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Simos 18 and Simos 19 torque and air model comparison

A source-based comparison of torque requests, air charge, boost and fast/slow responses in Simos 18 and Simos 19 EA888 examples.

Updated by llandowtuninguk@gmail.com   Revision 2

Applies to
Simos 18Simos 19

Check the hardware and software limits stated in this article.

Scope

Simos 18 and Simos 19 use broadly similar torque-oriented approaches in the EA888 examples described here: the ECU relates a torque request to the air charge required, controls the air and combustion systems, and estimates the resulting torque. EcuTek describes several Evo4 strategies as close to the earlier generation. Similarity does not make the calibrations interchangeable.

This comparison uses EcuTek's Mk7 EA888 Simos 18 description and COBB's Mk8 EA888 guide alongside EcuTek's Simos 19 Evo4 notes. These are examples of particular applications and tool definitions, not verified function diagrams for every 18.x or 19.x variant. Map names, selection rules, axes, units and hardware must be checked against the exact ECU software.

Side-by-side comparison

AspectSimos 18 exampleSimos 19 / Evo4 example
Driver demandEcuTek describes a pedal interpretation factor and maximum-torque maps that contribute to driver-requested torque.COBB lists driver clutch-torque and accelerator-pedal demand tables, with additional limits that can depend on gear, engine speed, air density and drive mode.
Torque to air chargeEcuTek describes a reference air-charge relationship using an indicated-torque setpoint. Its example accounts for losses and ignition and lambda efficiencies in relating the torque values.COBB describes mass-air setpoint tables indexed by requested torque and engine speed, alongside reference indicated-torque tables used to check the resulting relationship.
Choosing mapsEcuTek's example has different reference air-charge maps for intake flap, valve-lift and camshaft conditions.COBB lists 24 air-setpoint tables and 24 corresponding reference indicated-torque tables in its Mk8 example. It does not fully define when every individual table is used; the count is not a family-wide specification.
Air and boostEcuTek relates the reference air-charge output to manifold pressure and pressure upstream of the throttle in its Mk7 example.COBB describes an air target leading to a required boost target, with wastegate control and pressure limits in its Mk8 example. EcuTek also mentions intercooler and compressor-related models or limits.
Fast and slow responseEcuTek explicitly groups ignition and fuel interventions as a fast path and air-charge, throttle, turbo actuator and cam targets as a slower path.COBB lists fast and slow torque setpoints in its Mk8 logger. Those names alone do not establish identical internal routing or identical channel availability across Simos 19 versions.

What is shared?

In both examples, a torque demand, a torque limit and the ECU's estimated delivered torque are separate concepts. Air charge is related to the air entering a cylinder and may be displayed in milligrams per stroke (mg/stroke); it is not the same as total airflow in grams per second or kilograms per hour. Boost pressure is related to cylinder filling but is not itself the air mass in the cylinder.

Indicated torque describes combustion's contribution before mechanical losses. A clutch or output torque value accounts for losses differently. Logged and communicated values are generally modelled or requested quantities, so establish the definition of a channel before treating it as a measured crankshaft output. Gearbox coordination can depend on a representative torque estimate.

What differs in the documented examples?

The sources expose different map names and describe different levels of detail. The Mk7 guide spells out the indicated-torque and reference-air-charge relationship; the Mk8 guide describes air-setpoint and reference-torque table families and their stated use. This is evidence of how those examples are presented, not proof that either family has an exclusive model architecture. EcuTek's Evo4 guide explicitly reports substantial similarity with earlier strategies.

The engine hardware also matters to the calibration. Volkswagen's SSP 522 describes Simos 18.1 on CHHA/CHHB engines with both direct and intake-port injection. Its SSP 822223 describes direct injection on the documented Simos 19.6 EA888 Evo4 examples. These are application examples, not rules that all Simos 18 cars have port injection or all Simos 19 cars have the same hardware.

As an illustration, a 250 Nm request at a particular engine speed does not imply the same air-charge target on two different calibrations. Engine hardware, losses, temperature, valve state and other corrections can change the relationship. The number is illustrative; it does not describe a particular ECU or predict delivered torque.

Worked examples: torque request to air charge

Use the same illustrative operating point for both walkthroughs: a steady 3,000 rpm in one gear and drive mode, with the driver asking for 250 Nm. If an active torque limit reduces the accepted target, trace the value that the ECU actually uses at the torque-to-air step, not just the pedal request. The active air-charge table then returns a target in mg/stroke; call that calibration-specific result A. The cited guides do not publish matching map values for this exact operating point, so A must be read from the identified software and cannot be calculated from a generic boost value.

