diff --git a/rotatingMachine.js b/rotatingMachine.js
index 0f1abf4..21cb5e8 100644
--- a/rotatingMachine.js
+++ b/rotatingMachine.js
@@ -1,6 +1,7 @@
 const nameOfNode = 'rotatingMachine';
 const nodeClass   = require('./src/nodeClass.js');
 const { MenuManager, configManager } = require('generalFunctions');
+const { buildQHCurve } = require('./src/display/workingCurves');
 
 module.exports = function(RED) {
   // 1) Register the node type and delegate to your class
@@ -32,4 +33,20 @@ module.exports = function(RED) {
       res.status(500).send(`// Error generating configData: ${err.message}`);
     }
   });
+
+  // Q-H curve sampler — served on RED.httpNode (the dashboard/runtime
+  // router) so dashboard function nodes can fetch without admin auth.
+  // GET /rotatingMachine/:id/qh-curve?ctrl=<percent>
+  // Returns { ctrlPct, points: [{ Q (m³/h), H (m), dpPa }, ...] }
+  RED.httpNode.get(`/${nameOfNode}/:id/qh-curve`, (req, res) => {
+    const node = RED.nodes.getNode(req.params.id);
+    const source = node?.source;
+    if (!source) {
+      res.status(404).json({ error: `No rotatingMachine with id ${req.params.id}` });
+      return;
+    }
+    const ctrl = Number(req.query.ctrl);
+    const result = buildQHCurve(source, Number.isFinite(ctrl) ? ctrl : source.state?.getCurrentPosition?.() ?? 0);
+    res.json(result);
+  });
 };
\ No newline at end of file
diff --git a/src/display/workingCurves.js b/src/display/workingCurves.js
index 8141146..d4631bf 100644
--- a/src/display/workingCurves.js
+++ b/src/display/workingCurves.js
@@ -58,4 +58,58 @@ function showWorkingCurves(predictors) {
   };
 }
 
-module.exports = { showWorkingCurves, showCoG };
+/**
+ * Build a Q-H curve sample at a fixed control position.
+ *
+ * For each pressure slice the predictor knows about, evaluate predicted
+ * flow at `ctrlPct`, convert canonical Pa to pump head (m of water column,
+ * H = ΔP / (ρ · g)), and emit one (Q, H) point. Result is the pump's Q-H
+ * curve at the requested speed/control.
+ *
+ * State handling: temporarily writes fDimension to walk the slices, then
+ * restores the predictor's original fDimension and outputY by reissuing
+ * y(originalX) — so callers can hit this without corrupting live
+ * predictions. (Same trick as the existing benchmark scripts.)
+ */
+function buildQHCurve(predictors, ctrlPct, options = {}) {
+  if (!predictors || !predictors.hasCurve || !predictors.predictFlow) {
+    return { error: NO_CURVE_ERROR, points: [] };
+  }
+  const pf = predictors.predictFlow;
+  if (!pf.inputCurve || typeof pf.inputCurve !== 'object') {
+    return { error: NO_CURVE_ERROR, points: [] };
+  }
+  const x = Number.isFinite(+ctrlPct) ? +ctrlPct : (pf.currentX ?? 0);
+  const RHO = 999.1;   // kg/m³ — water at ~15 °C
+  const G = 9.80665;   // m/s²
+
+  // Allowed pressure range from the predict library; falls back to the
+  // raw inputCurve keys if fValues isn't populated yet.
+  const fMin = Number.isFinite(pf.fValues?.min) ? pf.fValues.min : -Infinity;
+  const fMax = Number.isFinite(pf.fValues?.max) ? pf.fValues.max :  Infinity;
+  const pressures = Object.keys(pf.inputCurve)
+    .filter((k) => /^-?\d+(?:\.\d+)?$/.test(k))
+    .map(Number)
+    .filter((p) => p >= fMin && p <= fMax)
+    .sort((a, b) => a - b);
+  if (!pressures.length) {
+    return { error: 'No pressure slices in envelope', points: [] };
+  }
+
+  const originalF = pf.fDimension;
+  const originalX = pf.currentX;
+  const points = [];
+  try {
+    for (const p of pressures) {
+      pf.fDimension = p;
+      const QM3s = pf.y(x);
+      points.push({ Q: QM3s * 3600, H: p / (RHO * G), dpPa: p });
+    }
+  } finally {
+    pf.fDimension = originalF;
+    if (Number.isFinite(originalX)) pf.y(originalX);
+  }
+  return { ctrlPct: x, points };
+}
+
+module.exports = { showWorkingCurves, showCoG, buildQHCurve };
diff --git a/src/prediction/efficiencyMath.js b/src/prediction/efficiencyMath.js
index 1aa7549..4d0478a 100644
--- a/src/prediction/efficiencyMath.js
+++ b/src/prediction/efficiencyMath.js
@@ -5,19 +5,32 @@
  * container and update the legacy fields (cog, NCog, currentEfficiencyCurve,
  * absDistFromPeak, relDistFromPeak) on it in place — matching the
  * pre-refactor surface tests assert on.
+ *
+ * Efficiency definition: hydraulic efficiency η = (Q · ΔP) / P_shaft —
+ * a dimensionless 0..1 ratio. The legacy pre-refactor implementation
+ * stored `flow/power` in canonical SI (m³/J), which (a) yields tiny
+ * numeric values that dashboards round to 0.0000 and (b) is monotonic
+ * in ctrl for centrifugal-pump curves so it has no interior peak — so
+ * NCog collapses to 0 and absDistFromPeak becomes meaningless. The
+ * hydraulic-efficiency form gives a real BEP (interior peak) and is
+ * directly comparable to nameplate efficiency. ΔP comes from the
+ * predictor's `currentF` (canonical Pa) because each fDimension slice
+ * IS the curve at that pressure differential.
  */
 
