Where there's smoke, there's adrenaline

The first time you hear a nitro engine run, it's a little frightening. It comes to to life like an angry badger ready to bite, spouting smoke and heat and singing a song of raw power that just needs to go. Then you grab the transmitter, hit the throttle, and it's all over for you. You're hooked.

We re-visit the question, which is better, electric or nitro? And again, no matter which side of the argument you are on, both have their advantages or drawbacks. As mentioned many times in this article series, which you choose is going to boil down to your personal preference and what places you have available to run your R/C.

Without a doubt, owning a nitro has a steeper learning curve than an electric. You need to learn to safely start and operate the engine, and probably the most frustrating part for most owners, you need to learn to tune it to run consistently. Running a nitro, as you will see, can require a great deal of patience, persistence, and caution.

How Nitro Powered R/C's Work

Nitro-powered radio controlled vehicles require four basic components, some of which are shared with electric powered vehicles:

1. A nitro engine
2. A radio system, composed of a transmitter to send signals to the vehicle and a receiver to receive them
3. A throttle servo to control engine throttle and vehicle braking
4. A servo to control steering

There are many sub-components in nitro vehicles associated with these, so let's take an overview of them all to help you decide if nitro is for you.

Nitro Engines

The Fuel
R/C nitro fuel is not actually a nitro-based fuel at all. It is actually an alcohol-based fuel. 50% - 80% of our nitro fuel, depending on the percentages of the other ingredients, is wood alcohol (methanol) with 12% to 18% synthetic or castor oils, and anywhere from 5% to 40% is a nitromethane additive. For more information on nitro fuel, see the RC-Resources article.

The Mill, the Powerplant, the ENGINE!
The heart of any nitro-powered vehicle is a nitro-powered two-stroke engine. Most nitro-powered vehicle run a .12 or .15 cubic inch engine, and many 1/8 scales run .26-.28 c.i. engines - but this is by no means a standard. At the time of this article, the current largest ground vehicle engine is a .46, standard with the CEN Genesis monster truck.

When selecting an engine size, look closely at the unit of measure used. One manufacturer produces a 2.5 engine. Being the standard is in cubic inches, this indicates something far larger than what we're used to - but the reference is 2.5 cubic centimeters, which is pretty close to .15 cubic inches. For extended information on nitro engines, see the RC-Resources article on nitro engines.

An oil-soaked air filter, usually with a one or two-stage foam element, is found over the air inlet of every nitro engine; the oil helps trap any dust that might otherwise find its way past the filter element. Never, ever ever run your nitro engine without an air filter! The slightest bit of dust will kill any nitro engine.

The Glow Plug
Nitro engines don't use an electrically charged spark plug but a glow plug that has a fine platinum element inside its hollow core. The coil of the glow plug is initially charged to red hot with a glow starter, a special tool that clamps onto the glow plug while it's installed in the engine head, powered by a single rechargeable sub-C cell. Once the engine begins running, a catalytic action between the alcohol fuel and the platinum of the glow plug's coil keeps the coil glowing bright and ready for each rotation of the engine. For more information, see the nitro engines article.

Starting
There are various methods of cranking the engine over to start it. Many engines have a pull-start, a spring-loaded mechanism similar to the pull-start on any lawn and garden equipment. Racing engines, generally without a pull-start mechanism, require a starter box, containing one or two electrical motors inside, powered by a 12 volt gel cell. A rubber wheel driven by the electric motor(s) protrudes through the top of the starter box and turns the engine over by rotating against the flywheel. In the last few years, onboard starting devices have appeared on nitro kit and RTR's. To explore the advantages and disadvantages of each, see the article on nitro engines.

Stopping
There are four ways to stop a nitro engine:

1. Run it until the fuel tank runs dry.
2. Using your shoed toe or a rag (it is hot!) plug the exhaust pipe. Many do not like this method claiming it floods the engine but is the fastest and most accessable method with the body on the vehicle.
3. Using a toe or soft item, such as a screwdriver handle, apply pressure to the engine flywheel from the bottom of the vehicle via the flywheel access hole. A small touch is all that is required; this stalls the engine without flooding it.
4. Pinch the fuel line at the carburetor to starve the engine.

Tuning
As previously mentioned, tuning an engine can be a frustrating experience for a beginner and is beyond the scope of this introductory article, but is mentioned here as one of the things you must consider when deciding whether or not you want to go nitro. Day to day changes in ambient air temperature, humidity, barometric pressure, and other factors demand that you tune your nitro engine every time you run. RC-Resources has many articles listed in its database that describe good tuning methods, ad we've got a decent tuning article here.

