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Nick(at)Scholtes1.com
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 Posted: Tue Dec 05, 2006 9:04 am Post subject: Oil Filter Thoughts |
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[quote]Randy and Jimmie,
I've been following this oil filter thread a bit, and couldn't help jumping in a bit. I'm not an oil-filter expert by any means, so I'm kinda' speculating here, but here goes:
I believe that the "number of compression strokes" and the "different pressure relief value" are totally different issues, and are totally unrelated. I also believe that the alleged "different pressure relieve value" of the Rotax filter is no reason whatsoever to purchase the Rotax filter, but it's the only thing that Rotax can point to to differentiate their filter and justify their price.
An oil filter's pressure relief system is a safety system and it only comes into play when the filter is completely clogged, and the pressure across the filter builds to the point where the filter may burst (or the engine may be damaged due to all of the pressure drop being across the filter). The filter has a valve in it that will open, bypassing the "filter" part, and simply allowing oil to flow past, unfiltered. Again, this only happens in a non-normal situation, and will only be brought on by the filter producing enough resistance to the oil flow that the pressure across the filter builds high enough to pop the bypass valve. And I emphasize that the pressure across the filter is what matters, just because a motor has a high pressure oil pump doesn't mean that the bypass valve should be bypassing, even with a high pressure oil pump the filter should still be able to flow enough volume of oil to keep the pressure drop across the filter to a minimum.
In an aircraft situation where the oil is changed religiously and the engine is maintained well, I just don't see the relief valve ever coming into play, and in the odd situation that it would, the value is somewhat irrelevant, as long as it goes into bypass before there's a catastrophic failure, that's all that matters. So, CarQuest or Rotax, who is to say that one picked a better pressure bypass number than the other? I want a bypass value high enough that it NEVER goes into bypass in normal operation.
Anyway, in my opinion, there are several things that can differentiate an oil filter: The "fineness" of the filter (usually measured in microns), the quality and hence longevity of the filter material, and the bypass pressure value. The bypass pressure value is a non-issue, in my opinion.
The "fineness" could be what is contributing to the different number of compression strokes, maybe the Rotax filter has a finer mesh than the CarQuest.
After I wrote the above, I did a Google search on "How an oil filter works", and there are a couple of really good pages there that talk about the bypass valve, and also a different type of filtering technique called "bypass filtering" (not related to the bypass valve), and pages that talk about differences in fineness, and also differences in quality. Interesting reading on this topic.
Nick
Time: 09:54:42 PM PST US
From: "Randy Daughenbaugh" <rjdaugh(at)rapidnet.com>
Subject: RE: Oil Filters for 912UL
Jimmie,
What does the amount of blow-by have to do with whether all the oil goes
through the filter or not? The number of
compression strokes should have everything to do with ring leakage and
nothing to do with by-passing the oil filter. ???????
I have been trying to get info on the pressure values for the pressure
relief valves. It is not easy to come by!
Randy
. [b]
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Fox5flyer
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| Posted: Tue Dec 05, 2006 10:13 am Post subject: Oil Filter Thoughts |
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Nick, that's good information and I agree that the bypass spring is most likely not the problem. However, I believe the filter's anti-drain back membrane (check valve) can be a possible cause. An ineffective check valve will let too much, or even all, of the oil to drain back into the crankcase which would take a lot of flips of the prop to create enough pressure to push oil past the filter and into the reservoir to the point that it "burps", which, as I see it, is nothing more than the air in the line being evacuated.
I might be totally wrong on this, but it makes sense to me.
A hundred or more prop pulls would wear a guy out!
Deke
[quote] ---
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kitfoxmike
Joined: 05 Dec 2006
Posts: 373
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| Posted: Tue Dec 05, 2006 10:27 am Post subject: Re: Oil Filter Thoughts |
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Jees,
What a mess that has brought up. I use the Carquest filter. I for one don't turn the prop over and wait to here that gurgle, or what ever. I did when I first got the airplane. What I do is this. I do my inspection of the airplane, I get to the prop and inspect that, look inside the front engine area. I turn the prop about 4 compression strokes, to make sure it isn't compression locked. Then I get in the airplane turn on the master only, keep the mags OFF, and turn the engine over with choke for about a count of 4 in the summer and 12 in the winter, while watching the oil guage to make sure I have normal pressure. Then I stop turning over the engine and turn on the mags, engine fires right up and pressure comes right up. Never had an issue, I put in over 200 hours this year and about that last year. I don't intend to change this, I also cut open the filters after an oil change and there is nothing in there. One last note: the filter isn't the real issue why the oil goes into the engine, it's the possision of the oil tank, sure the filter will cause it to flow into the engine faster, possibly, but the oil tank higher than the engine is what really does it.
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lcfitt(at)sbcglobal.net
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| Posted: Tue Dec 05, 2006 1:39 pm Post subject: Oil Filter Thoughts |
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I also agree with Nicks thoughts. The bypass comes in to play, in my
estimation with an abused system - inadequate oil changes.
