Nitro Powered RC Cars

Nitro RC cars are named for the special type of fuel that gives them and their motors such kick. Though not the best choice for beginners, they are the choice if speed and power are what you want from your RC. The great popularity of nitro RC cars and trucks is due not only to their speed, but is also because of the realism they offer—sights (smoke), sounds (tuned pipe) and smells (exhaust) just like the real thing! Over the last several years, the quality of nitro RC’s has been greatly improved, making them safer and more reliable than in the past.

There are four defining features of a nitro RC car:
• special nitro fuel
• high horsepower nitro engine
• tuned exhaust pipe
• Realistic, replaceable air filter.

Two different power sources are required for a nitro RC car, starting with battery packs for the transmitter and receiver. The car itself, as the name suggests, really does use a nitro methane fuel, much like a real top fuel drag car uses. There are two kinds of nitro motors: the 2-stroke and the 4 stroke engine. The more popular 2-stroke engine is similar to the kind of engine found inside motocross motorcycles, chain saws and weed whackers. This type of engine has no separate oil reservoirs, so the oil that lubricates it is included in the fuel mixture. Conversely, the less popular 4-stroke engine does have an oil reservoir and therefore depends less on a gasoline/oil fuel mixture for lubrication. When running or racing, the car’s fuel tank will need refilling every 5 to 10 minutes

Nitro Engines: 2-Stroke
The 2-stroke is the engine most commonly found in nitro RC’s. “Stroke� is meant by the number of times the piston travels through the engine sleeve in the combustion chamber. 2-stroke engines produce power in one cycle, which is divided into the two “strokes.� The piston has two positions: top center where the cycle begins and ends, and bottom center, which is the middle point of the power cycle. Combustion causes increased pressure in the chamber and forces the piston down. As this occurs, the exhaust ports are opened so gases can escape through the manifold. The second stroke begins when the piston reaches bottom center and the case and then moves back up the engine sleeve. This causes the pressure to build up again as the piston approaches TDC once again, completing the power cycle. The next stroke occurs as soon as combustion from the glow plug sparks it again.

Nitro Engines: 4-Stroke
Less common but more powerful, 4-stroke engines are more like what you’ll find under the hood of your real car or your lawnmower. Though similar to a 2- stroke, a 4-stroke engine has 2 full cycles with 2 strokes of the piston each (for a total of 4 strokes). Unlike the simpler glow-plug ignition that a 2-stroke uses, a 4-stroke regulates the air and fuel in the chamber with a geared cam mechanism. Intake timing is how much and when this air/fuel mixture enters the cylinder, while exhaust timing refers to the escape of hot gas from the cylinder. The easiest way to understand what happens in the 4-stroke power cycle is imagine the 2-stroke cycle simply stretched out to get the most out of each segment of the piston’s movement. The piston begins at TDC and as it travels down the cylinder the geared cam allows fuel and air into the combustion chamber.

The intake valve closes when the piston reaches the bottom of the cylinder, which is then forced back up by the flywheel and drive train components. This compresses the air and fuel, and the pressure causes combustion as the piston reaches the top of the cylinder again, completing what is referred to as the compression stroke.

As the fuel mixture ignites it initiate the so-called combustion-stroke, during which the piston travels back down the cylinder and up again. In the final “power� stroke the gases are forced out to the exhaust systems—just as in the 2- stroke engine. The cycle is then repeated.

4-stroke engines rely on intake and exhaust valves to complete their power cycle. This is combined with a number of other features—a moving shaft, several valve-train components, camshaft, rod and pistons and the geared cam mechanism—to make a more powerful, but more advanced engine. The improved management of fuel and air flow in and out of the engine makes the 4- stroke more efficient, though their advanced mechanisms mean they require meticulous attention and maintenance.

You’ll need a starter for the engine, of which there are two types:
• a pull-start nitro engine (these use a process like your lawnmower to start)
• Or a non-pull nitro engine (these fire up with a starter box).
The pull start nitro engines cost a little more, but you don't have to buy a starter box and it's less you have to carry around to run your vehicle. Just take it out, pull on the starter, and you're ready to go! Be sure to check your instructions to choose a starter that’s right for your car.

To keep your nitro RC running at its best, constant maintenance is necessary. This includes keeping the engine clean and well-tuned, setting it up correctly and using good clean fuel. As well, if you’re running your RC off-road, you’ll need to make certain it is properly cleaned after you run it, otherwise dirt and grit can slow down or even ruin your engine. Any special procedures particular to your car will be outlined in your owner’s manual. Remember that your engine will only run as well as you treat it—so take great care of it, and you’ll never have trouble on race day.

Fuelling Your Nitro RC Car
Nitro RC cars run on a blended fuel easily available at local hobby shops or online. It is made up of a blend of methyl alcohol (methanol), nitro-methane (nitro), and oil. In order to understand how nitro fuel work, you need to know what each of these three components does for the car:
• Methanol provides the main power to the engine and is the main ingredient in fuel. It has an ignition point that allows it to be ignited with the kinds of platinum-element glow plugs used in RC engines, and it releases more energy per pound of air than gasoline. Because it’s easy to get, it’s not expensive—you’ll find fuel much more reasonably priced than regular gas.
• Nitro-methane is added to assist the idle and acceleration and to enhance power output. Nitro is referred to as a “hot fuel,� and is only used in small amounts in fuels. It can be e if not handled correctly, so take care to read the fuel tips offered here, and always follow the manufacturer’s instructions when filling up your RC.
• Oil is need as a source of lubricant for all the moving parts in the engine. Here 2-stroke and 4-stroke engines will require different fuels, since 2- stroke engines have no separate oil reservoir, and need oil mixed in with their fuel. There are two types of oil found in fuels- castor oil and synthetic oil. These can be used by themselves or in a blend, with synthetics being far more common these days. This is mainly because synthetics are cheaper and less gummy than castor oil, which used to be the only oil used. For some engines, a blend with a large percentage of castor oil may work best, since it is actually a better lubricant at higher temperatures. The synthetics are far less messy, however, and leave less gum on your engine. You’ll be able to choose from blends of synthetic and castor oil that vary in their percentages- try out a few to find one that runs your engine best.

