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Help please, nitro engine not running properly

#1
Hello, I have recently finished restoring a great planes freestyle 46, I've decided to use my evolution 46 engine and it can only fit upside down, I did manage to install it about 30 degrees off upside down, I get it running but when I throttle up it sounds like it suddenly runs lean and loses power, I can get full throttle if I work it but only with the glow igniter plugged in, any thoughts??


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#2
Idle bar glow plug. If it was lean you wouldn't need the glow ignitor on it to transition to full throttle. It's getting excess fuel from being upside down. You'll need to close that low end needle or open the air bleed a bit at a time till it transitions. If its a brand new engine it might not do that well for a bit till its well broken in. Consider an on board battery in the fuse and adding a microswitch to your throttle setup to turn it on at low throttle settings.

Also, if you haven't done it yet and its still fairly clean, clean off that firewall and covering and then give that whole thing a thin coat of silicon calk. It'll seal that iron on covering and keep oil from seeping in under the covering and causing problems.

To check the richness of your engine at idle, run the engine full throttle then take it to idle for 30 seconds. Pinch the fuel line. If the engine increases rpms and then dies your rich. If it just starts to increase rpms and dies your there. If it just dies your lean. Newer engines usually need a bit more fuel till their broken in and being upside down leaves the excess residue drowning the glow plug.
 
#3
Yeah the glow plug is drowning, had it mounted vertically upside down to begin with as it fits best that way, and it didn't run too well, the engine isn't new, was in my hanger 9 solostar which had two short flights before the flight battery decided to disconnect itself mid flight, always secure your flight battery correctly!!
Can you get idle bar glow plugs for evolution 46 engines?? (Horizon), I will silicon the firewall thanks great tip!
 
#4
Idle bar glow plugs fit just like non idle bar. Just buy em at the hobby shop. Several flights on an engine does not make a broken in engine. Several hours usually will. You're polishing the engine parts by rubbing them together and while the majority of that happens at the first, it takes a while to get it good. It's always best to take an "experienced" engine and mount that one inverted rather then a new one BUT ya gotta do what ya gotta do.
 

xuzme720

Dedicated foam bender
Mentor
#5
For anyone, in this age of electrics, unfamiliar with the idle bar glow plug, here is an image.
ljozg2000.jpg
Simply put, the bar is there to help keep the cold fuel from splashing directly on the coil and putting out the "glow". Another option might be an onboard glow driver to keep the plug hot but that is going to be a lot pricier and more of a weight penalty than an idle bar plug.
 
#6
Thanks, yeah it's only had about 1 hour total running, I thought it was pre broken in but guess I mis understood that information, I've have a fair amount of glow experience, mostly with cars. I was told that the evolution motors require a special plug, hense why I asked if horizon supply idle bar glow plugs for the evolution.
Might do that remote glow igniter option, I hate being too close to the prop, tunings not a problem but taking of the glow igniter upside down is just a bit scary haha
I guess the other option is to ignore aesthetics and mount the engine up the right way.

Oh I read by chance that glow plugs with the idle bar should only be used with old baffle type engines, never heard of these, any thoughts???
 
#7
Don't know where you got that info from, the only problem other then a slightly higher cost is if the idle bar should detach from the plug. That can eat up a piston/sleeve real quick. However, since I've been running the things, and I started big engines back in 1976, I've never had a failure.

You understand Baffle engine right? That's where there is a fin on the top of the piston and a single bypass in the engine? The gas comes up the bypass, across the piston and hits the fin which deflects it up into the cylinder instead of just straight across and out the exhaust. Schneurle porting OR simulated ported engines (luckily he patented the number and degree of the ports so other manufacturers just changed number and where they were hence not paying the patent) bring the gasses up in several bypasses and aim those at each other so that the act of the gasses hitting each other does the mixing. No fin on top of the piston means a lighter piston, more gas and more efficient mixing, more power. Less chances of having big droplets of fuel too. But if you have a problem engine especially at idle, the bar keeps the bigger droplets from landing on and quenching the glow plug element.

Far as broken in. Your engine has been run and the needles set, it should and did run for you. But its not done. During manufacturer of ANYTHING mechanical stresses are put into those objects. In our case it's Piston/Sleeves and in a small part, bearing mesh. When you run the engine these areas will get hot, expand and relieve the manufacturing stresses. As they cool they will shrink, but not as much as they expanded. This happens less and less each cycle and then you have metal to metal contact that will, during running, start to polish themselves together. If you shoot guns and do detailed stripping, cleaning you may know about a technique called "the 25 cent trigger mod" Basically you just take the wear points on the trigger mechanism and polish them with metal polish. This takes the stock, treated metal parts of the trigger and brings them to a mirror finish that with the addition of a bit of oil, makes them slide real nice. Before your trigger feels gritty, after its smooth. Well, normally with enough use those parts would end up looking mirrored anyway, we just did it all at once. Same for your engine. Once you get the stresses out and the tolerances set you need to polish that motor in. There are tricks to doing it manually but normally most people, including me, just fly that sucker and have a good time. In an hour or two you'll have a reliably running engine that can idle pretty well. 5 or 6 and the idle can be lowered even more, reliably. By that time your motor is polished up and the bearings are also smoothed out. It last like that, with proper care and clean fuel, for quite a long time. Make sure there is some castor in your fuel OR if you're totally synthetic, get some after fun in the engine after every trip to the field. You're trying to save the bearings here.
So that is the difference between the Evos "Broken in" and true "Broken in".

