RC Gas Engines

What is better, RC gas engines or a nitro engines?

People new to this hobby often refer to glow powered engines as gas engines, I know I used to.

However, there is a big difference between actual gasoline powered engines and glow engines used in our hobby.

While nitro or glow powered engines are the best choice for smaller size airplanes, gas engines are the best choice for heavy giant scale RC airplanes.

Gasoline vs. Nitro

Which is better, a gas engine or a nitro engine?

This depends on the size of your airplane! For giant scale airplanes, gas engines are definitely better. For smaller airplanes around 10 lbs or less, nitro engines are the best and sometimes the only choice.

It takes a slightly larger gas engine to produce the same amount of power as a nitro powered engine. This is because the methanol/air mixture produces more energy than gasoline/air mixture during combustion.

A gasoline engine requires an on-board ignition system which adds to the weight even more. This is why gasoline engines are not practical with small airplanes. In fact, gas engines are only available from around 1.2 size and larger.

Ignition System

Gas engines use spark plugs where as nitro engines use glow plugs to ignite the fuel/air mixture. For this reason RC gas engines require on-board ignition systems which provide electricity to the glow plug at precisely the correct time.

Magnetos

There are two types of electronic ignition systems used with gas engines. The first type is a magneto. A magneto uses magnets attached to the rotating engine to create electrical pulses for the spark plug at precisely the right time. This eliminates the need for an on board battery.

Your weed-wacker or push mower uses a magneto to fire the spark plug. Magnetos are very reliable but add weight to the engine.

Since the magneto doesn’t produce electric for the spark plug unless the engine is turning, an engine with a magneto ignition system must be started with an electric starter just as a nitro engine does.

Electronic Ignition

Most RC gas engines available today use an electronic ignition system. This system uses a separate battery to provide electricity to the spark plug. This allows the engine to be hand started.

The timing of the spark is critical for maximizing the power from any engine. As the speed of the engine changes, the precise time that the spark plug should fire for optimal performance (in relation to the piston’s position) changes. An electronic ignition system accounts for this and adjusts the timing depending on the engine’s RPM’s.

A magneto engine is set for optimal performance at top speed only where as an electronic ignition engine adjusts for optimal performance at all speeds. An engine with an electronic ignition system will generally idle better and start easier than magneto engines.

Fuel Consumption

A gas engine consumes close to half as much fuel as a nitro powered engine. Combine that with the fact that nitro fuel costs roughly three times more per gallon than gasoline and you can quickly see why most large scale airplanes are gas powered RC airplanes!

RC gas engines have built-in fuel pumps. For this reason, it is not necessary to hook a vent line to the exhaust as is required for a nitro engine. With an RC gas engine you have the freedom to move the fuel tank anywhere you want within the fuselage.

The same fuel tanks designed for nitro engines can be used. However, the fuel lines must be designed specifically for gasoline. Nitro tubing will dissolve when exposed to gasoline.

A nitro engine utilizes methane in the fuel as a coolant. When the fuel is pulled into the carburetor, the methanol vaporizes. It requires a significant amount of energy to vaporize the methanol. This energy comes from pulling heat from the engine. This is why gasoline engines require more air across the cooling fins than nitro engines. This requires larger openings on the cowling of gas engines.

Radio Interference

Gas engine ignition systems are known for causing radio interference. As a general rule, the ignition system should be around 12 inches away from the receiver. Metal pushrods should not be used for the throttle.

A common source of interference from gassers is the use of a non-resistor type spark plug. When the electric arcs across the gap of a spark plug, an electromagnetic field is produced that can interfere with radio signals. A resistor type plug such as a BOSCH WSR6F(found at your local auto store) will greatly reduce this interference.

If special care is taken, radio interference can usually be avoided. If you have a spread spectrum radio system, interference should not be an issue. However, it is important to know that RC gas engines are very prone to cause radio interference with 72MHz radio systems.

Pros and Cons of Gas Engines

Pros

The biggest advantage of an RC gas engine is that fuel consumption is much cheaper when flying gas powered RC airplanes.

Gas engines do not make an oily mess on your airplane.

Gassers are easier to tune, and there are no glow plugs to deal with.

Gas engines are generally more reliable than nitro engines.

Gas engines have built in fuel pumps.

Cons

Gas powered RC airplanes are more prone to radio interference.

Lower power/weight ratio than nitro engines.

Two are batteries needed for the airplane (one for electronic ignition, one for receiver).
RC gas engines require more cooling than nitro engines.

Check eBay

Before making any purchases I'd suggest taking a look at what's on eBay. Many times you can be in the right place and the right time and get that unrealistic winning bid that almost makes you feel sorry for the seller!

If you don't have an eBay account just take two seconds to register by clicking the banner below.