Basics of RC Engines: Nitro Glow, Gas, Two-Stroke and Four-Stroke
RC models with engines use two families. Glow engines (called nitro in cars) burn a methanol fuel with nitromethane and oil, ignited by a glowing platinum coil in the glow plug; they’re small, rev high and power most engine cars, plus smaller planes and helicopters. Gasoline engines use petrol mixed with oil and a spark plug with electronic ignition; they’re used in larger planes, 1/5 cars and boats. Both come as two-strokes (simpler, more power for their weight) and, mainly in planes, four-strokes (more scale sound, less fuel).
By Kyle HilsonUpdated: October 20264 min read
Engine types compared
| Glow / nitro | Gasoline | |
|---|---|---|
| Ignition | Glow plug (heated to start) | Spark plug, electronic ignition |
| Fuel | Methanol + nitromethane + oil | Petrol + 2-stroke oil |
| Typical sizes | .12–.28 cu in (cars), .40–1.20 (planes) | 20–100+ cc |
| Running cost | Higher (special fuel) | Lower |
| Used in | 1/10 and 1/8 cars, planes, helis | 1/5 cars, large planes, boats |
| Cleanliness | Oily residue | Cleaner, less residue |
Engine sizes in cubic inches convert as .21 cu in ≈ 3.5 cc. What’s in nitro fuel is covered in what nitro fuel is.
How a two-stroke works
A two-stroke fires on every turn of the crankshaft. As the piston rises it compresses the fuel-air mix above and sucks fresh mixture into the crankcase below; at the top, the mix ignites and drives the piston down, which opens the exhaust port and then the transfer port, pushing fresh mixture into the cylinder. The oil in the fuel lubricates the engine as it passes through. Four-strokes have valves and fire every second turn, which gives a deeper sound and better fuel economy but more parts.
How glow ignition works
To start, a glow igniter heats the platinum coil in the plug. Once running, the heat of combustion keeps the coil glowing, so the igniter is removed. The nitromethane content (typically 10–30%) makes the engine easier to tune and gives more power, and the oil content (often 8–20%) protects it.
Needles and tuning
- High-speed needle: fuel mixture at full throttle.
- Low-speed needle: mixture at idle and part throttle.
- Idle screw: how far the carb stays open at idle.
Turning a needle in (clockwise) leans the mix: more speed and heat. Out richens it: more smoke, cooler, safer. A too-lean engine overheats and can seize. Step-by-step in how to tune a nitro RC car engine.
Break-in
New glow engines with an ABC (aluminium–brass–chrome) piston and sleeve are tight at the top of the stroke and need a gentle break-in: several tanks run rich, with cooling-off between them, before leaning out. Follow the manufacturer’s method; many modern engines need less break-in than older ones.
Maintenance
- Clean or oil the air filter often; dust destroys engines quickly.
- Run the tank dry and use after-run oil after each session (glow).
- Check and replace glow plugs or spark plugs when starting gets hard.
- Replace hardened or cracked fuel lines.
- Check the exhaust and engine mount screws for tightness.
Cleaning a nitro car is covered in how to clean a nitro RC car.
Engine or electric?
Electric brushless power is now simpler, quieter and often faster, which is why most new RC models are electric. Engines remain popular for their sound, quick refuelling and the mechanical side of the hobby: if you enjoy tinkering, an engine model is rewarding. Check local noise rules before choosing one; many parks and some clubs limit engine models.
FAQ
What is the difference between nitro and gas RC engines?
Nitro uses glow fuel and a glow plug; gas uses petrol and a spark plug.
Can I use petrol in a nitro engine?
No. Glow engines need glow fuel.
Are four-strokes better?
For scale sound and economy in planes; two-strokes are simpler and lighter.
How long does an RC engine last?
Many litres of fuel with clean air and after-run care.
More on this topic: the complete RC Cars guide covers the basics behind this article.
About 20 years in RC. Mostly boats in the NAVIGA Mini Eco Expert class, with many self-made parts; also a King Motor Baja 5B, a home-built electric plane, home-built nitro planes he has flown, and an RC helicopter. More about SwellRC
