mouthpiec

Dear Friends,

I have a problem with my engine (Thunder Tiger 46 Pro) which is not stable at all.
I am afraid that I have an air leak somewhere!

I have the following question;

If I blow in the silencer exhaust whole, air comes our from the carb (till now i think that it is normal)
But If I close the carb whole + the pipe nozzles wholes, I think that I will not be able to blow.

Is my assumption correct? because when I blow, air is going out from somewhere!


Furthermore, while the engine is running and I close the carb intake, the engine goes off after 20 secs, my other engine (also TT Pro 46) goes off in 1 sec!

flyX

I generally use selicone sealent on the backplate and use blue loctite on the screws.

if the leak is coming from between the carb and the engine, i just jb weld it.
You can check the O ring to see if it's cracked or dried.

It might be coming from the barrel depending how old the engine is and how it was handle.
R/C car engines has a plastic boot on them becuase they really dirty.
A plane engine get dirty too if it get barried and not flushed.

makesure all of the screws are nice and tight. i purchased a use OS engine that was
runing eratic, all I did was tighten down the head screws that was a little bit loose
and engine ran great. I cleaned it a little bit then the seller wanted it back.lol

mouthpiec

the engine ran for just 2hours, and it gave problems from the beginning.
today I will dismantle the engine to check for any leakes.

But in your opinion, when I blow air in the silencer, air should be blocked?

CGRetired

My Feedback: (1)

Blowing into the muffler pressure tube should push fuel out from the feed tube to the carb.

So, disconnect the tube from the carb, and blow into the pressure tube from the muffler end. Fuel (or air, if the tank does not have fuel in it) should flow out freely from the carb feed line.

If you suspect an air leak at the carb, remove it and check the o'ring (as already suggested). Even if you can't detect any defects, cracks, or splits, just replace it. They are inexpensive enough. Then put the thing back together and make sure the carb tube is pushed all the way down so as to seat against the O'ring, apply some downward pressure while tightening the securing screw(s).

CGr.

bkdavy

My Feedback: (1)

The amount of air you can blow through the exhaust back into the engine will be highly dependent on the position of the piston.

You say the engine is unstable, but don't give a better description. More info is needed to better assist you.

Will the engine idle? If not, how long does it take to quit? Will it idle with the glow charger attached?
Can you get the engine to peak RPM? If so, what prop are you using, and how fast is it turning? A tach will help if you have access to one.

Does it transition from idle to full throttle smoothly, or does it cough and sputter before it picks up?

Better information will lead to better answers.

An air leak doesn't always mean a poor running engine. A large airleak from the back plate or fuel intake lines will keep the engine from developing a good vacuum, which will prevent good fuel draw.

As for the time to shutdown, that may just be a mis adjusted throttle stop screw or a minor adjustment to the carb linkage.

Brad

CGRetired

My Feedback: (1)

Brad.. it isn't very clear as to what he wants to do here.. I was assuming that he wanted to blow into the pressure tube because that's where I would blow into if I suspected a blockage, which I was thinking he was trying to fix but he talks about an air leak.. so I'm not sure what he wants to try to fix here.

Your point is well taken and is a great suggestion. I hope he understands what we are trying to describe in our replies.

CGr.

mouthpiec

Hi,
First of all thanks for your replies! I appreciate your effort to try to help me.

These are the symptoms of the engine,

The engine is very difficlt to start (I use a chicken stick and the last time I tried it, a new glow plug was installed)

The idle usually is ok
On full rpm, once I find the appropriate rich/lean setting, is also ok

Transition from low to high revs is not always perfect.
The main problem of this engine is to start it, and that after a flight or 2, i need to set it again for optimum transition. (I am sure that the screws are not turning by vibrations, because I marked their position before the flight and the screws remained the same)

And what I meant when closing the carb intake, is that I close it with my finger, so I am sure that air is not going in, and still it takes too long to go off.

bkdavy

My Feedback: (1)

The fact that it is sometimes difficult to start, and then transition from low to high RPM are the primary indicators to focus on. When you say transition is not always perfect, I'm going to assume the engine hesitates when you throttle up, and then picks up to full throttle. Both the hard starting and the transition are indicative of an overly rich low speed mixture. These engines are sent from the factory with a rich low end setting. You are probably not dealing with an air leak, so I would not disassemble the engine yet.

Resetting the high speed needle after a flight or two is not uncommon, and is probably more due to the engine warming up, loosening up, and temperature/humidity changes that occur as the day progresses. Note that you do not set the high speed needle for transition. The high speed needle is set 200-500 rpm below peak RPM to the rich side. The low speed needle is adjusted for transition, and should only be adjusted in small (1/8 turn) increments at a time. After each low speed needle adjustment, the high speed needle should be readjusted before transition is checked. Once you get the low end set correctly, you shouldn't have to touch it again for the life of the engine.

