Moroso oil pressure accumulator

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Guy Croft
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Moroso oil pressure accumulator

Post by Guy Croft » July 12th, 2006, 7:20 pm

Guy Croft Racing Engines (GCRE)
Lincoln UK

see also my post re at

(simplified version of Moroso instructions)


1. Open or remove the brass manual gate valve and pre-charge via Schraeder valve with 60 psi air. This will force the accumulator piston down.
2. Bleed off air till 6-8 psi pre-charge shows on air gauge. This is the ‹Å“air-precharge¢ž¢ for normal operation.
3. Fit solenoid valve using connector supplied in solenoid kit, use teflon tape on threads and don¢ž¢t over tighten. …œA‚ goes towards accumulator.


1. Cut the oil feed hose from the remote filter to engine. The accumulator MUST be on this return hose ie: the filtered oil line that feeds the engine.
2. Fit T piece in this hose line to permit a single hose to be fitted to connect to the solenoid valve. Tighten the hose connections.
3. Refer to the recommended oil system layout below. Wire the solenoid valve into ignition switch and I recommend do not use the remote switch in the Moroso kit. Make sure the current does not overload the cables and make sure that the solenoid opens when the ignition is ‹Å“on¢ž¢.
4. Add 1.5 quarts extra oil to engine. (1 qt = 1.137 Litres).
5. Start engine and watch the accumulator air gauge pressure rise to engine oil pressure value. Allow engine to warm up.


1. First test the unit ¢‚¬Å“ rev up the engine to raise oil pressure and turn off the engine. When wired via ignition switch the solenoid valve will close and the high oil pressure will be held in accumulator ¢‚¬Å“ air gauge pressure should not drop or there is a leak.
2. Turn ignition on ¢‚¬Å“ accumulator pressure should drop to air pre-charge level (6-8 psi) as accumulator pre-oils engine. The hotter the oil, the faster the gauge will fall.
3. If oil delivery drops during racing, accumulator will automatically discharge into engine.

NOTES - Oil temperature must be sustained at 85-100 degrees C Maximum or oil pressure will be dangerously low ¢‚¬Å“ even with accumulator fitted.

Synthetic oil with 55 or higher upper velocity rating is strongly recommended.

Avoid sharp turns and long runs in oil lines. Always use straight or swept 45/90 deg fittings not cranked ones


Check engine sump oil level ¢‚¬Å“ engine must be run up to about 3000 rpm so accumulator is full, ie: showing 50 + psi pressure. If the solenoid valve is wired via the ignition switch the valve will close before the engine stops and the additional oil will be stored in the unit and thus not affect measurement of the sump oil level.
If the solenoid is wired via a remote switch it must be switched off before turning off the engine.
Accumulator can be mounted in any orientation Keep it away from hot areas (turbo/ex)
A thermostatic oil sandwich plate must not be used with an accumulator.
Accumulator must be downstream of filter ¢‚¬Å“ ie: receiving filtered oil.
Wet-sump system oil lines should be ‚½‚ or 5/8‚ BSP or US/metric equivalent.
The accumulator can be used on dry-sump systems as a pre-oiler only.
If the air pressure in the unit is high it is EXTREMELY dangerous to open the manual or solenoid valve if the unit is not connected to the engine; oil will discharge at very high velocity.
In very long turns the accumulator can run out of oil ¢‚¬Å“ you must slow down. Watch the oil pressure gauge when racing.
Moroso layout.JPG
Instalation diagram for Moroso accumulator - do not deviate from this with checking with GC!
Moroso layout.JPG (40.03 KiB) Viewed 12813 times
Moroso 1.5qt & clamps.JPG
1.5qt unit - about 10" x 4" dia minus air gauge (which can be remote mounted) and solenoid. Plenty big enough for a 2 liter 16v unit n/a or turbo.
Moroso 1.5qt & clamps.JPG (22.98 KiB) Viewed 12811 times
Moroso solenoid.JPG
Solenoid valve from Moroso (helpfully marked with an 'A' to indicate which end goes in the accumulator)
Moroso solenoid.JPG (17.79 KiB) Viewed 12804 times
1.5 qt Moroso recommended and supplied by me stopped continual blow-ups in Raeder M/Sport's 400bhp Mitsubishi Evo. Nurburbring 'taxi car'.
Gc-01.jpg (46.76 KiB) Viewed 12783 times


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