richrd

In these posts I keep coming across you can not tune well maybe it because of the following. One parameter is off ok tune along but if two or more then it just will not work therefore you can not tune…High speed needle being main tool.

1. Tank Pressure
a. Too low.. lean run at midrange. Click or two no effect. Pull muffler tube no effect or little. Raise vertical add slows
b. Too high.. rich midrange. Click or two and out of tune. Pull muffler tube and dies.

2. Air Leak
a. lean run at midrange. Click or two no effect. Must go rich.

3. Fuel Nitro
a. Too low.. rich run at midrange. Click or two no effect. Cold motor
b. Too high.. lean midrange. Click or two and out of tune. Hot motor

4. High Compression
a. Too low.. rich run at midrange. Click or two no effect. No Sensitivity
b. Too high.. lean midrange. Click or two and out of tune. Pinging

First off no statements on engine manufacture these could be on all makes.

I am trying to put a plan together on troubleshooting sequence that traces the problem so people can fix a weak setup. Listed in order how I find most problems. Any tips or secrets on these will be appreciated

Ed_Moorman

My Feedback: (1)

I am never surprised when people have trouble tuning an engine. Most have not run RC engines very much and never break n an engine. Unless the engine is well run in, it is difficult to get a good setting. OS engines have very tight tolerances so they come up to speed quickly. For the most part, Thunder Tigers do, too. The Chinese engines take longer due to wider tolerances in my experience. I have seem ABC engines take nearly a gallon to get good and broken in so you could really dial it in.

I see people come out to the field with a brand new engine, crank it up and try to tune the low end for a low idle. Just the extra drag of the internal parts before they have worn together will keep the engine from running at too low an idle. After they get the low end too lean, they proceed to complain about the mid-range and transition.

People also have not developed an "ear" for the sounds of the engine in flight. One of my friends landed his UCD 46 and asked me to look at it. He said it was running poorly. After I opened the needle valve 3/4 of a turn, it ran fine! Not a few clicks, but three quarters of a turn.

Hobby People had an article about a year ago asking if you were running too lean. What they had you do was to open the idle mixture 1/2 of a turn. That's right, a half turn. Then you went to full power and re-tuned. Then you reduced and tweaked the idle. People habitually try to get a great low idle by leaning out the low end before the engine is fully broken in. They get the low end so lean it won't let your top end give you full power.

I have talked to guys and they keep messing with brand new engines right out of the box. Horizon and the best idea so far-put a collar on it to lock the settings from getting too far out. The guys in my club who have just cranked the Evos up and flown have had really good luck.

I just keep the idle a little high on a new engine and fly. Normally, I do run it some on the ground, but not a gallon's worth, a few tanks. The low end I rarely mess with until I have flown nearly a gallon. I do have a Big Stick 40 and a Little Stick that I use to fly new engines on. Most guys have an old trainer they can use for the same thing. I think guys are trying to dial it in before the engine is ready.

Dr1Driver

Good post Ed, and correct on all points. I'll add that many "manuals" included with new engines do NOT recommend the PROPER method of breaking-in. I'll also add that it's been, in my experience, that STs take longer to break in than some other comparable engines. Webras take a while, too, but when they do; look out!!!

Dr.1

donkey doctor

Hello; I like what I read there, and agree. One thing I see quite a bit is twiddling the needles then if it's not right, twiddling some more, without giving the engine a chance to react to the first twiddle. Pretty soon the engine is way out of tune, and the "twiddler" thinks his engine is hopeless. Another thing I see a lot is people constantly trying to get every last rev out of their engine before they take off, then can't figure out why they have so many dead sticks. I guess lots of people don't have the patience to become good tuners.

Dr1Driver

It does take patience, donkey, some experience, and an understanding of how and why our engines run and how the carb works. However, it's easy to learn if the newbie will take it slow and listen to the people with engine experience. There are also some good books out there on engine tuning. The hardest part is probably the break-in period where the novice wants to stick the new engine on the plane, tweak it out, and go fly. That starts all his problems.

Dr.1

RaceCity

Wow. Great thread!

Sad to say, it's almost comical to read some of the posts that appear regarding problems that folks encounter with their equipment, and the "diagnostics" which ensue. Of all the excellent comments made thus far in this thread, it is worth recognizing that even the best motors cannot run properly given the disastrous installations they tend to receive. If a modeler doesn't know much about motors, it's almost a certainty he/she knows even less about proper fuel tank installation/padding, keeping the fuel lines short, free of leaks and pinches. "No Uncle Fred...it's not OK to coil up 36" of fuel line in the nose of yer old Kadet"

It's been my experience that 99% of the difficulties encountered with model engines are related to something external to the motor. When the basics have been addressed, even bargain priced "econo-motors" have the capacity to run exceptionally well.