The Tuned Pipe
The concept of tuned pipes first appeared in motorcycle racing. Racers found that sawing off portions of their exhaust pipe changed the way their engines ran, enhancing the performance of various parts of the power band. Studies into this phenomena revealed that the pressures created by the actual sound produced by the engine are resonated inside the exhaust pipe and back to the combustion chamber affecting, and often enhancing, engine performance in various areas of the power band.

Finding the right tuned pipe for your engine and conditions is as individual as choosing clothes. Most tuned pipes are fine off-the-shelf, but some specifically enhance lower-end power, others high-speed power. Before buying a particular pipe, locate a suitable message board and ask around for others who have had experience with particular pipes and engines to see if it will work in your situation.

The Engine Clutch
Another interesting feature specific to nitro engines is the engine clutch. A clutchbell, on which is mounted the main pinion gear that drives the spur gear, rides on an extension from the center shaft of the engine. Beneath the clutchbell are two, three, or four clutch shoes that remain retracted at idle speeds. When the engine revs up, the clutch shoes expand with the centrifugal force and engage against the inside of the clutchbell, turning the spur gear and hence applying power to the main drive, usually the transmission.

There are many configurations of the engine clutch, but the main idea is tha they provide a smooth transition between idle and applied throttle.

At the End of a Day
After each run, there are some maintenance procedures you should follow to get the longest life out of your engine, basically driving out all fuel residues and flooding the inside of the engine with a water-displacing oil. A full description of post-run nitro engine maintenence is covered in this article.

Modifying Engines
There are MANY things that can be done to modify a nitro engine to increase performance. The internals can be polished and intake/exhaust ports can be ported and polished to enhance the transport of the fuel to the combustion chamber; the shims between the head and sleeve can be changed in thickness to alter the engine's compression ratio to make use of a higher percentage of fuel; custom cooling heads can be refitted; even fuel changes and different tuned pipes can modify the way and engine runs and reacts in various stages of the power band. Most internal modifications are all or nothing. If you know what you're doing, you can gain alot of power by modding your engine. If you don't, you can turn it into a useless paperweight. Reserve internal engine mods for a time when you have a litte more experience in the hobby, or hand it over to one of the many professional engine modifiers that have demonstrated experience in engine modifying.

Throttle Servo

The throttle control on a nitro R/C vehicle is driven by one "horn" (actuating arm) on a servo connected to linkage which opens and closes the carburetor; when moved past the closed-carburetor position, an actual disk brake is applied that stops the vehicle. An important difference between electric and nitro throttle control is that the throttle servo takes time to move from one position to the next If you are moving along at full speed and hit the brakes, an average servo* may allow the car to continue rolling up to 20 feet before the brake is actually applied to the vehicle. The faster the servo, the faster the reaction time you are going to have between your throttle finger and the brake. When selecting a throttle servo, try to get the fastest servo available.

Radio System

Just as described in electric powered RC vehicles, the receiver accepts the signals from the transmitter and sends steering instructions to the steering servo, but instead of the speed control it sends throttle instructions to the throttle servo. Should the signal be lost while the vehicle is at full throttle, a runaway will occur and it won't stop until the engine blows or it meets with an immovable object, demolishing the vehicle. For this reason, extra precautions must be taken to insure reliable electronics every time you run the vehicle.. See this article for extended details on setting up reliable electronics for a nitro powered vehicle.

The Receiver Pack
Electric powered RC's generally power the servos and receiver from the main 6-cell battery pack that drives the motor. Since this pack is not present in a nitro, they must carry a receiver pack to power on-vehicle electronics, most nitro owners opt for a 5-cell 1100 mah pack in a shrinkwrap-sealed pack, which provides a solid 6 volts to the electrical system.

