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Author Topic: Lots of oil on the nose  (Read 1121 times)

Offline Niklas Löfroth

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Lots of oil on the nose
« on: May 19, 2019, 03:28:35 PM »
I have been flying my new model for a while now and I really love the power from the PA75 on Randy CF pipe.
I have a problem though. There is lots of unburned oil on the nose after each flight. It seems to be coming from the venturi. This makes me wonder if maybe the pipe leanght can have anything to do with the problem.
I know other pilots using the PA75 without this oil/fuel problem. I have used other piped engines and I have never had this problem before. I would be grateful for some help in this matter.
« Last Edit: May 22, 2019, 02:40:22 AM by Niklas Löfroth »
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Offline FLOYD CARTER

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Re: Lots of oil on the noose
« Reply #1 on: May 19, 2019, 05:07:58 PM »
I don't run tuned pipes, but if fuel is getting out of the venturi, how about covering it with some pantyhose material? I do that mainly to keep dirt out, but that should trap any fuel trying to come out.
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Offline Dan McEntee

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Re: Lots of oil on the noose
« Reply #2 on: May 19, 2019, 06:50:31 PM »
   I don't run tuned pipes either, but going by what I do know about model engines and engines with expansion chamber pipes, I think your first suspicion  may be correct. You do not say what type of fuel and oil content that you are running, and that may have a bearing on what is happening. Randy Smith is the moderator of this section, and the manufacturer of your components, and I'm sure he will see this and answer. He has been out of town at the Joe Nall event but should be catching up on things soon.
   In the mean time, I would not run the engine if at all possible, just to make sure the extra oil is not hurting the rod journals or anything else in the top end.
   Good luck,
  Dan McEntee
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Online Brett Buck

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Re: Lots of oil on the noose
« Reply #3 on: May 19, 2019, 11:01:24 PM »
Quote from: Niklas Löfroth on May 19, 2019, 03:28:35 PM
I have been flying my new model for a while now and I really love the power from the PA75 on Randy CF pipe.
I have a problem though. There is lots of unburned oil on the noose after each flight. It seems to be coming from the venturi. This makes me wonder if maybe the pipe leanght can have anything to do with the problem.
I know other pilots using the PA75 without this oil/fuel problem. I have used other piped engines and I have never had this problem before. I would be grateful for some help in this matter.

    This is sometimes caused by the pipe being too short. What pipe length and RPM are you running?

    Brett
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Offline Niklas Löfroth

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Re: Lots of oil on the noose
« Reply #4 on: May 20, 2019, 10:32:16 AM »
Here comes some additional information:

I’m using the following setup:

PA75 RE with Bru-Line air filter (green)
CF-pipe (75-size) from Randy
Pipe length:  19 1/4 inches
fuel:  7% nitro, 20% Klotz Super Techniplate, 73% Methanol
Prop: Brian Eather 3-blade, 13.2 x 4.2”
Release rpm: 9000
Model: Slightly modified Trivial Pursuit
Weight: 64oz
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Offline Niklas Löfroth

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Re: Lots of oil on the noose
« Reply #5 on: May 20, 2019, 10:49:02 AM »
Not 100% sure but when I remove the engine, the engine compartment is basically free from oil/fuel.
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Offline Niklas Löfroth

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Re: Lots of oil on the noose
« Reply #6 on: May 20, 2019, 11:05:33 AM »
Almost all oil is collected inside the cowling and then flows into the joint between the cowling and the fusulage towards the fuse mounted landing gear.
The engine comsumes 8oz fuel for 6 min, which strengthens my suspicion that all fuel is not combusted.
« Last Edit: May 22, 2019, 02:40:58 AM by Niklas Löfroth »
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Offline RandySmith

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Re: Lots of oil on the noose
« Reply #7 on: May 20, 2019, 06:44:13 PM »
Quote from: Niklas Löfroth on May 20, 2019, 11:05:33 AM
Almost all oil is collected inside the cowling and the flows into the joint between the cowling and the fusulage towards the fuse mounted landing gear.
The engine comsumes 8oz fuel for 6 min, which strengthens my suspicion that all fuel is not combusted.

Hi Niklas

Try moving the pipe  out a  1/4 inch  and  see  if that reduces  the  oil flow, if you have the  pipe tuned too  short it will  pump oil  out of the  front of the engine
Reason is  the pressure wave gets back to the engine  BEFORE the intake  shuts, this  just pushes  the charge  back thru the  engine

Randy
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