There's a lot to know about model engine
operation and adding this DVD to your library means you gain the benefit
of learing from an experienced pro. With an approximate run time
of 3-hours, topics covered include care, handling, break in,
disassembly, tips and tricks, fuel and it's composition, tuning,
selecting glow plugs, gasoline versus nitro fuel engines, how to work on
Walbro type pump carburetors, etc. Subsections include;
- Fuel Make-up
- Fuel Systems
- Engine Break-in
- 2-stroke Break-in
- 2-stroke Assembly
- 4-stroke Break-in
- 4-stroke Assembly
- Adjusting Valves
- Gasoline Engines
- Gasser Assembly
- Multi-cylinder Engines
- Walbro Carbs
- Spark Plugs
- Fine Tuning
it's how to break in an engine for a model helicopter versus a model
airplane, or how to adjust valves on a 4-stroke engine, we have you
covered. While you won't quite become an overnight expert just by
watching you will be able to handle breaking-in an engine, tuning it for
proper power, or selecting a propellor. That, plus you'll be able to
make repairs because you'll understand the ins and outs of disassembly.
Along with the many little things it otherwise takes a lifetime of
experience to gain, you'll be well on your way to being your club's go
to guy when the rest are stumped.
Q. Why does some fuel contain castor oil and other is full-synthetic?
A. Fuel with a bit of castor adds protection during a lean run, e.g. engine protection if I make a mistake on the needle valve setting. However, I'm a pretty experienced modeler and this really no longer happens to me. However, experience doesn't protect me from mechanical failure when the little bit of castor oil is like an insurance policy.
Examples of mechanical failure are a pin-hole leak in the line, or a tiny leak at the fuel filter body, or when a line begins splitting where it attaches to the carburetor nipple. Any of these may allow air into the fuel line. In turn this results in a leaner fuel mixture than you set with the needle valve. And if it's lean enough that the oil cooks off instead of lubricating, it'll kill an engine.
Q. Why does castor oil protect metal better?
The reason is the castor oil has a higher flash point than the
synthetic oil but more importantly, just as it begins burning (and any
oil will burn once it gets hot enough) it forms longer chain molecules
(this is the reason it stains mufflers with brown spots and splotches).
The longer chain molecules make it thicker and thicker just before it
flashes off. However, like the synthetic, it too will cook off.
Hopefully, however, in becoming thicker it may present enough drag on
internal components to slow the engine to a halt before it's damaged.
Thus, the film the castor oil makes while ugly often protects an engine.
Yes, it becomes a pain in the hind end to subsequently disassemble and
clean the engine up but this is better than slagging an engine in my
Q. Is there a downside to castor oil other than the surface stains on the metal?
While the stain on metal surfaces can be tough to remove, it can be by
cooking engine parts overnight in anti-freeze. Parts with a cosmetic
polishing will need to be polished once again. Moreover, th castor will
over time gum some components, which can be a little troublesome at the
start of the next flying season after an engine has been stored for the
winter. I lubricate my engines before putting them away (Marvel Mystery
Oils works well to ameliorate the issue). However, if you didn't run the
engine dry and lubricate before putting it away you may discover the
carburetor's throttle valve won't turn in the carb-body next spring
because it's gummed up by the residual castor oil.
Q. Why does fuel with full-synthetic oil exist?
It's because a lot of modelers don't like the staining and gumming
castor oil does to metal parts. This is why manufacturer's responded by
offering a full synthetic. As long as the engine never runs so lean the
oil in the fuel begins flashing off (burning) there's no downside to a
full-synthetic and the upside is the engine stays spotless inside and
Why does helicopter fuel have higher oil content than model airplane
fuel and will it hurt anything to run model airplane fuel in helicopter
engines and vice-versa?
Helicopter fuel often has 23% oil content and model airplane fuel may
be as high as 20% but as low as 20%. However, fine differences, e.g. 17%
vs. 18% oil content doesn't mean squat in the real world. Remember, the
oil in the fuel doesn't burn (or isn't supposed to). However, it will
burn during a lean run when it's no longer lubricating but instead is
burning up - just like the alcohol in the fuel. This is bad, very bad
because then it's not doing its job of lubricating and cooling the
metal. However, in and of itself, lower oil content won't hurt a thing -
except - if you run the engine too lean. This is when you face a
greater likelihood of ruining the engine. As for significantly lower oil
content, e.g. 17% vs. 23% . . . not 17% vs. 18% which is really a
rather inconsequential difference in the real world is usually a matter
of the intent of the fuel. Higher oil content is usually found in fuel
expressly for model helicopters because manufacturer's opt for thinner
oil and increased nitro to make more power.
