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DLE 55 Idles fast after flight

Old 07-22-2011, 10:11 AM
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John Raymond
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Default DLE 55 Idles fast after flight

EF 88 Yak with baffled cowl no problems for 30 + flights now when I land I have to Idle down several 3-4 clicks maybe more tp reduce airspeed.

The engine runs fine with no burbles and great transition, has been ran several hours (3-4) on 30-1 Klotz mix.

The problem did start this week after I adjusted low needle slightly leaner after running somehat rich- I thought due to much warmer weather

Should I richen the low needle?
Old 07-22-2011, 10:16 AM
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Default RE: DLE 55 Idles fast after flight

Yes. A lean idle often is slow to come down to a good idle.

AV8TOR
Old 07-22-2011, 11:00 AM
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pe reivers
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Default RE: DLE 55 Idles fast after flight

With hot weather, the leaning is done for the H needle only, or not at all.
Like AV8tor said, lean idle mixtures cause slow come down.
Old 07-22-2011, 11:06 AM
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Default RE: DLE 55 Idles fast after flight


ORIGINAL: pe reivers

With hot weather, the leaning is done for the H needle only, or not at all.
Like AV8tor said, lean idle mixtures cause slow come down.
I recently spoke with an rc gas engine manufacturer in the U.S. and they said that an engine that is slow to return to normal idle at the end of a flight may also be a result of the engine getting too hot during the flight. I realize this is not the case with the original poster in this thread since he said it only started recently after he adjusted the low needle, but is this also true? If so, I'd like to better understand what is happening in the engine to cause this (when the engine is too hot).

Thanks,

-Ed B.
Old 07-22-2011, 12:16 PM
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All Day Dan
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Default RE: DLE 55 Idles fast after flight

John, A throttle pushrod that is either lengthening or getting shorter during the flight or a servo with a worn feedback pot will have the same effect. The servo can be checked with a servo checker by stepping it through a millisecond at a time. If all else fails, set up the throttle channel with one of your dual rate switches to get what you need. Dan.
Old 07-22-2011, 02:14 PM
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pe reivers
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Default RE: DLE 55 Idles fast after flight

The engine getting too little cooling makes it run hot, which also has the symptoms of running lean. If you improve cooling, you often find you can lean out the engine quite a bit. That is a sure sign it ran to hot to begin with. The same happens if you go from air cooling to liquid cooling. More power and leaner settings.

So yes, a hot engine or a lean engine often show the same tell-tales.
Old 07-22-2011, 03:40 PM
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Default RE: DLE 55 Idles fast after flight


ORIGINAL: pe reivers

The engine getting too little cooling makes it run hot, which also has the symptoms of running lean. If you improve cooling, you often find you can lean out the engine quite a bit. That is a sure sign it ran to hot to begin with. The same happens if you go from air cooling to liquid cooling. More power and leaner settings.

So yes, a hot engine or a lean engine often show the same tell-tales.

Thank you Pe.

-Ed B.
Old 07-22-2011, 03:45 PM
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Default RE: DLE 55 Idles fast after flight

A hot engine actually becomes somewhat richer, not leaner. At least that's the results of exhaust gas analysis that are consistently presented when I'm doing higher temperature engine runs.

After our engines pass 150C a lot of bad and unusual things start happening.
Old 07-22-2011, 07:03 PM
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John Raymond
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Default RE: DLE 55 Idles fast after flight

Flew again this evening and richened the low end back, ran fine in the air but still required 5-6 clicks of trim to slow engine for safe landing, after reading the above posts it may be the cooling but I am sure I have at least 3-1 out-in ration on cowl
Old 07-22-2011, 08:41 PM
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Default RE: DLE 55 Idles fast after flight

So how warm is the engine when you set the initial idle? Did you do that with a cold engine? A couple short run ups and a little odling does not make for a warm engine. If so you just identified the problem. Get an engine warm before you set anything.
Old 07-22-2011, 08:45 PM
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Default RE: DLE 55 Idles fast after flight

/
Old 07-22-2011, 08:58 PM
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John Raymond
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Default RE: DLE 55 Idles fast after flight

ran the engine for about 3-4 mins b4 setting idle trim, then raised one click b4 takeoff just to make sure engine wont quit during maneuvers (I do this anytime I fly).
Old 07-23-2011, 12:10 AM
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Default RE: DLE 55 Idles fast after flight


