Let's discuss breather systems...
Turbo Mini Forums

This is something I've honestly never really paid much attention to, but now need to. My bores and piston rings are what I believe can be described as "seasoned" - but aren't worn out, giving quite acceptable leakdown readings. But I seem to be getting a lot of spray out of my breather. Clearly a catch can is in order, but what constitutes a "best practice"? I know bigger is ALWAYS better, but surely I don't want (or need) 30mm hoses everywhere?
I guess we can start critiquing this:


It's a little hard to make out, but the alloy cap is on a 1" dia tube that goes down to the breather flange on the transfer case. The breather hose on the valve cover also connects to this, as does the head oil drain ( level with the bottom of the main oil gallery in the head). At the bottom, just above the flange, is a –6 drain for the head, from one of the two long drains that are cast into the K head as the original drain.
I don't have a breather in the dizzy hole, and the more I think about it, i'm wondering if everything that's trying to drain down out of the head, is simply being blown upwards and out of the breather...
Maybe a dizzy hole breather would help, but I'm starting to think I made a boo boo on putting the drains into what is basically the breather stack?

Edited by TurboDave16V on 12th Sep, 2017.

I found this slightly less obstructed picture, but that was before I added the actual breather filter, and you can't see the head drain either...

http://www.turbominis.co.uk/uploads/i/wh12...bodave-4021.JPG

Edited by TurboDave16V on 12th Sep, 2017.

With the k head I was told not to bother with a breather off the rocker cover and that the oil drain on the side would be adequate. The reason was like you say, pressurising the head from the crankcase.

The other thing I was told to pay attention to was the oil feed for the head, you can supply too much which also doesn't help things. Using the smaller feed line restricts the flow to avoid this.

I must apologize, all this is theory to me at the moment, as I havnt even started my engine up yet. Its all advice from Brett Sims, who put my engine together.

The breather route recommended was as follows.

All the drains to the fuel pump area.
Big breather then from the crankcase (fuel pump or dizzy i guess) and a big breather from the transfer case

Ive always piped everything into the rocker on 5 ports and used that as a "seperator" I dont like the idea of venting the stack from the transfer housing as the drops can apparently throw up quite a lot of oil.

I think I would pipe all the breathers as you have and put a 1" hose into the front half of the cam cover with a sheet baffle behind it.

Likewise, there is a lot of oil thrown off the crank towards the dizzy hole so any air exiting will carry a lot of oil.

As Joe said take everything to the cam cover and put a big vent on it to a catch tank.

Edited by Paul S on 12th Sep, 2017.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Can you get a breather on the timimg chain cover.

I don't see why using the breather as an oil return is an issue.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

www.twin-turbo.co.uk

yeah, if you start a lump with no dizzy plug in the oil goes everywhere!!

apparently SC guears are worse for flinging the oil up cause it goes supersonic...

It's a small engine, it should not need huge lines.

Oil/air separation is key...few catch cans achieve this !
Make a custom one if need be.

And for the drain, ideally this will drain back into the sump below the level of the oil, this allows the can to work better because crankcase pressure isnt also blowing into the bottom of the can.

But some setups this isnt practical, and a return above the level of oil is still better than no return at all, during runtime it may not drain well, but should allow it to drain back into the engine after shutdown.

It makes for a maintenance free setup.

Although remote mounting a large catch can can often lead to a lot of mayo/condensation too. My V8 does this, but it never really has any negative effect on the oil or engine.

PCV...lots do prefer, including OEM's to oeprate a PCV setup. Where under most use fresh air is drawn into the crankcase via a small inlet, through the crankcase and then into the engine. Under normal operation this can even allow a small degree of vacuum in the crankcase, all good. Again effective filtering, oil/air separation before this is fed into the intake is important for us performance types.
But under boost provision needs to be made so the engine can breathe somewhere when the intake vacuum is no use.
Some also route a line to the air intake, turbo, whatever.
Some can use baffle setups to achieve oil/air separation, or some even have internal filters.

I cant find the drawing, but some BMW's use a good breather can, I nearly think it was someone here ages ago posted the drawing of it's design, compact, tapered cone shaped units.

Or here is an expensive filtered version

http://www.pacificp.com/store/index.php?ma...products_id=485

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

You guys who connect the transfer case to the rocker box, do you basically tee the breather / catch cam on the same hose, or make another hose out of the rocker box - basically using the volume in the rocket box as a "separator" allowing opportunity for the droplets to fall out of the vapors?
That sounds like the better way to go...

