Correct PCV/Catch Can routing.

90mkiiisupra400hp

90mkiiisupra400hp

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Mar 20, 2011
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Hey guys, I have been searching and searching, and couldn't find a definite answer on how to install a catch can. I found 6 or 7 different ways people installed them but others would chime in on how it wouldn't work, yet the ones who shot it down wouldn't give a clear answer on how it's supposed to go.

Well this is what I came up with, if anyone thinks it is wrong please let me know the right way to do it. Thanks

7M pic drawing pvc6.png
 
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Rcks4me

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Nov 3, 2011
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isn't the whole idea to catch oil coming from the valve covers? The way you have it drawn seems pointless...you would need the can between the valve covers and the tb
 
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Rcks4me

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Well doesn't vacuum come from the tb/intake? If so how will it draw air from the valve covers to the can to catch the oil? I'm pretty sure I understand the concept but I mite be missing something here.
 
90mkiiisupra400hp

90mkiiisupra400hp

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I suppose putting it between the valve covers and the throttle body would work to. When in vacuum it sucks the blow by into the throttle body, and under boost it pushes the blow by from the valve covers to the accordion hose, at least that's the way I understand it.

I am pretty sure though that there would be more blow by under boost rather then in vacuum, but I don't know that's why I put up the picture to get other peoples opinions. I also understand that being daily driven it's going to spend most of its time in vacuum rather than in boost, so I don't know which way would be better.

Hopefully someone that knows the answer will chime in.
 
toyotanos

toyotanos

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Diagram looks good, but don't put the check valve in.

Stock system flows 2 ways-
1- From accordian to throttle body at anything below atmospheric pressure (i.e. in vacuum)
2- Fromt throttle body to accordian pipe when in boost.

The reason for that is so there is positive ventilation at all times. You don't want the vapors to just sit in the crankcase, you want them to be drawn out. The check valve you propose would just put the crankcase under vacuum (not neccesarily a bad thing) but wouldn't move much vapor out of the crankcase. That's what the movenent of air does well. You also never want pressure to build up in the crankcase, so that's why the piping is so big going to the accordian pipe. There is a small restrictor in the throttle body where the PCV system hooks up, so its not an uncontrolled boost leak- its small and has been designed into the computer's calculations.
 
90mkiiisupra400hp

90mkiiisupra400hp

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Mar 20, 2011
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toyotanos;1827368 said:
Diagram looks good, but don't put the check valve in.

Stock system flows 2 ways-
1- From accordian to throttle body at anything below atmospheric pressure (i.e. in vacuum)
2- Fromt throttle body to accordian pipe when in boost.

The reason for that is so there is positive ventilation at all times. You don't want the vapors to just sit in the crankcase, you want them to be drawn out. The check valve you propose would just put the crankcase under vacuum (not neccesarily a bad thing) but wouldn't move much vapor out of the crankcase. That's what the movenent of air does well. You also never want pressure to build up in the crankcase, so that's why the piping is so big going to the accordian pipe. There is a small restrictor in the throttle body where the PCV system hooks up, so its not an uncontrolled boost leak- its small and has been designed into the computer's calculations.
Click to expand...

Ok thanks for the reply, I will keeps the check valve out as my original plans didn't include one anyway. The reason I added it was so when in vacuum it wouldn't be pulling air from the accordion hose, but rather just the valve covers. I know the stock system doesn't use a "check valve," but it has the small orifice to regulate the amount of boost that can escape. I will do it the way I did the drawing, but without the check valve.

Thanks again for helping me out with this.
 
90mkiiisupra400hp

90mkiiisupra400hp

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Gardiner, Maine
radiod;1827582 said:
If you want to do some more reading here's a good thread on catch cans and routing :)

http://www.supramania.com/forums/showthread.php?43167-oil-catch-can-install
Click to expand...

Thanks, I did read all 19 pages of that before I made this thread but I didn't really get a straight answer from it. There were so many different ways people were saying it and it confused me more then anything lol. I wound up just adding it in with the stock setup and figured the diagram would be useful for others when they are looking into installing one. Plus I figured I could get some other opinions on my setup.

Thanks again for the link, there was a lot of good info in there.
 
awsom-0

awsom-0

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Sorry for bumping an old thread but I was wondering if the way I have mine setup is correct. I have an n/a y pipe that goes into one side of the catch can and the other side i have going into the accordian hose that has a T fitting then goes back into the throttle body. lol sorry for my horrible mspaint skills
 

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hvyman

hvyman

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If its routed like stock.

Need both the tb port and the port on te accordion hose to pull vacuum from the valve cover ports.

The tb port is most important as almost always pulling vacuum.
 
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