Follow air mass into fuel mass and injector time
ME7 estimates the air entering the cylinders, selects the required mixture, and calculates the fuel quantity and injector operation needed to achieve it. Injector calibration, fuel pressure, sensor conversion and operating corrections all participate. A change that makes one log trace look better can affect other calculations if it changes the estimated air charge.
This page explains the map roles and relationships described by S4Wiki. Its numeric 2.7T injector examples and M-box-specific corrections are filed under ME7.1. Confirm which functions and data representations exist in a particular ME7.5 or other ME7 application.
Primary injector calibration
| Map or parameter | Role in the cited strategy | What to establish |
|---|---|---|
| KRKTE | Conversion associated with fuel quantity and injector flow | Injector flow at the actual differential pressure, cylinder displacement, units and definition factor |
| TVUB | Injector voltage-dependent offset or latency | A suitable injector characterisation and the relevant pressure/electrical conditions |
| TEMIN / TEMINVA | Minimum injector operating-time constraints | The actual injector’s usable short-pulse behaviour and the software’s time representation |
| FKKVS | Fuel-system correction for non-linearity or operating effects | Where the correction acts in the calculation and how it interacts with the primary calibration |
| Warm-up and wall-film functions | Additional fuel corrections during changing temperature and wall wetting | Operating state and injector/spray-pattern changes |
Keep primary flow and voltage offset distinct. A nearly constant proportionate fuel error is different from a voltage-dependent or short-pulse error. If learned corrections compensate for a poor base calibration, inspect the base model and the operating region in which feedback is available before relying on that correction elsewhere.
Injector flow data must refer to a known pressure difference across the injector. Identify the pressure regulator arrangement and how differential pressure changes with manifold conditions. The 2.7T worked calculation is in ME7.1 S4 fueling and MAF examples.
MAF conversion and its offset
MLHFM provides the air-mass conversion for the fitted sensor and housing. In the relationship discussed by S4Wiki, MLOFS is subtracted from the MLHFM output. If that offset is non-zero, scaling the stored curve directly changes the effective zero as well as the slope.
Where the documented conversion is effective_airmass = MLHFM - MLOFS:
new_MLHFM = (old_MLHFM - MLOFS) * scale + MLOFSKeep the offset and its location in the calculation explicit. The source also notes that changing MLOFS and shifting the curve together can alter behaviour because averaging occurs at a particular stage. Match the actual sensor transfer function and the firmware’s calculation order.
KFKHFM provides additional air-mass correction. Because air mass feeds the load model, using it to compensate for a fuel-system error can move the calculated load and the operating points used by torque and ignition functions. FKKVS and KFLF act elsewhere; identify their role before treating all three as interchangeable fuel corrections. S4Wiki describes KFLF as an injector-time scaling function despite lambda-oriented labels found in some definitions.
Which lambda request wins?
The source describes several enrichment requests, including driver demand, knock-related enrichment and component protection. Lower lambda means a richer mixture. Within the documented combination, the richer eligible request can dominate, with filters, delays, activation thresholds and warm-up behaviour affecting the result.
| Request path | Maps and signals discussed | Interpretation |
|---|---|---|
| Driver-demand enrichment | LAMFA, its torque-request axis, activation delay and filtering | A request-related target; verify the input quantity and axis scaling |
| Knock-related enrichment | KFLAMKRL, ignition correction inputs and associated configuration | Mixture demand can change in response to knock/timing conditions |
| Component-protection enrichment | KFLBTS, TABGBTS, DLBTS or KFDLBTS and KFFDLBTS as fitted | Activation depends on the model and conditions; the final target can include additional corrections |
| Warm-up enrichment | The application’s warm-up functions, including KFLAFWL in the cited path | A separate operating-state contribution, including its blending/filtering |
Log the intermediate requests and final requested lambda. A LAMFA edit may have little visible effect if another request is richer, if a delay or filter is still active, or if the edited table is not the active one. KFLBTS alone does not describe every correction or activation condition in its path.
Closed-loop feedback and adaptations
Short-term feedback responds to the current mixture error when that control loop is operating. Long-term adaptations store learned corrections over defined regions. Keep additive and multiplicative corrections, each bank, and the learning conditions separate.
The S4 narrowband discussion in the source describes feedback near stoichiometric operation and open-loop rich operation. Establish the sensor type and actual strategy of another application before transferring that statement to it. An external wideband measurement is especially important when the ECU’s own sensor/control arrangement cannot establish the delivered rich mixture.
Evaluate idle, part load and high load together. The source recommends establishing primary injector and MAF calibration before using idle trim to refine latency; otherwise a later primary correction changes the apparent latency error. Retain the adaptation state with a log so that a changed learned correction is not mistaken for an effect of a new map value.
Check the model as well as mixture
Review air-mass plausibility, calculated load and pressure-model behaviour alongside requested and measured lambda. Inspect the axes reached at the new operating point. Sensor saturation, internal representation limits or the end of a map axis can stop the expected correction even while the measured engine output continues to change.
Use the variant examples for concrete file details. Keep injector flow figures, stock offset values, time-conversion factors and table addresses tied to the source software and hardware.
Source context and adaptation
Adapted, paraphrased and reorganised from S4Wiki contributors’ Tuning, revision 5324, under Creative Commons Attribution 4.0 International. This wiki adds scope labels, cross-links and interpretation notes. The cited software observations have not been independently reproduced by this wiki.
Source sections: Primary fueling and MAF scaling, Idle and injector behaviour, Lambda request paths, Part-throttle adaptations.
Sources
Curated reference notes. Applicability follows the cited sources; hardware testing by this wiki is not implied.
- S4Wiki: Tuning — source for expanded ME7 references. S4Wiki contributors; Creative Commons Attribution 4.0 International. Paraphrased, expanded and reorganised by Tuning Wiki. Source revision oldid 5324; accessed 2026-11-10.