Accusump oil level?

[GrandSport]

what do you mean it's open all the time?

The tank should be pressurized and then open when oil pressure drops.

[ZDan]

Originally Posted by GrandSport

what do you mean it's open all the time?

The tank should be pressurized and then open when oil pressure drops.

You can run with the valve open all the time on the track. I've done it before on LS3 FD when the pressure switch quit working (apparently not uncommon). I would rather the accumulator *immediately* start pushing oil into the main galley as soon as pressure starts to drop, rather than waiting for it to hit a minimum threshold pressure to open. If I were to use a pressure control switch it would be the 55-60psi one, but at that point there's not much difference on track at temp to just running open all the time.

These guys had been using the 40psi sensor but decided to bypass it (run open all the time) on the track and got better results:

(2:00 - 3:00)

[GrandSport]

Isn’t “open all the time” basically the same thing as “overfilled?”

[Midtenn]

No, because the accumulator isn't just extra volume of oil, it is providing supplemental pressure to the system when oil pressure in the motor drops below the pressure in the accumulator.

When pressure from the oil pump is higher than what is in the accumulator, oil is moved into the accumulator.

So, on the track with the valve open all the time, the oil pump has higher pressure than what is in the accumulator, so oil is pushed into the accumulator until the pressure between the two equalized. Oil then just circulates through the motor (pan, pump, motor, drain, repeat) and no oil volume is exchanged.

[GrandSport]

Originally Posted by Midtenn

No, because the accumulator isn't just extra volume of oil, it is providing supplemental pressure to the system when oil pressure in the motor drops below the pressure in the accumulator.

When pressure from the oil pump is higher than what is in the accumulator, oil is moved into the accumulator.

So, on the track with the valve open all the time, the oil pump has higher pressure than what is in the accumulator, so oil is pushed into the accumulator until the pressure between the two equalized. Oil then just circulates through the motor (pan, pump, motor, drain, repeat) and no oil volume is exchanged.

I must be misunderstanding something. That's how it always works. For me, if oil pressure drops below 20psi, oil goes from Accusump to engine. If it's above that, oil goes from engine to accusump (until accusump is full). You just have it at a higher PSI.

I personally didn't like that, because then the engine is way over full. Even at 20psi, when we pit, it would overfill. We got motec to control it, and have a min speed/rpm for accusump to be on.

[blsfrs]

Originally Posted by GrandSport

I must be misunderstanding something. That's how it always works. For me, if oil pressure drops below 20psi, oil goes from Accusump to engine. If it's above that, oil goes from engine to accusump (until accusump is full). You just have it at a higher PSI.

I personally didn't like that, because then the engine is way over full. Even at 20psi, when we pit, it would overfill. We got motec to control it, and have a min speed/rpm for accusump to be on.

By my back of the napkin calculations (given 2 qt accumulator and 7 psi precharge): If you charge your accumulator to 70 psi, you have 57.6 oz of oil stored. At 20 psi you still have 41.6 oz remaining in the accumulator:. 26 oz overfill at 20 psi idle. Please check my math. It's hard to do math with crayons.

[ZDan]

Originally Posted by GrandSport

Isn’t “open all the time” basically the same thing as “overfilled?”

No, not at all. Open all the time at the track means that if oil level is at normal "full" level at nominal pressure (say 60 psi) you have 1.5 quarts (ish) in reserve if (when) pressure drops due to oil starvation. Normal level/volume as far as engine is concerned. But as soon as oil pressure drops, the accumulator feeds in oil at the main galley to prevent starvation. Bearings are like, "yeh!".

You are at "normal fill" level until pressure drops, then the accumulator shoves oil in. Nice...

[Midtenn]

Originally Posted by GrandSport

I personally didn't like that, because then the engine is way over full. Even at 20psi, when we pit, it would overfill. We got motec to control it, and have a min speed/rpm for accusump to be on.

I agree that a pit stop situation would complicate the issue.

In a sprint race format, I didn't have an issue with my Miata. I would open it for prelube when the motor was cold. Once the engine was running, would close the valve, trapping high pressure oil. Once the motor was warmed up, I would not prelube again. Once I was on my warm-up lap, I would open the valve and run the race. Once the race was over, I would close the valve on the cool down. When I got to the pits, I would rev the motor up to build more pressure, open the valve to refill the Accusump, close the valve, let the motor return to idle, then shut down. When I checked the oil it was always at the same level(ish).

In a competition pit stop, you don't have time for the "rev up to refill" step. It would likely take some playing around with oil levels in the pan and Accusump to find that comfortable level. There is likely a "perfect" balance between overfill and Accsump pressure that would keep everything happy.

[smackrel]

I was always under the impression that when the pressure dropped the Accu picked up the slack and injected oil under pressure to compensate for the pressure drop. Not once did I ever think of the additional VOLUME of oil that it was adding in.

Depending on where your oil level starts are you just overfilled from that point on or can you put some of that oil back into the Accu when you get back to the pits?

I just reread the reply above mine and this was answered lol thanks