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  #21  
Old 12-01-2020, 08:22 AM
RedRaider94 RedRaider94 is offline
 
Join Date: Nov 2014
Location: Celina, Tx
Posts: 55
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When you say low pressure lines, how do we define low and high pressure lines in the fuel system. Is high pressure up to the fuel divider on the top of the engine where the thin stainless lines take fuel to the cylinders or do they start at some point before that?
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  #22  
Old 12-01-2020, 06:50 PM
RedRaider94 RedRaider94 is offline
 
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Location: Celina, Tx
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I also just read another post by someone who had a valve that was sticking sometimes. Would I definitely see a sticking valve in the data set with my EGT and CHTís at my sample rate of 1000 ms (once every second)? Can I rule that out given the data I posted?
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  #23  
Old 12-01-2020, 07:19 PM
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1001001 1001001 is offline
 
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Quote:
Originally Posted by RedRaider94 View Post
I also just read another post by someone who had a valve that was sticking sometimes. Would I definitely see a sticking valve in the data set with my EGT and CHT’s at my sample rate of 1000 ms (once every second)? Can I rule that out given the data I posted?
Not likely. At full speed each valve is cycling open and closed at 22.5 Hz on a 4 cylinder engine. The valve would have to be sticking for quite a number of cycles and you'd see the EGTs drop and feel a lot of power loss, I would think.
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  #24  
Old 12-01-2020, 10:29 PM
lr172 lr172 is offline
 
Join Date: Oct 2013
Location: Schaumburg, IL
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Quote:
Originally Posted by RedRaider94 View Post
When you say low pressure lines, how do we define low and high pressure lines in the fuel system. Is high pressure up to the fuel divider on the top of the engine where the thin stainless lines take fuel to the cylinders or do they start at some point before that?
Fuel to the servo is 25 psi. Fuel after the servo is a much lower pressure. It varies based upon the flow rate commanded by the servo. Lower pressure fuel boils at a lower temp.

You want to protect from heat absorption at all points. However, the actual boiling is taking place in the low pressure lines. Goal is to keep the fuel below that boiling point by reducing heat absorption in all areas.

Larry
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  #25  
Old 12-01-2020, 10:33 PM
lr172 lr172 is offline
 
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Quote:
Originally Posted by RedRaider94 View Post
I also just read another post by someone who had a valve that was sticking sometimes. Would I definitely see a sticking valve in the data set with my EGT and CHT’s at my sample rate of 1000 ms (once every second)? Can I rule that out given the data I posted?

Sticking valves rarely present hot but not cold. Typically the opposite. They are also not limited to high power regimes. The symptoms appear (rough running in varying degrees from barely noticeable to shaking like a dog, depending upon the amount of sticking), typically at cold start, and continue for some period of time (minutes, not seconds) and then disappear as the engine warms up and not seen again until the next cold start. They do not just appear only during climb for a few seconds.

Larry
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Last edited by lr172 : 12-01-2020 at 10:37 PM.
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  #26  
Old 12-02-2020, 04:48 AM
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Walt Walt is offline
 
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Basic stuff, when was the last time the Magneto was serviced? A bad condenser in the mag (they often fail when hot) can/will cause problems.
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Last edited by Walt : 12-02-2020 at 04:51 AM.
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  #27  
Old 12-02-2020, 05:45 AM
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storm_pilot storm_pilot is offline
 
Join Date: Apr 2017
Location: ND, D54
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You mentioned grease coming from one of the prop seals?

This could be indicative of a very serious problem and may explain your RPM/power surge problem if your prop is binding and not adjusting pitch smoothly.

Losing a blade off your prop in flight would be catastrophic!

Last edited by storm_pilot : 12-02-2020 at 05:53 AM.
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  #28  
Old 12-02-2020, 06:45 AM
RedRaider94 RedRaider94 is offline
 
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Location: Celina, Tx
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Walt, the Mag went through a 500 hour inspection and rebuild about 150 hours ago. It was sent off to Aircraft Magneto Service in Montana. I'm only a 5-10 minute plane ride from you so need to bring it by to let you take a look someday (I'm at Aero Country).

The grease is very slight to where you can just see little lines of grease slung outward from the seal (it's not leaking real bad and A&P who did inspection a couple months ago wasn't concerned - I was more than him I believe).

When I fire it up everytime it sounds perfect and doesn't miss a beat so I guess between that and nothing indicating a problem in the data dump we can rule out stuck valves.

I am going to try and fly this afternoon and will record startup and then takeoffs again at 200ms just to see if anything else comes up at higher recording rates and if it does it again will start taking pictures of every fuel line to get everyone's thoughts on where the fuel might be getting too hot.
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  #29  
Old 12-02-2020, 07:14 AM
BoydBirchler BoydBirchler is offline
 
Join Date: Jul 2020
Location: Indianapolis
Posts: 74
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I had something similar. I checked plug,wires and changed the coil. It was still there. So I changed the plug and it went away!
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  #30  
Old 12-02-2020, 07:44 AM
patterson patterson is offline
 
Join Date: Mar 2005
Location: Queen Creek AZ
Posts: 575
Default I had this problem

The symptoms you describe were the same for my plane. Not sure if the problem i discovered is similar to yours though...

I had changed engines to a fuel injected motor with a new unfiltered airbox. The plane would surge, losing 100-200 rpm for 2 or three seconds, then develop full power again. After months of trial and error, Don at AFP suggested I send in my new airbox to be flow tested. He called a few days later to say the turbulence created by my airbox shook the room it was being tested in!

I changed the shape of the intake. Problem solved. Any chance the inlet air is developing turbulence in your bird?
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