Maximizing your engine performance and longevity should be an important goal for every modelist. The model engines need care and proper operations in order to enable output in the maximum range without sacrificing the engine’s durability. This being the case, we need to make sure to understand at least five of the most important methods available for improving the performance rate of the engines. The following tricks and tips will enable you to take good care of your engine in the best possible ways.
1. Ensure your engine has the right compression for the fuel and propeller being used (see the article “Get the compression right”)
2. Always break in cold first - remove the head and a glow plug, inject no more than 1/4 teaspoon of oil into the intake and the same to the cylinder and spin the crankshaft with a starter for one or two minutes.
3. Use the proper oil mixture. Requirements - minimum 18-22% oil in the fuel with
50% being Castor oil in engines smaller than .15 and at least 25% castor in larger
motors. If mixing fuel yourself, allow it to settle for a week before use.
4. Do not operate the engine at 100%. When reaching maximum RPM, enrich the mixture by
turning the needle valve counter clockwise 2-3 clicks or 300 to 400 rpm less than peak.
5. When in flight, operate the throttle smoothly without rapid acceleration/deceleration to avoid a
hydrodynamic ram on the connecting rod.
How do you determine if your model engine's compression is right? In modelengines, the only means of adjusting the compression accurately is by addingor removing glow head gaskets (copper shims). Using fuels with differentnitro content will change the effective compression ratio, while changingpropeller sizes will alter how much compression you can safely use.Compression is a process in which air or an air/fuel mixture is confined andpressed into a smaller volume within the area of an engine's cylinder. Thisprocess forces all of the molecules to be "pressed" together under highpressure. Having the right compression is crucial for your engine as iteffects the performance, fuel consumption, and longevity of the engine. Ifthe compression is too high, it can cause a problem known as pre-ignition ordetonation. This can be very destructive, causing damage to the internalparts of the engine. As an example of a too high compression could be thefast destruction of glow plugs. Take a new glow plug and look at the spiral with a magnifying glass - thespiral's shape is intact and it is shiny. Install the glow plug into theengine and after a flight remove it again. Take another look at the plug'sspiral - if the compression is right, the spiral will look as good as new.If the spiral is stretched, it means Low compression - remove one glow headgasket and do the test again. If the spiral is deformed or darkened (black),it means Excessive compression - add a glow head gasket. If the spiral haslost its shine and become dull it means the fuel has some contaminants andnot pure - try a different fuel brand.Another way of testing it is to go by how the engine runs and heat levelsdeveloped. If you run a large prop on an engine, it will run hot like it isover compressed even though you have extra shims in it. As a general rule, if it starts to sag after 20 to 30 seconds of high speed,you need to drop the compression (add gaskets) and/or use a propeller withless load. High compression combined with high nitro fuel works best withsmaller props at high rpm. But this is not an exact science as differentlubricants in the fuel will also cause your engine to react differently.As a general rule, the more nitro you run, the more shims you need. Weathercan also be a factor. You may need less shims (more compression) if the airis moist (after a rain) as moisture dilutes the fuel mixture in thecylinder. Conversely you need more shims (less compression) if the weatheris dry and hot. New NV engines are supplied with three glow head gaskets. It is recommendedto have less compression during break in. Over time you may start removingthe gaskets one by one, but do not remove them all as one gasket should bealways present.
Your engine has been preserved in a special lubricant for shipment. Rinse it before use with denatured alcohol and dry with a soft cloth.1. Mount engine in plane or model engine test stand. Never hold engine in hand or vise.2. Attach propeller. Do not use metal propellers. Place propeller between rear prop hub and propeller spinner. When propeller is secured, propeller blades should be horizontal when the piston is at top dead center. Attach needle valve by gently screwing it into throttle barrel.3. Position fuel tank so centerline of tank is on level with fuel jet.4. Break in time is approximately 15 minutes, but engine performance may improve over the first hour of running time. When new, your engine may seem too tight - it was designed this way. Before starting it with fuel, you MUST first break it in cold: remove the head and a glow plug, inject no more than 1/4 teaspoon of oil into the intake and the same to the cylinder and spin the crankshaft with a starter for one or two minutes. 5. It is VERY IMPORTANT not to use a rubber fuel bulb or syringe with black-rubber plunger for transferring fuel into the fuel tank. Use a plastic bottle instead.
1. DO NOT USE METAL PROPELLERS. A propeller, which has been damaged with nicks, chips, cracks, or one, which has been altered in any way, can break apart during operation of the engine and can cause serious injury to you and others. Inspect propeller before each use. Discard and replace nicked, chipped, cracked, or altered products. Use only propellers that have been approved for use with your engine.
2. Do not start the engine when the fuel tank, propeller, or engine is not secured.3. Do not smoke when fueling or operating your engine. model fuel is extremely flammable and burns with almost invisible flame.4. Do not fill the fuel tank when the engine is operating.5. Do not prepare fuel mixture or operate your engine in an enclosed space. be sure there is adequate ventilation.6. Methanol is a poisonous substance. if it gets on skin, nose, or eyes, wash immediately with cold water and seek medical attention.
