924Board.org

[Scorpio]

EFI.. Turbocharged 924

What should i do with the crankcase breather?...does it just pipe straight up into the intake manifold?.. PCV valve?..is that what prevents boost pressurising the block?

Also the dizzy has been removed (EDIS4) and so i have the option of a blank plate or putting some sort of breather....is it necessary...or helpful?

Almost have finished my first complete engine rebuild...and its loookiing sweeeetttt
_________________
1979 NA
MS1..EFI..
GARRETT T25 TURBO
BILSTEIN SHOCKS
GT BASED CUSTOM BODYKIT

Brisbane , Australia
Think mean think fast
all youll see is
my Porsches Arse!!!

[Smoothie]

The factory 931 breather system includes 2 air-oil seperators - one for the
crankcase (#1) and one for the turbo oil drain line (#5) -


The air return line (for both 924NA and 931) attaches upstream of the manifold
and TB. -Either at the airbox or chamber after the airbox for 924NA, and at the
airbox for 931. Either way it goes upstream of the throttle body, and downstream
of the filter element.

The factory 931 setup does not use a PCV valve.
_________________
"..it's made in Germany. You know the Germans always make good stuff."


'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

[ideola]

Smoothie, why doesn't that diagram depict the head breather update for the 931???

Scorpio, what you'll want to do is to purchase or fabricate an air-oil separator. The big line from the crank case should plumb directly into the air oil separator. Then you will need an oil line to plumb from the bottom of the a-o separator back to the second port on your oil pan (the one just above the drain plug). The topmost port of the separator should plumb into the intake path post filter but pre-TB.

As noted above, the 931 also had a "breather update". The funky block off plate on the LHS of the head (just below the oil filler cap facing the intake manifold) was modified on 931's with an elbow, which you can see about dead center in this early photo of my UWB engine bay:


Some of the early 931s did not have this, but my UWB was a 1980 series 1, and came stock with it. I've seen one 931 head that didn't even have the port opening on the side of the head, but most of the 931s I've seen in person already had the breather update. I can't recall off the top of my head where it plumbs back into the intake tract, but IIRC the metal tube you see in the photo above either connects to the recirculation valve or somewhere along the charge air path prior to the turbo.

For your application, you might want to consider just welding up your ignition distributor housing because there have been multiple reports of the block off plates not sealing correctly and leaking oil from the back of the head. Here's mine:


Rather than plumbing a breather port there, if you take a close look at your valve cover, you will see on the part to which the filler cap attaches, facing the intake, there is enough room there to weld on a small nipple suitable for a head breather, which is how it was done on this GTS:

Note in the photo above, the GTS doesn't use the 931-style breather update adapter on the head. Also, the issue you may get into with an EFI conversion is that the fuel rail will almost certainly interfere with the elbow on the breather update adapter, which is why I won't be using it when I build the motor for the UWB. Since I've welded my cam cover shut (due to the dry sump), I will either plumb a fitting on the sealed filler cap, or do it as depicted above on the GTS engine.

At any rate, from this location, I think you could probably just tee back into the pre-air-oil-separator line; you would probably want to install a one-way valve in that line to prevent crankcase pressure from coming back into the head.
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erstwhile owner of just about every 924 variant ever made

[Scorpio]

ok thanks Dan and smoothie i think ive got it..

so basically

1)
crank case breather -------->T junction-----> oil air separator

oil air separator to A) One way valve AND B)lower drain to oil pan

One way valve ---> air intake pre throttle body

2) Cam shaft breather (either in dizzy block off plate or above injector1 block off plate)-----> T junction as above

Questions
1) How necessary is a breather in the head?and what size breathing hose is required..ie just how much air needs to be vented?

2) Where do i get a one way valve/specs needed?

3) I think my sump only has the one plug and no other inlet/outlet? so just weld a return bung in or just let the oil separator collect the oil them empty when full?

4)If youve welded your cam cover shut how on earth do you get to your injectors...im guessing you just meant the breather plate openine?

