More info for Oil Accumulator Enthusiasts

Hello All,

No need to share views on the value of an accumulator, this post is for those who desire to operate one.

In the pursuit to make an automotive oil accumulator safer (they are not safe out of the box) I have made an interesting discovery.

My previous method of operation was to pressurize the oil gallery prior to start then re-pressurize the accumulator shortly thereafter.

One of my safety mods was to eliminate the air pressure gauge and its tiny tiny leaks, and install a oil pressure transducer feeding a signal to the engine monitoring system. This allows for me to track pressure rise as the engine compartment heats up. (which it turns out is rather nominal)

What I discovered is that the oil lines prior to the oil regulator get some serious pressure while the oil is cold. Between 120-140 psi has been seen with moderate temperatures outside. (60 degrees F)

So while my engine oil pressure was 60 ish that is not what I was charging my accumulator with. Now I am able to monitor recharge and stop at the pressure desired which for me is 55 psi.

If there is any interest in the other safety features I am glad to share.

Thunderbolt YIO 390, accumulator source Tee'd in on oil cooler path.

Summing up the new information

In the interests of safety and at the risk of being obtuse I'll restate my observation.

In a previous post I shared some rough math that suggested that because of the recessed space in the Moroso Accumulator's piston it is surprisingly easy to bottom out its stroke and achieve a hydraulic lock on the oil side that will pop the top off the bottle when the oil expands due to heat. (Happened to me)

Given a 10 psi precharge or 1.6-ish volumes of air it would take somewhere around 165 psi of oil pressure to bottom out the stroke of the piston. This is assuming a 50 degF rise in oil and air temperature once the bottle is charged and sealed.

The significance of my discovery that the oil lines contain much higher pressure than what is measured in the oil gallery when cold, is that it is very easy to push the piston dangerously close to the bottom of the bottle if we blindly recharge when the engine is warming up.

As stated I now monitor recharge, and use around two volumes of air on the gas side which still gives me around 1.3 quarts of oil at 55 psi.

Sorry if you already got that, just wanted to be sure I made that point. A burst can be an awful mess to clean up and dangerous if your valve is associated with the bursting parts.

Are you using a solenoid or mechanical valve? I use the Blue accumulator and have no valve, tee'd to the oil cooler. What spare pressure input did you use to read the value, that is a good idea. BTW - I try to preheat to 100F to lessen the higher TO oil pressure.

Set up

My set up uses a small 1/4" pipe ball valve controlled by a push/pull cable and failsafe sprung to the closed position.

I bought the same type oil pressure transducer as my electronic engine monitoring system (EMS) and installed an On / Momentary On push button to share the different signals to the same EMS input. This way my displayed oil pressure is engine oil gallery, and when I press the button I read accumulator air pressure.