VE Table¶
Volumetric Efficiency — how much air actually fills the cylinder compared to its theoretical maximum, mapped across RPM and load.
What it is¶
A cylinder of a given size should swallow a fixed volume of air on every intake stroke. In practice it never fills perfectly: airflow has inertia, valves open for a limited time, and the intake and exhaust create pressure waves. Volumetric Efficiency (VE) is the ratio of the air that actually got in to that theoretical maximum, expressed as a percentage. The VE table maps VE across RPM (horizontal) and MAP / load (vertical).
Why it matters¶
VE is the heart of the speed-density air-mass estimate. If the ECU's idea of VE is wrong, its idea of air mass is wrong, and the fuelling is wrong by the same amount. A VE error at idle is especially nasty: it makes the mixture wander, which makes RPM hunt up and down.
In Engone the underlying physics computes its own VE from the build — port flow, valve and camshaft timing, intake Helmholtz resonance, exhaust scavenging, and residual burnt gas from valve overlap (worst at low RPM). There is deliberately no temperature term in VE; intake-air temperature is handled in speed-density.
Changing the table never changes how much air the engine breathes — it changes what the ECU believes, and therefore how much fuel it injects.
The table is how you teach the ECU the shape the engine actually has. Stock tunes ship with the table equal to the engine's real VE. After you change a cam, head, intake, exhaust or the rev-limiter axis, the table is stale and needs re-tuning.
How to tune it¶
Read the table as a map of where the engine breathes well: peaks where intake and exhaust tuning line up, dips where they fight. Tune at a steady operating point, compare measured lambda to the target, and correct the cell you're sitting in. See Editing Tables for the selection and edit tools.
Rule of thumb
If measured lambda is leaner than target at a cell, VE there is set too low (the ECU underestimated air and under-fuelled) — raise it. If it's richer, lower it.
Watch out
Don't chase a hunting idle by hand-editing single idle cells wildly — small, smooth corrections keep the surface stable. A lumpy VE table makes transitions unpredictable.
Watch out
Closed-loop trim can hide a VE error. Check the STFT chip: if it keeps working near ±25 %, the table is wrong there.
In the game¶
FUEL page, left. A 16 × 16 heat-map grid. X is RPM (the axis stretches to your rev-limiter setting); Y is MAP, 20 → 101.3 kPa. Cells range 0–120 %. A live tracer dot marks the current operating point.
Under the grid are four readouts: RPM, MAP, TABLE (what your table says here) and ACTUAL
(the engine's real VE here). The gap between TABLE and ACTUAL is the tuning signal:
TABLE below ACTUAL means under-fuelled (lean); above means rich. The VE cell in the throttle
box shows ACTUAL too.