I'm trying to figure out in my head how that would work. Key on and no oil pressure would open the valve? So when motor starts and you have oil pressure the valve closes? I guessing that would need to be a switch that is set to an oil pressure that is higher than idle. Or I guess you could always rev the motor to charge the accumulator before you shut it off. I have only used accumulators for circle track racing back in the claimer days as a way to use a stock oil pan in a circle track car. Not for dry starts although you could do that also. We set the level like previously mentioned by raising the rpm a little above idle to get good oil pressure on a hot engine then closing the valve. Shut the motor off and set the oil level to normal spot on the dipstick, site plug or however you're setting the oil level. The accumulators that I had used air pressure on the back side of a floating piston as a "air spring". Adjusting the preload pressure had a small affect on how much oil discharged and how much it would hold. I think we ran between 9 and 14 psi. Also to get all the oil out of the accumulator during an oil change you would have to put a high charge of air in it to force the piston all the way to the end of the cylinder. I also had one that had to be mounted vertical (to keep air above the oil. It didn't use a piston only the air above the oil to push the oil back out when pressure dropped. I think it only held about a quart.