OK, I can't find a definitive answer to this so here goes. I need to know about venting my oil catch tank. The questions are:

1. How far down the transmission tunnel should I run the venting pipe? All the way to the back axle area? Or will just the end of the gearbox do? Any problems with fumes entering the cabin if I only go half way down the transmission tunnel?
2. Will my 1/2" hose, 2 to 4m long be sufficient to vent fully when it needs to? If I'm running the breathers through a catch tank there will be an issue with 'breathability' presumably. Looking at the RCM catch tank it looks like the vent pipe is at least 3/4" compared to the three 1/2" breather hoses. In fact every properly made catch tank I've seen always has a larger vent pipe.
3. Does the vent pipe from the catch tank need a breather filter on the end of it? After a lot of thinking about it, I've decided it will never be needing to breathe in, therefore I could just get rid of the filter, on the grounds of it being a further restriction and a magnet for oil, road crud and possibly blocking completely which would make the whole exercise pointless anyway.

Opinions on this will be much appreciated from those of you who have actually delved into these matters.

 

hi, i have got a 22mm breather pipe, and it has no filter on. it goes down to where the downpipe and gear box are.

i think it would be best for it to go past the geat box, as i get a few smells from time to time, and i think it is coming in where the gear stick is in the floor pan, so i would say to have it go past the gear box.

shouldnt think you would have any probs with it getting blocked with crud

 

22mm that's a monster pipe! Very useful to know you get a smell coming up, I was thinking of leaving it around the middle of the gearbox, but you've persuaded me not to run it that short. I might just use a Y adapter off the catch tank and run a pair of 1/2" hoses down to the same place.

 

this is a pic of my oil catch can

the big one at the back is the breather
far left and right go to the crank case each end
and middle goes the the block, just in front of the turbo

 

Nice. At the moment I'm using the standard tee pipe from the rockers under the manifold and just bringing a single 1/2" pipe off from this to the tank. I have been thinking about whether to just take the rockers up to the tank individually, like yours. So three separate 1/2" inputs, one big bore vent or perhaps a pair of 1/2" vent pipes.

 

i had my rockers T together, and found it collected scum/creamy/watery stuff in there, and it was abit of a blocking point, not to the point that it became compleatly blocked, but more than i would of wanted.

so went for the set up that i have now.

the idea of a bigger bore vent pipe to under the car, is that you have got 3 breathers going into your catch can, so you will need a big pipe to get the same amount of gas out.

 

Nice one. You've confirmed what I wanted to hear.

 

glad i could of helpted