Tuning Wiki

ME7.1 S4 load torque and ignition examples

M-box load/pressure and torque calculations, cam-dependent ignition, temperature correction and documented interpretation limits.

Updated by llandowtuninguk@gmail.com   Revision 1

Applies to
Bosch ME7.1

Check the hardware and software limits stated in this article.

Application and evidence scope

The calculations below are the M-box examples identified by S4Wiki for the S4 2.7T. They explain that implementation’s model. Keep the exact software, map definition and operating conditions with any derived value; an ME7.1 label or a matching map name alone does not establish identical code or stock calibration.

Requested load into requested pressure

The source’s FUEDK example converts requested charge into requested manifold pressure, then into requested pressure upstream of the throttle:

pssol = (rlsol / fupsrl + pirg) / fpbrkds
plsol = max(pssol / vpsspls + dpdk, pu)
TermMeaning in the source example
rlsolRequested relative cylinder charge / load
fupsrlCharge-to-pressure conversion including temperature effects
pirgResidual-gas partial-pressure contribution
fpbrkdsCylinder-filling / combustion-chamber pressure correction from the applicable model
vpssplsPressure ratio across the throttle from the applicable KFVPDKSD/E path
dpdkAdditional throttle pressure-drop term
puAmbient pressure, also the lower bound in this request calculation

The source explains modelled actual manifold pressure ps_w as a dynamic intake-manifold calculation: the difference between incoming air and cylinder outflow is integrated. It should not be calculated by simply substituting actual load into the upstream requested-boost formula.

The rough LDRXN-to-boost rule often quoted from this guide omits model and operating-condition effects. Use the actual signals and applicable calculation when diagnosing a request; ambient pressure, temperature, filling and cam state matter.

Torque request and the effective load ceiling

For the cited full-pedal M-box example, KFMIOP relates the effective maximum load to maximum relative torque; the pedal request is scaled against that result. Loss torque and efficiency terms participate before KFMIRL produces requested load, which is again limited by the permitted load.

Source model, simplified to its documented full-pedal path:
mimax   = KFMIOP(rlmax, nmot) * FMIVL
mifa    = mimax + loss torque, subject to the applicable torque cap
misopl1 = milsol / etazwbm / etalab
rlsol   = min(KFMIRL(misopl1, nmot), rlmax)

Read the complete source for the request conditions and intermediate functions. KFMIOP also estimates actual relative torque for monitoring; it is not solely a full-throttle boost adjustment. The source identifies shared load/speed axes between KFMIOP, KFZWOP/KFZWOP2 and KFMDS. Review all users when changing those axes.

Useful diagnostic relationships include permitted versus estimated torque (miszul and mibas), requested torque (mifa and related signals), maximum request (mimax) and ignition intervention (mizsolv). Interpret each through the matching function and scaling.

Cam-dependent base ignition

In this S4 example, KFNW selects a two-position intake-cam strategy. KFZW corresponds to the inactive position and KFZW2 to the active position. During changeover the source describes a weighting factor fnwue blending the tables:

base timing = fnwue * KFZW2 + (1 - fnwue) * KFZW

S4Wiki reports a 20-degree crank-angle reference in the M-box weighting and a stock KFNW map that is inactive at and above 3800 rpm. These are reported M-box settings. Verify another file’s cam strategy and calibration before interpreting KFZW2 through that example.

Temperature and knock interpretation

The source describes the correction dzwwl = KFZWWLNM * FZWWLRLN + KFZWWLRL as active beyond the “warm-up” wording in some definitions. In its M-box discussion this correction also interacts with knock-related enrichment through CWLAMFAW and KFLAMKRL. Review the active signals when both timing and requested lambda change with intake temperature.

Revision 5324 corrects an older description of KRANH: it is engine-speed-range hysteresis, not the rate at which timing is restored. KRDWA and the applicable advance-step/adaptation functions have separate roles. The source also notes that its M-box lacks KRFKLN even though some other variants have it.

Represented pressure range

S4Wiki gives approximately 2559.96 mbar absolute for the documented standard internal pressure representation, with the effective limit also influenced by conversion/offset. This is not gauge pressure or a sensor-upgrade instruction. Extended-range modifications require coordinated software and sensor changes documented for the exact image.

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: Load and manifold models, Requested boost, Timing, Torque monitoring, Knock recognition.

Sources

Curated reference notes. Applicability follows the cited sources; hardware testing by this wiki is not implied.