Pumping losses

[R.I.D.E.]

I was wondering what everyone here is trying to describe when they use the term "pumping losses". I understand that an engine basically moves air in much the same way as a compressor although less efficiently of course.

I am also aware that if you merely ground two opposing lobes on a camshaft a basic long block becomes a much more efficient compressor.

With the throttle closed "pumping losses" are greatly reduced since the force on the piston is 10X atmospheric (approximately depending on compression) with no throttle restriction, the same reason compression tests require wot to be accurate.

Pumping losses would probably be best listed in two cateogries.

First;
The actual losses due to moving the air into the engine, compressing the charge, and pushing out the exhaust.

Second;
losses due to continuous operation of the engine necessary in normal vehicle operation.

I will list a few, add anything you can think of.

All belt driven accesories
Reciprocation of pistons, pins and part of the connecting rod mass (include rings).
Oil pump
valve train
Flywheel
Increased load on water pump due to thermostat restriction to maintain operating temp
Exhaust restriction

regards
badger