Electrolysis Questions

Hey, I'm new to electrolysis, and electricity in general. Although I have done a considerable amount of research, I still have a few questions, the reason being that I am hoping of developing a new engine concept, much like a Stirling Engine, that uses pressure produced by the electrolysis of water (I thought the electronics section was proper for this subject).

1. For anyone with chemistry knowledge, in terms of volume, how many liters (or whichever unit of measurement you prefer) of HHO gas will be produced from one liter of gas at SATP?

2. In a hypothetical situation, such as conducting electrolysis inside an enclosed pvc chamber, will that process require more electrical energy in order to conduct under those pressurized conditions?

3. How fast, exactly, can electrolysis be conducted at a high voltage of around 40,000 volts in liters?