VE = volumetric efficiency.

Consider what would happen if you could keep the intake valve open for a long time. Say a minute

The pressure in the cylinder would equal the pressure in the intake manifold, right? If you measured the amount of air in the cylinder, it would be the highest possible amount of air you could get in it, the theoretical maximum.

Now get the engine moving, the valves are opening and closing fairly fast, and the cylinder does not get filled completely. Measure the amount of air that does get into the cylinder and you get the real life air flow.

Now divide one by the other, real life/theoretical maximum, and you get the volumetric efficiency. The close that number is to 1 (or 100%), the more air you are flowing for a given set of conditions.

This is important, because the computer can calculate what the theoretical maximum air flow is, but without a mass air sensor it doesn't know what the actual air flow is.

So it figures up the theoretical max air flow, and looks up the VE value that you gave it. It multiplies the 2 together to get the actual, real life air flow. Once it knows that, it knows how much fuel to squirt to match that air flow.

The VE should hit a maximum at your torque peak.

The VE is not a function of fuel injectors, it is a function of your engine mechanicals (heads, cam, intake, turbo, etc...) and rpm and boost.

Hope that helps

John Estill