4 liters in 30 seconds?? Are you sure? did you make sure the oil doesn't get in the cooling system? This is more than the rate you can put it back in, normal ways in mean ...
Tell us more about how did it all start or how did you get to find this oil absence from you sump, the whole story.
The proper way to test if the oil isn't going the turbo way is buy taking out one of hoses from the intercooler and see what's coming through, not by letting the turbo without lubrication. This way you can check the intercooler too and see if there's oil in it (so much that it can be drained). It would also stop the blue smoke on the exhaust.
Well, 5 secs with engine on idle can't harm the bearings so much ... i guess.
It starts and runns smooth on all cylinders but after about 2-3sec theres a low ticking/knocking, as one if of the cylinder runns unclean.
Some thoughts:
- the engine doesn't burn the oil; at least not most of it; it takes about 2-3 l/hour of fuel to run the engine on idle; at a 4l/30 secs rate of oil consumtion, which is 480 l/h, that engine would have been blown up by now (or at least you couldn't have been able to stop it by turning off the ignition key, that is cutting the fuel supply).
- if the oil gets in the cylinder (at this rate) and not burning this means it would have had the same effect as when the engine sucks water (when wading), the oil can't be compressed; so, if this is case, some noises can be heard and the compression is lost in that cylinder, conrod bent and so on (the engine hydraulicked on oil)
- if the piston is blown there's no effect on the breather, it can't push anything, so don't rule this out, although it can't push so much oil either.
I would run a cylinder compression test if i were you and go from there.