CASA 292/14 - Conditions and direction about Jabiru engines

[Olav]

Thanks Nev. I agree that of course any condensed water should not be led back and accumulated in the oil, so to make sure that does not happen the Jabiru way is the bullet proof way.

 

The combustion of 1 liter of gasoline produces approx 1 liter of water and there is also - depending on humidity approx 0,1-0,2 liter of water in the air taken in, but most of all water will leave via the exhaust. Only a proportinal part of the water will go with the by-pass into the crankcase and must be evacuated via the breather system.

 

My oil separator bottle is located just behind the cylinders on the right side of the engine. The breather hose is only 15 cm long. The hose and the separator will have at least the temperature of the oil so the water vapour will not condens here. Vapour and exhaust gases will escape out as they should. Only the oil is retained and led back via the dip stick tube

 

The oil going out with the by-pass is not in the form of vapour but a mist of tiny oil drops created in the crank case and carried by the by-pass gas flow out through the breather. When enterring the separator the flow velocity drops and the oil mist can settle, while the by-pass gas and water vapour will proceed out the went hose at the bottom of the cowling.

 

Olav.

 

 

[facthunter]

A proper through flowing filtered air system ending up in the inlet intake would be good, but with planes simplicity is reliability. You usually don't have a good airfilter either. The Rotax doesn't have much blow by due to close piston fits and it's only the blowby we are concerned with. The Rotax uses it to return the oil to the oil tank in one of the most stupid oil systems ever used in a plane relying on the crankcase being positively pressured all the time and small dia pipes to work. Nev

 

 

[Olav]

A proper through flowing filtered air system ending up in the inlet intake would be good, but with planes simplicity is reliability. You usually don't have a good airfilter either. The Rotax doesn't have much blow by due to close piston fits and it's only the blowby we are concerned with. The Rotax uses it to return the oil to the oil tank in one of the most stupid oil systems ever used in a plane relying on the crankcase being positively pressured all the time and small dia pipes to work. Nev

Not sure what you mean here. My plane has got a proper air filter like on any car. However sending the by-pass gas with water vapor back into the inlet - like on most cars - probably could increase the risk of carburetor icing. Also the hot gas with no oxygen content would reduce the power from the engine, and possible the content of oil might be a problem on the inlet valves if not separated properly in a kind of filter.

 

 

[facthunter]

All that bypassed stuff ends up with grunge in all the areas involved with it so it's probably better to not do it in an aircraft engine.. Some flow through in the crankcase would help though if it was vented overboard, but you would want to make sure it was filtered before allowing it into the case.in the first place... Car type treated paper airfilters may not put up with what some aircraft have to, Backfiring etc and even water and ice could get involved in bad weather.. The intake is usually directly into the carb on most installations, often facing forward.. Carb anti icing may involve injecting an alcohol solution in to the intake on a plane certified for IMC flight in Icing conditions. so a normal filter is out of the question. Nev

 

 

[jetjr]

Jabiru run a std Ryco panel filter. All air, heated or not, goes through it.

 

Bad weather isn't where they are often used Id guess but plenty of icing conditions.

 

A possible reason why Jabiru have return system is the very small oil volumes.

 

An engine could use up to 80+ ml/hr and only ~ 3000ml total.

 

Link this to some older worn engines which can use more and you could end up with problems.

 

 

[jetboy]

I'm a bit confused about the "Jabiru return system". Apart from mate with SK who would empty the catch container to the sump as part of preflight checks.

 

If done with a designed oil seperator, theres probably nothing bad about a return system, did Camit offer one?

 

My 2200 would fill 500ml catch bottle about every 15 hours. A bit less often now with new rings @ 500 hrs.

 

I have the original dipstick before Jab "fixed" the issue of blowby by shifting the full and empty marks down about 1/2"

 

I'd rather keep the level up at least the underbelly of my plane is corrosion treated daily.

 

I just had another pail of oil delivered, 19L cost $299. Maybe I should reconsider.

 

Jabiru run a std Ryco panel filter. All air, heated or not, goes through it.Bad weather isn't where they are often used Id guess but plenty of icing conditions.

A possible reason why Jabiru have return system is the very small oil volumes.

 

An engine could use up to 80+ ml/hr and only ~ 3000ml total.

 

Link this to some older worn engines which can use more and you could end up with problems.

[jetjr]

Theres been several catch can ideas, some just a bottle located along top of duct, Jabiru now have square thing on top of dipstick and yes CAE had a more thorough solution which drained back into extra case vent at top back of engine. It was developed to customer demand but I don't recall Ian wanting to do it.

 

 

[facthunter]

Jabiru have had a venting problem all along and with a small quantity you don't want to lose much. Slight overfilling seems to cause a quick loss to a more or less stable level. The vent system is of too small a cross section, plus a lot of Jabiru's would have a high blowby situation. If I was doing long trips often I would have an inflight top up capability. Nev

 

 

[jetjr]

The Camit system with second case drain at the back and separator gets oil usage back to near nil.

 

I think you are right, trying to vent and drain back down a small dipstick tube is asking too much

 

Overfilling for sure sees excess oil spat out and leads to overheating too. Id think many Jabiru dont hold the listed oil volume either at the max sustainable level.

 

 

[Jaba-who]

Jabiru have had a venting problem all along and with a small quantity you don't want to lose much. Slight overfilling seems to cause a quick loss to a more or less stable level. The vent system is of too small a cross section, plus a lot of Jabiru's would have a high blowby situation. If I was doing long trips often I would have an inflight top up capability. Nev

I’ve never heard of a jab needing in flight top ups. Of the five or so at our airport I think you’d not find a single one who fits that description (except for dumping excess rapidly and then becoming stable). Certainly I’ve had two 3300s which both dump down to about 2.9 litres ( in a few minutes of flying )and then stop. Mine go for 25 hours without needing more than maybe 50 or 75 mls top up.