 const { gravity, coolprop } = require('generalFunctions');
 
-function calcEfficiencyCurve(powerCurve, flowCurve) {
+function calcEfficiencyCurve(powerCurve, flowCurve, pressureDiffPa) {
   const efficiencyCurve = [];
   let peak = 0; let peakIndex = 0; let minEfficiency = Infinity;
   if (!powerCurve?.y?.length || !flowCurve?.y?.length) {
     return { efficiencyCurve: [], peak: 0, peakIndex: 0, minEfficiency: 0 };
   }
+  const dP = Number.isFinite(pressureDiffPa) && pressureDiffPa > 0 ? pressureDiffPa : 0;
   powerCurve.y.forEach((power, i) => {
     const flow = flowCurve.y[i];
-    const eff = (power > 0 && flow >= 0) ? flow / power : 0;
+    // η = (Q · ΔP) / P. Falls back to 0 when any factor is missing.
+    const eff = (power > 0 && flow >= 0 && dP > 0) ? (flow * dP) / power : 0;
     efficiencyCurve.push(eff);
     if (eff > peak) { peak = eff; peakIndex = i; }
     if (eff < minEfficiency) minEfficiency = eff;
@@ -31,10 +44,11 @@ function calcCog(host) {
     return { cog: 0, cogIndex: 0, NCog: 0, minEfficiency: 0 };
   }
   const { powerCurve, flowCurve } = getCurrentCurves(host);
-  const { efficiencyCurve, peak, peakIndex, minEfficiency } = calcEfficiencyCurve(powerCurve, flowCurve);
+  const dP = host.predictFlow.currentF;
+  const { efficiencyCurve, peak, peakIndex, minEfficiency } = calcEfficiencyCurve(powerCurve, flowCurve, dP);
   const yMin = host.predictFlow.currentFxyYMin;
   const yMax = host.predictFlow.currentFxyYMax;
-  const NCog = (flowCurve.y[peakIndex] - yMin) / (yMax - yMin);
+  const NCog = (yMax > yMin) ? (flowCurve.y[peakIndex] - yMin) / (yMax - yMin) : 0;
   host.currentEfficiencyCurve = efficiencyCurve;
   host.cog = peak;
   host.cogIndex = peakIndex;
@@ -86,14 +100,28 @@ function calcEfficiency(host, power, flow, variant) {
 
   const flowM3s = host.measurements.type('flow').variant(variant).position('atEquipment').getCurrentValue('m3/s');
   const powerW = host.measurements.type('power').variant(variant).position('atEquipment').getCurrentValue('W');
-  host.logger.debug(`temp: ${temp} atmPressure : ${atm} rho : ${rho} pressureDiff: ${pressureDiff?.value || 0}`);
+  // Prefer the measured pressure differential; fall back to the predictor's
+  // current fDimension (the slice the prediction is being read from) so we
+  // still get a meaningful efficiency for predicted-variant calls when the
+  // measured differential isn't available yet.
+  let diffPa = pressureDiff?.value != null ? Number(pressureDiff.value) : null;
+  if (!Number.isFinite(diffPa) || diffPa <= 0) {
+    const fF = host.predictFlow?.currentF;
+    if (Number.isFinite(fF) && fF > 0) diffPa = fF;
+  }
+  host.logger.debug(`temp: ${temp} atmPressure : ${atm} rho : ${rho} pressureDiff: ${diffPa || 0}`);
   host.logger.debug(`Flow : ${flowM3s} power: ${powerW}`);
 
