Let’s face it, nitro-powered cars and trucks absolutely rule. They’re fast, they sound cool, they have a ton of power, and they are a blast to drive. With the quality of sport engines getting better and better, more newcomers are seeing nitro as a viable option for their first vehicle. When it’s time to start your engine for the very first time, there are several key steps anyone would be wise to follow. There are a few post-run steps that will also extend the overall life of your engine and improve performance along with durability.
The Right Tools for the Job
Before you ever fire up your engine the first time, it’s important for you to have the right equipment that you’ll need to start, tune, and maintain your engine. The most common equipment you should have at your disposal can be found in Dynamite’s excellent Gas Car Starter Accessory Pack. This combo includes a rechargeable glow driver and charger, glow plug wrench, fuel bottle, spare fuel tubing and extra glow plugs. In addition to these accessories, you should also pick up a tuning screw driver for the carb such as the Dynamite 3mm flat-blade screw driver. In addition, you might want to pick up a temperature gun, such as the Pro Exotics PE1 infrared temperature gun. This is the same type of temperature gun that Team Losi’s Adam Drake and Travis Amezcua use as well.
The First Tanks
When you buy a brand new full-size car, the manual tells you not to exceed 55 mph for the first 500 miles. Why? To ensure proper break in before you romp on the gas. The same thing applies to your RC engine. Ok, I don’t mean that you have to drive 500 miles before you can stand on it, but there are proper break in procedures that you should follow to ensure maximum performance and durability. A little bit of extra time and care here will help your engine to run stronger, longer. Before you ever fire your engine for the first time, take a moment to read the instructions. There is a ton of excellent information in there regarding initial needle settings, fuel recommendations, and more. Please do not disregard this very useful information.
Once you have your fuel tank filled with the appropriate percent of fuel (Note: NEVER use airplane fuel; only use fuels blended specifically for car use, such as Dynamite Blue Thunder), it’s time to begin your break in process. Due to the tight fit between the piston and sleeve, it may take a few attempts to start your engine and keep it running. Once the engine is running, set the chassis so that the tires are off the ground; cars that use a starter box can just sit on the box there during the idling process. You can rev the engine occasionally to help clear out excess fuel and help aid in break in. You should generally run two very rich tanks of fuel through your vehicle like this before moving on.
Final Break-In Steps
After the second tank of fuel, it’s ok to begin leaning the engine out. Make small adjustments instead of drastic ones. When breaking in your engine , it’s helpful to have a temp gun of some type available to you. You will want to measure the engine head temp instead of just relying on the smoke to determine if the engine is too rich or too lean. You may actually notice that the engine’s head temperature climbs very fast initially in the first couple of minutes of break in. This isn’t completely abnormal, as the tighter fit between the piston and sleeve causes more drag and friction. This friction causes the temp to climb more than normal. After your second or third tank, however, the engine temps should be between 200–230 degrees.
After the second or third tank, you can actually begin to tune your engine and lean it out slightly. When leaning out your engine, it’s important to make small adjustments and not massive ones. If you lean your engine out too much too soon, you end up robbing your engine of key lubricants and oil that it needs for protection. When making adjustments, think of your needle as a clock face; one full turn in or out would be equivalent to an hour, a quarter turn is referred to as 15 minutes, and so on. You will find that you will make more frequent adjustments to your high-speed needle (the larger screw on top of the carb) than your low-speed needle (found on the side of the carb). In total, you should run about 3–5 very rich tanks of fuel through your engine before you really begin to open it up. After the fifth tank or so, you can begin to drive the car around and pick up more and more speed. It’s a tedious task, but it pays off big down the road.
Needle Tuning with John Adams
John Adams is one of the best engine tuners you will ever find, and he has taken the time to write down one of the best step-by-step guides addressing how to tune your needles.
Tuning Your Engine
When you are tuning your needle valves for maximum performance, adjust them in small increments, 1/16 turn at a time. An engine should not be run too lean as doing so will severely shorten the life of the engine. When an engine is set too lean, it will run very strong at first but soon begin to sag and hesitate or stall when accelerating. As you gain experience, you will be able to tune your engine based on its sound and feel during acceleration and at full throttle. Until you’ve developed this skill, I recommend the following method of engine tuning. Start your engine and drive around aggressively for about two minutes. At this point, you should measure the temperature of the engine head. If you have a temperature gun, the optimum running temperature is between 210 to 230 degrees. If your engine is below 210 degrees, you can lean out the high-end needle. If your engine temperature is above 230 degrees, then you should turn the high-end needle out to richen the mixture. If you don’t own a temperature gun, there is another way for you to test your engine’s head temperature by placing a drop of water on the cylinder head. If the water sizzles away (evaporates immediately), the needle setting is too lean. A correct needle setting will result in the water evaporating slowly, in about 5–10 seconds. If the water does not evaporate, the needle setting is too rich. Lean the high-speed needle 1/8 of a turn and run the engine again, adjusting the needle setting to the desired evaporation rate of 5–10 seconds. Check the temperature each time you change the needle mixture. Do not let the engine overheat, this will damage the engine.