ORIGINAL: Antique

/


Old 07-23-2011, 03:33 AM
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pe reivers
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Default RE: DLE 55 Idles fast after flight

The 3:1 rule means nothing if your cooling is not configured properly.
See http://www.prme.nl/forum/viewtopic.php?t=148
ORIGINAL: John Raymond

Flew again this evening and richened the low end back, ran fine in the air but still required 5-6 clicks of trim to slow engine for safe landing, after reading the above posts it may be the cooling but I am sure I have at least 3-1 out-in ration on cowl
Old 07-23-2011, 03:44 AM
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Default RE: DLE 55 Idles fast after flight


ORIGINAL: Tired Old Man

So how warm is the engine when you set the initial idle? Did you do that with a cold engine? A couple short run ups and a little odling does not make for a warm engine. If so you just identified the problem. Get an engine warm before you set anything.
Just refer to the " Running up to full throttle thread" Some tips there too ! Capt,n
Old 07-23-2011, 04:39 AM
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Default RE: DLE 55 Idles fast after flight


ORIGINAL: Flyfast1


ORIGINAL: pe reivers

With hot weather, the leaning is done for the H needle only, or not at all.
Like AV8tor said, lean idle mixtures cause slow come down.
I recently spoke with an rc gas engine manufacturer in the U.S. and they said that an engine that is slow to return to normal idle at the end of a flight may also be a result of the engine getting too hot during the flight. I realize this is not the case with the original poster in this thread since he said it only started recently after he adjusted the low needle, but is this also true? If so, I'd like to better understand what is happening in the engine to cause this (when the engine is too hot).

Thanks,

-Ed B.

Regarding the hot engine that's been returned to idle needing a few seconds to fully drop to idle speed, my thoughts are the engine has been depending on the fuel running through it for part of it's cooling capacity. Take that away from it by closing the throttle and many times you have an engine that gets/acts pretty warm until the airflow around it can cool it down - unassisted by the large amount of fuel it had going through it just a second ago. To help this situation, I found running the idle adjustment on the fat side works pretty good with no down side. This often will result in an unsteady idle, not as smooth as possible, but it will likely be a more reliable regarding quitting unexpectedly. One could use this fat idle to make a good case for running Iridium plugs to help smooth the idle, but not going to open that can of worms.

Old 07-23-2011, 04:45 AM
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Default RE: DLE 55 Idles fast after flight


ORIGINAL: Tired Old Man

A hot engine actually becomes somewhat richer, not leaner. At least that's the results of exhaust gas analysis that are consistently presented when I'm doing higher temperature engine runs.

After our engines pass 150C a lot of bad and unusual things start happening.

Interesting! You would generally richen a hot engine to prevent a burn down, no? Not saying your findings are wrong, only counter intuitive? What am I missing?
Old 07-23-2011, 06:36 AM
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Default RE: DLE 55 Idles fast after flight


ORIGINAL: ahicks


ORIGINAL: Tired Old Man

A hot engine actually becomes somewhat richer, not leaner. At least that's the results of exhaust gas analysis that are consistently presented when I'm doing higher temperature engine runs.

After our engines pass 150C a lot of bad and unusual things start happening.

Interesting! You would generally richen a hot engine to prevent a burn down, no? Not saying your findings are wrong, only counter intuitive? What am I missing?
I was waiting for someone to catch that.
The explanation should prove most entertaining!
Old 07-23-2011, 07:57 AM
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Default RE: DLE 55 Idles fast after flight

ORIGINAL: ahicks


ORIGINAL: Tired Old Man

A hot engine actually becomes somewhat richer, not leaner. At least that's the results of exhaust gas analysis that are consistently presented when I'm doing higher temperature engine runs.

After our engines pass 150C a lot of bad and unusual things start happening.

Interesting! You would generally richen a hot engine to prevent a burn down, no? Not saying your findings are wrong, only counter intuitive? What am I missing?
Probably a CO meter, real time telemetry, and a lot of reference data from hundreds of engine runs. I've deliberately destroyed a few engines to determine the effects of heat on engines along with establishing how long an engine can run at a given temp before initiating internal damage. Yes, it's counter intuitive but the facts are what they are. Worst case scenario has an engine entering uncontrolled detonation (melt down hot) where HC, CO and NOx rises faster than a meter can keep up with it, while CO2 falls rapidly.
Old 07-23-2011, 03:47 PM
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Default RE: DLE 55 Idles fast after flight



There are some good suggestions here from some of the responses.