   if (power > 0 && flow > 0) {
-    host.measurements.type('efficiency').variant(variant).position('atEquipment').value(flow / power);
+    // η_hydraulic = (Q · ΔP) / P_shaft, dimensionless 0..1. Stored as the
+    // primary `efficiency` so dashboards and BEP-distance math see a
+    // physically meaningful number instead of m³/J. `flow` and `power`
+    // here are canonical m³/s and W from the predictor.
+    if (Number.isFinite(diffPa) && diffPa > 0) {
+      host.measurements.type('efficiency').variant(variant).position('atEquipment').value((flow * diffPa) / power);
+    }
     host.measurements.type('specificEnergyConsumption').variant(variant).position('atEquipment').value(power / flow);
-    if (pressureDiff?.value != null && Number.isFinite(flowM3s) && Number.isFinite(powerW) && powerW > 0) {
-      const diffPa = Number(pressureDiff.value);
+    if (Number.isFinite(diffPa) && diffPa > 0 && Number.isFinite(flowM3s) && Number.isFinite(powerW) && powerW > 0) {
       const head = (Number.isFinite(rho) && rho > 0) ? diffPa / (rho * g) : null;
       const hydraulicPowerW = diffPa * flowM3s;
       if (Number.isFinite(head)) host.measurements.type('pumpHead').variant(variant).position('atEquipment').value(head, Date.now(), 'm');
diff --git a/src/pressure/pressureRouter.js b/src/pressure/pressureRouter.js
index cca7300..e27fed9 100644
--- a/src/pressure/pressureRouter.js
+++ b/src/pressure/pressureRouter.js
@@ -2,33 +2,44 @@
 
 /**
  * PressureRouter — routes a measured pressure value into the right
- * MeasurementContainer slot and triggers downstream side-effects
- * (position recompute + drift/health refresh) only when the source
- * is a real child (not a dashboard-sim virtual one).
+ * MeasurementContainer slot and triggers the downstream cascade
+ * (preferred-pressure resolve → predicted recompute → drift → health)
+ * on every pressure write, matching the pre-refactor
+ * `updateMeasuredPressure` semantics.
  *
- * Extracted from rotatingMachine specificClass.updateMeasuredPressure.
+ * Why the cascade runs for virtual sources too: dashboard-sim pressure
+ * sliders route through virtual children, and the operator expects the
+ * predicted flow/power/efficiency/Cog to refresh on every slider tick.
+ * The cascade is idempotent — running it on a virtual write is cheap
+ * and matches what a real sensor would trigger.
+ *
+ * Why getPressure() runs first: getMeasuredPressure() writes the new
+ * pressure differential onto predictFlow/Power/Ctrl.fDimension. Only
+ * after that does updatePosition() compute flow/power via
+ * predictFlow.y(x) — otherwise calcFlowPower runs against a stale
+ * fDimension and the prediction lags one update behind the slider.
  */
 
 class PressureRouter {
   /**
    * @param {object} ctx
    *   - measurements: MeasurementContainer
-   *   - virtualPressureChildIds: { upstream, downstream }
+   *   - virtualPressureChildIds: { upstream, downstream }  (kept for debug only)
    *   - resolveMeasurementUnit(type, unit) -> canonical unit string (throws on invalid)
-   *   - updatePosition?(): called after a real-source write
-   *   - refreshDrift?(): called after a real-source write (e.g. _updatePressureDriftStatus)
-   *   - refreshHealth?(): called after a real-source write (e.g. _updatePredictionHealth)
-   *   - getPressure?(): optional, returns the current preferred pressure (for logging)
+   *   - getPressure?(): resolves preferred pressure and pushes fDimension to predictors
+   *   - updatePosition?(): recomputes predicted flow/power/efficiency/CoG at current ctrl
+   *   - refreshDrift?(): refreshes pressure drift status
+   *   - refreshHealth?(): refreshes prediction-health status
    *   - logger
    */
   constructor(ctx = {}) {
     this.measurements = ctx.measurements;
     this.virtualPressureChildIds = ctx.virtualPressureChildIds || {};
     this.resolveMeasurementUnit = ctx.resolveMeasurementUnit || ((_t, u) => u);
+    this.getPressure = ctx.getPressure;
     this.updatePosition = ctx.updatePosition;
     this.refreshDrift = ctx.refreshDrift;
     this.refreshHealth = ctx.refreshHealth;
-    this.getPressure = ctx.getPressure;
     this.logger = ctx.logger || { warn() {}, debug() {} };
   }
 