The often heralded "Heli fuel", pumps,and pipes often only change the nature of the problems...rarely do they solve them.

Patience is a virtue! An extra hour at the beginning getting everything just-so is worth countless hours of enjoyment at the field.

'Race

Dr1Driver

Good point about the tank assembly and installation, Race. For starters, the tank should be:

1. Installed with the centerline of the tank within 3/8" either way of the centerline of the carb spraybar.
2. Well padded with at least 1/2" of insulation on the sides and underneath. Also don't forget to pad between the front of the tank and the firewall.
3. Be sure the lines are not kinked and don't make them longer than necessary.
4. Be sure the brass tubing used in the tank doesn't have any burrs on the ends.
5. Keep the end of the klunk at least 1/4" (I prefer a little more) away from the back wall of the tank.

That's a good start.

Dr.1

Runway

What an excellent thread!
Can I just mention two other common faults I've seen, fairly often, that affect engine performance . 1] Over propping and 2] not having enough outlet area in a cowl such that the engine tends to overheat.

Runway

Dr1Driver

Overheating IS a big problem in planes with full cowls. Over-propping can cause overheatnig, too. If you go up in diameter, you usually have to go down in pitch. There is a mechanical limit to the amount of diameter an engine can turn, no matter what the pitch is.

Dr.1

RaceCity

There's a million ways to have problems. At least for the beginner, is there any better reinforcement needed for "keeping it simple"?? Even a simple cowling has the potential to add needless grief.

It's funny that the flight simulator software available can instruct one to think they are much more qualified than they truly are. It only takes a newbie one afternoon with a .40 sized motor to prove it. <GGGG>

Great Planes would do well to release a motor operation "sim". Can we get a show of hands for "PINHOLE!!! GENERATION IV"

A couple hours chiseling your way through layers of epoxy and luan plywood to get at the leaky tank would give newcomers an appreciation for the fine art of simplicity.

'Race

Motorboy

Some brands of modelengines can be sensitive depent on tread size in fine or coarse + angle of taper at needle to mainneedle and idlingneedle..

Jens Eirik

Dr1Driver

A couple hours chiseling your way through layers of epoxy and luan plywood to get at the leaky tank would give newcomers an appreciation for the fine art of simplicity.

That's right, Race, it will. But they must first be taught simplicity before they can do it. I've been in R/C over 25 years, and I'm still learning better ways to do things.

Dr.1

RaceCity

Well Dr1....at least we know there's two of us in that boat !

<GGG>

'Race

richrd

This is great guys thanks for responding BUT !
Iam looking for clues to the problems of bad setups from your experiences
Dr1 so over propping does what to engine , make HS needle less sensitive, over heat, rich idle problems.

Foaming fuel always lean at WOT?? etc show up at midrange only. or hard to test on WOT ground tune up.
If suspect why not temp change to non foaming fuel, any suggestion of some or drops of ??armerall

If thinking over heating from cowling why do'nt remove cowl... to much work or just looks to bad to test ?


Yes I agree to all about over playing with the needles if not sure what you are doing.
I remember the first few times at the field and the instructor saw me playing with the idle. He was in total shock I'd had the gull to tune it. HA HA how esle do you learn??

RaceCity

You seem to be looking for a compilation of "absolutes" and quite honestly...they just don't exist. One can make fairly accurate generalizations provided the basic set up is solid. Deviations from this tend to make troubleshooting a bit trickier.

Let's take "Foaming fuel" for instance...

What is foam? Air. How does it get there? Minute holes in fuel lines can allow air to be drawn into the fuel flow. Air is also easily churned into the fuel in the form of bubbles (froth) inside the tank when steps haven't been taken to properly pad (isolate) the tank from vibration. Is this the only way air can sneak into the motor? No. Again...no absolutes.

What are the symptoms of excess air in the mixture? Lean, hot, often erratic, and unreliable operation. Is this an absolute? No, since some people wouldn't notice such a problem unless the motor physically fell off the plane.

When does fuel foaming occur? Usually at high power settings, but it can occur at any speed.

Should we add things to the fuel to prevent it? Maybe, but then the fuel becomes suspect in other ways and further...if it were such a great idea, why didn't the fuel manufacturer add it in the first place?

