PCV system theory and Oil catch cans.
May 14, 2006, 05:05 PM
#31
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good PCV system diagram
I found this here in EVOm but I forgot which thread. This is NOT my drawing.
I think this helps you understand why it is a good idea to have 2 separate catch cans.
One line goes to the intake manifold. Oil in manifold = bad
One line goes to the turbo. Oil in turbo and intercooler = bad
*the PCV valve is supposed to prevent this, but as mentioned before, under high boost the PCV valve could allow leakage from the valve cover area.
I think this helps you understand why it is a good idea to have 2 separate catch cans.
One line goes to the intake manifold. Oil in manifold = bad
One line goes to the turbo. Oil in turbo and intercooler = bad
*the PCV valve is supposed to prevent this, but as mentioned before, under high boost the PCV valve could allow leakage from the valve cover area.
May 14, 2006, 06:42 PM
#32
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Originally Posted by ShiftySVT
Also, it seems a couple people have noticed that a catch can in the vent tube doesn't collect hardly any oil, which indicates that the PCV leakage is minimal when it's properly functioning as a one-way valve. In this case, a single catch can between the crank and PCV valve is all that is necessary. If the PCV valve hardly leaks, then there's essentially no difference between a NA engine and a turbo engine when it comes to oil getting into the intake. NA cars run fine without a catch can, so why does a turbo charged car need one? Perhaps a small cans worth of oil going directly into the intake over the course of 5000 miles isn't all that bad.
Please let me know if I'm going wrong anywhere.
It's true NA cars run fine without a catch can. It's also true that Evos run fine without a catch can. I use to have a 5th gen prelude and I ran a Moroso baffled catch can on the PCV side just to keep the stuff out, to perhaps keep things clean on the inside. It's like changing your oil, bleeding the brakes, changing the coolant, you know, keeping things fresh and tidy.
But look at it this way: say you have a track day and it's 95 degrees out at 80% humidity (where I live). So, as a safeguard, you throw a couple of extra gallons of race fuel in to help stabilize the combustion mixture to prevent any unwanted pre-ignition. Makes sense right? A catch can in a way is going to do the same thing: it'll stabilize the combustion mixture by prevent oily vapors/oil from joining in. Oil's got a real low octane rating, so it's effect would be to unstabilize the mixture thus promoting pre-ignition.
Is it absolutely needed? Of course not. But then again, most everything we do to our car isn't needed. So in that respect, every little bit counts so why not? Especially when it's something fairly inexpensive with potentially large benefits and little to no known drawbacks.
May 14, 2006, 06:47 PM
#33
Originally Posted by ShiftySVT
That's definitely the wrong way to hook it up. The PCV (not PVC) valve should never run to the atmosphere. Look at the drawings and try to understand what is going on before you ruin your engine with sludge build up.
May 14, 2006, 06:47 PM
#34
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Originally Posted by Saikou_kun
Also, I have heard people saying that they don't have much oil collected in their catch cans...well, if they are running the most common cans that don't have anything designed to condense oil vapors, that would explain why. The vapor goes in one fitting, and goes out the other one.
Of course, there is going to be a little build up, but that is simply because the can has a large interior, and some oil will condense on the walls of the can. This also means that the same amount of residue is building up in the intake.
May 14, 2006, 06:54 PM
#36
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Originally Posted by denial
While it's true that the intake can doesn't seem to collect a lot of oil, it doesn't nescccarily mean that the actual leakage is minimal. Maybe it's just that you're not spending enough time in a positive pressure situation for there to have enough leakage. Maybe a hardcore track racer gets more in that can. Remember, it's not just positive pressure blowing past the PCV valve--there's also that aspirating effect from the intake nipple (as Saikou-kun pointed out). Just another way of looking at it. But either way the end result is still the same: not a lot of oil in the intake can.
It's true NA cars run fine without a catch can. It's also true that Evos run fine without a catch can. I use to have a 5th gen prelude and I ran a Moroso baffled catch can on the PCV side just to keep the stuff out, to perhaps keep things clean on the inside. It's like changing your oil, bleeding the brakes, changing the coolant, you know, keeping things fresh and tidy.