@@ -54,16 +65,19 @@ class PressureRouter {
     const isVirtual = this._isVirtual(childId);
     this.logger.debug(`Pressure routed: ${value} ${unit} at ${pos} from ${context.childName || 'child'} (${childId || 'unknown-id'}) virtual=${isVirtual}`);
 
-    if (!isVirtual) {
-      if (typeof this.updatePosition === 'function') this.updatePosition();
-      if (typeof this.refreshDrift === 'function') this.refreshDrift();
-      if (typeof this.refreshHealth === 'function') this.refreshHealth();
-    }
-
+    // Legacy order: resolve preferred pressure (writes fDimension to
+    // predictors) BEFORE recomputing predicted flow/power at the current
+    // control position. Skipping any of these on virtual sources broke
+    // the dashboard-sim demo (NCog / efficiency / absDistFromPeak stuck
+    // at 0, predicted flow/power not updating with the pressure slider).
+    let p;
     if (typeof this.getPressure === 'function') {
-      const p = this.getPressure();
+      p = this.getPressure();
       this.logger.debug(`Using pressure: ${p} for calculations`);
     }
+    if (typeof this.updatePosition === 'function') this.updatePosition();
+    if (typeof this.refreshDrift === 'function') this.refreshDrift();
+    if (typeof this.refreshHealth === 'function') this.refreshHealth();
 
     return true;
   }
diff --git a/src/specificClass.js b/src/specificClass.js
index 88c31a7..0790122 100644
--- a/src/specificClass.js
+++ b/src/specificClass.js
@@ -43,8 +43,24 @@ class Machine extends BaseDomain {
   // ES6 forbids `this` before super(). Single-threaded JS means stashing
   // on the class itself between the caller's args and super() is race-free;
   // configure() picks the extras up immediately after.
-  constructor(machineConfig = {}, stateConfig = {}, errorMetricsConfig = {}) {
-    Machine._pendingExtras = { stateConfig, errorMetricsConfig };
+  //
+  // Two call sites exist:
+  //   - nodeClass.buildDomainConfig() pre-sets Machine._pendingExtras and
+  //     then BaseNodeAdapter calls `new Machine(this.config)` (single-arg).
+  //   - Tests / direct callers pass (machineConfig, stateConfig, errMetrics)
+  //     explicitly.
+  // With default-param `stateConfig={}`, the single-arg path was silently
+  // clobbering the pre-set extras with an empty object, so the state machine
+  // booted with schema defaults (warmingup=5s, speed=1%/s, mode=dynspeed)
+  // regardless of what the editor saved. Only overwrite when an explicit
+  // value is provided.
+  constructor(machineConfig = {}, stateConfig, errorMetricsConfig) {
+    if (stateConfig !== undefined || errorMetricsConfig !== undefined) {
+      Machine._pendingExtras = {
+        stateConfig: stateConfig ?? {},
+        errorMetricsConfig: errorMetricsConfig ?? {},
+      };
+    }
     super(machineConfig);
   }
 
@@ -72,7 +88,7 @@ class Machine extends BaseDomain {
     // If the registry has no entry for this model, assetMetadata is null and
     // we'll error out with a clear message below.
     this.assetMetadata = this.model
-      ? assetResolver.resolveAssetMetadata('machine', this.model)
+      ? assetResolver.resolveAssetMetadata('rotatingmachine', this.model)
       : null;
 
     if (!this.model) {
@@ -81,7 +97,7 @@ class Machine extends BaseDomain {
       return;
     }
     if (!this.assetMetadata) {
-      this.logger.error(`rotatingMachine: model '${this.model}' not found in asset registry (datasets/assetData/machine.json). Cannot derive supplier/type/units.`);
+      this.logger.error(`rotatingMachine: model '${this.model}' not found in asset registry (datasets/assetData/rotatingmachine.json). Cannot derive supplier/type/units.`);
       this._installNullPredictors();
       return;
     }
@@ -291,6 +307,10 @@ class Machine extends BaseDomain {
       this.measurements.type('power').variant('predicted').position('atEquipment').value(0, Date.now(), pu);
     }
     this._updatePredictionHealth();
+    // Push port 0 deltas so downstream dashboards / probes see state +
+    // predicted-flow updates as they happen. BaseNodeAdapter listens for
+    // 'output-changed' on this.emitter to fire _emitOutputs().
+    this.notifyOutputChanged();
   }
 
   updatePosition() {
@@ -302,6 +322,7 @@ class Machine extends BaseDomain {
       this.calcDistanceBEP(efficiency, cog, minEfficiency);
     }
     this._updatePredictionHealth();
+    this.notifyOutputChanged();
   }
 
