Head Breather Pipe Investigations

[Rusty]

Following on from HPMuirt's question thread (in turn following on from ADI), I have been busy today doing some investigation into the head breather pipe as a source of oil getting into the inlet system.

Test Setup:-

• Firstly I disconnected my inlet return and plugged it with one of my 19mm bungs (shamless plug).
• I then set the catch tank to atmosphere through a breather filter.
• Next I disconnected the union pipe rubber joiner from the back of the head (grazed knuckles - this was a PITA!).
• I then tried to squeeze some 1/2" oil breather pipe onto the head breather outlet... it wouldn't go as it's 14mm as so much Aud stuff seems to be
• I then removed the ABY engine boost pipe...
• And then I shaved the inside of the 1/2" oil pipe, slitted it slightly and beasted it on - not much fun with the access I had and worse on a stock car!
• Finally I plugged the union pipe rubber joiner so that the block was breathing through only the catch tank - avoiding too much oil going where I didn't want it to!
• I then took a 500ml drinks bottle and cut holes at the top to allow it to breathe.
• I then fed the end of the oil hose (connected at the other end to the head breather outlet) into the drinks bottle and sealed it on with tape.
• I refitted everything, checked it all and went for a drive...

The Drive:-

• Firstly I trundled along to get the car up to temperature and to get to some 50/60 mph roads.
• Just before I joined the fast roads, I pulled over and checked - no oil in the drinks bottle.
• I then joined the road and accelerated hard in 1st and 2nd gear.
• 2nd in my car is ~0.5g (30-60mph = 3s).
• I managed to do 3 2nd gear runs and 1 rolling 1st gear run (~0.75g)
• I pulled over and checked the drinks bottle
• A small amount of oil was in the bottle.
• Again, a mixture of 1st, 2nd and 1st-2nd runs, no more than 5.
• 3rd wasn't really an option but I did touch it for 1-2s on a couple of occasions.
• I then pulled over and checked again, more thoroughly
• ~50ml oil in the drinks bottle!

Results

• 50ml of oil left the head breather after ~10 0.5g runs of 3 seconds each.

Relevance:-

• My car is fast for a stock car as it's got various lightwight spinning bits and is stripped of 75kg at the mo so I am confident that my results cover stock S2, chipped S2, stock RS2, mildly chipped RS2, S2 small hybrid.
• They can also be assumed for any car running 0.5g in the higher gears but for these cars the higher boost could mean higher crank case pressures due to blow by etc. There is also the question, how much oil is there to actually move?
• The results are for a straight line on level ground and do not take into account slopes or hard cornering effects.

Conclusions:-

• The amount of oil leaving the head breather is enough that it needs to be dealt with properly if using an S2 on track.
• For a road car running chipped RS2 spec or less and with the stock 14mm pipe leading from the head to the block, the breather system will cope OK under most conditions, a stock catch tank will help here but must not take a separate head feed without a wet sump return.
• Equally, for an occasional track car of chipped RS2 spec or less, again, a stock tank will work OK here with the same condition as above, just remember to empty the tank and that whever is in the tank isn't in the engine so if you're filling a 1 litre tank then that's bad m'kay!
• For higher powered cars capable of sustained 0.5g acceleration, the system will start to be overwhelmed and must be replaced.
• For all cars, hard acceleration under high right hander cornering load will overwhelm the system, luckily this is brief in most cases so can be managed.

Solution:-

• Non standard head breaher position.
• Baffles added to head breather.
• Swirl pot in the oil breather system will help.
• This can be replicated by a properly plumbed-in catch tank.
• < Chipped RS2 - wet sump return optional.
• > Chipped RS2 - wet sump return essential.
• For the standard oil system there are no effective solutions, only management using one of the above items and manual checking / emptying of any tank in the system.

And finally, for those who want a laugh at my expense. When I had checked the oil level in the drinks bottle, I decided to pour the contents back into the engine. When pouring I noticed that little oil was entering the engine... I then saw a pool of oil on the inlet/injector shelf and running down the side of the engine onto the floor. I refer you to this bullet point:-

• I then took a 500ml drinks bottle and cut holes at the top to allow it to breathe.

Holes + liquid =

[s2driveruk]

science in motion Mr casey. certainly demonstrates that there's plenty of fluid moevement and thats before you pour it all over the engine

[Rusty]

I'm pleased that I've now quantified the problem and the fact that there was a silly story was merely icing on the cake.

As for the exact interaction between the block pipe gas flow and this trickle of oil, we can only summise. Without taking the car round a track with a selection of breather system designs, 1 tank, 2 tanks fitted etc. I'll not be able to replicate the cornering forces on the road, I'm just not that mad.

Whatever the exact situation is, this oil needs to be dealt with effectively to ensure that it doesn't contribute to the issues raised in HPMuirt's thread and on mine and your cars.