Overpropping? Insensitive needles...hot running...poor power, etc. Always? No. Does it change the mixture? No...you do that when you twiddle the needles hither and fro trying to find out why the motor won't turn up. What is overpropped on one motor might be a bit underpropped on another motor of similar displacement. Ask the manufacturer what prop is good, or simply stated..look at the instructions for some guidance here if you don't already know.

The trick to troubleshooting isn't a list. It's experience. Take what you know about the proper function of the device at hand. Now compare what IS happening to that which is SUPPOSED to be happening. Armed with that, it's a bit easier to determine what would cause the difficulty. You HAVE to know how the machine works before you can tell what's wrong with it.

So go out and fly your airplanes. If you stay in the hobby any length of time...you'll have ample opportunity to debug problems and build your troubleshooting repertoire from there.

Have fun...

'Race

richrd

Yes RaceCity

Totally agree, so Iam trying to gleem your experiance. That's the point Iam making if more than one variable things get wackey. So I want to hear some isolation tricks like I said about fuel, only modify one tank did it fix it.. Maybe rubber band one to the side. Then go on.. isolation tank with foam etc.. or no not problem move on.

Tank level with needle jet is a fantastic problem, some can not be moved so what are some quick checks to prove low pressure or no suck because put in a racing carb..

I totally want to hear some tips on field evualtions techniques we all know you guys know lots of them.

RaceCity

Best isolation trick I can think of is wrapping the tank in good old fashioned latex foam rubber. It's worked for decades on this end, and I'm confident it'd work for you.

Take steps to minimize vibration at it's source as well. Carefully balance your props. Avoid cheap spinners. Make sure your motor is securely mounted. TIGHT. Since we know that air can get in a variety of ways...avoid gizmos in fuel line. Every connection is another potential air leak. Top shelf silicone fuel lines resist pin holes and tears. Brass fittings on the fuel tank itself will without a doubt cause you grief sooner or later, so why not use a better design to start with...GP or Hayes tanks are inexpensive and virtually maintenance free.

All this works together to reduce the chances you'll be trying to solve foam/air leak issues in the future.


"Tiny Bubbles......"

Don Ho.

blw

My Feedback: (3)

And another thing......(just had to say that)

Some engines run differently or tune differently than others. A good example would be an OS 4 stroke and a Saito. The OS seems more straight forward from what I've read. The Saito is more of a learned skill to tune, or it seems that way to me.

Speaking of Evolutions, I have 2 of them and they are very forgiving of sloppy tunings. They can be quite out of tune and still run fine without the crankcases loading up badly. The collars are nice but I end up taking the high speed needle valve ones off. The low speed ones are good to have.

Cyclic Hardover

My Feedback: (3)

This list is some possibilities but I find those who have engine problems just don't know what they're doing. A plane does not have to have anything on that list and RCers still could not properly dial in an engine if their life depended on it. I also beg to differ on your theory of the high end needle. A brain dead redneck can adjust that. IMHO the low end is the root of all evil and if you don't know how to get it right, nothing else will come around regardless.

bkdavy

My Feedback: (1)

While I applaud the idea of a trouble shooting flow chart, most people have different approaches to the same problem. Trying to collect their advice and come up with a standard approach - Good Luck! This forum is FULL of good advice. I would recommend you do a lot of searching in the existing posts, and you'll come up with a wealth of knowledge.

Just and example of some of the things you'll likely find - One of the more experienced pilots at our field likes to run his engines VERY rich. He also complains that the air bleed holes on many air bleed carbs are undersized. Anybody see a connection? Obviously, the rich settings require a larger air bleed hole in order to obtain a reliably low idle. He also likes to retaper the high speed needle to improve its sensitivity.

There are many variables affecting the engine performance, but I would make the following list of things that should be checked before the engine is even run:

Fuel tank height: Is the center of the tank within the manufacturers recommended height of the carb? If not, can it be moved? A high tank will cause flooding and require slightly leaner settings. A low tank will be subject to leaning at the end of the run and will require richer settings. If tank cannot be moved - can a fuel pump be installed? This introduces a whole new set of variables.

Fuel Tank Mounting: Is the tank adequatly mounted to 1: Prevent the tank from shifting during flight? and 2: Padded to minimize fuel foaming?

Fuel Lines: Is the clunk line short enough to prevent blocking by the back of the tank? (approx 1/4 inch clearance). Are the lines large enough to provide sufficient fuel flow (Larger diameter fuel lines allow longer runs of line)? Are fuel lines run such that there are no sharp bends?

