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Introduction to Nitro RC EnginesArm yourself with information before spending your money! Nitro RC engines are the most popular type of RC engines. It is common for people to refer to all types of RC engines as “Gas” engines. However, the vast majority and most popular type of RC engines burn nitro-methane fuel. This airplane fuel is commonly referred to as “glow” fuel because the engines use glow plugs to ignite the fuel. You can learn more about the different types of glow fuel here. Nitro RC engines are sometimes referred to as “glow” engines for the same reason. Table of ContentsBelow is a summary of just about every aspect of RC nitro engines. Consider this page Glow Engines 101. Take your time and read through this page and you will have the knowledge to make the right decision when purchasing your first glow engine.
Two Stroke vs. Four StrokesThere are two types of nitro RC engines used with radio controlled airplanes. There are two cycle (2-stoke) and four cycle (4-stroke) nitro RC engines. A 2-stroke RC engine fires every time the piston reaches the top of the cylinder. A 4-stroke fires every other time. Because the 2-stroke fires every revolution it has a high pitched whining sound when running. Two-cycle engines are cheaper and require less maintenance because there are fewer moving parts. The design of a 2-stroke engine is very simple as camshafts and rocker arms are not needed to open and close the valves. Two-stroke RC engines have a higher power to weight ratio than 4-stroke engines. Most beginners start with a 2-stroke engines because they are cheaper, easier to maintain, and easier to tune.
Four-stroke nitro RC engines produce more torque at lower RPM’s compared to a two-stroke RC engine. This means that four stroke will use a much larger diameter propeller than a two-stroke engine. Ball Bearings vs. Bushings Some nitro RC engines are available with ball bearings supporting the crankshaft. Others have bushings that support the crankshaft. The picture to the right is what the bearings look like. There are two sets of bearings. One set in the front and a larger set in the back.I've never had a bushed engine and don't have a picture to show you. A bushing is nothing more than a bronze or brass disc the with a hole in the center for the shaft.  It is easy to tell if a nitro RC engine has bearings or not just by looking at it. Take a look at this O.S. 46AX engine to the left. The area highlighted red is where the bearings sit in the housing.  If you look at this O.S. 46LA engine to the right you can see that the housing does not have these places for the bearings. Ringed vs. ABC Nitro RC Engines There are two different ways that nitro RC engine manufactures seal the piston with the sleeve. It is critical that the piston and sleeve form an airtight seal in order for the engine to produce compression. Some RC engines simply have a ring that goes around the top of the piston that seals with the iron sleeve. This is called a “ringed” engine. The picture to the right is cross sectional view of the piston/sleeve assembly of a ringed engine. It is greatly exaggerated in order to illustrate how a ringed piston seals with the sleeve. The portion in red is the ring.  Some nitro RC engines have an aluminum piston that moves in a tapered chrome plated brass sleeve. This type of engine is called an ABC engine for Aluminum, Brass, and Chrome. The picture to the left is exaggerated to illustrate what the piston/sleeve assembly looks like at ambient temperature. At ambient temperature the inside diameter of the sleeve is slightly smaller at the top of the stroke. The fit between the piston and sleeve gets tighter as the piston rises. When the engine gets to operating temperature the top of the sleeve expands and the sleeve is no longer tapered. The reason the top of the piston expands is because it sees all of the heat from the combustion.The bottom of the sleeve is much cooler and does not expand nearly as much. When the top of the sleeve expands the piston will fit perfectly with the sleeve at both the top and bottom of the sleeve. When the engine is cold the sleeve only seals with the piston when the piston is near the top of the stroke. This can make ABC engines a little more difficult to start, especially in cold whether. ABC engines are more tolerant if you accidentally run the engine slightly too lean.  