Jabiru oil seperator

[facthunter]

Its PCV Positive Crankcase Ventilation and it's crudely baffled  and only sucks when the MP drops at higher throttle positions.. Aero engines don't use such a system and it might be better in some ways if they did except it's something else to go wrong and a fire risk.  Nev

[skippydiesel]

PCV's are old technology (at least on my cars) 

[Blueadventures]

2 hours ago, onetrack said:

The centrifugal oil separators are a very popular addition to the large ships engines, and they're very effective.

And a bugger to pull apart and clean; including putting back together correctly.

[BrendAn]

58 minutes ago, Blueadventures said:

And a bugger to pull apart and clean; including putting back together correctly.

The smallest centrifuge I have seen would still be too heavy for an aircraft 

[skippydiesel]

1 hour ago, Blueadventures said:

And a bugger to pull apart and clean; including putting back together correctly.

How do you mean 'effective" - do they remove all disolved contaminants from the oil or just the larger carbon particles?

[onetrack]

Skippy, the better centrifugal separators contain a paper element which removes all the contaminants. The plain, garden variety of centrifugal separators only remove soot and other fine particles.

 

 

[Blueadventures]

2 hours ago, skippydiesel said:

How do you mean 'effective" - do they remove all disolved contaminants from the oil or just the larger carbon particles?

Skip this link will answer your question and any others you may have. Diesel Fuel Centrifuge | Sludge & Water Separator (dolphincentrifuge.com)  One I used was to clean the diesel in our onboard fuel tanks so the day tank (engine [two main at 3,000kw and two Gen sets] feed tank) fuel was suitable.

[skippydiesel]

So doesn't remove disolved contaminants - fuel contamination one of the main contaminants found in crankcase breather vapour.

[facthunter]

Often called crankcase  dilution where the oil thins and rises on the dipstick. (mostly with diesels). Sometimes done deliberately in intensely COLD regions to ease starting friction and be able to change gears.  Nev

[skippydiesel]

On 15/01/2024 at 9:03 AM, facthunter said:

Often called crankcase  dilution where the oil thins and rises on the dipstick. (mostly with diesels). Sometimes done deliberately in intensely COLD regions to ease starting friction and be able to change gears.  Nev

With diesels, the cause of "oil dilution" is,  in the first instance,  not usually crankcase vapours, but a leaking injector(s) delivering raw fuel after shut down. The fuel then dribbles down past the piston rings into the crankcase. Of course the resultant crankcase vapour, after engine start,  would be diesel rich and returning it to the crankcase would further compromise the "lubricity" of the crankcase oil.

 

FYI: Owners/operators of petrol ride mowers/small motors, where the fuel tank/level is above the carburettor.

Oil dilution, also known "as making oil" is a fairly common problem. (one of the many reasons why you should always check your oil level, "sniff" if in doubt, beforengine start)

The cause is the float chamber valve leaking, after engine shut down - fuel floods the carburettor, finds its way into the cylinder(s) and then down into the crankcase, raising the level of oil on the dipstick. In recent times the engine manufacturers have added an additional, electrically actuated, fuel shut off (found on the exterior bottom of the float chamber) unfortunately these can also fail.

I suspect that this is mainly a problem of engines that do not get used for an extended period eg winter when the grass doesn't grow. Fuel "varnish" builds up on the valve(s) reducing their sealing effectiveness.

I have seen several engines where the oil (diluted with petrol) has risen well up in the cancase. If you start the engine, there is the potential for an explosion and even if this does not occur, the contaminated oil will not adequately lubricate and you are likely to see catastrophic internal damage. Always drain as much of the contaminated oil as possible & replace with fresh.

 

Solution:  Strip carby, clean/replace the valve(s) Fit an inline manual fuel shut off (good practise anyhow).

[LoonyBob]

On 14/01/2024 at 3:15 PM, Paul davenport said:

ON the Contrary JUST asking WHERE you get this EVIDENCE BASED information.  Here SAY and some ones OPINION doesn’t quite qualify as scientific evidence .  

Try the second edition of "The High Speed Internal Combustion Engine", Ricardo & Glyde; or Lanchester's work for the RAE in 1916; or any edition of Judge, "High Speed Diesel Engines"; or "Diesel Engine Design" (ship engines, by whatsisface); or Ricardo's 1934(?) lecture to the SAE on the london bus engine life extenstion project; or any text on the cracking of aliphatic hydrocarbons...

 

[LoonyBob]

On 14/01/2024 at 9:07 PM, onetrack said:

Skippy, the better centrifugal separators contain a paper element which removes all the contaminants. The plain, garden variety of centrifugal separators only remove soot and other fine particles.

 

 

Physical contaminants, yes - the FIAT 850 Coupe used a centrifugal separator - but not the chemical upsets; neither the sulphuric acid that is active until the oil boils off the water, nor the various carbonic acids caused by cracking of the carbon chains...

 

Unfortunately, filtration does little for the upper cylinder... after about 0.4 zillion hours of experiment and study, Ricardo (and others) determined that corrosion was the major determinate of engine life; engine manufacturers have been addressing this issue ever since... chromed bores, anyone? Nikasil? chromeed rings?

[Grandpa]

Thank's guys lots of good advice I will just keep cleaning the aircraft.

[BrendAn]

58 minutes ago, Grandpa said:

Thank's guys lots of good advice I will just keep cleaning the aircraft.

I have a hose running from the catch can outlet down to undercarriage and cable tied off there. Before that I was getting oil soaking into the fabric skins on my ultralight.

[facthunter]

 Have a catch can and just empty it regularly to stop "OILY"belly.  Nev

[BrendAn]

2 hours ago, facthunter said:

 Have a catch can and just empty it regularly to stop "OILY"belly.  Nev

All jabirus have one