Oil/air sperators

[fester2au]

Was talking to a mate the other day about sperators and all the talk of them on various forums, especially a lot of talk from the 3.0 litre Nissan crowd. I know a basic can is near on useless but there is a lot of talk that basic home made baffled or filtered ones are better but not perfect. Seems a lot of support has gone up for the workshop air compressor based ones especially the centrifugal or cyclone styled ones that fling the oil out as well as using a filter medium.

Now I understand in their original environment given the pressure and CFM they deal with that this cyclonic effect may be very useful but does the rocker cover fumes actually generate sufficient flow rate to actually generate this in a motor vehicle. Maybe in 3.0 litre Nissans but really???? Or is it more the case that it is a co-incidence and that these seperators actually have a very good filter medium which in a vehicular situation is what is doing the work rather than the cyclonic/centrifugal action.

I have a couple of designs penned that I am soon to make for friends (and self) but I'm looking for the ideal filter medium any suggestions.

Stainless steel wool is considered but I'm also thinking that something a little denser would be more effective as per previous discussions but would a high density foam actually be too restrictive.

[nottie]

Filtration questions are best answered by Isuzurover.

[KiwiBacon]

If you don't have a cyclonic type, you need enough volume for the flow to slow down and the mist to settle out.

I replaced a steel wool one with a cyclonic one the same size (made it myself) about 5 years ago. Huge difference and mine only had two stages of centrifuge in it and no filter medium.

[tweak'e]

it depends a lot on how fine the oil mist is. the problem with the patrols 3 litres is the mist is so darn fine it doesn't settle out, even with BIG volume.
i know other vehicles with lots of blowby and a basic empty can works fine. but thats because its blowing big spits of oil out, not a super fine mist.

i simply used a breather filter as a coalescing filter. ie a filter big enough to flow well and let the oil held in the filter fibres catch the oil mist.
the same principle that air compressor filters work on, only the filter is a lot bigger.

[RED60]

If you don't have a cyclonic type, you need enough volume for the flow to slow down and the mist to settle out.

I replaced a steel wool one with a cyclonic one the same size (made it myself) about 5 years ago. Huge difference and mine only had two stages of centrifuge in it and no filter medium.

How about a dimensioned diagram and pix of your home brew separator Kiwi.......

[KiwiBacon]

If you don't have a cyclonic type, you need enough volume for the flow to slow down and the mist to settle out.

I replaced a steel wool one with a cyclonic one the same size (made it myself) about 5 years ago. Huge difference and mine only had two stages of centrifuge in it and no filter medium.

How about a dimensioned diagram and pix of your home brew separator Kiwi.......

Here's a see-through. It's 2.5" exhaust pipe outside and about 80mm long.


Air comes in the pipe at the back, gets thrown against the wall before turning up and running around the second wall and going out through the side tube. Undoubtedly not as effective as a Provent, but it only took me an hour to knock up with the TIG and fit the space I had.

[fester2au]

If you don't have a cyclonic type, you need enough volume for the flow to slow down and the mist to settle out.

I replaced a steel wool one with a cyclonic one the same size (made it myself) about 5 years ago. Huge difference and mine only had two stages of centrifuge in it and no filter medium.

How about a dimensioned diagram and pix of your home brew separator Kiwi.......

Here's a see-through. It's 2.5" exhaust pipe outside and about 80mm long.


Air comes in the pipe at the back, gets thrown against the wall before turning up and running around the second wall and going out through the side tube. Undoubtedly not as effective as a Provent, but it only took me an hour to knock up with the TIG and fit the space I had.

So the second inner tube is shorter and the air goes up over the lip and down into the central tube and out???? is that correct.

The design I was working on is 100mm tube about 150 long. Air comes in through tube in the side about 1/3rd up from bottom. There is a central 25mm tube running from top to bottom and it has a series of holes in a lline along its length at 180 degrees to the inlet. This has a foam filter meduim around it and therefore the air comes in and has to pass 180 degrees aroudn through this medium to then enter the central tube and exit out the top. Oil in the foam seeps down to the bottom and out through the exit in the bottom via slots in the central tube. Any oil that gets into the central tube can also drop down and out. Might put a small layer of stainless steel wool below the foam in the outer section and also a final course scrubber in the top of the central tube to catch any stray residue. There is a perforated divider just below the inlet pipe to hold the foam in place and seperate it from the collector section which would have the steel wool in it. The oil can drop through the perforations in the divider plate and it allows the foam to sit above the bottom giving a collection bowl or seperate area.