I have thought a lot about the tendency of the oil draining into the crank
case from the tank and possible solutions. I have to "burp" mine before
flight as well and in the past, it took fewer compression strokes after an
oil change, then progressively more as the hours mounted.
The geometry of the system is as mike states. The oil tank being higher
than the Rotax recommended position will siphon the oil in the tank back to
the crankcase. This actually sould be stated as "forward" into the crank
case as the return line is higher than the oil level in the tank and any
movement of oil from the tank to the crank case is in a forward direction
through the pick-up line - tank, pick-up tube, oil cooler, oil pump, oil
filter oil journals and crank case. Neither the bypass valve nor the
anti-drainback valve are involved with the movement of the oil because there
is very little pressure and the oil is moving from the tank to the engine in
the normal direction.
Since the oil is purged from the crank case by blowby gasses, I always
thought the relative fit of the rings and valves would determine the bypass
pressure and be the predominant factor in the number of compression strokes
needed to fill the oil tank, i.e., a good tight engine - low bypass gasses
and lots of strokes, a tired worn engine (or a new engine) with lots of
bypass - few strokes. I think other factors involved are oil temperatures -
thickness of the oil and the duration between flights. My guess is that
most of the flow from the tank occurs immediately after shutdown when the
oil is warm and relatively thinner. I have burped several days before a
flight and the oil remained fairly high on the dipstick at flight time.
Much of this is opinion and I am interested in other's thoughts.
Lowell
----- Original Message -----
From: "Fox5flyer" <fox5flyer(at)i-star.com>
To: <kitfox-list(at)matronics.com>
Sent: Tuesday, December 05, 2006 9:25 AM
Subject: Re: Oil Filter Thoughts
Nick, that's good information and I agree that the bypass spring is most
likely not the problem. However, I believe the filter's anti-drain back
membrane (check valve) can be a possible cause. An ineffective check valve
will let too much, or even all, of the oil to drain back into the crankcase
which would take a lot of flips of the prop to create enough pressure to
push oil past the filter and into the reservoir to the point that it
"burps", which, as I see it, is nothing more than the air in the line being
evacuated.
I might be totally wrong on this, but it makes sense to me.
A hundred or more prop pulls would wear a guy out!
Deke
---
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Bill Willyard
Joined: 10 Jan 2006
Posts: 34
Location: Grandville, Michigan U.S.A.
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| Posted: Wed Dec 06, 2006 7:21 am Post subject: Oil Filter Thoughts |
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Lowell I agree with your thoughts and have made the same observations.
Bill W.
DO NOT ARCHIVE
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I also agree with Nicks thoughts. The bypass comes in to play, in my estimation with an abused system - inadequate oil changes.
I have thought a lot about the tendency of the oil draining into the crank case from the tank and possible solutions. I have to "burp" mine before flight as well and in the past, it took fewer compression strokes after an oil change, then progressively more as the hours mounted.
The geometry of the system is as mike states. The oil tank being higher than the Rotax recommended position will siphon the oil in the tank back to the crankcase. This actually sould be stated as "forward" into the crank case as the return line is higher than the oil level in the tank and any movement of oil from the tank to the crank case is in a forward direction through the pick-up line - tank, pick-up tube, oil cooler, oil pump, oil filter oil journals and crank case. Neither the bypass valve nor the anti-drainback valve are involved with the movement of the oil because there is very little pressure and the oil is moving from the tank to the engine in the normal direction.
Since the oil is purged from the crank case by blowby gasses, I always thought the relative fit of the rings and valves would determine the bypass pressure and be the predominant factor in the number of compression strokes needed to fill the oil tank, i.e., a good tight engine - low bypass gasses and lots of strokes, a tired worn engine (or a new engine) with lots of bypass - few strokes. I think other factors involved are oil temperatures - thickness of the oil and the duration between flights. My guess is that most of the flow from the tank occurs immediately after shutdown when the oil is warm and relatively thinner. I have burped several days before a flight and the oil remained fairly high on the dipstick at flight time.
Much of this is opinion and I am interested in other's thoughts.
Lowell
[quote][b]
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Bill Willyard
Classic IV 912UL |
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Float Flyr
Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland
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| Posted: Wed Dec 06, 2006 11:05 am Post subject: Oil Filter Thoughts |
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Start your engine on a very cold day.... Your by pass will come into play.
Even the pressure bypasses on a 206 Jet ranger will pop on a cold day...
Once warmed up just reset the bypasses. (206 pressure by passes need to be
physically reset to indicate the next bypass episode.)
Noel
[quote] --
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Noel Loveys
Kitfox III-A
Aerocet 1100 Floats |
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Sjklerks(at)aol.com
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| Posted: Wed Dec 06, 2006 4:09 pm Post subject: Oil Filter Thoughts |
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Hi Bill, I installed a shut off valve in the oil line. Mine was filling the crankcase and causing a prop lock. If the prop was not locked up it would smoke and cover the underneath with oil. I also added some literature in my walk around check list to turn valve on and I also put a tag warning to turn valve on a clip and clip it to the master switch before putting plane back into hangar. I haven't had a problem since. JIm
[quote][b]
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