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Discussion Starter · #1 ·
I tried to fit a meaningful title in here. I know there are billions of threads and how-to's on oil catch cans and PCV breather systems.

I read that under normal load, the PCV system w/ the OEM oil breather works decent and the intake manifold provides enough vacuum to move the air.

I also read that under high load, the stock PCV system cannot handle the increased pressure and thus, venting to open air is recommended.

What if one were to design a system to work with the PCV and NOT vent under low load and then switch to PCV AND vent to open air under high load to keep the flow of fresh air and not pressurize the engine??

If I have somehow missed this in the plethora of threads on this site and others, I am sorry and will take the n00b lashes...
 

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i just took my black box off and put breathers on the back of the block and valve cover to relieve pressure. they run into catch cans. check this thread out. Official Crankcase Thread

i did that and put breathers on the valve cover.
 

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if there isnt enough pressure, then nothing will be relieved anyway. only when pressure builds will be able to exit since you have the lines and catch can placed higher than the exit
 

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Discussion Starter · #6 ·
yes, but this is also to be run under vacuum in conjunction with the OEM oil breather. the vacuum draws the oil vapor into the breather and subsequent catch can, the baffle filters the air, then the air is sucked in to the intake manifold much like the normal PCV system.

Then, when high load or boost kicks in, the PCV system simply cannot put up with all the extra air and in this case, the vent to open air would be great, b/c then, the PCV wouldn't get over-stressed, and the air would still be flowing into and out of the PCV and oil breather and oil catch can (the catch can i refer to would be aftermarket).
 

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I'm thinking hobbs switch set to any pressure connected to a solenoid...but valving is going to be the issue.

Hmm...or maybe a Toyota VSV (vacume switching valve) of some kind would be of use here. They are very common on the MR2 (3sgte) and Supra turbo for the OEM wastegate/twin turbo configuration. As I recal, they switch between vacume sources when +12V is applied...but I could be wrong- it's been a while since I've looked at Toyota motors.

just my .02
 

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OK. Further thinking about this...

-Take a look at This Diagram. It shows how crazy the stock 2JZ-GTE vacuum system is. Also, here's the explanation. While this is actuating wastegates to spool turbos, I think a similar idea could be used.

-Simply using a VSV would not work...I wouldn't want blowby/PCV gasses going through a VSV...I would assume that doing so would destroy it reeeaaal quick.

-You could use a VSV to keep some kind of "mini-wastegate" closed. This wastegate would sit between the OEM PCV valve location and the manifold. When boost comes up, the OEM PCV closes, so the VSV would need to switch over, allowing boost to actuate the wastegate to open, allowing the PCV gasses a different route to flow- that being said, it would have to be a very low spring rate if you want it to open on very low boost.
 

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Yea...they're not working for me either. Must be down- even though I looked at them just this morning.
 

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I've been thinking more about my catchcan setup...this afternoon, I'm going to fab a "catchcan-box" that will be mounted between the battery and the stock fuel filter. If you can imagine a box with the approximate dimensions of 7"H x 5"W x 2.25"D. I've put 2 large fittings in the stock catchcan on the back of the block- I'll get a picture of that later. Here are the fittings:



I will be utilizing the Exhaust evacuation method mentioned in the H-T thread...but I will be including a PCV valve such that the catchbox (and whole rest of the crankcase) does not ever see positive pressure...for whatever reason, the exhaust evac method had possitive pressure readings under certain load conditions. In that situation, the PCV valve would close which prevents pressurization of the crankcase. BUT now the gasses are containted in a closed system...not good.

My thought is to divide the box down the middle, so that there are 2 "columns" but at the bottom, they are connected, so think of a square "U" shape. on the right hand column there will be the connections to the engines crankcase, as well as the PCV valve and connection to the downpipe. on the right hand column, I am contimplating having an open air filter. The problem with that is when the exhaust is creating good vacuum, I don't want it to all just go out the open air filter- I want the crankcase to be under vacuum- thus the whole point. What I'm thinking is another PCV valve that is backwards...so it will be closed when the exhaust is providing vacuum, but then when it is not, the crankcase will have the ability to evacuate through the now open PCV valve and out the open air filter.

Sorry that's kinda hard to explain, but I'll post photos of the box when it's done.
 

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Ok. Here are the fittings on the OEM catch can which I will be using.


And here is what I have fabbed thus far...please excuse the ugly slag as I'm out of gas and stuck with fluxcore...buuuh.


It fits perfectly between the battery and fuel filter. As for the explanation- see the diagram below:

OK. So the valve in line with the exhaust evacuation line will only allow flow out of the catch can. At the same time, with the catchcan under vacuum, the valve to the open air filter will be closed as it only allows flow out. If for whatever reason, there is backpressure, or the exhaust flow pulses back and creates pressure in the line, this valve will close. In that case, the PVC gasses are free to go out the open air filter.
 

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I need to do some research on PCV valves...or just valves in general. I'd like to go buy a few valves from autozone and just see how they react to positive and negative pressure. I'm thinking that the valve to open air needs to be "open by default" but close under vacuum. I'm wondering if the inline brakebooster valves would work...
 

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And now to bring this back. I think I've finalized (a little bit more) the design for my catch-box....though I do still have some questions in my head.

-First, on the left side (the thinner column) of the box, I am going to baffle the heck out of that. Then at the top, I'm going to put an OEM PCV valve and plumb it back into the intake manifold as it was stock.

-Then on the right side (the larger side) is where I am going to plumb to the exhaust downpipe evacuation. There is going to be a brake booster valve in line here.

-A breather filter will be placed on the valve cover.

-The 2 ports on the OEM catch can as well as the port on the block directly above the OEM can will be routed into the larger side of the catch box. A drainback will be routed back into the bottom of the OEM can.

Some thoughts/concerns I have:
*While not boosting, the catch box will operate very similar to the OEM system: Vacuum will be pulled out the intake manifold, thus applying a vacuum to the box, and back to the crankcase. A freshair supply will be provided to the crankcase via the breather filter on the cover. When under boost, the PCV valve should close (another concern- does it close enough to prevent pressurization of the crankcase while under boost???)

*When in the non-boosting state, the vacuum pressure applied on the box should be greater than the vacuum pressure applied by the slashcut tube in the downpipe. Therefore, the brakebooster valve should be closed...this remains to be seen as I don't know if the .6-1.0 PSI of vacuum from the exhaust evacuation is going to be enough to even open the valve, as it is a normally closed valve...

*one other thought is to remove the brake booster valve and just replace it with another OEM PCV valve to prevent a possible positive pressure in the system from the exhaust evacuation setup.

I am hoping that this setup will yield excelent vacuum when not boosting, and good vacuum from the exhaust evac while boosting.

...thoughts?
 

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Discussion Starter · #20 ·
At first glance, it seems like a good idea. If you have a good regulator, you can make a quick, fabbed, out-of-car system to test that valve w/ a cheap dustbuster or something.

you can test if the PCV holds pressure by doing the same system, only using compressed air instead of a vacuum source.
 
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