   // ── mode + input dispatch ──────────────────────────────────────────
@@ -371,7 +392,8 @@ class Machine extends BaseDomain {
     const powerCurve = this.groupPredictPower.currentFxyCurve[this.groupPredictPower.currentF];
     const flowCurve  = this.groupPredictFlow.currentFxyCurve[this.groupPredictFlow.currentF];
     if (!powerCurve?.y?.length || !flowCurve?.y?.length) return 0;
-    const { peakIndex } = this.calcEfficiencyCurve(powerCurve, flowCurve);
+    const dP = this.groupPredictFlow.currentF;
+    const { peakIndex } = this.calcEfficiencyCurve(powerCurve, flowCurve, dP);
     const yMin = this.groupPredictFlow.currentFxyYMin;
     const yMax = this.groupPredictFlow.currentFxyYMax;
     if (yMax <= yMin) return 0;
@@ -381,7 +403,7 @@ class Machine extends BaseDomain {
 
   // ── efficiency math (delegates) ────────────────────────────────────
   calcCog()                            { return eff.calcCog(this); }
-  calcEfficiencyCurve(p, f)            { return eff.calcEfficiencyCurve(p, f); }
+  calcEfficiencyCurve(p, f, dP)        { return eff.calcEfficiencyCurve(p, f, dP); }
   calcEfficiency(power, flow, variant) { return eff.calcEfficiency(this, power, flow, variant); }
   calcDistanceBEP(e, max, min)         { return eff.calcDistanceBEP(this, e, max, min); }
   calcDistanceFromPeak(e, peak)        { return eff.calcDistanceFromPeak(e, peak); }
diff --git a/test/basic/pressureRouter.basic.test.js b/test/basic/pressureRouter.basic.test.js
index f76e123..61d1bd9 100644
--- a/test/basic/pressureRouter.basic.test.js
+++ b/test/basic/pressureRouter.basic.test.js
@@ -35,42 +35,63 @@ test('route("upstream", 1, ctx) writes to the upstream pressure slot', () => {
   assert.equal(meas.writes[0].u, 'mbar');
 });
 
-test('virtual source: refresh hooks NOT called', () => {
+test('virtual source: full cascade still runs (dashboard-sim must update predictions)', () => {
   const meas = makeFakeMeasurements();
-  let posCalled = 0, driftCalled = 0, healthCalled = 0;
+  let pressCalled = 0, posCalled = 0, driftCalled = 0, healthCalled = 0;
   const router = new PressureRouter({
     measurements: meas,
     virtualPressureChildIds: { upstream: 'sim-u', downstream: 'sim-d' },
     resolveMeasurementUnit: () => 'mbar',
+    getPressure: () => { pressCalled++; return 100; },
     updatePosition: () => { posCalled++; },
     refreshDrift: () => { driftCalled++; },
     refreshHealth: () => { healthCalled++; },
     logger: SILENT,
   });
   router.route('upstream', 7, { childId: 'sim-u', unit: 'mbar' });
-  assert.equal(posCalled, 0);
-  assert.equal(driftCalled, 0);
-  assert.equal(healthCalled, 0);
+  assert.equal(pressCalled, 1);
+  assert.equal(posCalled, 1);
+  assert.equal(driftCalled, 1);
+  assert.equal(healthCalled, 1);
 });
 
 test('real source: all refresh hooks called', () => {
   const meas = makeFakeMeasurements();
-  let posCalled = 0, driftCalled = 0, healthCalled = 0;
+  let pressCalled = 0, posCalled = 0, driftCalled = 0, healthCalled = 0;
   const router = new PressureRouter({
     measurements: meas,
     virtualPressureChildIds: { upstream: 'sim-u', downstream: 'sim-d' },
     resolveMeasurementUnit: () => 'mbar',
+    getPressure: () => { pressCalled++; return 100; },
     updatePosition: () => { posCalled++; },
     refreshDrift: () => { driftCalled++; },
     refreshHealth: () => { healthCalled++; },
     logger: SILENT,
   });
   router.route('upstream', 7, { childId: 'real-pt-1', unit: 'mbar' });
+  assert.equal(pressCalled, 1);
   assert.equal(posCalled, 1);
   assert.equal(driftCalled, 1);
   assert.equal(healthCalled, 1);
 });
 