This design has a threaded base to accept BSP fittings so it can have a hose barb for direct drain back to sump or a bung or tap so it can be manually emptied.

I think this format should work fairly well if we get the foam density right and I am looking at making a couple for mates who all have either 4.2 TD Nissans or Toyotas so no 3.0 litre issues.

Just not sure what foam to source and from where. Needs to be oil resistant and not sure on density. Haven't had chance to get to Clark Rubber or equivalent.

Sorry no fancy pics, haven't learnt enough CAD to do so.

[KiwiBacon]

So the second inner tube is shorter and the air goes up over the lip and down into the central tube and out???? is that correct.

Yep.

The design I was working on is 100mm tube about 150 long. Air comes in through tube in the side about 1/3rd up from bottom. There is a central 25mm tube running from top to bottom and it has a series of holes in a lline along its length at 180 degrees to the inlet. This has a foam filter meduim around it and therefore the air comes in and has to pass 180 degrees aroudn through this medium to then enter the central tube and exit out the top. Oil in the foam seeps down to the bottom and out through the exit in the bottom via slots in the central tube. Any oil that gets into the central tube can also drop down and out. Might put a small layer of stainless steel wool below the foam in the outer section and also a final course scrubber in the top of the central tube to catch any stray residue. There is a perforated divider just below the inlet pipe to hold the foam in place and seperate it from the collector section which would have the steel wool in it. The oil can drop through the perforations in the divider plate and it allows the foam to sit above the bottom giving a collection bowl or seperate area.

This design has a threaded base to accept BSP fittings so it can have a hose barb for direct drain back to sump or a bung or tap so it can be manually emptied.

I think this format should work fairly well if we get the foam density right and I am looking at making a couple for mates who all have either 4.2 TD Nissans or Toyotas so no 3.0 litre issues.

Just not sure what foam to source and from where. Needs to be oil resistant and not sure on density. Haven't had chance to get to Clark Rubber or equivalent.

Sorry no fancy pics, haven't learnt enough CAD to do so.

I think it'll work fine. I'd even not worry about the perforated plate etc in the bottom, having enough depth will keep the liquid oil in the bottom and the vortex created will keep throwing oil against the side walls where it'll run down to the bottom.
This is one reason why I kept my inlet at the top, so the air movement helps chase the oil down the sides.

Maybe Ben (Isuzurover) will chime in with an idea for your foam screen in the middle. Do you have enough room for a small breather filter instead?

[+dj_hansen+]

Just find someone with an oilable air filter that they dont want anymore?

Or just use the stainless scourers available from the super market

Once you have made them fester.. post some pics

[fester2au]

Thers is plenty of room for just about anything in there. I like the stainless steel wool principal but the idea for this design that I have seen used a foam of some sort. It was from a foam block where the cylindrical shape was punched out just not sure of density. The onyl thing that steered me off stainless wool was the 3.0 litre Nissan chat where guys were using that (admittedly in a different design) and it wasn't really scouring enough oil. I've also read write up where the medium was scotchbrite pads.

The onyl real reason for the perforated divider was to keep the foam medium up off the bottom to partly give an oil cavity and also allow me to weld the end caps on without burning/melting the foam medium. Having said that I could use some stinless steel wool in the bottim as a buffer and have the foam sitting on that.

As far as using a breather filter do you mean using it inside. I did look casually at some of the cartridge style element oil filters that wee in Supercheap the other day but none wee the right size. These are like the oil filters found on most older motorbikes that are basically like an air filter cartridge. The outer can as said is 100mm so 94mm i/d and the central exit/drain tube is 25mm so there is a fair bit of space inside. Length is not fixed, I was originally thinking 100mm long but this looked a bit short and the ones I read about were 170mm from memory so depending on fitment/packaging constraints I'm thinking somewere around 150mm would be plently.

[ISUZUROVER]

Stainless steel wool is considered but I'm also thinking that something a little denser would be more effective as per previous discussions but would a high density foam actually be too restrictive.

Cyclones will remove 50% of the mass at best (if properly designed).

Stainless steel wool will be useless. Foam will be almost as bad.

Filtration efficiency is inversely proportional to fibre diameter - filters are NOT sieves - and the particle sizes olf oil mist from a TD are small.

Your best bet would be to buy a Provent element and make a housing to suit. You cannot buy anything close to the efficiency they use in Provent elements.