The way I break the motors in, the way George Aldrich told me how (old, dead, famous engine guru if you hadn't heard of the man) was to get a ANC, ABC, AAC engine with the most pinch. Get it set up on the running bench with a prop with a little less pitch and an inch less or more (depending,experience thing there) and the fuel you intend to run. Leave the muffler off. Pull the motor through to suck the fuel up to the motor, If it's really stiff, heat it with a heat gun or tactfully with a butane torch, prime the exhaust port and get that motor running full blast. Adjust the needle so that it's just rich of dead lean and let it run for a minute. Shut it off and let it cool completely, overnight. Do it again tomorrow. Maybe another couple times, you have to judge the engine and the feel. That will pretty much set the engine. Now put the muffler on, the prop you intend to run and get a tank or two of fuel through it on the bench. Now, try and get the low end somewhat set so that the motor will idle long enough for you to get in the air.
Put it on a plane and go fly. If it's a really tight engine still, set your engine so that in vertical the engine just goes lean and then go fly big loops. The motor will cycle between lean going up and rich coming down. A couple flights of that while adjusting needle for optimum and you will find you put the needles in a little more and the idle will become more reliable. I took a tight pig to the field one day that I couldn't win any races with and after breaking in this way I was leading the packs. IF I hadn't had my eyes worked on that year I would have one the season. but it was still a lot of fun.

Also, with these engines, full out is how they were made to run. When they are cooler then full temp the pinch is tighter (hence heating it with a gun when new) SO while you are idling, you are wearing it out quicker. Not a big deal if you're sport flying but if it's a competition engine, try not to idle it so much. We really should all be running ringed engines, but thats another story and it will be moot in 10 years when everyone flys electric except in the Nostalgia classes.
 
#8
Wow your a wealth of information! Thanks!!
Can't imagine the "nostalgia class" will last too long as the veterans get older and engine manufacturing gets more expensive as sales decline. Electric is far cleaner and so much easier but it doesn't give me that same feel as hearing that noise and the smell and that "always in the back of my mind" risk of amputation


Taken from http://www.rcgroups.com/forums/showthread.php?t=1098888

"K&B long and the Fox Miracle plug for the 4 cycle or any of the 2 cycle engine that still won't transition well. For use in Schnuerle ported engines (what you have) avoid glow plugs with an idle bar. Idle bars should only be used with the old baffle engines! Idle bars disrupt flame propagation across the combustion chamber. This isn't a problem with the old baffle engine as that baffle already does this!"

In any case, it seems as though I should mount the engine vertical without the cowl and get a few hours on it until it's proper broken in and then go back to upside down, maybe with an idle bar glow plug if it's still not running right??
 
#9
Don't misplace high performance and trying to get it to idle inverted with don't run idle bar or not. You won't have one on your Jett 40 that puts out about as much as 2 OS 46's. Most os 46's will put out quite a bit of power and run fine without a plug, till you put em in upside down and don't run them full out all the time. Other then that I've used them interchangably except in some combat planes where I just used the heavy element Enya #3 which in 2001 was going for like 9 bucks but they lasted and lasted. Also, I said combat. I must admit I did have plenty of periods where I wouldn't run my engine full out. I mean, if I did I'd constantly overfly the targets.

Ok, most everyone in combat forgets and uses the left stick as the landing initiator only. It's a big rush.

You can still get the Harry Higley books on engines and I thought they updated those bad boys too, a wealth of engine knowledge. Battery power is probably here to take over and it pains me to think there will be a generation some day that doesn't know the smell of Castor or the darn near perfume of synthetic oil exhaust.

I'll save you the chapter on my favorite flying jacket that I lost and found, by the smell. Must run a Fox 35 soon and I've got the gallon of 28% Castor to do it on.
 

Mike oxbig

15% nitro is my cologne
#12
Good points in this thread but I thought I might add my 2 bits.

Your problem may also be coming from your carb being below your tank's centerline. This causes a siphoning effect and floods your motor, especially at low speeds.

I run Kline regulators on my inverted 2 and 4 strokes. They are a little tough to find but they will solve most problems with inverted mounting. Basically they meter the fuel to only allow fuel in from suction by the motor, not by the force of gravity on the fuel. I like them on all my glow set ups as the consistent flow of fuel at any orientation makes tuning much easier and a more reliable tune.