Jaba, I was little bit thinking about all this catch can project, let me say it loud
this catch can is good idea not to make bad impact on environment, but I think bringing it back again after catch can to the inlet manifold, will not stop the remaining oil list to make trouble with the carbonation and dirt collection
e-VAC scavenger sounds good (in theory). it really can help the pistons when they move from TDC to BDC position, since the lower pressure acts in favour of creating the force ==> momentum. but, in opposite direction (BDC towards TDC) it works in opposite direction. ok, the pressure on the other side of the piston are not the same. so lets see the cycles:
- air/mixture suction (TDC to BDC) on piston head side pressure would be max ambient, more likely bellow the ambient, cranckshaft side lower than ambient ==> not really big gains
- compression (BDC to TDC) higher pressure on piston head side means e-vac works against us
- expansion (TDC to BDC) gives the biggest pressure difference and the biggest benefit
- exhaust (BDC to TDC) again high (but not the highest pressure difference, since exhaust valves opened) pressure difference again working against us
to be perfectly honest, one can not give direct answer if this is effect neutral or some real benefit could be gained, since there are other bits in that system like length of scavange duct/pipe which is also prone to losses, scavange "probe" shape inside the exhaust pipe needs to be optimised for the biggest gain and minimum obstacle for the exhaust gasses. That obstacle also creates the back shock wave towards the engine and if this is not tuned properly, might be even counter-productive to designed ventilation of the cylinders.
with whole honesty, think that nice solution (personal opinion) would look as follows:
have the catch can (something like from that link), but do the outlet really to ambient, somewhere at the bottom of the car (outside the engine tray). Also add the drain pipe with quick release valve for quick and easy emptying of the can. try to hide both such that TÜV/MOT do not complain. The mist is already pretty good cleaned, so the remains should not be that big for environment, although, they will little bit make oily surface. Under the car (normal to the surface) the pressure (static) is lower than ambient, meaning you'll still have the sucking effect and, caution, this will be very dependent on the speed of the car. Now, use the old oil vent port on the inlet manifold to do following: either organise the water/ethanol injection or maybe add the Flashlube (main product of the guy selling that catch can) which is supposed to be very good for the valves. Also, same systems/port could be used for using other treatments for cleaning the valves and inlet ducts from carbonisation and tuning the engine.
food for a thought?