RC fuel blends are expressed in percentages based on the amount of each component ingredient used, and of course the one right for you will depend greatly on your car and engine. Most fuels contain mainly methanol, to which about 20-22% oil and 10-15% nitro is added. Be sure to check your owner’s manual for suggestions and guidelines about which blend is correct. Bear in mind that you may have to try out a couple of different types and blends before you find the one that’s right for the way your engine is tuned. And if your engine isn’t running properly, one of the first things you should do is change the fuel. Taking proper care of your nitro car’s fuel is extremely important. Not only will it help your car run better and make for less wear on the engine, fuels are flammable and could be dangerous if not properly stored.
• Nitro fuel should not be stored in unsealed containers. Because methanol mixes easily with water, the container you store it in should be completely air tight. Otherwise, air could get in and evaporation or condensation could occur, ruining the fuel. It will cause your engine to run too hot and be quite damaging to your car’s fuel and exhaust systems.
• Store your fuel at room temperature, and at a constant temperature. Again, you want to avoid any air in your container or in the fuel, which temperature swings can cause to condense. Do not store your fuel in a room that varies widely from hot to cold or vice versa.
• Keep fuel away from light. Nitro methane degrades in light, which means you need to store your model fuel in a cool, dark place. If you leave it exposed to sunlight or store it in a brightly lit place, the nitro will degrade completely, as though it hadn’t even been added to the fuel in the first place. This will cause your engine to run very poorly, or cause poor starts or stalling.
• Do not store fuel more than a year. In addition to following all these steps, you must also replace your fuel frequently. Though proper storage will keep your fuel fresh and running clean, it cannot be stored for years and years. Most manufacturers offer some guarantees on their fuel, but these will not apply if you have stored it for an extended period of time. Most importantly, old fuel can be dangerous, so don’t leave it stored indefinitely.

Nitro Maintenance and Tuning So now that you know what’s under the hood of your RC, there are few more tips that will help your car run better:

! Improve your acceleration by proper preparation of your clutch. Over time, a glaze can form on the clutch and the clutch bell, which causes the car’s acceleration to noticeably decrease. Scuffing both the clutch shoes and the clutch bell with fine-grit sandpaper or steel wool and a good cleaning with motor-spray will remove this glaze, and prevent the clutch from slipping against the clutch bell.

! Extend the life of your car’s differential by breaking your motor in gently. Your car’s differential filled with small, complicated gears that make them both complicated and expensive. This is not a part you want to replace frequently, but carefully breaking in your car before racing or running it full out can greatly extend the differential’s lifespan. To break in your engine, run it at ¼ power a few inches off the ground, and then run some slow, steadily powered figure-8’s. This should set the gears in the differential and you can run it full out without damaging the engine. Make sure you keep your header in position.

Your car’s header is attached with a tiny spring, meaning it comes off very easily if you hit something or if your car gets hit by something. If you’re racing, this can be a huge problem to put back on in a hurry, so be sure to attach your header to the engine block more firmly using a small piece of safety wire. Make sure you twist the wire firmly around the header and be sure to cut off any excess.

! Brace your air filter to prevent losing or damaging it. The small piece of the same safety wire that secures your header should also be used brace your filter. Again, twist it tightly to prevent the filter from becoming loose and remove any excess.

! Protect your pull-start cord from fraying and breaking. Over time, the cord of a pull-start engine can often become worn and frayed. This can be prevented by covering the edges of the opening- try duct tape or cutting up a small section of fuel tubing. Make sure not to obstruct the opening, but rather create a smoother edge to the opening for the cord get in and out of with out fraying. Never leave your pull start cord pulled all the way out- if this happens, it could get stiff or be impossible to reinsert

! Follow your manufacturer’s instructions for the best results. Your car will come with complete instructions and owner’s manual, which you should read carefully for all specifications and any technical issues you have with your RC. Should you run into something you can’t fix or an engine that simply won’t run properly (or at all!), it’s best to consult your local hobby shop for some expert advice and help.

There’s nothing like the realistic roar and smoke of a nitro RC, which are fast powerful enough to make for some exciting races. Bear in mind however, that nitro cars and the engines that power them are very complex, and as such require frequent tuning and meticulous care—much more so than an electric RC. Because of greater complexity, you will also find they tend to be more expensive, as well. What this means to you as a driver is that you need to decide in advance what your budget is and just how experienced you are with engines and RC racing.

If you’re beginner but you still have your heart set on a nitro car, they can be purchased in ready to run versions that will get you in the race as soon as you open the box. Although these still require the same ongoing attention and maintenance, you will be saved the initial trouble of building the car from scratch.

Ready to run nitro cars and trucks are more expensive than the ones you build yourself, but they’re far easier if you’re still unsure about your mechanic ability. Also, since even ready to run kits contain complete instructions on how they go together, you can rest assured you’ll be able repair, maintain and add on to your car for a long time to come.

The main attraction of nitro RC cars is their realism and their power—they’re fast, they roar and they smoke—just like real cars! They can be tuned to reach speeds up to 60 mph and they can race as long as you keep filling the gas tank. Though not recommended for complete newcomers to RC racing, nitro RC’s are by far the most popular.

Next: Build Your Own RC Car