Do I really need Oil Catch Can (OCC) in 2012 Prius?

That's pretty close to what I am thinking of doing too, thanks for sharing.

 

I can tell that this manual is wrong, at least for my 2012 model. To change oil the whole underpanel can stay in place or I missed something here. I only need to undo a few retaining clips on the oil pan drain and filter access panel, which is a part of underpanel and then bend that panel piece towards the front with a bungee cord or something so it is out of the way.

 

You obviously have much more knowledge and experience on the subject than I do. There is probably not much risk of cracking the plastic hinge in a warm weather/place as opposed to below freezing temps. Taking off the whole panel obviously eliminates such risk and give more than needed access for more areas for inspection. I wonder if a dealer or service shop follow this manual and remove the whole panel, but that could be off topic.

 

After about 800km of driving in colder temps with new OCC I found that my Intake Manifold(IM) under Throttle Body(TB) got a small amount of same "coffee and milk" emulsion residue as in OCC. The amount of blowby emulsion in IM is comparable to the amount in OCC. I wonder whether it is my OCC kit that is not performing well, or the blow-by(BB) gasses make their way into IM from above, as there is also valve cover vent that is going into IM above TB downstream of MAF sensor location? I am very new with reading here and did not find whether another OCC is being installed on that upper vent hose as well or it would be considered too many of OCCs , or there is no such thing as too many OCCs and I should keep adding them down (in series) and also above?
I checked the engine valve cover vent hose above and it is pretty clean and dry and does not have any PCV, so it looks like a direct vent from the valve cover into IM. The fact that is it clean and dry does not mean that BB gases may not enter into IM that way. The engine block PCV hose OTOH was very oily, so I am suspecting that my OCC might not catch (very roughly/maybe) 30% of oil and passes the BB gasses into IM bottom where they continue to reside... I was expecting a little better performance from this OCC...
Any other hoses or ways the BB gases can get into IM and reside under TB?

Any thoughts on all the above?

 

I just discovered that my OCC kit fittings have exact same M16 thread size as Prius OEM PCV.

So I decided to do this experiment...

Installed 1/2" fitting (from OCC kit) at engine block PCV location.
Ran 4' of 1/2" hose up to OCC input.
Installed the OEM PCV at OCC output.
Added transparent 5/16" fuel filter after PCV to see how much of blow-by residue and how quick will be collected there.

I hope in theory that the bigger diameter and longer 1/2" hose at the OCC input will slow down the blow-by gases and increase condensation before they go up into OCC. Transparent fuel filter should show any residual blow-by that passed through OCC and going into IM.

Will watch closely. So far engine is running smooth, new OEM PCV on OCC output is clicking and working.

 

I frankly have no idea why, just wanted to try one that had many positive reviews and still do not know what are the high end brands and where to buy them, apart from Moroso brand that you have, I saw that sold on Amazon. I did not do a lot of research on this, just went with the one mentioned in the OCC thread here.

Do you see any potential issue with PVC being relocated at OCC output? I came across some videos and chats discussing this kind of mod.

 

I am not a Process Engineer by background, but let's compare logically at what has changed between 1) Conventional setup and 2) The new setup process flow. Underscored items below are the areas where IM vacuum can be present in both scenarios. I hope below explanation is more or less clear.

1. The conventional OCC setup (Crankcase->PCV->OCC->IM) causes vacuum appear inside OCC and all its hoses. It must be the IM vacuum that makes OCC separating oil/water/exhaust gas job so difficult because all contents inside turn into a vapor and mist when vacuum is applied from IM. This is what we can see in the video with homemade transparent OCC which shows vacuum to happen during normal acceleration, so that must be happening constantly inside OCC. It would be challenging to design a very effective OCC for such conditions.
2. PCV valve relocated from Crankcase to OCC output (Crankcase->OCC->PCV->IM). I would expect this should change what happens in the input hose and OCC chamber. Logically PCV is now preventing OCC chamber to go into vacuum, i.e. same way as it protects Crankcase from the same IM vacuum. I am expecting that this change should translate into a better condensation of blow-by in hose going up into OCC and inside OCC itself. To repeat, the effects of vacuum on OCC are now at least reduced and this, I assume, was the main idea (not mine) behind this modification.

Time will tell whether it brings positive results. Downside (or upside?) is I am no longer driving for work these days, WFH now.
Cheers

 

I feel that short answer is yes, PCV location does matter. I understand (see PCV diagram attached) that PCV acts as a check valve and closes when there is a pressure in IM and becomes a baffle or a throttled valve when there is a vacuum present in IM and therefore the vacuum level in OCC(and evaporation) get reduced in this new configuration. When I installed the valve on OCC output I could hear how it functions: once the engine shuts off PCV first hisses(letting higher pressure air from OCC and crankcase into IM) and then finally clicks(closes). Now I got some very initial, experimental data to report below.

I have 265,000km on my 2012 Prius odometer. Drove about 350km round trip today with hills, passing, acceleration, stops, mostly highways and some city driving today with 3C ambient temperature in high humidity, in other words good testing conditions for water vapors condensation in OCC circuit. This time I specifically did not want to drive for highest fuel economy as I sometimes try, switched Cruise Control on at times, accelerated to higher speed, etc. My fuel economy for these 5 hours driving round trip showed 4.4l/100km, which is somewhat better than usual 4.6-5.0l/100km range I get, but again this could one off time, shall continue monitoring.
Engine is running smoothly, all systems appear normal, no trouble codes from my little scanner. After getting back home I could not help but check what happened with the new setup and how much residue I would find in IM. I took the TB off and found a very little, maybe a few drops of milky stuff in IM (see photo with the minimal residue wiped with paper towel) under TB. The transparent fuel filter downstream of PCV also had mostly only some condensation inside and after vigorously shaking I managed to get a few drops out of it. OCC on the other hand had a few grams of milky residue. Will continue to collect the residue into two separate small bottles - 1) from OCC and 2)from post PCV Filter+IM(if I get any) to assess the new configuration OCC efficiency.

So far the initial collected data is, let's say, somewhat encouraging.