what is piston pumping loss
Over the intake stroke, the piston is being acted upon * by the intake manifold pressure (vacuum) minus (even more vacuum) pressure drop across the intake valve/port.On the exhaust stroke it is being acted upon * by the exhaust manifold pressure PLUS pressure drop across the exhaust valve/port.Both of these strokes are thus resisting the motion of the crank, and therefore absorbing power. This power goes toward heating the air that is pumped through the engine.This is pumping loss. Since exhaust manifold pressure (assuming a decent exhaust system) is typically near ambient, pumping loss is mostly a function of intake vacuum.ver the intake stroke, the piston is being acted upon * by the intake manifold pressure (vacuum) minus (even more vacuum) pressure drop across the intake valve/port.