+test('cascade order: getPressure runs before updatePosition (fDimension must be fresh when calcFlowPower runs)', () => {
+  const meas = makeFakeMeasurements();
+  const calls = [];
+  const router = new PressureRouter({
+    measurements: meas,
+    virtualPressureChildIds: { upstream: 'sim-u', downstream: 'sim-d' },
+    resolveMeasurementUnit: () => 'mbar',
+    getPressure: () => { calls.push('getPressure'); return 100; },
+    updatePosition: () => { calls.push('updatePosition'); },
+    refreshDrift: () => { calls.push('refreshDrift'); },
+    refreshHealth: () => { calls.push('refreshHealth'); },
+    logger: SILENT,
+  });
+  router.route('upstream', 7, { childId: 'real-pt-1', unit: 'mbar' });
+  assert.deepEqual(calls, ['getPressure', 'updatePosition', 'refreshDrift', 'refreshHealth']);
+});
+
 test('rejected unit returns false and skips the write', () => {
   const meas = makeFakeMeasurements();
   const warns = [];
diff --git a/test/integration/bep-distance-cascade.integration.test.js b/test/integration/bep-distance-cascade.integration.test.js
new file mode 100644
index 0000000..017afe3
--- /dev/null
+++ b/test/integration/bep-distance-cascade.integration.test.js
@@ -0,0 +1,92 @@
+'use strict';
+
+const test = require('node:test');
+const assert = require('node:assert/strict');
+
+const Machine = require('../../src/specificClass');
+const { makeMachineConfig, makeStateConfig } = require('../helpers/factories');
+
+/**
+ * Reproduction harness for the dashboard report: after the pressure-router
+ * fix, the user sees absDistFromPeak=0, NCog=0, efficiency=0, predicted
+ * atEquipment flow blank, even after the machine is running and pressure
+ * sliders are being moved.
+ *
+ * This test mirrors the actual dashboard interaction:
+ *   1. start the machine (reach operational at ctrl=0)
+ *   2. set virtual pressure (dashboard slider equivalent)
+ *   3. move setpoint to non-zero ctrl
+ *   4. read the host fields + measurement values
+ *
+ * Every value should be non-zero after step 3. If anything is 0 here, the
+ * failure is reproducible at the unit level and we can patch it directly.
+ */
+
+async function makeRunningMachine() {
+  const cfg = makeMachineConfig({
+    general: { id: 'rm-bep', name: 'BEP-test', unit: 'm3/h', logging: { enabled: false, logLevel: 'error' } },
+    asset: {
+      supplier: 'hidrostal', category: 'pump', type: 'Centrifugal',
+      model: 'hidrostal-H05K-S03R', unit: 'm3/h',
+      curveUnits: { pressure: 'mbar', flow: 'm3/h', power: 'kW', control: '%' },
+    },
+  });
+  const m = new Machine(cfg, makeStateConfig());
+  await m.handleInput('parent', 'execSequence', 'startup');
+  assert.equal(m.state.getCurrentState(), 'operational');
+  return m;
+}
+
+test('after startup + pressure + ctrl move: NCog / efficiency / absDistFromPeak / flow-at-equipment are all non-zero', async () => {
+  const m = await makeRunningMachine();
+
+  // Dashboard slider equivalent — fire as virtual children (this is what
+  // simulateMeasurement does):
+  m.updateSimulatedMeasurement('pressure', 'upstream',  200,  { unit: 'mbar' });
+  m.updateSimulatedMeasurement('pressure', 'downstream', 1100, { unit: 'mbar' });
+
+  // Move to a non-zero ctrl position.
