I know that any signal with a period less than 60ms is applied, the coil just hums.
I have a 5V pulse wave going to the Base of a TIP3055 (1k resister in series), both the board and the car battery are grounded to the Emitter, the positive side of the battery goes to the coil and the other side of the coil goes to the Collector. And I do have a 1N4004 diode on the coil to protect the transistor.
On a 3/2 valve is it just a input pressure, output, and exhaust? I would have thought that the air pressure assisted valves would be faster.
BTW the valves open and close at the same speed. If there is a difference it is very very small.