Nitro engine

A nitro engine generally refers to an engine powered with a fuel that contains some portion (usually between 10% and 40%) of nitromethane mixed with methanol. Nitromethane is a highly combustible substance that is generally only used in very specifically designed engines found in Top Fuel drag racing and miniature internal combustion engines in radio control, control line and free flight model aircraft.

The term "nitro" has only come into use in the last few years to describe these engines, and has its origins in marketing hype in the model car market. For the fifty or so years prior to this term since the engines were first developed, they were simply referred to as "glow engines", but the term "nitro" has more impact in ad copy. These engines are actually fueled by methanol, but the fuel is often doped with nitromethane as a performance additive. The ignition system consists of a glow plug - hence the older term "glow" engine - which has a coil of platinum containing wire alloy, usually platinum-iridium. The glow plug is heated with electric current for starting, after which power is disconnected and the combination of residual heat and catalytic action of the platinum alloy with methanol ignites the fuel mixture.

Nitro engines for models can turn in excess of 50,000 RPM. Typical operating rpm for sport model aircraft engines is 10,000-14,000 rpm. For radio control (RC) boats and ducted fan aircraft engines, 20,000-25,000 is the usual range, and for cars rpm in the range of 25,000-37,000 is common. With this much movement, a lot of frictional heat is generated and the fuel used for these engines usually contains between 12-20% oil content depending on the nitromethane and methanol percentage, the engine type and application. Most engines in RC cars today are 2 stroke engines, which means that it takes 2 strokes of the piston (one revolution) to complete the engine cycle. On the first stroke as the piston travels upward, a mixture of fuel and air is sucked into the crankcase, from the carburetor. When the piston travels downward the new fuel air mixture travels into the induction port and finally into the combustion chamber. As the piston travels upward the mixture is compressed which causes the fuel/air mixture to ignite, producing hot gas under pressure to force the piston down. As the piston travels downward the spent exhaust gases escape out of the combustion chamber through the exhaust port, and the cycle starts over by the fuel mixture being again pushed into the induction port.

...
Wikipedia