Hella-Buggin'

OK, I know that it supplements oil pressure when the PSI drops below drops below a pre-set threshold.

My lack of understanding comes into play regarding a natural drop in pressure say during idle or braking or just lower rev situations. Does the accusump just start pumping it's oil even in a situation, like listed above, where it's not needed?

It seems dangerous to flood the case with an extra 2 or 3 quarts of oil.

Am I missing something?

CTS

Yes, that's exactly what it does. And yes, the extra oil can cause problems.

Cars with accusumps will usually have a low oil level while running unless the owner/mechanic has been trained up on how to check the oil. The accusump discharges most of its oil when it sees the normal low oil pressure of a hot idle. Then the engine is shut off, the oil checked, and the level is much too high. The excess oil is removed, (or more likely not put in in the first place) and now the running oil level is a couple quarts lower than desired.

You can work around this is you are aware of what is happening.

Also the accusump gives you a built in oil level reduction as the oil pressure climbs. Again, you can work around this if you know what you are doing.

IMHO it is not realistic to expect a normal DE or Club Racing owner/operator to get this right 100% of the time.

Chris Cervelli
Cervelli Technical Service

rlm328

http://www.accusump.com/accusump.pdf/instructions.pdf

See page 5.

Once the Accusump™ is mounted and the plumbing installed take some time to set the Accusump™'s precharge.
Improper pre-charge can result in many problems. To ensure your Accusump™ will work correctly follow
the steps listed here.
With the valve in the open position (electric units energized) and the engine not running; pressurize the
Accusump™ to 60 psi. This will ensure all the oil is out of the unit and the piston is all the way to the oil end. While
the Accusump™ is pressurized to 60 psi check all the fittings (gauges and lines) for leaks. Apply soapy water to each
area and check for bubbles. If possible, wait overnight to ensure there is no loss of pressure. For the unit to operate
correctly there cannot be any leaks in the air side. Temperature change will affect pressure.
Once you are sure there are no leaks, bleed down the air pre-charge to between 7 and 10 psi. Now when you
start the engine and open or energize the valve, the pressure in the air side of the Accusump™ should increase to
approximately that of your engine oil pressure. After you close the valve and shut your engine off, check your oil
level. Add oil as required to compensate for the oil being held in the Accusump™.
Under normal conditions the pre-charge should not need resetting after the initial set up. However, if a leak occurs
or if the unit's pre-charge seems to have changed you may need to reset your pre-charge to ensure your Accusump™
performs correctly. To reset your pre-charge, set the valve to the open position (electric units energized) while the
engine is not running; and pressurize the Accusump™ to 60 psi. Next bleed down the air pre-charge to between 7
and 10 psi.
Under no circumstances should the safety valve be removed, as this will void the warranty. If oil leaks from the
safety valve, be sure that it is sealed with Teflon tape and tightened; the safety valve is hand tight when delivered and
requires final tightening after installation of the Accusump™ valve. If oil still leaks from the safety valve, there is a
problem in the installation. These valves are very reliable and are set to open at 175 PSI, which is far above the
pressure the unit would see if installed correctly.

txhokie4life

The accusump is a dual chamber system, one side is filled with air, the other side with oil,
as the engine revs, the accusump fills with oil, the pressure compresses the air side of the chamber.

If the oil pressure drops, the air chamber will press the oil back towards the engine.

There was a check valve installed in the oil return flow which forces the oil to flow the through engine path in our setup.

I'm not sure how you don't just end up with an extra N quarts in the sump.

Mike

dan212

Its an interesting product. One way to address the problem of oil starvation under lateral load in a wet sump engine.

As an alternative, many shops such as BodyMotion also build aftermarket oil pans with better than X51 baffles to address issues of starvation under lateral load.

But consider what this Accusump tank is doing. It maintains engine oil under pressure. Thats nifty. But things break. Fittings break. Do you really want to put this next to you in your cockpit?

Best to mount it outside of the cockpit where a failure will not spray the hapless driver with hot engine oil.

Hella-Buggin'

Thanks Guys, I have a Mantis Deep Sump but my pressure are still dropping to 2.5 Bar on sustained right sweepers. My mechanic suggested an Accusump and I know lots of the Boxster guys run them.
My car is a street car that sees about 10 track days a year. I would probably mount it in the Tunnel in front of the gearbox in case of a leak.

CTS, I understand what you're saying. Make sure the chamber is full and valve closed for actual il level check.

It sounds complicated for sure, which is why I went with a deep sump, but the sump alone isn't making me feel confident. Coming down out of the Crow's Nest and through Turn 5 @ Thunderhill I'm watching the pressure drop to 2.5 Bar and it stays there until I'm straightened out almost to T6. My RPM's are exceeding the 10PSI / 1k RPM delta at the point.

AO

Under normal conditions, the oil in the accusump will not get very warm at all because it's not circulating. So even if it was inside, it shoudl not scald you. But I agree, and external mounting is ideal.

On my track car I have an accusump. I energize the system on the first start of the car (after it has been sitting for 24 hours or more). This ensures oil is flowing to the bearing on startup. Once the engine has started, (cold) oil pressure will refill the accusump chamber. This is usually the extent of the oil circulation that happens in an Accusump.

While running the car, the system stay on. If the oil pressure falls below 10(?) psi, the check valve opens and 50+psi of oil from the Accusump flows into the system, saving bearings and other stuff inside the engine. In a proper running engine, this shouldn't happen too often. (928's have a history of filling heads with oil in long sustained turns at high RPMs leaving the oil pickup uncovered - which is why I run one).

Then on my cooldown lap I turn off the system as to prevent the contents of the Accusump from being pushed in the the sump of the engine. Yes, I have forgotten once or twice - But I'm now in the habit of hitting the switch when I see the checker flag or begin a cooldown lap.If it dumps, it's no big deal. Just re-start the car and keep oil pressure above 3-bar for about 30 seconds and the Accusump will refill.

The Accusump is one of those things you shouldn't notice - kind of like an airbag. It's there to save your bacon if something goes wrong.

BTW, they do get old. When I got mine (used) the diaphragm was leaking. I send it off and for $100 or so, they rebuilt it and sold me on updating the check valve to a newer style. I'm very happy with it and am glad I have one.

Hella-Buggin'

Thanks AO

If I set the pressure to fill at 10 PSI, that would alleviate my concern about overfilling the case during low rev driving since my hot idle, even on track, is closer to 20 PSI. But that won't do much to solve my issue of pressure dropping in right sweepers as it seems to hold steady at about 35 PSI. That wouldn't bother me too much accept when acceleration through and out of a corner.

Quadcammer

I'm surprised you still have this issue with the mantis. I'm assuming this is the 2qt unit with the horizontal baffle?

OBehave2.0

Definitely mount outside cockpit. If you leave your car inside an enclosed trailer
for any length of time in hot weather,The canister is full and already pressurized then it cooks in the heat. The end caps blow off and soak the inside of your car. Ask me how I know? And yes it was installed correctly and it has happened to others as well.
Ed

jdistefa

An accusump is an expensive ballast system that occasionally spews oil all over the place.

Hella-Buggin'

I have the 1.2 Liter Sport one. It's still a street car and I was concerned about banging it on a speed bump.

OBehave2.0:

I saw your picture before and knew not to put it inside. I don't even want to put it in the trunk after seeing that mess.

PLNewman

I recently removed my Accusump and came in 23 pounds underweight during qualifying and had to start at the end of the field.
Accusump=Oily Dead Weight.

mark kibort

and is often forgotten to be turned on causing things to go boom.