That seems to be the norm. This concept of jabs losing oil is pretty much an artefact of people expecting that there should the book value of 3.4 l in it. Every time they do it dumps it and people then top it up again and feel it loses oil.

 

I tried an oil recycling system ( built my own - a baffled tube with convoluted path for condensing the oil out. ) but in the end I took it off. Can’t recall exactly why. But I don’t lose any anyway so it was an experiment in superfluous redundancy anyway.

 

 

[Old Koreelah]

... Id think many Jabiru dont hold the listed oil volume either at the max sustainable level.

...I've never been able to get more than the two quart bottles into mine, even with a new (and empty) oil filter.

That's quite a bit less than the official capacity.

 

 

[kgwilson]

I put 2 quarts of Aeroshell 100 plus in with a new filter every 25 hours. My Engine is a Generation 3 3300 with roller cam followers. I have a Positech 7 row oil cooler mounted low on the firewall which holds a good 1/2 litre including the oil hose lines. The oil level is about 3-4mm below the top of the knurled section of the dipstick. After 25 hours the oil level is about 6mm below the top of the knurled section. I do not top up at all. The oil catch bottle usually has a small amount of condensate and sludge in it which I tip out and then replace the bottle on the firewall. The only issue I've had was a loose hose clip which allowed the sludge to drip down the firewall on to the bottom of the cowl and along the underside of the fuselage. It was surprisingly hard to get off.

 

The secret is do not overfill the engine and it will perform well using little oil and won't throw any out. Don't baby the engine either. My minimum cruise is 2800 rpm up to about 3000 rpm in a cruise climb.

 

 

[Keenaviator]

I’ve been using the Jabiru top of dipstick condenser for a while now. It works. It no longer dumps oil. Recommend.

 

 

[Jaba-who]

I’ve been using the Jabiru top of dipstick condenser for a while now. It works. It no longer dumps oil. Recommend.

I will cut and paste your post but change by just a few words and it’s just as valid.

I’ve been using a mark on the Jabiru dipstick where it stabilized at for a while now. It works. It no longer dumps oil. Recommend.

 

 

[kgwilson]

I put 2 quarts of Aeroshell 100 plus in with a new filter every 25 hours. My Engine is a Generation 3 3300 with roller cam followers. I have a Positech 7 row oil cooler mounted low on the firewall which holds a good 1/2 litre including the oil hose lines. The oil level is about 3-4mm below the top of the knurled section of the dipstick. After 25 hours the oil level is about 6mm below the top of the knurled section. I do not top up at all. The oil catch bottle usually has a small amount of condensate and sludge in it which I tip out and then replace the bottle on the firewall. The only issue I've had was a loose hose clip which allowed the sludge to drip down the firewall on to the bottom of the cowl and along the underside of the fuselage. It was surprisingly hard to get off.The secret is do not overfill the engine and it will perform well using little oil and won't throw any out. Don't baby the engine either. My minimum cruise is 2800 rpm up to about 3000 rpm in a cruise climb.

Oops my mistake. An oil change with a new filter is 3 quarts, not 2 as I originally said.

 

 

[Jaba-who]

Oops my mistake. An oil change with a new filter is 3 quarts, not 2 as I originally said.

In that case, you have same engine as me:thumb up:

 

 

[fly_tornado]

motionaero make a nice one

 

 

 

[facthunter]

That's perfectly designed to condense the water and return it to the engine. Just what you don't want.. Instead of returning it, just allow it to go into a receptacle which when you examine the contents you will surely not wish to put into a motor.

 

This is an old question found to be more likely to cause a problem rather than fix one. It was thoroughly covered more than 15 years ago. Its not clever to repeat mistakes..

 

 

[fly_tornado]

you'll have to let them know

 

 

[facthunter]

Really? Letting ALL of the "makers " of untested gadgets know is not my calling in life. I have let a few here know. Some will listen some won't. .

 

You baffle to stop oil drops and reduce the velocity of the flow of gas in the vent if you want to keep it in the engine. You don't condense oil as you do water where it goes from vapor to a liquid. The water should remain as a vapor and exit the engine in that form. The best way is to keep it hot, and not let it drain back. Nev

 

 

[fly_tornado]

wouldn't it stay hot on the top of the engine?

 

 

[facthunter]

Not above boiling point, which would be needed to be effective. ALL baffled breathers get a lot of grunge in/on them. It's full of condensate and rotten acids from combustion of impurities, like Sulphur phosphorus etc. I've seen coarse steel wire matt just crumble to pieces in a short time and fall into the engine. Have a look at your typical PC valves and downstream piping, especially in short trip vehicles. Even the cooler parts of the rocker boxes accumulate sludge. Aviation engine oil goes milky in planes that have engines that don't get fully hot when operated intermittently for shorter than desired periods. Standby generators are another example. That water in the oil allows acids to form that pit and corrode internal gears and camshafts and aluminium/magnesium alloy cases. Nev

 

 

[Keith W]

I’ve been using the Jabiru top of dipstick condenser for a while now. It works. It no longer dumps oil. Recommend.

I have a Jabiru condenser i bought a while a go but haven’t fitted it yet, worried about what’s going back into the engine, hows your oil look after 10 or so hours have you had any problems at all cheers Keith.

 

 

[Keenaviator]

I’m confident with this device. Oil looks good. The original catch can gets the muck. According to Rod S at Jabiru the top dipstick device is more a muffler to smooth out the crank case pulses that pushes the oil out.

 

 

[Keith W]

Thanks mate I will give it a try