But look at it this way: say you have a track day and it's 95 degrees out at 80% humidity (where I live). So, as a safeguard, you throw a couple of extra gallons of race fuel in to help stabilize the combustion mixture to prevent any unwanted pre-ignition. Makes sense right? A catch can in a way is going to do the same thing: it'll stabilize the combustion mixture by prevent oily vapors/oil from joining in. Oil's got a real low octane rating, so it's effect would be to unstabilize the mixture thus promoting pre-ignition.
Is it absolutely needed? Of course not. But then again, most everything we do to our car isn't needed. So in that respect, every little bit counts so why not? Especially when it's something fairly inexpensive with potentially large benefits and little to no known drawbacks.
It's true NA cars run fine without a catch can. It's also true that Evos run fine without a catch can. I use to have a 5th gen prelude and I ran a Moroso baffled catch can on the PCV side just to keep the stuff out, to perhaps keep things clean on the inside. It's like changing your oil, bleeding the brakes, changing the coolant, you know, keeping things fresh and tidy.
But look at it this way: say you have a track day and it's 95 degrees out at 80% humidity (where I live). So, as a safeguard, you throw a couple of extra gallons of race fuel in to help stabilize the combustion mixture to prevent any unwanted pre-ignition. Makes sense right? A catch can in a way is going to do the same thing: it'll stabilize the combustion mixture by prevent oily vapors/oil from joining in. Oil's got a real low octane rating, so it's effect would be to unstabilize the mixture thus promoting pre-ignition.
Is it absolutely needed? Of course not. But then again, most everything we do to our car isn't needed. So in that respect, every little bit counts so why not? Especially when it's something fairly inexpensive with potentially large benefits and little to no known drawbacks.
May 14, 2006, 06:58 PM
#38
Originally Posted by evodan2004
what catch cans ARE BAFFLED. i would like to pic 2 up but would like to know witch ones are and arent. i cant find ones that are.
May 14, 2006, 07:00 PM
#39
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Originally Posted by evodan2004
what catch cans ARE BAFFLED. i would like to pic 2 up but would like to know witch ones are and arent. i cant find ones that are.
Originally Posted by ShiftySVT
Thanks. You make some very good points.
EDIT:
guys, word of caution. If you are really thinking about putting a can in the PCV position, keep in mind that it's going to experience ~-20 psi of NEGTIVE pressure as well as ~20 psi of POSITIVE pressure. Now if you stick a check valve inline like Fourdoor suggested, that'll keep out most of the positive pressure. But a can like the Perrin, placed in the PCV valve position, will literally collapse on itself when exposed to that much negative pressure. You're going to have to stick something in it to prevent that (like a metal cylinder or something). Just don't ask me how I found that one out...
Last edited by denial; May 14, 2006 at 07:05 PM.
May 14, 2006, 07:10 PM
#40
Originally Posted by denial
PM Saikou-kun or check out his website in his signature. His are very nice in design, and pretty much the only baffled can I've seen to date that could be used in our application.
no problem, glad I could contribute.
EDIT:
guys, word of caution. If you are really thinking about putting a can in the PCV position, keep in mind that it's going to experience ~-20 psi of NEGTIVE pressure as well as ~20 psi of POSITIVE pressure. Now if you stick a check valve inline like Fourdoor suggested, that'll keep out most of the positive pressure. But a can like the Perrin, placed in the PCV valve position, will literally collapse on itself when exposed to that much negative pressure. You're going to have to stick something in it to prevent that (like a metal cylinder or something). Just don't ask me how I found that one out...
no problem, glad I could contribute.
EDIT:
guys, word of caution. If you are really thinking about putting a can in the PCV position, keep in mind that it's going to experience ~-20 psi of NEGTIVE pressure as well as ~20 psi of POSITIVE pressure. Now if you stick a check valve inline like Fourdoor suggested, that'll keep out most of the positive pressure. But a can like the Perrin, placed in the PCV valve position, will literally collapse on itself when exposed to that much negative pressure. You're going to have to stick something in it to prevent that (like a metal cylinder or something). Just don't ask me how I found that one out...