The repair cost for a ringed nitro RC engine is much less that that of an ABC engine. The ring itself is usually the only thing that fails in a ringed engine, provided that you run the engine with the correct fuel mixture. The rings are very easy to replace and are inexpensive. The cost for replacing the ring is typically under $20. To rebuild an ABC cylinder you will need to buy a new sleeve and new piston. As with anything, the sum of the individual parts of an engine cost a lot more than the whole. It is usually not economical to rebuild an ABC engine.The benefit of an ABC engine is that the break-in time is a lot shorter. An ABC engine will tolerate the occasional lean run, as where a ringed engine will be damaged immediately with a lean run. The benefit of a ringed engine is that it can be rebuilt relatively cheap. A ringed engine will tend to hold its maximum power longer than an ABC engine which slowly decreases in power as the sleeve and piston wear. If you’re new to the hobby I recommend getting an ABC engine. It is much more forgiving and easier to break in. It’s worth noting that just about all four-stroke engines are ringed engines. Nitro RC Engine Sizes When you buy a nitro RC airplane it will always have a number associated with it that gives you an idea of what size engine it will need.For example, the Hangar 9 Arrow 40 would require at least a “40 size” nitro RC engine. The size of the engine corresponds to the displacement of the cylinder.  The Evolution .40NT would be a good fit for the Hanger 9 Arrow 40 nitro RC airplane. An engine slightly larger than the number on the airplane will certainly give the airplane a little more spunk! However, you should never exceed the maximum recommended engine size for any airplane. The maximum recommended size is usually slightly larger than the size of the airplane. For example, the Hanger9 Alpha 40 could be flown safely with a "46 size" engine. Since a four-stroke RC engine has a lower power to weight ratio you will always need a slightly larger 4-stroke engine then the actual size of the airplane. A 40 size airplane may require a 60 size four-stroke engine. Go by the recommendations of the airplane manufacturer when sizing the engine. Where to Buy Nitro RC EnginesRed Rocket:Now you are armed with the information needed to make an educated purchase when buying a nitro RC engine. Red Rocket Hobby Shop offers Evolution 2-stroke engines as well as 4-stroke Saito Engines. Saito Engines are top-of-the-line as far as 4-strokes go. Evolution Engines offer a great Trainer Power System for beginner pilots. Red Rocket is a reputable, secure online store. Their customer service is great because the owner is "Hooked on RC Airplanes" just like the rest of us! With Red Rocket's Price Matching Policy you never have to wonder if your getting the best price. Ebay: Ebay is also an excellent place for buying nitro RC engines. Many times you can get engines for a fraction of the retail price. Make sure to click the "view all" link in the yellow box at the bottom to show all of the engines available. Many times you have to dig deep to get the best deal. Make sure that you take the price of shipping into consideration before making a purchase. It is always best to buy NIB if possible, meaning new in box. You can get some killer deals by buying used, but you can also get ripped off if you're not careful. If you see a used item that truly looks like a great deal, then check the seller's feedback at the top left of the screen after you click the item. If the seller's feed back is near %100 then they have a good reputation and you can probably trust them. Don't have an eBay account? No problem! It's completely free to sign up. Click the link below to set up your account and start bidding on these engines in a matter of seconds! Sizing the PropellerSizing the propeller for your airplane is just as important as choosing the correct size engine. The propeller is what converts the power that is produced by the engine into thrust that is needed to fly the airplane. With a vehicle, the transmission converts the engine power into torque that turn the wheels to propel the car forward. With an airplane the propeller is the transmission.The transmission of a car gives the driver a range of gears to choose from depending on whether he wants speed or torque. If the driver is taking off from a stoplight he starts with first gear because more torque is needed to get the car moving. As the speed increases, the car gains momentum and needs less torque to continue at the current speed. Each time the driver shifts to a higher gear the transmission produces more speed and less torque for a given engine RPM.
Sizing a propeller is exactly the same as choosing the right gear when driving your car. With a model airplane you can only "change gears" in between flights by changing the propeller. This means you must find a happy medium between speed and thrust when choosing the propeller. Just like a gear, a propeller sized for very high speed will not be very good for taking off. A propeller sized for extreme thrust for “unlimited” vertical climb would not be able to pull the airplane through the air very fast. So it is a trial and error process to find the propeller that is just right for you and your airplane! Follow for more information on how to choose the right propeller. Spinners The spinner is the nose cone of the airplane. The spinner increases the efficiency of the propeller. The base of the propeller blades are very blunt and do not push any air. The spinner diverts air around this portion of the blades to the portion of the blades that actually moves the air. Full-scale airplanes have spinners for this reason.
