Running In A New Engine

Bench Running-In Method:
With this method you must have access to a HUDY type Running-In Bench with Propeller. If you have one or have access to one then this method is the most desirable.

Step 1. Mount the engine onto the Running-In Bench. Fit the propeller securely onto the clutch end of the crankshaft. Connect up the throttle linkage, fuel and pressure tubing and finally connect the exhaust pipe. You will need a 'Turbex' type starter as used on aircraft.

Step 2. Run the engine at tick over speed for the first tank of fuel.

Step 3. Now increase the engine speed to 30% throttle opening for four tanks of fuel, ensuring that the engine mixture is very rich (with lots of smoke showing).

Step 4. Stop the engine and allow cooling down for 15 minutes ensuring that the piston is not at the top of the cylinder.

Step 5. Now increase the engine speed to 50% throttle opening for six tanks of fuel, ensuring that the engine mixture remains very rich (with lots of smoke showing).

Step 6. Stop the engine and allow cooling down for 15 minutes ensuring that the piston is not at the top of the cylinder.

Step 7. Now increase the engine speed to 70% throttle opening for six tanks of fuel, ensuring that the engine mixture remains very rich (with lots of smoke showing).

Step 8. Stop the engine and allow cooling down for 15 minutes ensuring that the piston is not at the top of the cylinder.

Step 9. Remove the engine from the Running-In Bench and install it in your car. Start your engine and it's time to begin leaning the top end needle and making some power! Begin by leaning the top end needle (by turning it inward, or clockwise) by about 1/8th of a turn at a time. Run the car for a minute or so, then bring it back in and lean the needle by another 1/8th of a turn increment. Repeat this process until the engine begins to achieve good rpm, but it shouldn't be allowed to "scream" quite yet. The engine should still be creating lots of blue smoke from its exhaust. Before you achieve that screaming race setting, we recommend that you run your engine for a few more tanks in this "almost race" setting. Once you get the needle set to where your engine is making good rpm, richen it (by turning the needle counter-clockwise) by about a quarter of a turn-this is your final setting.

Running In at the Track Method:
Step A. Once your engine starts, place the car on a stand so that its wheels cannot touch the ground. Let the engine idle at low rpm for a few minutes (5 to 10 minutes will do), then shut the engine down and let it cool. During this procedure, it's also important that the piston is not at the top of the cylinder while the engine is cooling down. Part of what is happening during the Running In period is that the engine's mating parts are being heat-cycled, which means they are expanding when the engine is hot and contracting when it cools. Heat cycling stabilizes the metal and allows mating parts to fit better against each other. Keeping the piston out of the upper portion of the cylinder (which is smaller in diameter than the lower portion in order to create a better seal during combustion) will allow the cylinder to properly contract as it cools-without interference from the piston. To figure out where the piston is in relation to the cylinder, just turn the flywheel-it will become difficult to turn when the piston is at the top of the cylinder, where the fit between the piston and cylinder is its tightest. Just turn the flywheel until the piston is in the middle of its "easy turning" part. Repeat the above steps three or four more times.

Step B. After you've heat-cycled your engine, you can finally put it on the track. But don't get too excited yet - you must run it with a very rich top end needle setting. Lots of smoke should be coming from the exhaust, and the engine should four stroke (really rough). During this procedure, it's vital that you avoid prolonged use of full throttle, which could strain the engine. You should instead "blip" the throttle as you drive the car to avoid spending too much time in one particular rpm range. Run the engine using these settings for three or four tanks of fuel, allowing the engine to cool in between runs.

Step C. Once you've put about six to eight tanks of fuel through the engine (as outlined above), it's time to begin leaning the top end needle and making some power! Begin by leaning the top end needle (by turning it inward, or clockwise) by about 1/8th of a turn at a time. Run the car for a minute or so, then bring it back in and lean the needle by another 1/8th of a turn increment. Repeat this process until the engine begins to achieve good rpm, but it shouldn't be allowed to "scream" quite yet. The engine should still be creating lots of blue smoke from its exhaust. Before you achieve that screaming race setting, we recommend that you run your engine for a few more tanks in this "almost race" setting. Once you get the needle set to where your engine is making good rpm, richen it (by turning the needle counter-clockwise) by about a quarter of a turn-this is your final setting.

Step D. Once you've found a good setting for the top end needle that allows the engine to make good power yet still push plenty of blue smoke from the exhaust (especially when the car exits a turn), it's time to set the bottom end needle and the idle-stop screw. For now, set the idle-stop screw so that the engine will idle at a moderate rpm without stalling. Bring the engine up to operating temperature by driving it for a few minutes. Now stop the car and listen to the engines idle speed. If the engine idles fast but then slows down in just a few seconds, the low-speed needle is probably set too rich. Lean the low-speed needle (by turning it clockwise 1/8th of a turn) until, after running a few more laps, the idle stays high for about twenty seconds or so when you stop the car. Once you've done this, use the idle-stop screw to make the final adjustment of the idle speed. Setting your engine's idle speed isn't a contest to see how low you can get it without stalling the engine! Your goal when setting the idle speed should be to allow the engine to run at moderate rpm without the clutch being engaged whatsoever. Your car should be able to sit at a standstill when idling. If you have to hold the brake, the idle is too high. If you have to 'blip' the throttle to prevent the engine cutting out, the idle it too low.

Note: Nitro powered R/C vehicles can be lots of fun, or they can cause lots of frustration. The difference between success and failure lies with the break-in process. If you follow these steps, have patience, and use your head, you're assured of success. Rushing through the break-in procedure or worse, forgetting it altogether, is a recipe for disaster. Tuning your engine is the hardest part of nitro racing. But once you've learned how the carburettor works, and which screw does what, it will all become second nature. So when you're running your car, you'll always know exactly what to adjust to gain the highest level of performance possible.