May 14, 2006, 07:16 PM
#41
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Originally Posted by atlvalet
Ditto on this. I have the Perrin, which has zero baffles. What are you guys using to help collect condensate? And any hints on where to buy/get it? Thanks.
If you have the older Greddy, or a Greddy knockoff that opens, you are kinda ok but you need to do a couple mods.
#1) First, on the incoming line from the PCV, you need to add a little piece of pipe that sticks down into the can, not ALL the way to the bottom but about 3/4 of the way down. Use epoxy or something to hold it in place permanently.
#2) Go to a hardware store, or supermarket and buy yourself some STAINLESS pot scrubbers (not copper or plastic) BE CAREFUL <----READ AGAIN
BE CAREFUL AND USE GLOVES and kinda puff a pad apart...you kinda need to pull it so it gets spread out and puffier.
#3) Push the new tube through this puffed pad and reassemble your catch can. The tube should be somewhere in the middle of this stainless scrubber ball.
Now, tell Greddy to send me a thank you note for making all their catch cans work
Thanks for looking !
Mr. Saikou ^^V
May 14, 2006, 07:24 PM
#42
Originally Posted by Saikou_kun
I will help you out. Since you guys probably already bought one. If you bought the newer Greddy or Cusco...you are SOL because they are sealed.
If you have the older Greddy, or a Greddy knockoff that opens, you are kinda ok but you need to do a couple mods.
#1) First, on the incoming line from the PCV, you need to add a little piece of pipe that sticks down into the can, not ALL the way to the bottom but about 3/4 of the way down. Use epoxy or something to hold it in place permanently.
#2) Go to a hardware store, or supermarket and buy yourself some STAINLESS pot scrubbers (not copper or plastic) BE CAREFUL <----READ AGAIN
BE CAREFUL AND USE GLOVES and kinda puff a pad apart...you kinda need to pull it so it gets spread out and puffier.
#3) Push the new tube through this puffed pad and reassemble your catch can. The tube should be somewhere in the middle of this stainless scrubber ball.
Now, tell Greddy to send me a thank you note for making all their catch cans work
Thanks for looking !
Mr. Saikou ^^V
If you have the older Greddy, or a Greddy knockoff that opens, you are kinda ok but you need to do a couple mods.
#1) First, on the incoming line from the PCV, you need to add a little piece of pipe that sticks down into the can, not ALL the way to the bottom but about 3/4 of the way down. Use epoxy or something to hold it in place permanently.
#2) Go to a hardware store, or supermarket and buy yourself some STAINLESS pot scrubbers (not copper or plastic) BE CAREFUL <----READ AGAIN
BE CAREFUL AND USE GLOVES and kinda puff a pad apart...you kinda need to pull it so it gets spread out and puffier.
#3) Push the new tube through this puffed pad and reassemble your catch can. The tube should be somewhere in the middle of this stainless scrubber ball.
Now, tell Greddy to send me a thank you note for making all their catch cans work
Thanks for looking !
Mr. Saikou ^^V
May 14, 2006, 07:28 PM
#43
Guess I am retarded. I was told to "T" with the PCV to one side (in) of the catch can and the other side (out) of the catch to the intake pipe. Is this right or should the out of the can go to the intake manifold???? Thanks for any help.......
Last edited by 04 evo; May 14, 2006 at 07:51 PM.
May 14, 2006, 07:36 PM
#44
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this mod will be done tomarrow. sweet. but how dose the pot pad stay up top of the can??
worst case is you have to buy another pad, but they are like $3.00 each
May 14, 2006, 07:44 PM
#45
Originally Posted by Saikou_kun
The pad is puffy and actually fills up the whole can pretty good if you do it right, you'll see
worst case is you have to buy another pad, but they are like $3.00 each
worst case is you have to buy another pad, but they are like $3.00 each