What You'll Need

In addition to the vehicle itself, a basic checklist for what you will need to own and operate a nitro-powered radio controlled vehicle:

• Reliable electronics. If you opt for a kit as opposed to an RTR, choose the best electronic equipment you can afford, and the fastest servos available.
• Transmitter batteries. Use nicad or nimH rechargeables, and keep them in good shape. Transmitters require 8 AA sized batteries. If the radio system doesn't come with a charger, you'll need a method of charging these too.
• Failsafe. These seldom come standard in a kit or RTR.
• Nitro fuel. 20% nitro content is a good place to start. Airplane fuels are not the "standard," but many owners use it without difficulties. When in doubt, used what's formulated for ground vehicles.
• Fuel Filler Bottle. With a long filler tube extending out of the top of the filler, squeeze the air out of the filler bottle and insert it into the fuel container to draw the fuel out of the container; use this to fill your tank.
• Glow starter and charger. There are many variations of these from sealed "use 'em till they drop" units to units that unscrew with a replaceable and rechargeable battery. Whichever you choose, be sure to get a charger for it as most of these require a plug that is the same shape as a glow plug for charging. Most glow starts slow-charge on a wall-plug transformer, and take between 8-14 hours for their first charge.
• Receiver pack and charger. Receiver packs can be slow or fast-charged depending on available budget for a charging device. You can use single-cell packs with a battery case, nicads or nimH; if you opt to use nicads, be sure to discharge them regularly per the battery recommendations on the electric powered rc's section of this article. Buy at least two receiver packs!
• Spare Glow Plugs. The rich condition of break-ins will be hard on a glowplug, you will need to replace it immediately after break-in and at regular intervals. Try to stick with the size and temperature that came with your engine, but feel free to expirament with the various temperature ranges and observe the effects it has on engine performance.
• Starting Equipment. If you do not select a pull-start engine for your nitro vehicle, you will need a starter box, 12 volt gell cell, and a float charger, or two standard electic R/C packs and a means of charging these.
• After Run Oil. Recommended after each run, but only required for long-term storage, exceeding a few days.
• Tools. In addition to the small tool set needed to wrench on your R/C, you will need micro-drivers to adjust tuning, a glow plug wrench to extract the glow plug, and any special sizes of allen wrenches or allen drivers to remove and replace engine bolt heads and engine mount heads. Do not skimp on allen wrench tools. Cheap ones will round off and strip out hex head fasteners and wind up costing you more time and money in the long run.
• Model- and Engine-specific spare parts. As metioned many times, the throttle, engine, and electrical components must be reliable and solid. Have replaceable parts available for anything that may fail, such as throttle linkage parts, electrical parts, replacement fasteners, and anything else specific to your vehicle. Always have a few spare air filter elements on hand.
• Optional: various clutchbell/pinion sizes and spur gears. Getting the most power out of your nitro under different track conditions can require changes in the gearing of the vehicle. Most racers maintain a range of clutchbells with varying sizes of pinions for this purpose. Additionally, the high torque of nitros is notorious for stripping spur gears, especially in offroad models; it's always good to have a few spares.
• Optional: Temperature gauge. A hand-held temperature gauge or gun is handy to have but the "spit test" will suffice.

Bringing it All Together

There certainly is a lot to learning to run a nitro, but once you get it under your belt it becomes second nature and every bit as easy to run as an electric powered RC. To be fair in comparing nitro with its electric brethren, in this author's opinion here are the three best things about nitro powered vehicles:

• Scale engine realism. This one speaks for itself. The sound, smell, and gut-wrenching acton of a nitro-burning R/C can't be beat. If you've got any gearhead in your blood at all, an internal combustion engine is the obvious choice. If you don't agree with this one, here is the R/C for you.
• Near unlimited run time. Once you're set up and tuned for the day, all you have to do is bring the vehicle aside for refueling and you can run all day. Nitro racing classes are usually 45 minute races; in electrics, they are six or seven minutes. 'Nuff said.
• Exceptional torque and horsepower. Although lighter electrics hold the trophy for top speed, currently they don't have the torque and horsepower of nitro powered engines. Nitros rule in the brute force category, hands down.

Some drawbacks:

• Steeper learning curve. There is a a lot more to learn to geting up and running with a nitro than there is with an electric.
• Noise. Most of us dig it, but your neighbors may not. If you don't have an acceptable place to run, nitro may not be an option for you. In fact, many areas are putting legislation into effect - that's new laws - restricting the use of nitro-powered vehicles due to irresponsible use.
• Mess, Maintenance, and Hazards. Okay I sqeezed three in there. Nitro vehicles are plagued with drips, splatters, oils, and smells and your mom or wife will probably make you keep your hobby in the garage. Furthermore there's a lot more to do to keep it running well, and there are some cautions required in handling the flammable fuel and working with a live internal combustion engine.

We've covered a lot of territory here, and believe it or not the info in these pages barely scratches all there is to learn about R/C vehicles. But now you sohuld be armed with sufficient information to make an informed decision on the original question: What R/C Should I buy?

Let's wrap it up with a brief summary.