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Home > Technical Chat > Let's discuss breather systems...

TurboDave16V
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10669 Posts
Member #: 17
***16***

SouthPark, Colorado

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.

On 17th Nov, 2014 Tom Fenton said:
Sorry to say My Herpes are no better


Who remembers this first time around: https://www.youtube.com/watch?v=JF0a5aoEGsw


TurboDave16V
Forum Mod

10669 Posts
Member #: 17
***16***

SouthPark, Colorado

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.

On 17th Nov, 2014 Tom Fenton said:
Sorry to say My Herpes are no better


Who remembers this first time around: https://www.youtube.com/watch?v=JF0a5aoEGsw


JetBLICK

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190 Posts
Member #: 1261
Advanced Member

Rugby/Droitwich

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


Joe C

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11947 Posts
Member #: 565
Carlos Fandango

Burnham-on-Crouch, Essex

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.

On 28th Aug, 2011 Kean said:
At the risk of being sigged...

Joe, do you have a photo of your tool?



http://www.turbominis.co.uk/forums/index.p...9064&lastpost=1

http://s95.photobucket.com/albums/l154/min...2006/?start=all



Paul S

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8468 Posts
Member #: 573
Formerly Axel

Podland

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."


wil_h

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9115 Posts
Member #: 123
Post Whore

Betwix Harrogate and York

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

On 2nd Jan, 2013 fastcarl said:

the design shows a distinct lack of imagination,
talk about starting off with a clean sheet of paper, then not bothering to fucking draw on it,lol

On 20th Apr, 2012 Paul S said:
I'm mainly concerned about swirl in the runners caused by the tangential entry.


Joe C

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11947 Posts
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Carlos Fandango

Burnham-on-Crouch, Essex

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...

On 28th Aug, 2011 Kean said:
At the risk of being sigged...

Joe, do you have a photo of your tool?



http://www.turbominis.co.uk/forums/index.p...9064&lastpost=1

http://s95.photobucket.com/albums/l154/min...2006/?start=all



stevieturbo

3303 Posts
Member #: 655
Post Whore

Northern Ireland

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


TurboDave16V
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10669 Posts
Member #: 17
***16***

SouthPark, Colorado

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...

On 17th Nov, 2014 Tom Fenton said:
Sorry to say My Herpes are no better


Who remembers this first time around: https://www.youtube.com/watch?v=JF0a5aoEGsw


TurboDave16V
Forum Mod

10669 Posts
Member #: 17
***16***

SouthPark, Colorado

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?

On 17th Nov, 2014 Tom Fenton said:
Sorry to say My Herpes are no better


Who remembers this first time around: https://www.youtube.com/watch?v=JF0a5aoEGsw


wil_h

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9115 Posts
Member #: 123
Post Whore

Betwix Harrogate and York

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

On 2nd Jan, 2013 fastcarl said:

the design shows a distinct lack of imagination,
talk about starting off with a clean sheet of paper, then not bothering to fucking draw on it,lol

On 20th Apr, 2012 Paul S said:
I'm mainly concerned about swirl in the runners caused by the tangential entry.


metroturbo

739 Posts
Member #: 989
Post Whore

North Yorkshire

I think it is called evacusump.


On 12th Sep, 2017 TurboDave16V said:
Wasn't there discussion on using the exhaust flow to pull a vac for breathers or something similar?


Kean

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2380 Posts
Member #: 341
aka T2clubby

South Staffs

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.


stevieturbo

3303 Posts
Member #: 655
Post Whore

Northern Ireland




On 12th Sep, 2017 TurboDave16V said:
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?


You can use exhaust gases via a non return valve to try and pull vac...but again, if no adequate oil/air separation...it's going to pull your oil out too.

ie this type of thing, the little cans are supposed to be separators, intended for a V8 here, they'd usually pop into holes in the rocker covers.
These setups do need a free flowing exhaust too. Not sure how effective they are at low gas speeds in the exhaust though. I did buy a set many many years ago for my old RV8, but never fitted them

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

The yanks also like using mechanical pumps to pull vacuum in the crankcase. Again not totally sure how they deal with not actually yanking all the oil out from in there too lol

Something based around an OEM type PCV is probably best though, which can maintain clean fresh air in the crankcase as well as pulling a little vacuum in there. ( Although for simplicity I do just vent my own to atmosphere, no PCV )

I'm not endorsing this product, but they post a video explaining it and it does look fairly decent

https://www.youtube.com/watch?v=ai-s5azMLsU

Another is the Mightymouse. Some info and pics here.

https://drive.google.com/drive/folders/0Bxb...X3pfdjVIaTNKT0E

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

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