RWD19T has shown that a properly installed swirl pot solves the issue, others have demonstrated the effectiveness of modified head breathers. Both solutions require modification to the standard car. My aim is to investigate bolt on solutions and see what results I can get from that. For those who want to cut, drill or weld, the methods and results are well documented. Thanks to Terry and J for initially mentioning this effect to me

[JP]

On a stock/chipped car you could get away with just using the rear rocker cover outlet and routing that into the separator instead of welding an additional outlet/baffling to the rocker cover. So you end up with;

14mm outlet on back of rocker cover (fit 16mm hose) to oil separator
19mm crankcase to oil separator
16mm oil return to a fumoto valve on the sump with 16mm to 19mm adapter elbow
19mm from oil sparator to 19mm catch tank
19mm from catch tank to intake tract

[jade]

On a stock/chipped car you could get away with just using the rear rocker cover outlet and routing that into the separator instead of welding an additional outlet/baffling to the rocker cover. So you end up with;

14mm outlet on back of rocker cover (fit 16mm hose) to oil separator
19mm crankcase to oil separator
16mm oil return to a fumoto valve on the sump with 16mm to 19mm adapter elbow
19mm from oil sparator to 19mm catch tank
19mm from catch tank to intake tract

Would you not take the hose from the vent on the oil separator too vent too the intake ?

I go sump to separator

Head to separator

Breather on Separator to inlet track

Drain on separator to catch tank

Drain catch tank to sump with a one way valve in the line

[Rusty]

Good, glad you agree with what I proposed but with teh addition of the Fumoto valve as a wet sump return.

I've seen that setup before, was it Doug's car that ran it? What's the availability of the fumoto valve and is it vulnerable to damage if running without an undertray?

16mm = 5/8" as near as makes no difference.

JP, have you measured the OD of the block breather union? I've been informed it's @~30mm but not checked one myself. Merlin Motorsport sell some 1.25" over braid but not oil resistant hose Would need some 30mm stuff.

Audi part numbers for the ABY joiners are

14mm - Head outlet to union pipe - 034 133 999 J
19mm - PCV to union pipe - 034 133 999 H
30mm - Block to union pipe - 054 103 223 A

I wonder if any are pipe from a reel.

I've included pics of both ABY and 3B breather systems. I need to get my head round a 3B next.

[Rusty]

Would you not take the hose from the vent on the oil separator too vent too the intake ?

It is overkill but RWD19T is running 500bhp+ so it needed it, just to be sure! You should see the catch tank, it's a beast!

I'm looking at a separator as a solution for the 3B's 'tight on space' engine bay.

[prj]

I have another approach, and also a few questions.
Many set the crankcase ventilation system to atmosphere. But aren't you supposed to suck out the blow-by using vacuum?
If you route it to atmosphere, there is no more vacuum.

Here the other approach (critique welcome):
* Plug the connection from the check valve (under the IM), to the ventilation system on both ends. Leave the check valve in tact, so the evap system works correctly.
* At the back of the head, add a catch tank. But instead of routing it to the atmosphere, keep the system sealed and route it back to the intake (through the catch tank).

This way you:
* Eliminate the chance of the check valve going bad and boosting your crankcase
* Have vacuum sucking out the blow-by
* Prevent oil contamination, by having a catch tank, that catches almost all of the oil.

What do you think?

[Rusty]

That's exactly what I have so you're on the right track

N80 direct to the head (thanks JP).
Union pipe to a catch tank and then to the inlet via the head through breather pipe.

What that doesn't address is the oil from the head hitting the airstream from the crank case breather and being 'blown' (for want of a better word) into the catch tank.

I am going to replace the union pipe with something larger and fit a swirl pot at the junction between the head and crank case breather pipes.

JP has gone one further and has drained the swirl pot back to wet sump (below the oil level). This is the correct way to do it.

[prj]

Oh, okay

[A80Avant]

some pictures would be nice of the system you propose, as i think i lost it somewhere. With all that in mind, i think i may have something similar to that system you are proposing.

i vent back to inlet track to keep the vacuum but i havent attached the drain of the tank to the sump. I empty it from time to time. BUt i also use a T piece from the narrow of the 2 metal tubes at the back of the head, that goes to the crank case and i route some of that blowby to the catch tank/swirl. Should i take that track completelly to the tank?(the small metal tube im referring to is 1a on the picture you posted on the aby)

[jade]

It is overkill but RWD19T is running 500bhp+ so it needed it, just to be sure! You should see the catch tank, it's a beast!

I'm looking at a separator as a solution for the 3B's 'tight on space' engine bay.

Well yes I am running 500hp and more shortly

I have separator and a catch tank so the separator is always empty

Is he also venting the separator ?

Not sure I understand correctly his set up then because if you vent from the catch tank is that not where the oil is, I just thought it would be better to vent from the separator as there should not be oil there it should be draining to catch tank ?

[s2driveruk]

Fumoto valve is ok if you angle the lever i have found - mines been on for years without the undertray and I've not damaged it - great little accessory actually

[HPmuirt]

I'll not be able to replicate the cornering forces on the road, I'm just not that mad.

Ah hah, that sounds like my cue

Good work Mr Casey, I'll take one

Cheers n

Si
(Owner and abuser of the jelly-mould express :mischeif

[JP]

The catch tank is used to separate moisture/oil vapour from the airstream so the intake tract remains dry whereas the oil separator gets rid of the fluid so the catch tank doesn't fill up. Pretty much the same the Jap drift cars do and they go through some extreme G's on the cornering side of things. As the catch tank is only there to catch the oil incase of extreme engine failure as per the rules and regs where the volume of the catch tank must be equal to the oil capacity of the engine.

Run the catch tank first and the mesh will get saturated and not remove vapour from the air stream.

I need to finish machining some bits up for my sons skateboard after which I'll do a quick sketch of the proposed road going space friendly idea. Including suggested hoses.