However, usually, the
reason why some fuel has 23% versus 17%, in some cases is because it's
the manufacturer's choice of oil itself. For example, a popular brand of
fuel is Cool Power. They first popularized the high oil content fuel
for helicopters. In their case, they were using a thinner oil and made
up for the difference in lubrication qualities (versus thicker oil) by
just using more of it. This, of course, resulted in a power loss so they
made up for it by adding more nitro. Power loss? Yes because what burns
to make power is the alcohol, not the oil. Remember, the oil is part of
a total loss oil system. It just flows through the engine whilst
lubricating and cooling the parts . . . but the oil really doesn't burn.
Anyway, this is where using 30% nitro first became popular.
Q. What happens with adding nitro to make more power?
Basically, the more oil in the fuel the less power it can make because
you've reduced the alcohol content. Alcohol is what actually combusts
(what burns) to make the explosion within the combustion chamber to
drive the piston on the power stroke. Oil is added to lubricate and
cool. More oil lubricates better but you have to recover the power
somehow. The 'somehow' is the added nitro, which bonds with oxygen
molecules in the air and this is what allows more fuel to burn within
the combustion chamber. After all, alcohol won't burn without oxygen,
remember? Added nitro results in more oxygen in the liquid fuel and this
added oxygen allows a richer mixture, which means more alcohol to make
more power to compensate for the added oil (as a percentage) and thus,
make more power. Think of the nitro as chemical supercharging, which
lets you run the engine richer yet still burn the alcohol completely
thus making more power.
Q. What's too little oil?
As a practical matter, I have run engines with as little as 12% oil
content. However, while this gives you almost no margin for error, the
engine will run happily enough 'and' make great power. Why? It's because
there's more alcohol burning within the combustion chamber (instead of
oil flowing through for cooling purposes). But there's really no margin
whatsoever for a mistake in fuel mixture. Understand?
Q. I've seen fuel marked FAI in model shops and been told it has no nitro at all. Why is this?
FAI fuel is 80/20, or 80% alcohol and 20% oil. This came about because
in the rest of the world nitro is very, very expensive. With a slight
modification to the engine ( higher compression ratio) they run just
fine on no-nitro fuel. However, just a little bit of nitro makes engines
easier to start and handle because they idle better. This is what nitro
really does for model airplane engine.
Q. What about using FAI, or low nitro fuel in model helicopters?
European engines are generally manufactured for no-nitro operation.
American and Oriental sourced engines are designed with lower
compression ratios for using nitro in the fuel. Personally, I have flown
many, many model helicopter flights with 5% nitro fuel (with Japanese
engines). Why? it's because I don't give a darn about 3D-flight which
needs as much horsepower as you can throw at the rotor blades.
Basically, this means I never need the ultimate in horsepower making
ability from my engine because my flying style is principally big air
maneuvers (with lots of slow hovering maneuvers thrown in to replicate
scale like flight). This flying style simply doesn't need as much
horsepower as the power sapping maneuvers like a rainbow or tick-tock
that constitute what's called 3D.
to which, I'm an old hot rodder and thus, when I feel the need for more
horsepower I prefer to install a bigger engine. In normal operation I
don't pay any penalty because I can throttle back but when there's a
need for more power, there's really no substitute for cubic inches. This
is why I simply opt for a much bigger engine in many of my models for
when I want more horsepower. Basically, a big engine loafing is - in my
opinion - better than a small one screaming its guts out to make
Q. You seem to prefer fuel with castor oil included, why is this?
Yes, I do prefer my fuel with a little bit of castor oil in it. This,
in part for the insurance value despite my being very experienced.
Basically, I accept it will stain my engine and muffler and gum up the
insides and the carburetor over time. Why? Simply because I especially
LOVE how it smells when I catch a whiff of exhaust. For me it's an
essential part of the modeling experience.