Simos 18: follow the reference air-charge path

  1. Resolve driver demand and torque caps. At 3,000 rpm, follow pedal position through the active Driver Interpretation Map for the selected mode, cam state and transmission. Its output works with the relevant Maximum Torque AT/MT table. Check the applicable indicated-torque limits, including Maximum Torque Final, Maximum Reference Indicated Torque, and the Basic Indicated Maximum Torque Full Load maps by power class and gear spread, before treating 250 Nm as the target that reaches the air model.
  2. Convert the torque target. In EcuTek's documented Mk7 example, the torque value is combined with frictional losses and lambda/ignition efficiency terms to form the indicated-torque setpoint used for air mass. That value indexes the active Reference Air Charge map.
  3. Read the correct air-charge map. The active reference map depends on intake flap position, valve lift and intake/exhaust cam phase. For the guide's wide-open-pedal example, the state is open flap, no lift, and the stated In1/Ex1 cam selection. Read or interpolate the map at the operating point: its output is A mg/stroke. A different flap, lift or cam state can select another reference map.
  4. Follow the air target into boost control. EcuTek describes the reference air-charge output feeding manifold-pressure and upstream-throttle pressure calculations, then boost offset and turbo/wastegate control. If air charge is capped or the target is not met, inspect the relevant air-volume and cylinder-air setpoint caps, manifold/charge-pressure limits, turbo-speed and pressure-ratio limits, plus temperature protection.

Useful Simos 18 logs: accelerator pedal percentage; driver/allowed torque and Torque Actual at Clutch where exposed; Air Mass Charge Setpoint and Air Mass Charge from Manifold; manifold absolute pressure and Pressure Upstream Throttle; wastegate position and setpoint; turbine actuator proportional/integral and final values; exhaust/intake pressure flow factors; turbo speed and setpoint. Add lambda target/actual, ignition by cylinder, knock correction and relevant air, coolant and exhaust temperatures to explain why estimated output may differ. EcuTek names the air-charge and pressure/turbo channels in its Mk7 guide; channel names and availability vary by logger.

Simos 19: trace the torque-intervention air setpoint

  1. Resolve the request and limits. Start with pedal position and the active Driver Clutch Torque Demand or Torque Demand From Accelerator Pedal table. Check Maximum Torque Request and the applicable gear-, rpm-, air-density- and drive-mode limits. EcuTek's Evo4 guide also identifies a Torque Limit at Clutch set by drive mode, power class and gear; the exact active limiter depends on the calibration and transmission.
  2. Look up torque to air. In COBB's documented Mk8 example, Requested Torque and Engine Speed index the Mass Air Set Point for Torque Intervention tables. The guide lists 24 tables: 12 for high runner-flap state and 12 for low state. The ECU interpolates the active relationship; the exact conditions selecting each individual table are not fully documented. For the accepted torque at 3,000 rpm, read the applicable table output as A mg/stroke, then check that the corresponding Reference Indicated Torque table remains consistent with the air target.
  3. Check air and pressure ceilings. The Maximum Cylinder Air Set Point limiter can cap the target. COBB describes the next step as air target to boost target; check the active boost-target limit, then whether pressure and wastegate control achieve it. EcuTek's Evo4 notes also identify Reference Air Charge/Reference Indicated Torque maps, intercooler and catalyst pressure-ratio maps, and compressor-surge limits that can constrain a target. These names and availability are application/tool specific.
  4. Compare target with response. If the logged torque target is lower than driver demand, identify which torque or protection limit is active. If the air target is present but air mass or pressure falls short, inspect throttle, runner-flap state, wastegate response, turbo limits, temperature and sensor scaling. If air tracks target but estimated torque does not, review ignition, lambda and knock response before drawing a conclusion.

Useful Simos 19 logs: Accelerator Pedal Position and Driver Requested Torque; Engine Torque (Max Allowed), main torque limitation and clutch limitation/protection where available; engine speed, gear and drive mode; Air Mass Per Stroke Set Point, Air Mass Intake Manifold Per Stroke and Air Mass Predicted; Boost Pressure and Boost Pressure Setpoint; Intake Manifold Pressure and its setpoint; runner-flap position/setpoint; wastegate duty cycle/setpoint and modeled turbine speed. Add lambda target/actual, ignition timing, knock correction, charge-air/coolant temperatures and fuel-pressure target/actual for context. These are examples from COBB's Mk8 monitor list, not a universal channel set for every Simos 19 variant.

For both families, confirm the ECU/software identity, map axes, units and logger scaling before comparing traces. A logged torque value is usually a model or request, not a direct crankshaft measurement; a plausible-looking air or boost trace does not prove that the torque model is accurate. The source examples describe particular applications and should not be treated as calibration instructions or as a reason to move a protection limit out of the way.

Comparing a real calibration

  1. Record the vehicle, engine, ECU variant, hardware, software and calibration identifiers, injection equipment and tool version for each example.
  2. Identify which torque is requested, limited, indicated or estimated at the clutch. Verify the map axes, scaling, units, operating mode and definition before comparing values; do not transfer addresses or assume similarly named tables have the same function.
  3. Where available, compare driver request, active torque limit and estimated torque with air-charge target and estimate, manifold pressure and upstream-throttle pressure, lambda, ignition timing, knock correction and relevant temperatures. Distinguish absolute from gauge pressure and sensor readings from modelled values.

Channel availability and meanings depend on the software and logger. COBB's Mk8 monitor list includes both measured and explicitly modelled quantities; its labels are not a universal Simos 19 channel list. Raising a single limit does not guarantee the requested air or torque, and making torque reporting inaccurate can affect vehicle-system coordination.

For the individual family overviews, see Simos 18 and Simos 19.

Sources