Here is what I believe is happening to your engine causing it to idle down slower than normal. I may be wrong but since I own one of these engines and fly it pretty regular, here is my 2 cents.

To me it sounds like you have an air leak. Please check the 2 bolts that hold the carb on. Ensure they are tight but not gorilla tight. If they are, the next thing you need to do is check your phenolic block and see if it has no cracks. Real simple here. an engine that is drawing air anywhere except where it is supposed to will also cause this malady.

If your carb is tight and the phenolic block is crack free, next thing to do is check your gaskets and then check your fuel line. When the engine is running with the cowl off, check to see if the line providing fuel to the carb is bubble free. If there are bubbles present you might want to change out your tygon tubing.

If all seems to be in order, the next thing to look at would be the screens in the carb and when you remove the backplate off of the carb look at the diaphragm and make sure you put it back on the exact same way it came off. Also mark your phenolic block to the carb and ensure the phenolic block goes back the same way it came off.

If you have been running the engine for sometime and the symptoms just appeared the carb may be due for an overhaul. If there is trash in the screens (it will be very light and hard to see, use a magnifying glass if needed) you can buy a carb overhaul kit at your local lawn mower repair shop. Or you can send it in to Jedi Jody, Antique etc for overhaul.

I dont think your problem is due to heat at this time. I would also make sure you are running a filter inside your fueling station tank and a clunk that has the felt around it. (you can by the clunk at your lawn mower shop as well) and the fuel filter can be bought at your local hobby shop.

Good luck and keep us posted.

Regards
Glenn Williams
[email protected]

Old 07-23-2011, 05:58 PM
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Default RE: DLE 55 Idles fast after flight

After reading all the new posts I have taken the cowl off and verified all is tight on engine and servo works properly, I will now open the outlet some more to better airflow and then fly tomorrow pm and let you know what happened, I'll also take a pic or two, thanks
Old 07-23-2011, 08:08 PM
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Default RE: DLE 55 Idles fast after flight

Touch the engine immediately after landing, it should be not too hot to touch.

The color of the spark plug is a good indicator of whether the engine runs lean.

TIght all the screws/bolts on the engine as a precaution. Air leaks can progress to a situation where it quits in the air.
Old 07-23-2011, 09:22 PM
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Default RE: DLE 55 Idles fast after flight

Yeah. I call my brother a "jinx". We live far apart but he came to visit and we went flying. I haven't had a crash in years, but that day we crashed two planes! Then, to end the day I was flying my 30cc Giles 202. I had a hard time getting the idle to go low enough to get the airplane to land when I was done flying. I finally ended up landing it a bit fast, and damaging the tail wheel assembly on my rough strip. Come to find out the cylinder had loosened up on the engine, creating a vacuum leak and the high in flight idle. I told my brother "You really are a jinx because I've flown that plane for several years with no problems, and now that you are here we crash two airplanes and this one all of a sudden has the cylinder come loose!!!"

AV8TOR
Old 07-24-2011, 01:01 AM
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Default RE: DLE 55 Idles fast after flight

You are made of tougher stuff than I. If I crash one model, the only thing that I will fly that day is a small floater (glow powered) before going home. I'm not made of the same tough stuff as I used to be. Then again, who is? (smile)

I have three brothers (all younger), but none has the slightest interest in model airplanes. Dang!


Ed Cregger
Old 07-24-2011, 06:48 AM
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Default RE: DLE 55 Idles fast after flight

Dang, I must admit this richer/leaner cooler/hotter stuff is intriguing me. On full size aircraft, a richer mixture setting results in a cooler CHT. I am finding the same thing happens on my models. Too lean used to mean melted pistons and burned valves on my small block chevy oval track motors. What gives?

Also, Glen Williams hit on the issue that fixed my DL50 when acting that way although instead of the carb block, on mine it was the front bearing seal leaking. I changed the front bearing, problem solved. Oh yeah, I was just starting to see a little grease around the inner race where it protrudes from the seal. Look down behind the prop hub with a flashlight and if it has any grease showing I would replace the bearing.

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