+  await m.handleInput('parent', 'execMovement', 50);
+
+  // Read every metric the user reports as 0.
+  const flowDn       = m.measurements.type('flow').variant('predicted').position('downstream').getCurrentValue('m3/h');
+  const flowAtEq     = m.measurements.type('flow').variant('predicted').position('atEquipment').getCurrentValue('m3/h');
+  const powerAtEq    = m.measurements.type('power').variant('predicted').position('atEquipment').getCurrentValue('kW');
+  const efficiency   = m.measurements.type('efficiency').variant('predicted').position('atEquipment').getCurrentValue();
+
+  console.log(JSON.stringify({
+    state: m.state.getCurrentState(),
+    ctrl: m.state.getCurrentPosition(),
+    flowDn, flowAtEq, powerAtEq, efficiency,
+    NCog: m.NCog, cog: m.cog, cogIndex: m.cogIndex,
+    absDistFromPeak: m.absDistFromPeak, relDistFromPeak: m.relDistFromPeak,
+    minEfficiency: m.minEfficiency,
+  }, null, 2));
+
+  assert.ok(Number.isFinite(flowDn) && flowDn > 0, `flow downstream should be > 0, got ${flowDn}`);
+  assert.ok(Number.isFinite(flowAtEq) && flowAtEq > 0, `flow at-equipment should be > 0, got ${flowAtEq}`);
+  assert.ok(Number.isFinite(powerAtEq) && powerAtEq > 0, `power at-equipment should be > 0, got ${powerAtEq}`);
+  // Hydraulic efficiency η = (Q·ΔP)/P is a dimensionless 0..1 ratio. For
+  // a reasonable pump operating point it should be at least a few percent.
+  assert.ok(Number.isFinite(efficiency) && efficiency > 0.01,
+    `efficiency should be a meaningful 0..1 ratio (>1%), got ${efficiency}`);
+  assert.ok(efficiency <= 1.0,
+    `efficiency must be <= 1 (dimensionless ratio), got ${efficiency}`);
+  // Peak efficiency (cog) likewise should be a meaningful ratio.
+  assert.ok(Number.isFinite(m.cog) && m.cog > 0.01 && m.cog <= 1.0,
+    `cog (peak efficiency) should be a meaningful 0..1 ratio, got ${m.cog}`);
+  // NCog is the normalized flow at peak — depending on the curve, BEP can
+  // land at peakIndex=0 (yielding NCog=0). Just require finiteness here.
+  assert.ok(Number.isFinite(m.NCog) && m.NCog >= 0 && m.NCog <= 1,
+    `NCog should be finite 0..1, got ${m.NCog}`);
+  // Distance-from-peak is what the user actually reads. It should be finite
+  // and at non-BEP positions it should be > 0.
+  assert.ok(Number.isFinite(m.absDistFromPeak) && m.absDistFromPeak >= 0,
+    `absDistFromPeak should be finite >= 0, got ${m.absDistFromPeak}`);
+  assert.ok(Number.isFinite(m.relDistFromPeak) && m.relDistFromPeak >= 0 && m.relDistFromPeak <= 1,
+    `relDistFromPeak should be finite 0..1, got ${m.relDistFromPeak}`);
+  // At ctrl=50 the current efficiency must differ from peak (we're off BEP),
+  // so absDistFromPeak should be non-zero.
+  assert.ok(m.absDistFromPeak > 0,
+    `absDistFromPeak must be > 0 when off BEP, got ${m.absDistFromPeak}`);
+});
diff --git a/test/integration/efficiency-cog.integration.test.js b/test/integration/efficiency-cog.integration.test.js
index 1735e79..2d74af2 100644
--- a/test/integration/efficiency-cog.integration.test.js
+++ b/test/integration/efficiency-cog.integration.test.js
@@ -33,22 +33,25 @@ test('calcCog peak is always >= minEfficiency', () => {
   assert.ok(result.cog >= result.minEfficiency, 'Peak must be >= min');
 });
 
