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Hey SK. I've done my own diagrams from my own understanding, if you'd like to tell me what’s right & wrong 'advantages - disadvantages' about each diagram that would be great.

Owww & please automatically assume that the PCV & so forth are blocked like in your first Zero% plumb back diagram.

From my can design i would think i could only use the B. or C. setup. Personally I think i'd like the A. setup but would need a can with valve at top & bottom?

12805catchsetups.jpg

If anyone wishes to do diagrams too here is a pic they can use. :D

12805engine1-med.jpg

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OK... i am making my own catch can this weekend

100% plumback, on a rb25det

my first question is.... where is the pcv valve?? can someone please circle it in the picture above? I roughly get the idea.. but perhaps a picture of the pcv valve once it has been moved and whatever else that has to be done to it.. and the blocking off of the camcover?

2nd question, where can i get Braided Stainless hoses from?

all i have seemed to find are braided sleeves that fit over the original silicon hoses... like this http://i12.ebayimg.com/02/i/01/3e/34/47_1.JPG

Is this how it is done, or is there an actual hose that can be purchased sumwhere?

Thnx

cant upload picture of my layout? but if sum1 willign to host i can email

This one I call the 50% plumb back, because half of the time (no boost times) the air from the catch can is being sucked into the inlet manifold via the PCV valve;

rb25det50PlumbBack.jpg  

It is not my favourite, because you can still get a bit of oily air into the engine, but since it doesn't go in under boost (the PCV valve is closed then) detonation isn't much of an issue.  At least you don't get any oil into the intercooler and its pipework.

Hope that helps:cheers:

SK - I was looking into this setup and i think i understand the concept but do you think there could be a problem with this sort of setup.

From my understanding it would be bad to pressurise the sump but it seams that's what it would happen while under boost as the oily air would have nowhere to go.

Did i miss something?

Yah,

I’m thinking the same thing. Although, under vacuum, the vapor would flow through the PCV valve, and be ingested. Under boost, the valve would close, ( and with the pipe in front of the turbo blocked) the canister / crankcase would just slightly pressurize, more importantly, LACK any cross flow of air to rid the oily vapor.

In any case, I thought of running a crank case vacuum pump --> http://www.aerospacecomponents.com/vacp.htm

Id could then hook up a filtered intake to the sump / crankcase and have a continuasally flowing draft through the engine, removing oily vapor and achieving slight power gains from a higher pressure deferential from combustion chamber to crankcase....?

Just some mental vomit

I'm still waiting for Sydneykid's comments on my post above.  :)

Sorry, been a bit busy...

Being a one way valve, the PCV valve stops any boost (pressure) getting into the hoses and the catch can. The only "pressure" is blow by, and the volume of the can and hoses can accomodate this. The small amount of contained pressure is rapidly relieved every time you back off (eg; change gear).

I would not suggest this option for cars with lots of blow by or automatics or cars that spend a lot of their time under boost (eg; circuit work). As I said in the original post it is not my system of choice, it's a compromise to keep oil out of the turbo, intercooler and pipework and still be sealed to atmosphere (legal).

I have set this system up on a number of cars and it works OK Monday to Friday. On weekends the guys stick a filter on the can (to replace the flow that goes to the plenum). The "filter" can be a simple plastic fuel filter like you see on non fuel injected cars, it just plugs in to the can outlet hose.

Hope that clarifies:cheers:

Thanx. SK that clarifies things.

I was looking into the 50% plumb back option as i'm mainly concerned in blow by under boost causing detonation and i also wanna keep my new cooler piping nice and clear. My car is also an Auto so this option would not really suit me.

So basically if i wanna make sure i get no blow by under boost i would have to go the 100% not legal way and filter it to atmo. :)

I just may leave everything intact on the intake manifold side and intercept the blow by hose going into the duct and put a can in between hoping it catches as much as possible.

Would that be OK? It would still be 100% plumb back but only the on boost blow by would be goin thru the can eliminating the detonation and you would possibly need less outlets on the can.

Thanx. SK that clarifies things.

I was looking into the 50% plumb back option as i'm mainly concerned in blow by under boost causing detonation and i also wanna keep my new cooler piping nice and clear. My car is also an Auto so this option would not really suit me.

So basically if i wanna make sure i get no blow by under boost i would have to go the 100% not legal way and filter it to atmo.  :)

I just may leave everything intact on the intake manifold side and intercept the blow by hose going into the duct and put a can in between hoping it catches as much as possible.

Would that be OK? It would still be 100% plumb back but only the on boost blow by would be goin thru the can eliminating the detonation and you would possibly need less outlets on the can.

If you take the velocity out of the air flow (use a big enough can and large diameter hoses) and fill the can with stainless steel wool, then you should clean up the air pretty well. You could also put a filter inline with the hose, one of those cheap plastic fuel filters with right size fittings. That will trap any oil that escapes the can and stop it going into the inlet. Keep an eye on the filter and when it gets black change it, they only cost a couple bucks. We use them on the gearbox and diff breathers on the race cars, so only the air escapes, no oil.:)

Would it be possible to do a diagram for a Rb20 ....coz i'm still not quite clear on how i would fit mine up properly.....  

thanks

Matt

Hi Matt, the only difference between an RB20 and an RB25 is the PCV valve is screwed into the plenum chamber on the RB20. So it makes it easier, you don't have to remove it from the cam cover.:)

So do i run both lines from both cam covers to the catch can? as my can has a breather on the top

or do i block the (lookin from the front) left side cam cover and run the line to the catch can from the right cam cover and a line out of the can back into the turbo inlet hose with a inline plastic filter like u suggest.

thanks

Matt

So do i run both lines from both cam covers to the catch can? as my can has a breather on the top

Option 1, that's how ours is plumbed, OK on a race car but illegal on a road car.

or do i block the (lookin from the front) left side cam cover and run the line to the catch can from the right cam cover and a line out of the can back into the turbo inlet hose with a inline plastic filter like u suggest.

Option 2, you can do that, at least its legal.

Option 3, same as option 2 but no inline filter and into the PCV valve instead of the turbo inlet. That way its plumb back (clean) when no boost is present, sorta 50% legal.

Option 4, same as option 2 but remove the filter from the can and run the hose to the PCV valve. That's fully legal and only the "under boost" oily air goes through the inlet (fuel) filter. You won't have to change it so often.

Hope that makes sense:cheers:

SK - Since I have an Rb30 block I don't have one of these, but the pipe coming out of the two bolt flange on the exhaust side of the RB25 (near the first head bolt), does this just join to the crankcase with no valves etc? Is it just for pressure equalisation of the top and bottom like on the old cosworth motors? It looks that way from the one I had a glimpse at.

SK - Since I have an Rb30 block I don't have  one of these, but the pipe coming out of the two bolt flange on the exhaust side of the RB25 (near the first head bolt), does this just join to the crankcase with no valves etc? Is it just for pressure equalisation of the top and bottom like on the old cosworth motors? It looks that way from the one I had a glimpse at.

Correct, drain from the front of the cylinder head to the sump. :D

So do i run both lines from both cam covers to the catch can? as my can has a breather on the top

SK, My can doesn’t have a breather on top, just two nozzles, can i run both cam cover lines to the can or must i have a breather to release pressure? If so I spose I could run one line to the can & put a filter on the end of the other nozzle, but i dont really want to have an atmos setup & i also dont want oil going into my plenum & so forth, thats why i thought I could run 1 line in & the other line to the sump?

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