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-   -   Mike Busch's thoughts on oil separators (https://vansairforce.net/community/showthread.php?t=112353)

vanremog 07-12-2020 04:16 PM

Quote:

Originally Posted by RV6_flyer (Post 887095)
Over 2,800 hours operating time based out of SoCAL dumping oil separator condensate back into the engine. Pulled cylinders at 2,200 hours and found NO wear on the cam. Engine came off a Piper that had an oil separator that dumped back into the engine using the same port that I am using. Total Time on engine since new is over 5,700.

I'm with Sobek on this subject. A properly plumbed and sited separator is a good feature, but even better is a drainable separator. It tells me a great deal about the blow-by characteristics of my engine every time I drain it at oil change.

DanH 07-12-2020 07:55 PM

Quote:

Originally Posted by vanremog (Post 1445683)
The exhaust is not a vacuum. The intake would be, but not the exhaust.

Actually, both intake and exhaust have periods of positive and negative pressure.

An exhaust tap with a one way reed valve exposes the separator to repeating periods of negative pressure, much like a diode being used to rectify alternating current.

Taltruda 07-12-2020 09:42 PM

Quote:

Originally Posted by FasGlas (Post 880608)
A point of contention... If you install a crankcase evacuation system on the engine ( one way valve on the exhaust connected to the breather hose ), what would be the purpose of the separator? All the moister and blowby goes into the exhaust and burns off so there's nothing on the belly anyway.. Maybe a few drops of oil would get returned to the engine but other byproducts you might not want also returns.
Race engine builders have been using crankcase evacuation systems for as long as I can remember. I've used them on cars, boats and motorcycles and they work. They are cheap and easy to install. Mr. Gasket and Moroso sell a pair for less then $50 with all the parts for two planes. I use one on my IO-360.
The added advantage is negative crankcase pressure that stops oil weeps and also the theory it increases HP by removing pressure on the piston down strokes.

As a former machinist and race car engine builder, I can add some to this. Vacuum in the crank case does produce horsepower, but it is really when you combine low tension piston rings that you see the most gains. Low tension piston rings reduce internal friction, but don’t seal without the differential pressure above and below the ring package. Some really low tension rings, we used 18 inches of vacuum, but then we saw increased wrist pin bushing wear. A fix for that was oil squirters into the bottom of the piston.

PerfTech 07-13-2020 10:16 AM

OIL SEPARATORS?
 
.... Oil control and blow-by issues are not an aircraft only domain. The main
difference between antique aircraft engines, and everything else is the lack of
desire to make any improvements or modernize, unless absolutely necessary.
The aircraft manufacturers for many years didn't really care if the engines dumped
oil out on the ground at every stop, or left a trail as they flew over. All other
(than aircraft) engine manufacturers, in every industry wide application,
addressed this issue some fifty years ago. All modern engines basically have an
oil separator built internally into the engine, and none of them have a pipe or
hose that spews oil out on the ground. Everything is contained inside the engine,
and these engines run two hundred thousand, or more miles with virtually no
major maintenance or repairs. I am certain everyone reading this is driving an
automobile so equipped. All certified aircraft manufactured for decades are
equipped with an oil separator from the factory, and those all return the oil to
the crankcase where it belongs. I am confident that were this the wrong approach,
the thousands of real engineers involved, with deep pockets, and unperilled
facilities to address this would be doing it differently. My thoughts on oil separators.
Thanks, Allan..:D


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