7. Be careful when adjusting your running engine. Stand behind engine when operating.
8. A model engine is very hot. Do not touch any part of your engine until it has cooled.
STARTING THE ENGINE
1. Set the throttled carburetor to an open position by moving the throttled lever (17) to the rear of the lever’s full range of movement (towards the rear of the engine).2. Close needle valve by turning clockwise. DO NOT FORCE OR OVERTIGHTEN.3. Fill fuel tank and attach fuel line to R/C fuel jet.4. Keep throttle lever to rear (open). Open needle valve 1-2.5 counter-clockwise turns.5. Put 3-5 drops of fuel into the venturi and rotatepropeller 3-4 times counter-clockwise. This procedure primes your engine. Another option is to place your finger over the carburetor and rotate propeller until fuel draws from fuel tank through the fuel line and into the carburetor.6. Attach a 1.2 volt power supply to the glow plug using a glow head clip. 7. Start the engine using a safety stick or an electric starter. Using a safety stick, slowly turn the propeller counter-clockwise through the compression stroke of the engine. If the engine has fuel, air, and a good glow plug, you should feel a bump against this movement. When you feel the bump, give a quick flip to the safety stick and the engine should start. 8. Using an electric starter, bring the starter into contact with the spinner nut or spinner and depress the starter switch for a few seconds. When the engine fires, withdraw the starter immediately.NOTE: Electric starters can cause damage to your engine. This damage occurs when the starter is applied to an engine that is flooded with fuel. Because of the high torque of the starter and the fact that you cannot feel the resistance caused by the flooding, there is a possibility that you will damage one or more parts of your new engine. Whenever you use an electric starter, be sure to flip the propeller through several compression cycles (without glow plug battery attached) without feeling a heavy resistance to this action. Only then should you attempt to start the engine with the electric starter.9. If after a few attempts the engine does not start, open the needle valve another half turn and repeat steps 5, 6, and 7. If engine still doesn’t start, refer to trouble-shooting section in this instruction.10. Once the engine is running, keep the glow clip on the glow plug for 30 seconds to allow glow plug to warm up, turn the needle valve screw clockwise until a high-pitched exhaust note begins to be superimposed on the lower-pitched sound. After this period disconnect glow clip. When adjusting the rotation speed of the engine, always turn valve very slowly (no faster than 0.5 turns per second).(FOR BREAK IN ONLY. After 30 more seconds turn the needle valve screw counter-clockwise to enrich the mixture and lower the RPM’s. Run the engine at this setting back and forth from lean to rich every 2-3 minutes for a total of 10-20 minutes)
11. Adjusting the throttle lever stop screw will vary the operating range of the throttle lever, which varies the operating range of RPM. Adjust the screw to obtain the best operating range.
TO OBTAIN MAXIMUM PERFORMANCE
1. Maximum power is obtained by increasing engine compression. Remove one or two copper gaskets from underneath the glow plug to decrease the size of combustion chamber thus increasing compression.2. Use a fuel with higher nitromethane content (35% nitro is the maximum recommended amount of nitro for your engine). However keep in mind that excessive nitro shortens the engine life as it applies more pressure on parts. Running helicopter or R/C car fuel will quickly ruin the engine as they contain a lower percentage of lubricants.3. Use the pressure fitting on the muffler to improve performance and fuel draw. Connect one end of small fuel tubing to the pressure tap on the muffler and the other end to your fuel tank. If your tank has more than two outlets, plug one or use a different tank.
MAINTENANCE AND ENGINE CARE
1. Protect engine from impact, dust, dirt, and moisture. Disassemble and clean engine when it is dirty. Always disassemble after a crash or when you suspect any dirt has contaminated engine parts. Dirt in engine will drastically shorten engine life.2. To clean engine, remove head and rear cover plate. Wash with denatured alcohol and rotate crankshaft. If engine will not be used more than for 24 hours, oil it completely. Do not use any type of brush when oiling.3. Never remove head or glow plug when they are still hot. A hot glow plug sticks and forced removal may damage cylinder. To cool head or glow plug in emergency condition, pour fuel over it.4. When disassembling and assembling engine, clean movable parts with a soft cloth and lubricate with oil.
1. Engine will not start
a) Poor connection of Power Supplyb) Low voltage of Power Supplyc) Head/Glow plug is burned outd) Fuel was not injected into engine
a) Check wire and connection to glow plugb) Replace Power Supplyc) Replace Head/Glow plugd) Inject a few drops of fuel into venturi and start again
a) Engine is flooded, too much fuel in cylinder
a) Close needle valve completely. Remove power supply from glow plug. Drain all fuel from engine. Unscrew needle valve 1-2.5 turns and start again.
3. Engine starts then slows down and stops
a) Excess fuel in venturi
a) Close needle valve. Start engine to burn extra fuel. Unscrew needle valve 2.5 turns and start again.
4. Engine starts but stops after a short time
a) Needle valve closed too muchb) Fuel line blocked
a) Unscrew needle valve 0.5 turn and start engine. Repeat this procedure opening needle valve an additional 0.5 turn each time.b) Clean fuel line
5. Rough sounding, sluggish, weak power
a) Loose Head/Glow plug
a) Tighten Head/Glow plug