REFLECTOR: Blow by

[Mark Magee]

Hi Renee,
Previous Post early morning Pilot Error :(.
No your right on, as was posted earlier I neglected the issue of
overfilling the crankcase and the crank windage slinging more oil into mist
and overboard venting. I mentioned the negative G issue for few folks
discuss it, it is there however. No matter how slight the negative G is
(Type Negative G into Youtube and you'll get some humorous vids), the oil
is rising to the top of the engine. In even light to moderate chop the
overfilling and crank windage-slinging will be greatly magnified, as well
as some pure oil vs vapor being blown out the CC vent.
Mark

On Sat, Mar 10, 2012 at 10:19 PM, David Rene Dugas <renedugas at gmail.com>wrote:

> My IO 540 does the same at 8.5 quarts it burns almost no oil but if I fill
> above 9 qts it blows out in 30 min of flight.  I don't know this but I
> always thought it was from standard blow-by forcing many more and bigger
> droplets out because of climb and descent causing the oil to slosh and stay
> either forward or aft and the oil is now being struck by the crank as it
> turns throwing large drops around and some go out the breather instead of a
> faint mist it is like a storm.  I get very little actual negative G flight
> experiences but with our plane the angle of the engine is fairly dramatic
> in climbs and descents.  I don't have an engine to test this but sure would
> like to hear from someone who tilts and engine 15 degrees up or down and
> see where the oil strikes the internal rotating parts.
> I may be way off and I'll probably be bashed but seems reasonable.
> Rene'
>
> On Mar 10, 2012, at 11:01 AM, Lou Stedman wrote:
>
>   Last week we were discussing the amount of oil different engines burn
> in a given time. I mentioned that I do not fill up my crankcase because the
> first quart will blow out within an hour if I do that . However if I fill
> to six quarts I don’t go through another quart for about four to five
> hours. After that I got a note from someone that I should not do as I
> described as it is a indication that there is a blow by problem with my
> engine (Lyc IO-360). If this is true, what is the cause of blow by?
>
> Lou Stedman
> Velocity SEFG
> N7044Q
> Olean, NY
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