trbst

Hello Everyone,

I have a problem Idesperately need help with.

I have a .60 trainer with an Evo .61 NXengine on it. The engine kills the glow plugs once every 2 flights if I'm lucky. 1 plug per flight if I'm not. The outside temperature varried between 25-33 degrees Celsius. Irun a 10%Nitro fuel and a 12x6 prop.

The first plug that died was the original Evo plug. Then, I wasted an OS #8. Then, an OSF(being longer it suits this engine better), and then another #8. I am unable to find a solution.

I admit that in the beginning the mixture was way too lean - the prop would spin at 11,500RPM(maxIcould ever achieve). But then Irichened the mixture, and then richened it some more. Last time Iflew, Ithe engine would achieve max RPM of 10,000 (quite rich). Yet again, after landing, I'd notice that the plug's coil / fillament would be all sort of chewed, or rather, collapsed.

I am in no way able to solve this puzzle and need serious help Iwould be highly grateful if you could share any thoughts.

P.S. I ordered a Cold O'Donnell plug out of desperation, and a #8Fox Pro Long plug.


Thanks in advance !

jaka

Hi!
It's very simple!
Your engine is running too hot!
Either you are leaning it too much or use fuel with too much nitro or too little oil.

Good glow plugs for all modern engines are OS 8 or Enya 3 or 4...or Rossi 3, 4 or Nova Rossi 4, 4A or 5.

trbst

The engine is definitely very hot - but as I mentioned, the settings are 1000 RPM less than max on the rich side. Also, the fuel is only 10% Nitro. []

red head

I know you said the plane is a trainer but you didn't say if it has a cowl or is closed in. If the engine is closed in be sure you have enough air flow going in and 3 times the opening for air exit. You might also want to try a couple different props just to see what happens. I use FOX Miracle plugs with NO problems.

A few years ago I had a well known flier show me how he tuned his engines and it's worked great for me. : Get it started and let it run for a few seconds then take it to about 1/2 throttle and tune it to it's highest RPM then richen the needle about 1/8 of a turn. Now try full power, it should take it and run smooth - leave it alone !!!! ENJOY !!! RED

trbst

It's a Hobbistar 60 so no cowl. But I'll try your advice about tuning it ! Thanks. Still, guys, if anyone has any similar issues, or has ideas on how to solve my overheating problem, please let me know Thanks !

jester_s1

Three questions: Are you using a commercially blended fuel or are you making your own? The oil content has a lot to do with cooling, so if you don't have enough that will cause overheating and premature wear. How long are you letting the engine run before tuning? If it's not up to running temperature, you will tend to tune lean. And how consistently does the engine run? If there is an air leak or an issue with your plumbing, a properly tuned engine can go lean during your flight.

trbst

Hello,

I'm running a 10% Jets Nitro (http://rcshop.uits.bg/images/5L-JETS.jpeg).

Yes, I do leave the engine to heat up before tuning. The fact is, that with 89F degrees outside temperature, the engine heats up pretty quickly. Overall I'd say it runs as smooth as silk - it's just that once you kill the engine you can't start it again (dead plug).

jetmech05

eating glow plugs if your power source is ok is a sign of being too lean, or too hot.....what are you using for a power source for the glow plug? it should only be 1.5V....I know that if you're using a programable on board glow, and reverse the polarity you'll eat glow plugs

trbst

The igniter is a standard one - 1.5 v I think. I've used it in my other plane without any issues so no reason to be concerned here.

As mentioned, the engine DOES get hot, a LOT, but I've richened the mixture as much as possible - at WOT it runs 1000 RPM below maximum because of being rich. If I richen it some more, It'll just choke/drown and die mid-air.

jester_s1

I looked at your fuel and it only has 15% oil. That may not be the problem, but that is a little low. Adding some castor oil to bring it up to 18-20% would provide additional cooling.

Another question: what is your fuel tank setup? If you don't have enough muffler pressure or have too much line between your tank and engine, you might have a good tune with a full tank but go lean when the tank gets low.

azrenagade

I.m runing the same engine in my Sig Senior. I run 15/20 nitro oil premix & have no problems with it. im not runing a onboard glow. sounds like you need more oil in your mix
Mike

jetmech05

Don't worry about RPM....tune the high end to max by ear then richen it up about an 1/8 to a 1/4 turn...then tune the low end.....
better to be off of some lab spec RPM than to have a motor sieze or eat glow plugs...

red head

Another thought that will eat glow plugs is " Dirty fuel ". ENJOY !!! RED

jaka

Hi!
All trainers have the tank mounted too low! That means the engine leans out more than it has to when the fuel level in the tank gets lower.

Thats why I rekommend sidemounting engines!

jester_s1

Not true. Every trainer I've seen has enough fuselage height to mount the tank properly. Sticks are notorious for needing a side mount, but generally not trainers.

That said, you probably should check your tank height. The centerline of the tank should be even with the spraybar of the carburetor. Up to 1/2 inch difference up or down is acceptable, but more than that will cause fuel mix problems if you aren't running a pump.

trbst

both my trainers had the fuel intake a little higher than the tank, but the previous one ran just fine. I am super reluctant to mount my engine sideways because that would mean cutting the plywood around the engine mount and that's something I don't want to do. I doubt the fact that this has THAT much influence over the performance of the engine but I do agree it does influence it.

JohnBuckner

My Feedback: (1)

The oil content and and type is a vital factor in the cooling system systems for our engines. There is no way you would catch me knowingly using any fuel with a total oil content of only 15% if in fact that is the case with the stuff you are using.

In addition with only a few exceptions I want in most cases the added protection of those few extra degrees that even only a small percentage of that total oil content castor does offer. To each his own.

John

Elwood

My Feedback: (2)

Try a fuel with 20% oil. Make sure at least 1/2 of that oil is castor oil.