Final Design

The final design, as shown below, uses an engine control unit (ECU) and solenoids to control the valves rather than a camshaft. The ECU brain uses the speed sensors to determine the current engine speed and piston position. Using this information, the brain determines when the valves and injector should be opening, closing, or injecting. The brain then sends a switch signal to the relays which toggle power to the solenoids and injector. In example, when the brain determines that the intake valve should be opening, it sends a signal to a relay which turns on the power to the correct solenoid. In this way, the ECU monitors and controls the engine to run in six strokes. In addition, the ECU brain uses a thermocouple, mounted on the engine head, to determine the current engine temperature. If the engine is cold, the ECU runs in four stroke mode; if the the engine is hot enough to sustain water vaporization, the ECU runs in six stroke mode.

The final prototype is shown below. The ECU brain and relays are mounted on the boards in the foreground. The speed sensors are mounted on the bracket on the driveshaft. The solenoids and injector are mounted to the cylinder head. A pressurized water tank (on the right) is used to pressurize the water injector.