Oil Accumulator questions

MTPyle

Well-Known Member
Oil oil capacity of our LT1 is pretty small. Was thinking about adding a oil accumulator to add volume and protection for pressure fluctuations.

My questions are:

Will a Accumulator use the additional volume during normal use? In other words does the oil get circulated or just stays in the Accumulator?

Does anyone know how it works on a engine with variable oil pump? our LT1 has ECM controlled oil pressure. How would it deal with the Accumulator?

What are the benefits other than starting?

Mike
 

43mod

Well-Known Member
No clue on v pump. But all pumps are variable due to rpm changes. Accusumps are a great benefit in my eyes, my engine builder was always amazed how good our bearings looked on freshen up. You set the pressure w air to equal the point you want the sump to flow back into the engine. Ei set it at 100 psi and it will probably never accept any oil from engine, set at 30psi and it will fill when op exceeds 30 and deliver when op below 30. Like when your hard on the brakes on two wheels turning. There is no way te stock wet sump is not pulling air. The accusump will feed in 2-3 qts at 30 psi. If you set it a few pounds above your min hot op it will cycle some oil every time engine op goes below set pressure and could help in oil cooling a bit.
hope that is helpful
 

MTPyle

Well-Known Member
Thanks for the feedback Mod

I wonder if it circulates the oil? in other words will having a Accumulator be like adding a larger pan? Or does the oil in the accumulator just stays where it's at?

For the last year I have been putting our truck on a diet and its lost a lot of weight. But now I think I can add more weight but it needs to be in the right spot. CG is important to me. So adding this low in the truck it might actually help us.

I keep watching that latest video with Luke at the Mint400 and his truck is so dialed. I am thinking more and more its not so much how much the truck weighs as the correlation between sprung and unsprung weight. His suspension can't move his truck. Its like the truck is heavy and stable and the unsprung weight is light and nimble.

Not really part of this thread but this idea has opened me up to adding weight in the right place.

Mike
 

jon coleman

Well-Known Member
accusump is an accumulator, like a shock resovoir, , a dividing piston, gas one side oil other, as oil psi cycles, oil flows in & out of accusmp, so it does circulate to a certain extent, i would say run dry sump pick up style pre screens for big trash& clean it on a set prep interval
 

Zambo

Well-Known Member
IMO accusumps are awesome if you don't have the wallet for a dry sump. The nitrogen preload you put in the accusump when the valve is closed only really adjusts the position of the floating piston inside. Once you open the valve, the pressure of the nitrogen will equal the pressure of the oil in the engine unless the piston bottoms out. When the engine is running if its putting out 60psi then the pressure of the nitrogen will be 60 psi. If the oil pump slows way down when you let off the gas, the inevitable drop in oil pressure will be reduced as the nitrogen behind the piston pushes oil into the engine. Same when you get back on the gas, the pressure spike will be absorbed by the accusump. The best way to think about it is like a shock absorber for the oil system. It dampens out pressure spikes and pressure drops. Especially handy in the rough when the oil pickup might be having a hard time scavenging from the pan.

One of the best uses for it in a race car is as a pre-oiler. These motors often sit for long periods of time without running. If you shut the accusump valve while the motor is running you will lock in some pressure. You can then open the valve before you start the engine next month and pre-oil everything before you engage the starter.
 

43mod

Well-Known Member
Also after pre oiling it acts as a buffer to keep cold start oil pressure from splitting filters or blowing them off. 50 wt on a cold day can see 110 psi at low rpm.
 

MTPyle

Well-Known Member
Great feedback, thanks!!

One more question:

If you have a 3 quart Accumulator and you turn off the engine all the oil in the accumulator goes into the engine, where does it go? What happens when you overfill a engine by 3qrts?

I assume that if the engine is not running its not as big deal to be way over full. But as it starts can it blow out the excess before the accumulator take it back?

Mike
 

isdtbower

Well-Known Member
I believe if you leave the valve open, it drains back into the pan. The issue for me is that when you start up, it fills the Accusump first/momentarily before feeding the engine bearings. (Accusump might be at 0 pressure or low pressure empty. And probably the reason to have some pressure on the bladder side when empty) ) I have been hesitant to add it but will on my next build. I intend to use a electric solenoid valve. Solenoid wired to the key on but with an inline switch on that circuit to close the valve when you are stopping and starting alot...or need the engine run switch on for some reason.

Unintended consequences.
 
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Nessy

Well-Known Member
I have one on one of my UTV's and when you shut the car off it shuts the valve leaving pressure in it. I usually rev it up before shutting it off to get as much oil and pressure in it as possible. When you turn on the ignition it pre oils the motor before cranking.
 

MTPyle

Well-Known Member
I guess my main concern and reason to add the accumulator is to add volume to the oil system and to make sure the engine has pressure under extreme circumstances like we see in a offroad race. I am less worried about the engine bearings at start up, we get a new engine each year. When the engine is cold and has been sitting we turn it over before we add ignition to get the pressure going before start.

I would want to get the extra 3 quarts to go into the engine at shut down and then back into the accumulator after start up. Basically getting fresh and cool 3 quarts every time I shut down the engine. We only have 7 quarts total so getting 3 extra quarts is like getting an oil change. Thru out a race the engine oil breaks down with fuel and heat.

We could have a manual valve that we close when we are getting ready to store the engine then re open before start. But in race conditions we would not use the valve.

Mike
 

MTPyle

Well-Known Member
I am sure I am overthinking this like I do with most things. LOL

Mike
 

jon coleman

Well-Known Member
yup, wet sump eng .you over fill by about the amount of volume your acc.sump holds at a good average psi, but if you shut off eng and Dont close valve, solenoid or manual, 3 quarts flows into oil pan, then, upon starting, 3 quarts , or there abouts, fills up acc. sump , until it hits the psi you set it at, operating temp psi at race rpm( a good average is your best psi setting
 

43mod

Well-Known Member
I like man valve. I want to control pre oil w out needing spark to do it. Probably insignificant. I also dont believe in electricity.
 

isdtbower

Well-Known Member
No doubts about what you are doing with a manual valve. But another thing to think about.

A key on would open without start. And dump it for oil change. An interrupt switch would allow moving up in a line without constant discharge. That was all I was trying to do. They do have an elec valve that manually closes when dumped down to a certain value.

I am not a fan of hot liquids near bodies But also not a fan of solenoid fail to closed position... Maybe a remote plunger to the manual valve??
 

Zambo

Well-Known Member
I used a manual valve. I would run the engine at normal psi, then shut the valve and trap that amount of oil in the accusump. Then I would service the engine to the proper amount on the dipstick. If I ever forgot to open the valve, the engine would simply run as normal but without the shock absorbing capability of the accumulator.

The oil doesn't just sit in there statically during operation, the floating piston is moving back and forth as the psi fluctuates. Therefor the oil inside isn't static, those extra 3 quarts are circulating throughout the whole system.

I used to love turning on the ignition, then opening the valve, and seeing oil pressure before I even started the motor. Fantastic peace of mind.
 
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