[Z()LTAN]

have a look here ladies

http://www.westernfilters.com.au/docs/Mann_Pro-Vent.pdf

[tweak'e]

As far as using a breather filter do you mean using it inside. I did look casually at some of the cartridge style element oil filters that wee in Supercheap the other day but none wee the right size..........

yes, just use the breather filter inside on the breather inlet side.

one person made one out of a Z9 oil filter.
i had thought you could use a fuel filter. theres a few that have 1/2" ports and the paper filter would catch the oil quite well. they usually have drain with tap built in as well. a long skinny one would work well.

[ISUZUROVER]

As far as using a breather filter do you mean using it inside. I did look casually at some of the cartridge style element oil filters that wee in Supercheap the other day but none wee the right size..........

yes, just use the breather filter inside on the breather inlet side.

one person made one out of a Z9 oil filter.
i had thought you could use a fuel filter. theres a few that have 1/2" ports and the paper filter would catch the oil quite well. they usually have drain with tap built in as well. a long skinny one would work well.

Sorry, but using a fuel filter a breather is a bad idea. Unless it is HUGE it will eventually clog and you will probably blow seals.

The Mann Provent that Z()LTAN posted above has a valve in the cap which vents the blowby gasses to atmosphere if the pressure drop across your filter element gets too high - saving your engine seals.

The filter element (without casing/housing) in the Provent is about the size of a coke can. it also has a 1" inlet and outlet.

[tweak'e]

As far as using a breather filter do you mean using it inside. I did look casually at some of the cartridge style element oil filters that wee in Supercheap the other day but none wee the right size..........

yes, just use the breather filter inside on the breather inlet side.

one person made one out of a Z9 oil filter.
i had thought you could use a fuel filter. theres a few that have 1/2" ports and the paper filter would catch the oil quite well. they usually have drain with tap built in as well. a long skinny one would work well.

Sorry, but using a fuel filter a breather is a bad idea. Unless it is HUGE it will eventually clog and you will probably blow seals.

The Mann Provent that Z()LTAN posted above has a valve in the cap which vents the blowby gasses to atmosphere if the pressure drop across your filter element gets too high - saving your engine seals.

The filter element (without casing/housing) in the Provent is about the size of a coke can. it also has a 1" inlet and outlet.

the fuel filter i was thinking of is about double the size of the provent.
i can't remember is the provent filter is a multilayer filter or not. single layer filter (eg like a typical air filter) won't clog up as the oil just gets blown out of it when its under pressure.
however after a long length of time it will be clogged with other particles so its best to be washed or replaced at a reasonable interval.

one thing most/all homemade catch cans lack is pressure valves. the provent is a great product just wish it was more accessible.

[fester2au]

Yeah the problem, if you can call it that, with the provent filter and for that matter any other filter be it oil or fuel is that it will fill up eventually and need replacing complicating the construction of the can as it needs to be openable. I guess that is wh the majority use a reasonably permanent medium like foam, scotchbrite or steel wool.

The provent is nice but far more expensive than my current budget would allow and far more than the cost of makign myself. However using the provent filter doesn't look too bad given some US pricing I saw ($45USD)but I was quoted today by an Aussie supplier $105+GST + $12 postage. ?I saw a complete Provent on ebay for $175 not long ago.

So possibly now thinking of a flanged top on my can so I can use a 5mm plate top so I can machine an o ring groove into it to seal it. Bit more work but certainly still cost effective if I can fit the provent filter in correctly.

The design I was working off was actually a commercially produced item with the oil resistant foam inside and they sell them apparently for around the $200 mark which doesn't stack up very well against the provent in that case.

[Z()LTAN]

IMHO PCVs are not this technical...

My SOA75 and ash's competition winning GQ ute both run PCV hoses straight into our custom air boxes.

Ash's 200rwkw 30psi GU runs a custom catch can which is of his design, basically just a can with a baffle using gravity to filter the oil.

In all 3 setups the oil aspiration into the intake if Very minimal.

With my setup, i have a drizzle of oil in the bottom of the airbox that i just wipe out when i clean the filter...

If your engine is breathing heavy enough to produce alot of PCV oil bypass then you have other issues.

Dont tell me boost makes it worse... it may but my car runs 20psi, the GQ ute runs 15 and the GU wagon runs 25-30....

[fester2au]

IMHO PCVs are not this technical...

My SOA75 and ash's competition winning GQ ute both run PCV hoses straight into our custom air boxes.

Ash's 200rwkw 30psi GU runs a custom catch can which is of his design, basically just a can with a baffle using gravity to filter the oil.

In all 3 setups the oil aspiration into the intake if Very minimal.

