How to Tune a Nitro TC3 Carburetor

Tuning a Nitro TC3 carburetor should only be done after the break-in process for the engine has been completed. Follow the factory instructions for carburetor settings during the break-in period. After that, fine-tuning will probably be necessary to get maximum performance out of the engine. A rich condition means there is too much fuel and not enough air going through the carburetor, and a lean condition means there is too much air for the amount of fuel flowing.

Difficulty: Moderate

Instructions

Things You'll Need:

• Small flat head screwdriver
• Filter or 40-weight oil
• RTV silicone (optional)

1. Adjust the Low Speed Needle while the engine is idling. If your nitro engine is spitting out a lot of fuel from the tail pipe and experiencing sluggish acceleration from take-off, the LSN is probably running too rich. Using a flathead screwdriver, turn the LSN clockwise an eighth-turn at a time until only small amounts of smoke emit from the tailpipe and low-end performance improves. On the flip side, if there is zero smoke coming from the exhaust at takeoff, the LSN could be tuned too lean and turning it 1/8-inch counterclockwise will be necessary.

2. Do a few full-throttle passes with the nitro car, and then adjust the High Speed Needle as necessary. The same basic theory applies to the top-end as far as rich and lean conditions. If the engine seems to cut out at wide-open throttle, turn the HSN out a little to give it more fuel. If the engine temperatures are getting dangerously high (above 230 degrees F) but the car seems to have a lot of power, there is a lean condition present. Turn the HSN counterclockwise a little to allow more fuel when the throttle is applied. If there is a lot of white smoke at full throttle and the engine seems to hesitate, it is getting too much fuel. Turn the HSN clockwise an eighth-turn to decrease the amount of fuel flowing into the engine.

3. Seal the carburetor well and always oil the air filter. There is an O-Ring on the bottom of the carburetor to seal it inside the engine, but if the engine is old, the O-Ring may need replacement. In a pinch, RTV silicone can be coated along the mating surface, as well. Oiling the air filter should always be done, even if you aren't running the car in dirt. Small particles can easily make their way into the engine through the foam alone, but the oil catches them inside the filter. Filter oil is always best, but 40-weight motor oil works well, too. Only tune the carburetor with the filter fully oiled, because it will affect the air/fuel ratio.

Tips & Warnings

• After tuning your carburetor, it is a good idea to replace the glow plug.

References

• The R/C Car Bible: How to build, tune and drive electric and nitro-powered radio control cars on and off-road; Robert Schleicher; 2006