5) why not just vent the air to atmo if its oil free after the air oil separator?
_________________
1979 NA
MS1..EFI..
GARRETT T25 TURBO
BILSTEIN SHOCKS
GT BASED CUSTOM BODYKIT

Brisbane , Australia
Think mean think fast
all youll see is
my Porsches Arse!!!

[ideola]

I've welded the oil filler cap (at bass gt's recommendation) to prevent any air leakage in the crankcase, ideally maintaining as a high a vacuum as possible due to the dry sump. It will still be bolted on as normal:


As for venting air to atmo, you could do that, but don't tell Nobbi or any of his environmentalist friends
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erstwhile owner of just about every 924 variant ever made

[Chrenan]

I run this breather can on my 924:



http://www.saikoumichi.com/951_page.htm

Its for a 951, but the 3/4 hose barbs work for a 924 as well. It goes between the crankcase breather and the intake tract. I empty it every couple of months, a little bit of liquid comes out, not a whole lot. There is no oil in my intake tract, it catches everything coming out of the crankcase breather hole.
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1987 951 - M193 Version for Japan

[Scorpio]

I have a new Monza Catch Can...unfortunately it has no baffel material inside it. (to separate the oil and air)....its good quality alloy with all the appropriate connections......

Ive read of people filling There catch cans with Stainless steel scouring cloths to act as a oil/air separator/condensor......could this be used in my Monza?
_________________
1979 NA
MS1..EFI..
GARRETT T25 TURBO
BILSTEIN SHOCKS
GT BASED CUSTOM BODYKIT

Brisbane , Australia
Think mean think fast
all youll see is
my Porsches Arse!!!

[Smoothie]

What does the manufacturer recommend?
If the oil vapour entry is directed to swirl around the inside wall of the can, maybe you don't need/want to add anything.
Got a pic of it?
_________________
"..it's made in Germany. You know the Germans always make good stuff."


'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

[Scorpio]

[tuurbo]

Scorp far be it from me to educate you on the crankcase breathing apparatus - the other guys here know way more than me.

But I gotta emphasize, that piece that Dan is pointing out, the piece going from the head down to I think the oil drain off from the turbo, was actually helpful in that these tend to let the turbo drain itself of oil much better, I think. It's an upgrade worthy of the name upgrade.
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1980 924 turbo, MSD, Meth. Inj, otherwise stock.

[Smoothie]

Yes, the diagram I posted above is of one of the earlier versions. It shows crankcase breathing Tee'd into the turbo drain breather. They found this was causing water vapour to accumulate in the turbo drain breather line and turbo drain line (which when mixed with oil and oil vapour formed sludge). This slowed and/or eventually blocked turbo oil drainage. The final design, 2 or 3 versions later seperated the two breather systems by doing away with the T (actually more of a Y in real life) and connecting the turbo oil drain breather to the cyl head instead.
_________________
"..it's made in Germany. You know the Germans always make good stuff."


'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

[Rocco R16V]

[Scorpio]

1) Does anyone see a problem with the following....?



2)Any requirements for catch can elevation?

3)I was thinking of sticking in an internal wall with holes drilled in to force oil air mix through more scourer....waste of time?

4)Is there a point to a cam cover breather on a newly rebuilt engine (turbocharged)....would i want vacuum if there is no blowby in the cam cover section?

5) would vapours from crankcase breather go up through pipe into cam cover?..or is that stock metal T/Y pipe venturi?
_________________
1979 NA
MS1..EFI..
GARRETT T25 TURBO
BILSTEIN SHOCKS
GT BASED CUSTOM BODYKIT

Brisbane , Australia
Think mean think fast
all youll see is
my Porsches Arse!!!

[ideola]

I do believe the stock pipe is a venturi. It would be best to have a one-way check valve to prevent crankcase blowby from going back into the head. Elevation wise, I would mimic the factory 931 setup, which has the catch can mounted to the LHS frame rail on a bracket that puts the top of the can just about level with the lower (inside) edge of the shock tower.
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erstwhile owner of just about every 924 variant ever made