Although they’re normally associated with racing (which is why I thought some of you rev-heads might know about them), these seem like a good, simple way of addressing a, perhaps the, basic flaw in the standard lubrication system : the fact that the engine is essentially unlubricated on cold startup.
So simple and obvious, in fact, that I’m surprised I didn’t think of it myself. I probably did, and then forgot. 
I’m not surprised, OTOH, that (AFAIK), they aren’t fitted as OEM to production cars. I can probably guess why that is.
Described here:-
http://www.moroso.com/articles/articledisplay2.asp?article=AboutAccumulator.html&catcode=13600.
They make a “light duty” simpler version for street use that has no internal piston so can only be installed vertically.
One thing that isn’t clear from the decriptions I’ve seen: If I understand it correctly, the accumulator is connected downstream of the oil filter, so it recieves, and is charged with, freshly filtered oil.
This seems to imply that when the accumulator is used to pre-lube the oil galleries, (unless there is an additional non-return valve fitted, which I havn’t seen a mention of) it temporarily applies a back-pressure and flow to the oil filter, which will presumably have the effect of lifting debris off the filter surface.
This wouldn’t matter too much in normal operation, since when the flow direction is almost immediately restored most of the debris will be re-trapped by the filter.
At cold-startup in a street-car, however, especially towards the end of filter life, when it has trapped a lot of debris, the filter is quite likely to be initially in bypass, so a cloud of debris back-flushed off the filter surface would then go straight through the filter and into the bearings. This seems a BAD THING.
Anyone know if there is in fact an additional non-return valve, or some other means of ensuring this doesn’t happen?
EDIT: Hmm…I suppose on a good oil filter the anti-drainback valve might be robust enough to withstand the, what, 20-30 psi (?) that might be delivered by an accumulator, so maybe it isn’t an issue.
I think they’re only intended to prevent drainback under gravity though, and I’ve seen reports where people have cut open filters and been pretty unimpressed by the quality of some of these internal valves. ENDEDIT