-test('calcEfficiencyCurve produces correct specific flow ratio', () => {
+test('calcEfficiencyCurve produces hydraulic efficiency η = (Q·ΔP)/P at every point', () => {
   const machine = makePressurizedOperationalMachine();
   const { powerCurve, flowCurve } = machine.getCurrentCurves();
+  const dP = machine.predictFlow.currentF; // canonical Pa
 
-  const { efficiencyCurve, peak, peakIndex, minEfficiency } = machine.calcEfficiencyCurve(powerCurve, flowCurve);
+  const { efficiencyCurve, peak, peakIndex, minEfficiency } = machine.calcEfficiencyCurve(powerCurve, flowCurve, dP);
 
   assert.ok(efficiencyCurve.length > 0, 'Efficiency curve should not be empty');
   assert.equal(efficiencyCurve.length, powerCurve.y.length, 'Should match curve length');
 
-  // Verify each point: efficiency = flow / power (unrounded, canonical units)
+  // η = (Q·ΔP)/P. flow and power are in canonical SI (m³/s and W), so η is
+  // a dimensionless 0..1 ratio. dP is the pressure differential the slice
+  // represents (host.predictFlow.currentF).
   for (let i = 0; i < efficiencyCurve.length; i++) {
     const power = powerCurve.y[i];
     const flow = flowCurve.y[i];
-    if (power > 0 && flow >= 0) {
-      const expected = flow / power;
-      assert.ok(Math.abs(efficiencyCurve[i] - expected) < 1e-12, `Mismatch at index ${i}`);
+    if (power > 0 && flow >= 0 && dP > 0) {
+      const expected = (flow * dP) / power;
+      assert.ok(Math.abs(efficiencyCurve[i] - expected) < 1e-12, `Mismatch at index ${i}: got ${efficiencyCurve[i]}, expected ${expected}`);
     }
   }
 
diff --git a/test/integration/qh-curve.integration.test.js b/test/integration/qh-curve.integration.test.js
new file mode 100644
index 0000000..3a90122
--- /dev/null
+++ b/test/integration/qh-curve.integration.test.js
@@ -0,0 +1,76 @@
+'use strict';
+
+const test = require('node:test');
+const assert = require('node:assert/strict');
+
+const Machine = require('../../src/specificClass');
+const { buildQHCurve } = require('../../src/display/workingCurves');
+const { makeMachineConfig, makeStateConfig } = require('../helpers/factories');
+
+async function makeRunningMachine() {
+    const cfg = makeMachineConfig({
+        general: { id: 'rm-qh', name: 'qh-test', unit: 'm3/h', logging: { enabled: false, logLevel: 'error' } },
+        asset: {
+            supplier: 'hidrostal', category: 'pump', type: 'Centrifugal',
+            model: 'hidrostal-H05K-S03R', unit: 'm3/h',
+            curveUnits: { pressure: 'mbar', flow: 'm3/h', power: 'kW', control: '%' },
+        },
+    });
+    const m = new Machine(cfg, makeStateConfig());
+    await m.handleInput('parent', 'execSequence', 'startup');
+    m.updateMeasuredPressure(0,    'upstream',   { unit: 'mbar', timestamp: Date.now(), childName: 'pt-up' });
+    m.updateMeasuredPressure(1500, 'downstream', { unit: 'mbar', timestamp: Date.now(), childName: 'pt-down' });
+    await m.handleInput('parent', 'execMovement', 60);
+    return m;
+}
+
+test('buildQHCurve returns one (Q, H) point per pressure slice in envelope', async () => {
+    const m = await makeRunningMachine();
+    const r = buildQHCurve(m, 60);
+    assert.ok(!r.error, `should not error, got ${r.error}`);
+    assert.ok(Array.isArray(r.points) && r.points.length > 0, 'must return points array');
+    for (const pt of r.points) {
+        assert.ok(Number.isFinite(pt.Q), `Q must be finite, got ${pt.Q}`);
+        assert.ok(Number.isFinite(pt.H), `H must be finite, got ${pt.H}`);
+        assert.ok(pt.Q > 0, `Q must be > 0, got ${pt.Q}`);
+        assert.ok(pt.H > 0, `H must be > 0, got ${pt.H}`);
+    }
+    // Centrifugal pump: as head rises (higher pressure slice), flow drops.
+    // Verify monotone non-increasing Q across rising H.
+    const sortedByH = [...r.points].sort((a, b) => a.H - b.H);
+    for (let i = 1; i < sortedByH.length; i++) {
+        assert.ok(
+            sortedByH[i].Q <= sortedByH[i - 1].Q * 1.01 + 1e-6,
+            `flow should be non-increasing as head rises: ${JSON.stringify(sortedByH)}`,
+        );
+    }
+});
+
+test('buildQHCurve does not mutate predictor state', async () => {
+    const m = await makeRunningMachine();
+    const beforeF = m.predictFlow.fDimension;
+    const beforeX = m.predictFlow.currentX;
+    const beforeOutputY = m.predictFlow.outputY;
+
+    buildQHCurve(m, 60);
+
+    assert.equal(m.predictFlow.fDimension, beforeF, 'fDimension must be restored');
+    assert.equal(m.predictFlow.currentX, beforeX, 'currentX must be restored');
+    assert.ok(
+        Math.abs(m.predictFlow.outputY - beforeOutputY) < 1e-9,
+        `outputY must be restored, before=${beforeOutputY} after=${m.predictFlow.outputY}`,
+    );
+});
+
+test('buildQHCurve handles no-curve gracefully', () => {
+    const r = buildQHCurve({ hasCurve: false }, 50);
+    assert.ok(r.error, 'must report error');
+    assert.deepEqual(r.points, []);
+});
+
+test('buildQHCurve uses current ctrl when none provided', async () => {
+    const m = await makeRunningMachine();
+    const r = buildQHCurve(m);
+    assert.equal(r.ctrlPct, m.predictFlow.currentX,
+        `ctrlPct should default to current x, got ${r.ctrlPct} vs ${m.predictFlow.currentX}`);
+});