Spinners also provide a place for the electric starter to grip when turning the engine over. If you live in the United States you should know that the AMA requires that every nitro-powered airplane have either a spinner or AMA safety nut such as the one to the left. Engine InstallationAfter much research you have finally purchased the perfect RC engine for your new airplane. Installing the engine is one of the most exiting parts of putting an airplane together.This is one of the last steps before you can enjoy all of the hard work and time you’ve spent getting your bird ready for the sky! Please don’t rush the engine installation. Installing the engine is not difficult, but it is very important that everything is done properly. The alignment of the engine is critical. If the engine is installed crooked, the thrust from the engine will be applied crooked! This could leak to some awful flight characteristics and in extreme cases could make the airplane completely uncontrollable. If you take your time and follow the directions to a “T” you and make sure everything is good and tight you will have nothing to worry about. Installing the RC engine entails more than just bolting the engine to the firewall. The fuel tank must be installed with the fuel lines ran correctly from the engine’s carburetor and exhaust to the correct ports in the fuel tank. It is necessary to connect the control linkage from the throttle servo horn to the carburetor arm in a way that it is not in binding and is the correct length. If your airplane has an engine cowling it will be necessary to mount the engine sideways or inverted. You will also have to trim the cowling to fit your engine. The cowling must be positioned properly to prevent the engine’s back plate from rubbing it. It also may be necessary to install an exhaust deflector to route the exhaust out of the cowling. For a more in depth look at installing RC engines, fuel tanks, and control linkages feel free to take a look here. Accessories Needed for Nitro RC EnginesTo start your nitro RC engine you must have some means of spinning the propeller. You can either use a chicken stick or an electric starter to flip the propeller. But never ever use your fingers unless you are wearing thick leather gloves. These engines won’t hesitate to put a gash in your fingers! Trust me I know! If the carburetor settings are off you may be flipping that prop with a chicken stick until the end of time before it fires! Everyone has days when their engines just won’t cooperate even with a 12-volt starter. An Electric starter really is a necessity when flying glow-powered airplanes. Save yourself the headache and go ahead and order one ... You will thank me later! Secondly, you will need a way to provide power to the glow plug. You can use either a glow igniter or a glow plug clip. Both an electric starter and a glow plug clip requires a 12-volt battery. Most people buy a flight box which houses the 12-volt battery and power panel. The power panel clips to the 12-volt battery and supplies power to the starter, fuel pump, and glow igniter. If you stay with the hobby you will definitely have a flight box like everyone else. When I started flying my goal was to get an airplane in the air with the least amount of money possible. It was hard enough convincing my wife to let me buy the airplane, radio, and engine! So I got by for a little while with a glow stick, electric starter, and a hand fuel pump. I had an old 12-volt car battery that I used to power the starter. This was not exactly an optimal set up, but it got me by until I could save money to buy a flight box, power panel, and a 12-volt battery! Operation & Maintenance of Nitro RC EnginesA nitro RC engine will last you a lifetime if properly operated and maintained. On the same toke, the engine could last a very short time if not cared for properly. The life span of your engine is in your hands.Some engines such as the Evolution Engines Trainer Power System are broken in at the factory. Regardless of what type of nitro-powered engine you have, it is absolutely critical that it be broken in properly. This is the first step that will determine how long your engine lasts! For more information on how to break in your engine click here. The most important thing to know about nitro RC engines is that they are cooled and lubricated by the fuel. You, the operator, determine how much fuel is going to the engine by adjusting the needles valves. If the needles valves are adjusted too “lean” it means that not enough cooling and lubrication is getting to the engine. The quickest way to destroy an engine is to run it lean! If the needles valves are adjusted too “rich” it means that too much fuel is going to the engine. When the mixture is rich the engine may not run at all, or it will with a lot less power than its capable off. The mixture should always be slightly rich to be completely sure it doesn’t lean out while in the air. Finding that sweet spot that is not too lean and not to rich is called tuning your engine. Follow for more information on how to tune your engine. If you will not be using the engine for an extended period of time (over a month), it is a good idea to run some after run oil through your engine. This will prevent the inside of the engine from developing rust. Hooked on RC Airplanes Home Page
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