Some topics will probably continue even after time has stopped, I think PCV systems is one of them.


I have been reading an unhealthy amount of material lately on PCV systems. A lot of people are concerned with draining the can contents back into the sump due to containment build up. Seeing some of the horrifying pictures, I dont blame them. However most if not all OEM vehicles to drain what will form as oil contaminants within the system back into the sump. I have a ST205 Celica which has a catch can from factory and it is drained into the sump.


I am suspect that most of these horror pictures of nasty water / fuel contaminants is as a result of vented systems which do not actively burn the contaminant vapors. Is there any good pictures / documents showing catch can contents of a vented vs closed system? I would be inclined to bet a closed system will not form the nasty contaminants usually posted because they are being drawn into the intake and combusted. I would like to think if you seen your catch can contents of a closed system, you would feel much better draining it back into the sump like every OEM car does.


I hope this was not asked yesterday, but given the topic, I would not be surprised!

 

It really depends on the setup, I build enough pressure in my setup that I push about a half a quart of oil to my rear catch can.

 

Ha!, I've also fallen down that same path of reading an unhealthy amount of PCV and catchcan information, even then it still doesn't seem like there is correct answer outside of a vacuum pump. The VW forums I am on, everyone loved showing their catchcan contents and some of the classic american car forums, there is a lot of advocating for keeping a PCV instead of running breathers that make a huge mess. And reading s2ki and the ap1's pcv issues was quite interesting.

Any pictures of that ST205 celica's breather setup? Honda b series motors have a breather blackbox that also drains back into the sump, but it seems like it gets overwhelmed easily and you get lots of smoking with oil coming up the PCV.

But in my opinion, it seems the general consensus is for track car like drag cars making huge power and road racing, venting to atmosphere works, but for street/daily drivers at moderate power levels, it seems keeping the PCV seems more beneficial than venting to atmosphere.

 

Again it really depends, for street cars making 500whp you can have a catch can system that vents from the valve cover and drains back into the back of the block ports. The back of the block ports not only act as a drain back but they also let crank pressure out as well. Now the more power your car makes and the amount of boost you make, it starts to create issues where the crank pressure starts to push out so much oil it fills the box and pushes out of the filters causing a mess.

For example: I had 1 catch can that had a -16 line coming from the oil pan to the catch can and 2 -10's coming from the valve cover to the catch can. when I made a pass with a bigger turbo creating way more power and boost it pushed a **** ton of oil out the filters getting everywhere. So back to the drawing board, I ended up putting restrictors on the inside of the oil pan, valve cover and catch can to try and help keep the flow of oil from pushing out. Took the car to the track and it still pushed out oil everywhere.

Next test, a lot of big horsepower guys started running two catch cans however one going all the way to the back of the car running long lines that give more room for the pressure to travel. So what I did was created a catch can that fit in the old location of my fuel tank and connected the old gas filler neck to it as a breather. I connected 1 -10 line from the valve cover to the this box and again went out to test. Same thing happened, oil still shot out of main catch can filters but interestingly the back catch can that was hooked up to the valve cover when I went to drain it didn't have oil but fuel.

So my last option was to take the main catch can, remove the filters and in its place weld two -12 bungs. One of the bungs I capped off as a just in case and the second bung I ran a -12 line all the way back to the rear catch can. Took the car back to the track and made a pass with no mess, however after each pass I double check the oil level and would end up adding close to half a quart of oil. When I got home and drained the rear catch can it had about 1 quart of oil that pushed its way to the rear because of the pressure.

I've seen a lot of big power guys who have had to do the same exact thing because of the filters shooting oil everywhere. So what I've learned is that when you're making up to 200 to 900 whp you can get away with a normal catch can setup with filters and drain backs and all that good stuff. You can also utilize what the Shodan has posted about utilizing the stock pcv setup but the point is, it really depends on what your setup is, there is no best answer that will work for everyone so you will just have to play around with your car until you find the right one that works for you.

 

Your wish is my command. Ignore the PVC tubing, literally just broke my PCV valve trying to play with it......and.... of course being the exotic pet that it is, the PCV valve is unique to the ST205. Toyota did a shockingly good job NOT sharing parts between models with this car. New one is coming!

Intake manifold under vacuum:







Intake manifold under boost:




whole system under vacuum:




Yes, I have gone full circle I think. From stock (talking Honda now) is good to catch can madness all the way back to thinking I am just going to run a stock system. I am NA, probably making around the 230 mark, rev to 9k. I do track the car, it drives itself on the street to get there. I am still pondering with the idea of a catch can somewhere but most likely closed. My main question is contaminant production of a vented vs sealed can. I will have to look into the AP1 debacle, sounds interesting.

I will share you what I consider a good little secret. How about a 153 page paper on crankcase ventilation!? This is a very well written paper, it is easy to read and will give you A LOT of knowledge on the topic. Highly recommended.

Forgive me if I am wrong but I think you may have presumed I was asking about what PCV route to take. My question is will a closed system catch can have much cleaner contents thereby draining it back is no issue vs a vented systems contents which is water, fuel, and shmoo which you wouldnt feel good draining back into pan. I would like to think that a closed system does not create the shmoo that a vented system does.

 

You will still get contaminants returned to the oil pan even with a closed system. In fact one could argue the contaminates are already there.