As you get the low speed needle close to perfect, your starting will improve and your reliable idle will drop. I have two of these engines, and they both start with a quick back flip of the prop.

As for shutoff, make sure the throttle servo is adjusted to completely close the throttle with the trim switch or throttle cut, and make sure the throttle stop screw will allow the barrel to rotate fully closed.

These engines are designed to allow oil to flow to the front bearing along the crankshaft. The result is there will always be some air leakage in around the front bearing. If the throttle doesn't go fully closed, you'll never get the fuel shut off, and the engine will take a long time to cut off.

mouthpiec

Hi,

Thanks for the useful information.
I think while you was typing, I was disabling the engine at my friend and your last point is very interesting.

We noticed that apart from the small slot behind the front bearing there is also a small hole. Do you have this hole?

bkdavy

My Feedback: (1)

I'm not sure exactly where you're referring to a small slot and hole. If you go look at http://www.acehobby.com/ace/PDF/Engine/PRO_Eng.pdf
You will find an exploded view of the engine. The view doesn't show the kind of detail you're talking about, but perhaps you could refer to its location in relation to the part numbers on the diagram. I've only taken one of these engines down in the past 4 years, and I don't remember the specifics behind the front bearing.

Brad

mouthpiec

The red line indicated the position of the hole.
hope this works

bkdavy

My Feedback: (1)

In that location, its probably a port thats been drilled to improve oil flow to the front bearing. Perhaps you can post a picture.

If it were me, I'd put the engine back together, get it back on the plane, and start messing with the tuning.

You didn't mention prop or fuel choice. My personal preference for this engine is an APC 11X5 or 12x4, and Omega 15 for fuel.

Looking at your website - Which plane is this engine on - the trainer or the Mustang? If its on the Mustang, you're going to want to remove the cowling until you get the low end mixture adjusted. The low end needle adjustment isn't accessible with the cowling installed, and you will want to go through several cycles of adjust and test before you're ready to reinstall the cowl.

Brad

mouthpiec

it is installed on the mustang. The one installed on the trainer works perfectly! (it even survived a crash)

And regarding the cowl, there is a hole on the side, and adjustments are made easily.

As a prop I am using an 11x6 and the fuel is the same as the one i use for the trainer.

Right now I blocked that hole, which on the other engine do not exist (maybe only a small batch of engines had this hole) because when I blow from the silencer a huge amount of air is going out from that hole.

bkdavy

My Feedback: (1)

Remember the adjustment I'm talking about is the small screw that is inside the throttle lever, not the high speed needle adjustment. Its not clear from the pictures that you have access to that screw with the cowl on. Just checking.

Assuming you purchased the engine from a dealer, not second hand, I wouldn't plug the hole. The designer put it there for a reason, and modifying it will probably void the warranty. If you reduce oil flow to the front bearing, you'll greatly shorten the life of your engine.

Brad

mouthpiec

I understood you.
You are talking for the screw that is located in the part where the throttle servo arm is attached.
For that I a made a hole on the side of the cowl, about 1 cm diameter. And right now the cowl is not installed before I resolve the issue of the engine.

I bought this engine from the internet, that is why I am "experimenting" with it.
And besided that I am working always with local experts, members of my club.

And regarding settings with the needles I wasted a hole summer with this engine, and there is nothing to do.
Even my club members told me that the engine is behaving in a strange manner.
The only thing that should be tried is to close that small hole. Bare in mind that there is another slot that lubricates that front bearing.

Thanks for the help my friend

jaka

Hi!
Don't dismantling the engine...there is probably nothing wrong with it!
The problem you have seems to be the idle speed needle! If it is turned in too much the engine will be very difficult to start because ithe low speed needle stops the fuel from entering the carb when the throttle drum is set to idle position.
Just upen the idle needle some and see what happens.

Second are you using the correct fuel?
You should use at least 5% nitro and not more than 15%. Prop should be 11x6 , preferably APC.
Glow plug OS or Enya 3,
High speed needle open 2-2 1/2 turns.
Fuel tank size : 8-10oz.

mouthpiec

I am using all the correct items you mentioned.

Engine already opened and closed back and now I am waiting for a good weekend to go and try it out

Flypaper 2

The crankcase pressure pushes air and fuel out the crankshaft and through the front bearing. The hole is to draw that excess back into the engine through the carb so you won't have oil over the bottom of the plane. Nothing to worry about.

OzMo

My Feedback: (3)

Hi mouthpiec,
one of the most aggravating things I have run into is a simple worn out O ring on the needle valve. very hard to see, but you can SOMETIMES tell if its bad by gently wiggling it when the motor is running you will see air bubbles entering the fuel line. This can be very intermittent.

mouthpiec

thanks for the advice OzMo