I am struggling with tuning a relatively new Evolution 46NX engine(roughly3 Gal of fuel run through it). It is mounted on a Hangar 9 Twist 40 3D V2 with a 11X6 prop.

I have set the high speed needle via the pinch test achieving a slight increase in rpm when fuel is restricted at full throttle. Low speed has been set with a smooth transition when moving from idle to WOT with no hesitation if you do not allow the engine to idle too long. The engine will idle indefinitely but if it idles for more than 15 - 20 seconds, it will stumble(or cut-out)when the throttle is quickly moved to WOT. I have read that during long idles, the fuel will "build up" and needs to be cleared periodically. This is how the engine is performing.

Here is the problem; when performing low speed maneuvers (throttle @ roughly 25%) for a few minutes, when WOT is demanded to get out of trouble, I do not need the engine to stumble or worse, stall.

I have read and researched many threads and have not found the answer. A flying friend has an Evolution 36NT(Hangar 9Tribute w/11X4 prop)that we fly slow for most of a 20 minute flight and when WOT is demanded the engine responds with no hesitation.

Thanks in advance for any constuctive assistance.</p>

There's your problem. It's still too rich on idle and is gradually "loading up" with fuel in the crankcase. Lean it about 1/4 turn more on idle and try again. Does it smoke when you try to rev it up after a long idle?

1/4 turn towards leanon the low end needle? If that doesn't clear the problem should I continue to go lean?

I have tried a more lean setting on the low end needle and instead of stumbling, the engine just cuts out when idling a short time (less than 15 seconds) and then WOT is demanded.

It does not smoke when rev'ing from idle but it does have some oil in the flow. Is that what your calling smoke? I assumed that when moving the throttle quickly, some un-burned oil was going to come out of the exhaust.</p>

Not sure I would go 1/4 turn, more like 1/8. I think it is a pretty fine line between to rich and to lean. As it gets closer then the turns become less, i.e., 1/16th first senario was to rich, 2nd was to lean.

You can also use the fuel tubing pinch test at idle - you want just a slight increase in rpm at idle before it dies. If it dies right away it's to lean. Go about 1/16 at a time like gorish suggested.

"goirish" is right, turn the low end maybe 1/8 at a time. It doesn't take much. If the problem continues, you might try a hotter plug.

With my OS 2 strokes I lean the low end until I can idle for 10 seconds and then immediately go to WOT without any hesitation. On my engines, if it sputters and spits before going WOT it's too rich. Conversley if it just immediately stalls and dies when going to WOT I've over leaned it. I make very small adjustments each time....about 1/16th of a turn clockwise.

Also, when first starting up the engine after making an adjustment, I go to WOT first for a few seconds to clear out any fuel build up in the carb. I also leave the glow ignitor on until I'm at WOT. Then I take it off and idle it down for the 10 second period. This process has always worked for my OS 2 stroke engines.

A lot of good information. I have not tried the pinch test for low end.

Regarding the glow plug, I am still using the stock plug that came with the engine. I will put in an OS #8 if I can't achieve the performance I'm looking for with the low end pinch test. I'm a big believer on changing one thing at a time.

Does the engine actually have this problem in the air, or is this simply an assumption of performance, that you are making?

If the latter, don't sweat it.

The engine will tend to run a bit leaner in the air, and idle at a faster speed due to the motion through the air and the prop.


Also check the needles while working the throttle back and forth WITH the engine running on the ground.

The Evolution engines are notorious for having the needles "walk".

What happens is that as you advance and retart the throttle the LS needle setting will change with the engine vibration and heat making the needle easier to move.


Take off the clip and bend it back to put more force on the detents.

You may also want to try a piece of fuel tubing around the clip and the needle too.

Update: Tuned the engine moving the Low End needle more lean. Rotated the needle in small increments while checking with idle pinch test. Ultimately rotated about 1/2 turn. RPM increased slightly when idle pinch test performed. Low End Needle is now close to completly closed. Transition from idle to WOT continues to have oil mist in exhaust. Transitions well when rev'ing engine but still has some small hesitation after allowing engine to idle @ 25% throttle for more than 30 seconds.