Throttle linkage: Is the linkage adequately braced along its entire run between the servo and the throttle arm? Are the control arm throws set such that the throttle is fully shut with the throttle lever on the transmitter closed, and throtte trim fully closed? Is the throttle open slightly with the trim in the full open position? Does the throttle fully open with the transmitter at full throttle?

Engine Mount: Is the engine securely mounted?

Once you've checked all those things, and corrected them, now you can begin running and trouble shooting the engine because you've limited the number of variables to: Fuel, glow plug, glow igniter, engine compression, high speed needle, low speed needle, prop.

Fuel: Several variables come into play here. Nitro Percentage, Oil Percentage, and possibly age of the fuel.

As you increase the percentage of Nitro, you increase the speed at which the fuel mixture burns, thus increasing the temperature. Too much Nitro with too hot a plug, and you burn out glow plugs. The higher burn speed causes much higher compression, which can lead to failure of the engine itself, possibly requireing another gasket shim to reduce compression. Higher operating temperature also causes the fuel mixture to ignite sooner in the compression stroke. If it ignites too early, the engine will simply stop running. Best bet is to stick to the Manufacturers recommendations.

Oil percentage: Again, most commercial fuels have 17%-20% oil, some with a small amount of castor oil. The oil is not intended to burn, but it will affect how the rest of the fuel burns. More oil in the mix means less fuel, consequently, you may have to run a slightly richer mix. Unless you make a drastic change, there shouldn't be any changes necessary.

Age of fuel: Nitromethane is not photo stable - meaning it breaks down in direct sunlight. Do you keep your fuel in the shade at the flying field? Over time, nitro percentage may drop. Also, some believe that methanol fuels will collect water. I believe there have been some trials actually adding water to the fuel that show it takes a LOT of water to have a noticable effect, but why risk it. Bottom line: Don't troubleshoot with old fuel.

Glow Plug: ALWAYS start troubleshooting with a new, manufacturers recommended glow plug. Once the engine is fully broken in an running well, you can experiment with other plugs.

Glow igniter: Fully charged. Should have greater than 1.2 volts, but not more than 1.5 volts.

Engine compression: Is there noticable compression? There are compression gauges, but this is beyond basic trouble shooting. As noted above, for high nitro fuels, you may need to reduce compression to prevent early ignition and over heating.

If you've followed the manufacturers directions and recommendations, you should now be down to the high speed and low speed needle settings. These will be affected by tank pressure. As you change tank pressure, you change the needle settings. Higher tank pressure causes richer runs, lower tank pressure causes leaner runs. Tank pressure is affected by tank integrity (pin holes in vent line or tank?), Exhaust system design (baffle inserted or removed?), exhaust pipe extensions (longer extensions increase muffler pressure, increasing tank pressure).

Needle settings: Start from the manufacturers recommended settings. How to tune has been covered MANY times, so I'm not going to repeat it here.

Prop: Are you using the manufacturer recommended prop?

All this should get you a good running engine. What if it doesn't? Go back and try again, from the beginning. You probably missed something. Then you may have to look at other causes, including air leaks in the engine casing (carb, back plate), head gasket, muffler connection. You may have bearings going bad. You could have a bent crank shaft, worn cylinder, worn piston, misaligned rings, burned rings.... I don't know of a cookbook approach to identify these problems other than experience.

Good Luck!
Brad

richrd

Thanks bkdavy

Maybe it can'nt be done Iam not writing a book. Just thinking out loud. I hear and see most of these problem at our field. But besides just redoing it my way Iam looking at ways to prove them. Yes HS needle is brain dead but! just the way it feels when fiddling tells me alot about the engine, max rpm and the prop thats on it. So I thought this might be fun to hear lots of tips on ... watch if we do this to it and this will prove your problem ...
I know any one problem could be a long post, just dreaming one night about some techniques that are out their to prove each problem.

Over prop dud! try a smaller, or check tach, verse manufacture statements but this is hard at the field my thoughts are why is'nt it spooling up and why is HS needle a pain and why is engine just loading up type thoughts.

On tank problems yea just rebuild it I bet if you replace all the parts it'll fix the problem it's what I tell them. but at the field tank pressure is more than hieght, like could I just put on a foot long tube on muffler lets see if our vertical problem goes away ????

Well any way just thinking out loud [>:] thought this mite be fun and hear some really odd ways to test some suff.

Thanks again for you guys thoughts

Rich out their screwing around Ha