The combustion process is poor(even on modern engines) and all of the fuel isn't burned. Additionally, there is enough moisture from both the combustion process and atmosphere, where water will also be introduced into they PCV system. EGR also adds contaminates and finally oil quality has it share of contaminates.

These are collectively known as blow by gasses and are introduce to the crankcase(and the oil), essentially when ever the engine is running.

Finally, engine health. Metals and rubber from the various seals and moving components in the engine are in a constant state of decay and are "shedding" bits and particles that add up too contaminates as well.

All in all, it is impossible to have a "clean " PCV system when the base of the system(the oil) isnt very clean to begin with.

Hence the whole point of the PCV system.....

 

The gross stuff you find in the catch cans is from it sitting in the open catch can. As the engine runs a LOT of air is moving in & out in puffs, which means lots of moisture. If fluid is sitting in the can, it absorbs the moisture. If it drains back right away, it's not there to absorb it & the gunk you see won't be created in the first place. You'll get some extra moisture in the oil tho, since air is drawn in as the car cools and will condense on cool nights.

Ideally you'd have a PCV-like one-way valve between the catch can and filter, but that's not really possible. The next best idea is a long neck or tube between the can & filter so that moist air doesn't enter the catch can as easily. If that tube has an S or loop in it, moisture will condense & stay in the tube, then be blown out as the engine warms up. The prob is none of that looks cool, so it's a choice of function or form.

 

Yeah I have thought about that as well too. I would think in one form or another, the by products are in the system.

I am thinking I will go to a completely stock system after all this! My latest idea before going to stock did involve check valves. I also fixed the above pictures of the GT4 PCV system.

 

Good pics & posts. I've been pondering for a while a two-step system like your diagram above - thinking for a high-strung street car or NA track car that it might be a good all around compromise. The check valve on top of the can is key. When you're under vacuum, it could operate as a closed system and "scrub" the blow-by, but the check valve allows it to "blow off" if/when the can goes into pressure. You may even be able to do a second vented can (off of the first can's check valve) to catch that junk if you are still making a mess in the bay, but I think you might have bigger issues if you are NA and that is happening. I don't know how I feel about the check valve on the fresh air inlet though. I guess the idea is to keep any mist out of the intake tract altogether?

 

Good analysis without any comment from me! You are exactly right. I would not have the fresh air check valve there if I DID NOT have a 'positive pressure' valve on top of the can. I would want to let any pressure escape any means it could. However having the valve on the can would be suffice to relieve any pressure IMO so why not close off possible oil mist ingestion. Oh and bang on too about having it 'closed' under normal operation.

However, upon taking a close look (I have my engine all apart right now) I am making full circle and going right back to completely stock. I did not know it, but the OEM system is more than meets the eye. Maybe I will post some pictures but the breathing chamber that the OEM chamber connects to is actually not part of a oil drain back at all and all to do with ventilation. People who claim the left side rear port filling up their catch cans well no doubt, it is a giant oil return. But I was also under the impression the right side is too but difference being it has more baffling in the crankcase to reduce windage however this is untrue. It is NOT an oil drain back at all.

 

Correct. In the later non-vtec blocks that did not have the breather box, the separation baffles are in the valve cover - hence why you have the PCV valve right there on top of the cover and going straight to the intake manifold. The thing is, for an NA street engine that will see the part throttle for the bulk of its life, the stock system is just fine. For a turbo engine that is obviously going to have way more blow-by than an NA engine, you want to take whatever measures you can to get that junk out of the crankcase and to keep it out of the intake tract. Those are the extreme cases. An NA engine that sees a high WOT duty cycle is the middle ground in my opinion.

I'm taking a wild *** guess that you are looking at a b-series engine here. The stock system capacity is probably still alright, but could likely benefit from a bit more flow and the ability to scrub the blow-by more thoroughly. Without adding sensors and making a big engineering project out of it, I bet you could weld a -8 fitting in place of the PCV valve on the stock chamber, run that to your Radium can with a PCV valve on the outlet, then back to your intake manifold. That might give you the drain-back benefits of the stock system with the extra scrubbing of an external can, all while keeping your sealed system.

 

Perhaps the answer is simply a quality catch can:

 

I might post pictures of the system as a separate thread later on. It is super interesting, and nothing like my head imagined so maybe others are in the same boat. Yes we are talking a B18C R.

Only thing with your idea is that the PCV will still be the bottleneck to flow as it is the smallest orifice.. I have done quite a full circle on this subject. I still might throw a simple AOS from PCV to intake. But I am willing to try stock and go from there. Before this build up, I ran my PCV as the typical person that looked at any 'emissions' system and went what? no. Dont need that. Then of course now I am a lot more savvy to the importance of crankcase ventilation. I will be spinning 9000RPM and it will see track days.

 

Any reason why you want the check valve direction pointed to the head?

So I tried something very similar to your diagram while forgetting about this thread, only I am venting from the valve cover front baffles on my B18c to my old endyn can. The PCV is on top of the catchcan which goes to the intake manifold and whatever is inside the can is being drained back to the oil pan. I also added the check valve to the fresh air inlet, but I am going in the opposite direction to the intake tube similar to the s2000 krankvent.

My only concern is the check valves may fail and plan on replacing them yearly. And it held up at a track event and didn't notice anything unusual outside of my bumper looking a lot cleaner compared to when I vented to atmosphere.