Hi guys,

Ive just bought a Thunder Tiger GP 25 ABC w/Muffler. Would it be any good if I cut to intake air holes in my engine cowl to cool the engine during flight or wont it affect the engine?

Thanks

Matthew

G'day Mate,
Did you get instructions with the motor, If so, follow the run in procedure in the instructions, to the letter, with the motor mounted on the plane, then fly it, RICH, & all will be well.

Thanks a lot Allan.

Matthew

This is a personal thing, but I find it much easier to get familiar with an engine when I can tinker with it on a test stand. Once it's in a model, it's always harder to work on, and you greatly increase the probability of damaging the plane.

Why not invest in a cheap test stand? (~$20) Most of them are adjustable enough to take almost any engine you're likely to own in the next few years.

For break in, you should follow the instructions reasonably closely. That said, it's worth reading this thread if you want to know more about ABC engines:

http://www.rcuniverse.com/forum/Tape...1850473/tm.htm

I wouldn't be too worried about using really high oil content, but it helps to understand what's best for a tapered bore engine.

Matthew

Thanks alot Matthew Allen for the advice going to read the site.

Matthew

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You can fly it in on the model. Just don't tune it super rich. No need to do so and it isn't good for ABN engines to be ran super rich, although many of them won't be hurt by it. Still, a slightly rich two-stroke is preferred.

Try not to fly it at full throttle all of the time, if you can help it. Let it build up some heat and then throttle back and let it cool down. Four or five flights like this should have your engine broken-in satisfactorily.


Ed Cregger

Run one tank on the ground then fly it. If it has a nice cowl please TAKE IT OFF. You can get easy access to the controls and the engine is well cooled.

IN FACT THE COOLING WHILE FLYING IS BETTER THAN GROUND RUNNING.

Avoid long periods of full throttle operation and land if the engine seems to be going "OFF" [ Hint the RPM will drop and the engine note will sound "hard".]

Here is another vote for running on a test stand first-set up when you have nothing else to worry about-concentrate on getting the engine broken in properly, following the mfgs recommendation, generally, or some of the great threads posted on RCU. After all an engine is a decent investment-do the break in correctly and you will be rewarded with a sweet running engine and minimim problems at the field.
I see a lot of flyers at the field, tinkering and puttering around with engines. Three of us that fly together all break in engines on a test stand, and when we go to the field, we fly, fly. Not to say you will not have an occasional problem, but it cuts the odds.

Thanks guys,

Would it be any good if I bench ran the engine and put the prop on to blow air to keep the engine cool? Or doesnt it matter?

Thanks a lot.

Matthew

Hi Matthew

Are you asking if you should test run an engine with a prop on? The answer is yes, always! The prop is needed both for cooling, as you suggested, but also to provide a load on the engine. Too little prop, and the engine will over-rev at full throttle. too big of a prop, and it will struggle to turn it, and probably overheat. Usually, the manual will suggest a prop size for breaking in an engine.

Sandy T

The prop I would use to run in the engine would it be the same one as the normal prop you use while flying the plane after running it in? If the prop had to come off during flight (this after running in on a nornal flight) would you shut down the engine so it wouldnt damage the engine or just idle?

Thanks a lot

Matthew

G'day Mate,
Are you saying that your prop came off in flight?
If so, shut it down IMMEDIATELY. or it will over rev & possibly damage your motor.
And about using the same prop for flight as you did for running in, would depend on the prop that you used, for running in, I have an OS 25FSR, & I ran it in on a 9x6, & I fly it with a 10x4.
But it would depend on the plane to a large extent, a slower plane I use the 10x4, a faster pattern type plane I use the 9x6.

Matthew,


Your engine is actually an ABN; not an ABC (unless, possibly, if it is a very old example).
Please follow [link=http://www.rcuniverse.com/forum/m_1850473/tm.htm]this RCU thread[/link], for a good break-in.

It will be done on the bench, but will give you a long engine life and less trouble.

ABC and ABN engines should get the same treatment.

Thanks a lot Ill check the page.

Matthew

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You know me. I'm usually the first to jump up and recommend using a test stand for break-in, but I guess I'm getting lazy these days.

Is the test stand running in best? Yes.

Is there a huge difference in the results? I doubt it, for this type of engine. Other types of engines, yes.


Ed Cregger

How should I run in the engine at max RPM or what?

Thanks

Matthew

Matthew,


As the procedure states specifically, running the engine at part throttle settings during the break-in will achieve nothing.
It will just prolong the break-in process.

So yes, full throttle only with the engine 500-800 RPM richer than peak.

You can momentarily peak the engine, to find the peak and no damage will result to this type of engine.

The ideal setting is full throttle and just a little leaner than where the engine goes from 4 stroking to 2 stroking, in other words as rich as you can go but still have the clean 2 stroking sound. This is usually somewhere around 2000 revs below peak.

Brian,


If the engine peaks at 14K and you run it at 12K, the engine is only making only ~63% of peak horsepower on the given prop.

It is likely running at a four-cycle at this setting.
The alternate firing strokes when a two-stroke engine is four-cycling is significantly more powerful than the consecutive firing strokes when it is two-cycling.

I prefer to have the engine running a bit hotter and closer to peak (500-800 RPM less).

If the engine is in a consistent two-cycle at P-2,000 RPM, than it is good enough also.

Arrrg! More break in arguments! Just run it! It's ABC, no big deal!

Hey guys if the engine specs say the engine runs at : Power Output: 0.6 at 15,000
Practical RPM range: 2,500 - 16,000

I should run it at 15,200-15,300. How will I know when it is at that RPM? Im a newbe.

Thanks a lot

Matthew

You could buy a Tach. But even I wouln't run it that fast. Just ignore what anyone says here and follow the manufactures instructions. That engine should break in very quick. A good bench stand is a good investment, but if you are a newbie who doesn't know how long you may be in this hobby, that isn't a requirement either. You might be better off asking the question on the beginners forum. Too many people argue exotic theories here which do little to help a beginner.

Thanks a lot

Matthew

Matthew,

a couple of things. The engines specs give you the theoritical maximum performance. It does not mean you engine will turn that fast or deliver that horsepower, it just means that it might under most ideal circumstances. So do not be concerned about those numbers, but do follow the instructions and advice given. Your engine may peak at say 11,000 RPM on the ground, and it may peak in flight at 12,000 or so RPM. That is the reason why one must always run his engine on the slightly rich side to ensure that there is not a lean run which gets very hot.

When dealing with a cowled engine, one must make sure that there is an ample exhaust path for the cooling air out of the cowl. It is not so much the intake, it is where it will go after entering the cowl and cooling the engine. If there is not complete path, the cool air will stagnate in the cowl and the engine will overheat for a lack of cooling air. So the openings in the rear, around the cowl, etc. need to be equal to the intakes and if you can, make them a little bigger so that there is always positive flow out of the cowl.

Read up on all the threads. Follow the advice. Provide cooling paths and you will do just fine.

Cheers,

Chip

If you do not have holes in your cowl to permit cooling air in and the expanded air (heat expands air) out, your engine will burn up. That is not covered under warranty.

You are expected to make a pretty good size hole in the front of the cowl, so that cooling air blows onto the cylinder. Then you are expected to make a hole two to three times as large somewhere in the rearmost part of the cowl to let the expanded heated air leave the area. Yes, it might ruin the looks of your model in your eyes, but that is what has to be done, or the engine won't run well and it certainly won't last long. Good luck.


Ed Cregger