With my setup, i have a drizzle of oil in the bottom of the airbox that i just wipe out when i clean the filter...

If your engine is breathing heavy enough to produce alot of PCV oil bypass then you have other issues.

Dont tell me boost makes it worse... it may but my car runs 20psi, the GQ ute runs 15 and the GU wagon runs 25-30....

Which takes us back to the successful use of diverters and foam/steel wool seperator mediums hummmmm

[Z()LTAN]

exactly, dont over dramatize a very simple system with all this crap...

Run a 3/4 hose from the PCV port to a 3/4 barb 1" from the bottom of your airbox.

Simple, non restrictive and best yet.... works perfectly fine...

[ISUZUROVER]

Modern CCV filter systems came about because turbocharger and engine life (talking big diesels here) was being shortened by routing the breather back into the intake with little or no filtration (because of tghe soot in the oil).

Just because your engine doesn't breathe much, doesn't mean engines don't need CCV filters.

The added benefit, is that if you blow a ring, your engine doesn't start running on its own oil and self destruct completely.

[tweak'e]

IMHO PCVs are not this technical...

My SOA75 and ash's competition winning GQ ute both run PCV hoses straight into our custom air boxes.
Ash's 200rwkw 30psi GU runs a custom catch can which is of his design, basically just a can with a baffle using gravity to filter the oil.
In all 3 setups the oil aspiration into the intake if Very minimal.
With my setup, i have a drizzle of oil in the bottom of the airbox that i just wipe out when i clean the filter...
If your engine is breathing heavy enough to produce alot of PCV oil bypass then you have other issues.
Dont tell me boost makes it worse... it may but my car runs 20psi, the GQ ute runs 15 and the GU wagon runs 25-30....

if you routed the breather to the air box on a ZD30 you would blow the motor easy enough. 300-500mil per 5000km is reasonably common and normal. fill your air filter with that much oil it will get clogged and sucked into the turbo.

trouble is a lot of modern motors throw a lot of very fine oil mist. you even get oil soaked air filters just from the bit of oil mist that floats up after engine shut off.
then theres the MAF sensors modern diesels have which can get oil fouled.

these motors are somewhat different to the old 4.2 and you simply can't get away with the old tricks.

[me3@neuralfibre.com]

If you don't have a cyclonic type, you need enough volume for the flow to slow down and the mist to settle out.

I replaced a steel wool one with a cyclonic one the same size (made it myself) about 5 years ago. Huge difference and mine only had two stages of centrifuge in it and no filter medium.

How about a dimensioned diagram and pix of your home brew separator Kiwi.......

Here's a see-through. It's 2.5" exhaust pipe outside and about 80mm long.


Air comes in the pipe at the back, gets thrown against the wall before turning up and running around the second wall and going out through the side tube. Undoubtedly not as effective as a Provent, but it only took me an hour to knock up with the TIG and fit the space I had.

So the second inner tube is shorter and the air goes up over the lip and down into the central tube and out???? is that correct.

The design I was working on is 100mm tube about 150 long. Air comes in through tube in the side about 1/3rd up from bottom. There is a central 25mm tube running from top to bottom and it has a series of holes in a lline along its length at 180 degrees to the inlet. This has a foam filter meduim around it and therefore the air comes in and has to pass 180 degrees aroudn through this medium to then enter the central tube and exit out the top. Oil in the foam seeps down to the bottom and out through the exit in the bottom via slots in the central tube. Any oil that gets into the central tube can also drop down and out. Might put a small layer of stainless steel wool below the foam in the outer section and also a final course scrubber in the top of the central tube to catch any stray residue. There is a perforated divider just below the inlet pipe to hold the foam in place and seperate it from the collector section which would have the steel wool in it. The oil can drop through the perforations in the divider plate and it allows the foam to sit above the bottom giving a collection bowl or seperate area.

This design has a threaded base to accept BSP fittings so it can have a hose barb for direct drain back to sump or a bung or tap so it can be manually emptied.

I think this format should work fairly well if we get the foam density right and I am looking at making a couple for mates who all have either 4.2 TD Nissans or Toyotas so no 3.0 litre issues.

Just not sure what foam to source and from where. Needs to be oil resistant and not sure on density. Haven't had chance to get to Clark Rubber or equivalent.

Sorry no fancy pics, haven't learnt enough CAD to do so.

Hey Kiwi
Maybe I'm mistaken - but the diagram looks more like the air comes in 2/3 of the way up, goes round and down, then across the bottom and up inside the second cylinder before going intot he pipe with the opening near the top.

