Volumetric Efficiency (VE)

A measure of how effectively the engine fills its cylinders with air, used by the speed-density model to estimate airflow.

Volumetric efficiency (VE) describes how completely the cylinders fill with air on each intake stroke relative to their theoretical capacity. In a speed-density tune the PCM uses a VE table, indexed by RPM and manifold pressure (MAP), together with air temperature and the ideal gas law, to calculate airflow and therefore fuel. Accurate VE is essential for a safe tune because every fueling decision rests on it; a low VE cell commands too little fuel and leans out under load. It matters most on MAF-less or blended setups, and after cams, heads, or forced induction change how the engine breathes. In HP Tuners VCM Editor the VE table sits under Engine > Airflow > Volumetric Efficiency (often a main and a secondary VE table on GM). VCM Scanner's VE-tuning workflow logs wideband-derived error so you can correct cells. Tune VE with a wideband connected and confirm delivered AFR, never trusting commanded alone.