Centrifugal blowers are used by most two-stroke diesels; they tend to be more efficient than positive displacement pumps, like Rootes blowers or piston pumps.
In as little as 3 1/2 years - if you don't pay the maintenance fee on time. Normal is now 20 years, but there are apparently some kinds of "legal shenanigans" that can effectively get the patent updated or reissued and start the clock over. Haven't bothered to investigate all of the details but it's generically referred to as Evergreening.
Oil and or oil vapour is fed through fine holes between the 2 upper piston rings. Some gets from the lower chamber as well via being washed by the passing fuel and if no fuel, vapour. You would be surprised how little it takes.
If you read the succession of Hooper's patents, you will see he renewed via small modifications using is own previous artwork as reference. I forget the date of the last one, but it wasn't that long ago.
For aviation use, I wonder if you could just mix the oil (50:1?) with the fuel rather than depend on the metering system for the oil lube (same as the Mazda fliers do). It's more reliable, lighter, and not much trouble.
Well, lube oil would probably muck up the injectors. It's not unusual for diesel injectors to run at 10,000 psia or more; at those kinds of pressures, lubricating oil frequently has some odd properties.
As a diesel with it's natural lubricating properties it may be ok by itself, not 100% sure.
Actually the Rootes blown "Jimmy" Detroit Diesels would be the "most".
I am pretty sure a two stroke engine by its very nature is less efficient then a four stroke. The question is if the two stroke can deliver more power per pound to reduce the weight to make up in the lack of efficiency or reduce the parts count to increase reliability to the point it is an overriding issue(ports versus valves for example).
Besides the world's most efficient engine is a 2 stroke, there's millions of 2 stroke engines running around that are incredibly more powerful per pound than 4 strokes. Anywhere from double to 4 times the hp per lb dependent on cylinder capacity.
I was ignoring traditional gas engines and only thinking of compression ignition.