Under normal flight, engine "felt" like it ran better. No more dead sticks. However, during slow flight for 60 seconds or more, engine continued to have small hesitation when throttle was moved quickly to 3/4. (Did not have the guts to go WOT).

In response to one question regarding if this is a problem only on the ground or also in the air. Fortunately, this is aflightproblem that shows itself alsoon the ground.

Try an OS A3 glow plug. Evolutions need something hotter than a #8.

When you let it sit and idle for a long time, what happens? If it gurgles and loses RPM before dying, it's rich. If it increases and then dies, it's lean. If it does nothing and dies, your glow plug is too cold or too old.

You might also check for air leaks. That will give you fits on transitions as the engine sucks extra air in while accelerating making it lean out. I had an older Evo that wouldn't run for beans until I tore it down and pushed the rear bearing on a little farther. That sealed up the leak on the crank and it's run like a top since.

I have one of these engines and all it says on it is "E", don't know if the carb. is the same but!

Minnflyer posted a way to set my carb. if I needed to. Its different from our normal way of setting them. You might get in touch with him and ask about it. I can't find the directions right now.

I will try later when I have time.

sticks

Like he said.

Most Evolution engines come with a long nose plug.

This keeps the coil out of fuel when the engine is inverted, and also acts to retain heat, so the default plug is indeed hotter.

Crank the LS needle down even more, until the engine will not run, then move it up to the point the engine WILL idle. Then give it a click or two more, and you're set.

But MAKE SURE you increase that clip friction. The Evolutions WILL "walk" on you.

Update for 4/15:

Obtained information via MinnFlyer via e-mail with an alternate method to set the Low End needle back to factory setting.  Achieved near normal flight.  Now very small changes are taking the engine either lean or rich.  I have it narrowed down to 1-3 clicks on the High End needle and 1/16th of a turn on the Low End.  Engine is running much smoother on Low Throttle settings.

Thanks for all the information.  RC Universe is a great resource for information.

In case anyone needs the alternate set-up for the Low End I will include below the instructions Minnflyer provided.

<p class="MsoNormal" style="MARGIN: 0in 0in 0pt"><span style="FONT-FAMILY: "Arial","sans-serif"; FONT-SIZE: 10pt; mso-fareast-font-family: 'Times New Roman'">1)  Remove the blue collar from the low end needle.</span><span style="mso-fareast-font-family: 'Times New Roman'">

</p></span></p><p class="MsoNormal" style="MARGIN: 0in 0in 0pt"><span style="mso-fareast-font-family: 'Times New Roman'"><font size="3"><font face="Times New Roman"> 

</p></font></font></span></p><p class="MsoNormal" style="MARGIN: 0in 0in 0pt"><span style="FONT-FAMILY: "Arial","sans-serif"; FONT-SIZE: 10pt; mso-fareast-font-family: 'Times New Roman'">2)  Open the carb 1 millimeter (You can approximate this by inserting a heavy T Pin in the carb and closing the barrel on the pin)</span><span style="mso-fareast-font-family: 'Times New Roman'">

</p></span></p><p class="MsoNormal" style="MARGIN: 0in 0in 0pt"><span style="mso-fareast-font-family: 'Times New Roman'"><font size="3"><font face="Times New Roman"> 

</p></font></font></span></p><p class="MsoNormal" style="MARGIN: 0in 0in 0pt"><span style="FONT-FAMILY: "Arial","sans-serif"; FONT-SIZE: 10pt; mso-fareast-font-family: 'Times New Roman'">3)  Close the low end needle</span><span style="mso-fareast-font-family: 'Times New Roman'">

</p></span></p><p class="MsoNormal" style="MARGIN: 0in 0in 0pt"><span style="mso-fareast-font-family: 'Times New Roman'"><font size="3"><font face="Times New Roman"> 

</p></font></font></span></p><p class="MsoNormal" style="MARGIN: 0in 0in 0pt"><span style="FONT-FAMILY: "Arial","sans-serif"; FONT-SIZE: 10pt; mso-fareast-font-family: 'Times New Roman'">4)  Open the low end needle 1 1/5 (One and one fifth) turns</span><span style="mso-fareast-font-family: 'Times New Roman'">