Steve, thanks for that info - I'm now remembering the big yellow book has a section on breathing unless I'm mistaken? Wasn't there discussion on using the exhaust flow to pull a vac for breathers or something similar?

Can you see how I did mine here?

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

www.twin-turbo.co.uk

I think it is called evacusump.

There is detail in the yellow book re. Exhaust drawn ventilation, but you need an anti backfire valve to stop grenading the sump.

Back when I had the turbo I ran a small vacuum pump after the catch can to aid evacuation. Seemed to work quite well.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

I've been looking into the evacusump system. I'm mainly interested in it to see if it would help with oil leaks that I seem to keep getting.
At the moment I have the breathers going into the rocker cover then to a catch can. Would a empty catch can act as a oil separater? I'd probably have to make a return to the sump so it doesn't fill up with oil all the time.
Or do I just keep it simple and leave it venting to air via a breather filter?

My build thread..

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=542985

Well I thought I'd post and update as JT bought this to the top again.

I modified all the drains from the head to go down to the fuel pump hole. The 1" pipe going vertically of the transfer case (which also has an oil fill cap on the side) goes into the end of the rear half of the 'K' valve cover, with nothing else plumbed into this.
Out the end of the front half of the valve cover i have a 3/8 bore hose, going to a catch tank I knocked up. The tank has a baffle plate just above where the pipe comes in, in an attempt to separate the mist from the oil.
I routed the outlet of the tank to a temporary plastic water bottle on the inner wing to determine the effectiveness, and it is a world of difference; no oil, no oil mist, just condensate which has gathered.

I'm absolutely sure that dumping the K head drains into the transfer case breather is a very bad idea, and that having two ports (in and out, at opposite ends of the valve/rocker cover) is a good idea, as it aids in seperatimg the oil/air mist from the breathers.
As I'm now very satisfied with my breather setup, I'm going to look to pull even a small vacuum with one of the many ideas above.

Edited by TurboDave16V on 23rd Sep, 2017.

Again very expensive, but these do some nice designs.

http://www.killerbmotorsport.net/oiling-pr...separation.html

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

Similar is available if you want the oem look.

Look at this on eBay http://www.ebay.co.uk/itm/291547992154

Yep, that's the BMW ones I mentioned earlier

Found the pic.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

I ran an evacusump setup on my old motor, exactly like this link steve put up

http://static.speedwaymotors.com/RS/SR/Pro.../54525900_L.jpg

For me the results were inconclusive. I'd be interested to see how you get on.

Its hard to quantify any results, as your just firing everything out the exhaust For me it was the fumey oily smell that used to permeate my clothes that I was trying to get rid of, and the evacusump didnt really help. Thats not to say it didn't work tho.

JetBLICK that is exactly what I'm trying to get rid of... Strangely, someone asked me if the centre exit exhaust does any funny stuff, and it got me wondering could this be part of the problem. I might try a side exit for a while and see if it's any different.

Yea, its really annoying! Cant go anywhere nice. I'm thinking of trying a windage tray on the new motor.. Only thing worrying me through lack of understanding, is how much the pistons rely on the oil being thrown up there.

Never thought about the exhaust, interesting theory, if nothing else it puts the exhaust away from you, the driver.. something for the passenger to deal with

So if i read all this correct. A good catch tank with steel wool in it with the top above the valve cover and a return to the sumpplug ( with a banjo fitting sandwich between a lengthened plug) and a breather on dizzy hole and fuelpump hole ( since in my example the breather hole from the clutch housing is taken for the oil retutn of the turbo) would be an ideal set up. ??

you can do anything if you set your mind to it...
i rather blow it up winning than keep it together losing.

finish date set for project 1... march 2018

I've got an extra breather from
The dizzy hole , basically a six inch pipe pointing upwards with a filter on top. Seems to work ok , no oil or crap coming out of it

Folks normally just drain and dump the catch tank fluids. If you did insist on returning them to the engine (why not if it is indeed clean oil - verify first) you'd need to put a ball valve or similar on the drain, opening it when you put the mini in the garage at the end of the day, and closing it before you next start it up. Otherwise, it's a almost a closed system, and no oil will drain to the sump with the engine running...
I guess you could put a solenoid valve on it, but you'd need a huge flow (large port) to effectively dump it.