gearbox or traction-control interventions where fitted, can also request a change.
- Coordinate and limit: The ECU takes applicable requests, operating conditions and limits into account to determine a permitted target. Driver request, an active limit and estimated delivered torque are different values.
- Plan and control the air: Torque and air-charge relationships help relate the desired output to the air needed by the engine. Air-path controls, such as the throttle, turbocharger actuator and camshaft timing, act to achieve the applicable targets.
- Control combustion: The ECU controls fuel delivery and ignition, applies feedback and corrections, and estimates the resulting output. The achieved result can differ from the request.
This flow is conceptual. Corrections, limits and interventions can act at several points or in parallel; it should not be read as a fixed order of maps.
What is the torque model?
The torque model is a calibrated representation of how engine output relates to air charge and operating conditions. It helps the ECU relate a torque demand to the air the engine needs and estimate output from the operating state. This is an explanatory model, not a direct measurement of crankshaft torque.
EcuTek's Evo4 guide identifies both reference air-charge and reference indicated-torque maps. A useful way to think about them is as related descriptions of air and combustion torque at reference conditions, but their exact axes, direction and use must be verified for the software being examined. The guide does not establish one universal map sequence for all Simos 19 ECUs.
Indicated torque describes combustion's contribution before mechanical losses. Engine or clutch torque values take losses into account differently. Requested, limited, estimated and measured torque are therefore not interchangeable. A gearbox controller may use communicated engine torque in its own control; deliberately making the reported figure inaccurate can affect shift quality or clutch control, as EcuTek notes for its documented Mk8 application.
Air charge and the air system
Air charge describes the air associated with a cylinder's combustion cycle. A tool may show it in milligrams per stroke (mg/stroke), while another channel shows total airflow in grams per second or kilograms per hour. These are different quantities; air in mg/stroke is also not a diesel's fuel injection quantity, even if the unit looks the same.
The ECU's air estimate and targets depend on operating conditions such as pressure, temperature, engine speed and valve operation. The throttle, turbocharger wastegate and camshaft settings affect the air reaching the cylinders. EcuTek's Evo4 material also refers to intercooler and compressor-related models or limits. Their details and calibration are application-specific.
Boost pressure alone does not describe cylinder air charge. In a log, distinguish manifold pressure from pressure upstream of the throttle, requested pressure from its measured or estimated counterpart, and absolute pressure from gauge pressure. A modelled turbo speed or temperature is an estimate, not automatically a sensor measurement.
Fast and slow responses
Air-path changes take time, whereas ignition changes and some combustion interventions can act more quickly. COBB's Mk8 monitor list includes fast and slow torque setpoints as well as air, ignition and wastegate channels. Those names are useful clues when investigating a response; they do not by themselves prove the exact internal control sequence or availability on every Simos 19 software version.
Fuel, lambda and ignition
Lambda is the air-to-fuel ratio relative to the stoichiometric ratio for the fuel: 1 is stoichiometric, below 1 is richer and above 1 is leaner. Fuel delivery is coordinated with the estimated air and applicable lambda target. Target selection and corrections can change with operating mode or component temperature.
Volkswagen describes direct injection in its Evo4 example; injection equipment varies by application, so identify the hardware before assuming port injection is present. Ignition timing affects combustion and torque, and knock or temperature corrections can change the final value. A target in a calibration is not proof of what happened in a log.
Limits and protection
Torque, air-charge and pressure limits can restrict the result. Gearbox requests, turbocharger conditions, temperatures, engine speed and faults may also lead to interventions, depending on the application. Raising one limit does not ensure the requested air or torque will be achieved, and removing a protection can hide a fault or overload components.
A practical starting point
- Record the vehicle and engine, injection equipment, ECU variant, hardware number and exact software and calibration identifiers. Keep a recoverable original read and establish a healthy baseline.
- Match definitions to that software. Verify each relevant map's axes, units, scaling and function; do not assume a Simos 18 address or familiar name transfers to Simos 19.
- Where the tool and software support them, compare driver request, torque limits and estimated torque; air-charge target and estimate; manifold and upstream-throttle pressure; lambda target and actual; ignition timing and knock correction; fuel-pressure target and actual; and relevant temperatures. Investigate the active limit or discrepancy before changing a calibration.
COBB's Mk8 monitor list is an example of tool-specific channels, including modelled quantities. Availability, scaling and definitions must be checked for the actual vehicle, software and logger.
Family scope
Alientech's cited release lists Simos 19.3 and 19.6. This family index keeps each variant's software and tooling context separate.
Reading the sources
Use Simos 19 support and logging evidence to record what a source actually demonstrates. Follow a variant below for its applicable material.
Sources
Curated reference notes. Applicability follows the cited sources; hardware testing by this wiki is not implied.