Tuning the Low-Speed Needle
The low-speed needle (also referred to as the idle mixture or idle needle) should be set after you’re satisfied with the high-speed needle setting. After achieving the engine’s proper operating temperature, reduce the engine throttle to idle for about 15 seconds. Now pinch the fuel line with your fingers close to the carburetor fuel inlet nipple while carefully listening to the engine rpm. If the engine dies immediately without an increase in rpm, the low speed needle is set too lean. If the rpm’s increase dramatically and then the engine dies, the setting is too rich. The ideal setting results in the rpm’s increasing a slight amount (about 200 rpm's) after pinching the fuel line before dying.
Post-run Care for Your Engine
Far too often, hobbyists neglect to perform the proper post-run maintenance on their engines, only to wonder later why they are having problems. There are several key steps you should make sure you do after each and every day of running. The first is to make sure you place a drop or two of after-run oil in your engine. There are two ways to do this; one is to remove the glow plug and put a drop or two directly in your combustion chamber or remove your air filter and put a couple of drops in the carb. Either way works just as well.
To maintain the pinch and compression of your engine, the placement of your piston in the combustion chamber as the engine cools has a major impact. You will want to rotate your engine’s flywheel until your piston is at bottom-dead-center (BDC). If you leave your engine’s piston at top-dead-center (TDC), the sleeve’s pinch will be reduced as the sleeve will not contract fully when it’s cooling, affecting your compression.
Once you are finished running for the day, make sure you drain all the fuel out of your fuel tank and fuel lines as well. The fuels we use in RC cars and trucks have a specific oil content in them which provides proper lubrication for your engine’s moving parts. Along with providing protection for your engine components, any unburned lubricants left in your fuel tank can begin to settle, break down, or gum up. It is for these reasons that you should always properly drain your fuel tank after each run.
Nitro Fuel Basics
As someone who is predominantly an electric racer, one thing I really had trouble wrapping my head around was the different types of fuel, percentages, oil mixtures, and all that are available. One of the biggest things to remember about nitro fuel is that you should never use airplane fuel in your RC car or truck engine. The fuel blended for RC cars and their engines face a totally different sort of running environment when compared to an airplane engine. Airplane engines are generally run near or at full rpm for extended periods of time and are cooled by the airflow generated by the prop. Additionally, since airplanes only tend to accelerate and decelerate on takeoff and landing, the throttle response isn’t as important as in an RC car. Conversely, an RC car’s engine rarely reaches max rpm for more than a few seconds, acceleration is extremely important in pulling a car out of a corner, and RC car engines use an oversized heat sink head to provide cooling. Given these extreme differences in the running environments, fuel manufacturers blend the fuels for the engine’s needs. Airplane fuel tends to have higher oil content and a higher nitro percentage. While you might think that a higher oil percentage would help to protect your engine better, it really doesn’t. True, you can get a cool plume of smoke out of your pipe, but would you really rather blow smoke or blow away your competition?
So what type of fuel should you be running? After all, there are different combinations of nitro percentage, oil content, synthetic oils, caster oils, different colored fuels, you name it. First, if you’re going to be backyard bashing and are looking for maximum durability and easy needle tuning, you’ll want to stick with one of Blue Thunder’s Sport blends. Blue Thunder Sport has been specially blended to protect an engine in the event of an over-lean needle setting while burning clean, providing excellent power, and it’s easy to tune your needles with. If you’re running a .12- to .18-size engine in a race vehicle, Blue Thunder Race is perfect. It has the right oil and nitro percentages to make your small-block engine into a big-time performer. For .21 and larger engines, Blue Thunder HP8 is at the pinnacle of performance. Blue Thunder HP8 is 100% made in the USA and features a mixture of 2% synthetic oil and 6% AAA-grade Caster oil. When you combine these two oil types, you reach a total oil content of 8%, which has proven to provide the best power delivery and engine life available.
Once you’ve determined which type of fuel to go with (Sport, Race, or HP8), you’ll need to determine what nitro percentage is best for you. Fuels with a higher nitro percentage, like 30% for example, burns hotter and creates more power, but the engine also consumes fuel faster and you have a greater chance of overheating your engine. 10% nitro burns cooler and is a little more efficient fuel, but it doesn’t create as much power. 20% fuel is a good all-around mix between the 10% and 30% as you’d assume; it burns hotter and creates more power than 10%, yet is cooler and doesn’t deliver as much power as a 30% fuel would.
The world of Nitro engines can be a confusing one, but there are some basics to remember as you break in, tune, maintain, and fuel your car. While some may look at the different variables of engines as a deterrent, I’d rather think of it as a scenario that is almost infinitely adjustable. Simply take your time and think things through, that way you won’t adjust yourself out of the game.