So the inside cylider is fixed to the roof of the design - is that right?

What motor are you running that on?

Thanx
Paul

[KiwiBacon]

Hey Kiwi
Maybe I'm mistaken - but the diagram looks more like the air comes in 2/3 of the way up, goes round and down, then across the bottom and up inside the second cylinder before going intot he pipe with the opening near the top.

So the inside cylider is fixed to the roof of the design - is that right?

What motor are you running that on?

Thanx
Paul

The inlet tube is the tangential one you can see at the top of the picture. It enters the outer casing.
The outlet is the one at the centre of the vortex.

Yes the inner tube is welded to the top.

I designed, made and fitted this one so I'm quite confident that's how it works. It's on an Isuzu 4BD1T and takes the place of the factory air/oil seperator. The factory seperator simply blew the blow-by against a flat plate and had the collection tube as close to the top as it could run. With worn rings (as found in a dusted engine) the factory seperator was capable of sending all your engine oil out the breather.

[me3@neuralfibre.com]

So the second inner tube is shorter and the air goes up over the lip and down into the central tube and out???? is that correct.

Yep.

Nope - clarified - see question above.

[KiwiBacon]

Nope - clarified - see question above.

Good spotting. I missed that.

[me3@neuralfibre.com]

What about air filter foam?
Possibly too open to be honest.
Finer - visit the local rubber supplies. Just make sure it's not closed cell.

Alternately - what about cotton? I reckon an old T shirt would work.
So long as it's big enough to slow the gasflow and fine enough to "scrub".

As indicated - it prod does depend on mist size.

I need one for mine. Sick of ppl telling me my turbo leaks oil when it's the breather from the rocker cover dumping oil into the turbo intake.

Paul

[tweak'e]

What about air filter foam?
Possibly too open to be honest.
Finer - visit the local rubber supplies. Just make sure it's not closed cell.

Alternately - what about cotton? I reckon an old T shirt would work.
So long as it's big enough to slow the gasflow and fine enough to "scrub".

As indicated - it prod does depend on mist size.

I need one for mine. Sick of ppl telling me my turbo leaks oil when it's the breather from the rocker cover dumping oil into the turbo intake.

Paul

both will work. someone on patrol forum got unifilter (i think) to make a foam replacement for the compressed air filter they where useing. personally i think its to small.

with whatever you use, the hard part is making it so gas can't get around it. big problem i had with foam is that the gas and oil got past around the edges. it needs to be sealed so the oil has to go through the filter.

even a bit of cotton shirt would do, as long as it flows gas well enough. once its wet with oil the oil itself is what filters out the oil mist.

[me3@neuralfibre.com]

with whatever you use, the hard part is making it so gas can't get around it. big problem i had with foam is that the gas and oil got past around the edges. it needs to be sealed so the oil has to go through the filter.

even a bit of cotton shirt would do, as long as it flows gas well enough. once its wet with oil the oil itself is what filters out the oil mist.

Woohoo - a get rich quick scheme. I'll sell my old jocks on ebay as an oil scrubber and claim the elastic as a new high performance oil seal.
The soaked up gas may even improve vehicle performance

Paul

[ISUZUROVER]

What about air filter foam?
Possibly too open to be honest.
Finer - visit the local rubber supplies. Just make sure it's not closed cell.

Alternately - what about cotton? I reckon an old T shirt would work.
So long as it's big enough to slow the gasflow and fine enough to "scrub".

As indicated - it prod does depend on mist size.

I need one for mine. Sick of ppl telling me my turbo leaks oil when it's the breather from the rocker cover dumping oil into the turbo intake.

Paul

both will work. someone on patrol forum got unifilter (i think) to make a foam replacement for the compressed air filter they where useing. personally i think its to small.

with whatever you use, the hard part is making it so gas can't get around it. big problem i had with foam is that the gas and oil got past around the edges. it needs to be sealed so the oil has to go through the filter.

even a bit of cotton shirt would do, as long as it flows gas well enough. once its wet with oil the oil itself is what filters out the oil mist.

Actually neither will work (well).

Filtration efficiency is inversely proportional to fibre diameter. Cotton fibres are large and foam is crap.

But don't listen to me. I just do filter R&D for a living so I wouldn't know anything.

[mud4b]

Well i have been reading this and searching the terms mentioned but honestly im lost, do these not work for a diesel?
http://shop.ebay.com.au/i.html?_nkw=oil ... 86.c0.m359

cheers mark.