I have 220v charger for electrical vehicle. It comes with 3 wires and need to connect to plug L14-20, which has 4 connectors. I think green --> G, black --> X, red ---> Y, and nothing --> W. This means W should not connect anything. Is this correct? Please advice.

If it's 240V why is the plug an L14-20? It should be an L6-20.
Are you using an existing 120/240V circuit?