</p></span></p><p class="MsoNormal" style="MARGIN: 0in 0in 0pt"><span style="mso-fareast-font-family: 'Times New Roman'"><font size="3"><font face="Times New Roman"> 

</p></font></font></span></p><p class="MsoNormal" style="MARGIN: 0in 0in 0pt"><span style="FONT-FAMILY: "Arial","sans-serif"; FONT-SIZE: 10pt; mso-fareast-font-family: 'Times New Roman'">5)  Replace the blue collar.</span><span style="mso-fareast-font-family: 'Times New Roman'">

</p></span></p><p class="MsoNormal" style="MARGIN: 0in 0in 0pt"><span style="mso-fareast-font-family: 'Times New Roman'"><font size="3"><font face="Times New Roman"> 

</p></font></font></span></p><p class="MsoNormal" style="MARGIN: 0in 0in 0pt"><span style="FONT-FAMILY: "Arial","sans-serif"; FONT-SIZE: 10pt; mso-fareast-font-family: 'Times New Roman'"></span></p><p class="MsoNormal" style="MARGIN: 0in 0in 0pt"><span style="mso-fareast-font-family: 'Times New Roman'"><font size="3"><font face="Times New Roman"> 

</p></font></font></span></p>

I will tell you after fighting with one of these engines for a couple of months off and on that if the carb is set right (simple to do, actually) and there aren't any air leaks, the engine will idle smoothly and transition quickly. I can slam the throttle from a 1 minute idle and be at full RPM in 2-3 seconds. With mine, once the air leaks were fixed, I set the high end just off peak, and then set the low end to idle well and then to transition right. The low end is very sensitive on these engines when it gets close, so once you get it to idle for more than 10 seconds make the tiniest movements to dial it in.

I agree with tthe Low End needle being very "touchy".  I would like to check for air leaks but have not taken one of these engines apart.  Is there a way to check for air leaks without too much dis-assembly?  If possible, I want to live by the "Don't fix something that isn't broken"  

I just installed an older Evo on my SSE and it would not run right. It had an air leak and would not shut down even with the throttle completely closed. Found that the carb [which is held in place by a friction collar unlike the OS wich is positaviley located with two screws] was not seated on the o-ring seal to the block causing an air leak. I loosened the collar and while pressing the carb into the o-ring retightened the colar, I also for good measure resealed the back plate even though it showed no signs of leaking. She runs like a dream now. I did order two kits from Horizon, the carb and small parts kits, both were around $8.00 total.

One more thing, I also replaced the OS A3 plug with a McCoy long plug.

Gary

You can check for leaks without taking anything apart. Get a straw that fits the carb opening, and put the piston just below TDC. You should be able to blow air in the carb without it leaking out anywhere except maybe the muffler. If it does, put the engine in a bowl of water and blow, looking for the bubbles.

Eh most glow engines will purposely "leak" around the bearings, to keep them oiled.

Usually the amount is low enough not to cause engine problems, but this often throws newbies...

If as you say you have the wide open throttle setting correctly adjusted...usually "peak rpm + enrich fuel by 1/4 - 1/2 turn" you can put that phase behind you providing you do not change the type of fuel (low/higher %nitro) or drastic changes in atmospheric conditions. Next the idle can be adjusted low enough to give rapid response to full throttle (WOT) and at the same time the model should not taxi rapidly across the ground. When you have completed the above & the idle still continues to be uneven connect your glow plug igniter to the engine while running & check the idle operation. If the idle remains steady then you should replace the glow plug with a hotter type until the idle stabilizes. Remember also in flying the performance of the engine depends on your operating technique...time in WOT & time in idle. Continuous WOP overloads the engine/igniter (Heat)) & prolonged idle cools the igniter with the possibility of engine shut down.

Hey Rodrigues welcome to RCU, your input is welcome. Not sure if you noticed or not but this thread is over five years old, The original poster is likely long since moved on.

I have made that mistake also as lots of others too. I eventually learned to check dates but no never mind and do post and participate

John

Thanks John. I stumbled onto this site & decided to offer a solution & never noticed the date...Opps! Nevertheless anyone with a similar problem may hopefully find my advice helpful. Perhaps that's the reason why this thread is still here.

Yes and agine welcome to the forum