Accusump Oil Accumulators - how do they work?

Accusump Oil Accumulators

The Accusumps we stock here at Merlin are the original and best oil accumulators available on the market. For over 25 years the Accusump’s simplicity and effectiveness has made it the accepted method for providing continuous oiling whilst adding longevity to road and race engines alike. Also supplying oil pressure to the engine before startup for the purpose of pre-lubricating engine components.

What is an Accusump?

The Accusump is a cylindrical shaped aluminium storage container that acts as a reservoir of pressurised oil, to be released when there is a drop in the oil pressure. The Accusump is connected to the pressure side of an engine's oiling system and is charged by the engines own oil pump. Its simple, efficient design revolves around a hydraulic piston separating an air pre-charge side and an oil reservoir side. On the oil side of the Accusump it has an outlet that goes into the engine's oiling system, controlled by a valve. On the air side it's equipped with a pressure gauge and a Schrader air valve, which allows you to add a pre-charge of air pressure to the Accusump.
Accusump oil accumulators also deliver oil to the engine before starting to eliminate dry start scuffing (pre-oiling) and discharges oil during low oil pressure surges to protect against engine damage during demanding racing conditions e.g. hard cornering and braking.

How does it work?

The primary function of the Accusump is to collect pressurised oil from your engine and store it so it may be released later. At the time when the engine is switched off, the Accucumps valve is closed (or closes if using electric valve) and any oil pressure within the Accusump is held there. On engine start-up, when the valve on the oil side is opened, the pressurised oil is released into the engine and thus pre-lubricates the engine prior to start-up, limiting wear often caused in this scenario.

After the engine is started and the engine’s oil pump has taken over, oil is pumped back into the Accusump. This moves the piston inside the Accusump back and pressurises the Accusump unit until it equalises with the engine’s oil pressure. Whilst driving, if the engine’s oil pressure is interrupted for any reason, the Accusump releases it’s oil reserve once again, keeping the engine lubricated until the engine’s oil pressure returns to ‘normal’. This release of oil could last from 15 to 60 seconds depending upon the size and speed of the engine. In racing and hard driving conditions, the Accusump will automatically fill and discharge when needed such as during heaving braking, accelerating and cornering.

Which Valve suits my Application?

The Accusump units require a valve to control the flow of oil between the engine and the Accusump. This valve is crucial to close the unit off after shut down in order to hold pressure inside for pre-lubing the engine upon next start-up.
In most racing applications, a manual valve is used due to it’s simplicity. This valve can be mounted either on the Accusump directly, or plumbed in anywhere convenient along the feedline to the Accusump. With this valve, the user must manually open the valve before starting the engine. And likewise, close the valve off before turning the engine off.

For applications where it may be difficult to access a manual valve, a standard electric valve is used. The valve is designed to slowly refill after any discharge from the Accusump. This electric valve can be opened and closed from a remotely mounted switch on the dashboard, or hard-wired directly into the vehicles ignition so it will open and close automatically when the ignition is switched on and off.

If your application requires the convenience of an electrically operated valve but a faster refill rate, as in many racing vehicles, an Electric Pressure Control (EPC) Valve is highly recommended. The EPC valve system keeps the electric valve in the off position during times of normal oil pressure. With the valve in the off position it is able to quickly recharge the Accusump with oil pressure after discharge, thus making it ready for the next oil surge. When the engine’s oil pressure drops below the EPC Valve’s preset level, the valve opens and releases the stored oil in to the system. This valve, as with the standard electric valve, can be wired using a separate switch on the dash board, or hard wired in to the vehicle’s ignition switch so it will turn on and off with the ignition.
These EPC valves are available with three pressure activation variants, 20-25 PSI, 35-40 PSI or 55-60 PSI.