Nitro Engine Basics
Nitro engines run on a highly combustible mixture of methanol, nitro methane
and castor or synthetic oil. Rather than using spark plugs, such as in typical
4-cycle engines, these engines use a method of combustion similar to diesel engines
(granted diesels are generally 4-stroke).
Using electrical current and a glow plug, a hot spot is created in
the combustion chamber. This, in addition to the compression of the moving
creates the combustion cycle. Within seconds, the combustion chamber and glow plug
become extremely hot and maintain subsequent combustion without the need for the
electrical "jump start". This is what is often referred to as
"dieseling". The only thing that breaks this cycle is either lack of
oxygen or fuel (or an un-timely death of the engine).
Fuels are rated by their nitro-methane content, typically 10-40%. The
higher the nitro-methane, the more power to the engine. Typically in 1/10 scale cars
(with .12 engines), 10-20% is plenty sufficient. More than that on these smaller
scale cars will go wasted, since the engines to not efficiently convert use the
extra-potent fuel and the hookup (traction) is usually marginal, at best. They
heavier 1/8 scale and larger cars can see significant increases in usable power by using
these higher (30% and higher) nitro-methane ratings
These engines do not use any auxiliary method of lubrication. Instead, they
use the same method of lubrication found in most other 2-cycle engines. Because of
the physics of 2-cycle engines, the fuel passes both sides of the piston, including the
crankcase. This allows a convenient method of lubrication. By actually
combining the lubricants with the fuel, you can continually coat all the moving parts of
the engine as the fuel makes its way to the combustion chamber. Whatever
lubricants are not absorbed by the metal they come in contact with are either burned in
the combustion chamber or are discharged through the exhaust port. This is why
you will often see these broken down oils seeping from the mufflers or tuned pipes.
It is just the normal process of cycling through the lubricants.
Most nitro-engine manufacturers recommend using a special
"break-in" fuel which contain a higher percentage of lubricants for the first
few dozen tanks or so. This is to insure that the engine has plenty of lubrication
in order to properly break in and maintain a good seal in the combustion chamber.
This is also why we encourage users to tune their engines slightly
rich (see Engine Tuning & Maintenance) so that there is a sufficient supply of these
lubricants to the engine. Although running your engine lean may increase
performance (temporarily anyways), it will be short lived if the engine doesn't have
enough lubricant to maintain proper engine temperatures.
An important and often, overlooked procedure in maintaining your engine is after-run
lubrication. The benefits from this are two-fold. First, as the engine cools
after being run, moisture can build up inside the engine, causing corrosion. The
next time it is run, the engine will typically see some undue wear from the corrosion
buildup. Secondly, the lubrication process often enhances the starting ability by
providing a better piston to cylinder seal. Until the engine has had a chance to
warm up, this seal is often sloppy, and just like the engine in your real car, a majority
of the engine wear happens in the first few seconds before the lubricants in the fuel get
a chance to recoat the engine's working parts. You can find these
"after-run" lubricants in your hobby store. Usually a few drops down the
glow-plug hole or in the carburetor right after you have run your car can significantly
add life to your engine.
I cannot stress enough how important this is. Just like
running your engine rich is important for your engine's life, so is this simple process.
Don't let this one go unchecked.