Over the years Nitro engines have come a long way in design and engineering. The typical Nitro engine is built using incredibly accurate tolerances and must be worn in properly. Unfortunately, many times (especially on Ready to Run vehicles) the break in procedure for your new Nitro engine is lacking. Before we begin let's quickly discus how a typical Nitro engine is built.
For the porpoise of this article we are assuming our engine is standard non-ringed engine that is commonly found in RC vehicles that would have been purchased by a first time buyer. I hope you are reading this because you're a first time Nitro engine user rather than a "what went wrong" investigator.
Before we get started let's make sure we have everything we need for our break in.
We will need:
- RC Vehicle with fully charged receiver and transmitter batteries
- Outdoor space to run the vehicle on a smooth surface (no grass, hills or deep sand for now)
- Glow Fuel recommended for your vehicle
- Glow plug warmer with a full charge
- Laser temperature gun (optional)
- About 60 minutes from start to finish
The starting and tuning procedure for a Nitro engine will not be discussed in this article as it can be a full lesson in itself. If you need help with the tuning of your engine RCU has a lot of information, tips and tricks.
After fueling you vehicle and starting the engine, tune for a rich setting. We are not looking for blubbering rich, we just do not want the engine to go lean and start building heat. If you have a temperature gun or other reliable way to measure the head temperature of your engine, about 200 degrees F is a good target. Because we are just breaking in the engine, and we do not want to build too much heat let's leave the body off the vehicle for now. (If you have a buggy or other type of vehicle that the body does not cover the engine, feel free to keep your body on).
Run the vehicle around in circles (the drive way works good for this) for about 5 minutes trying not to go more than th throttle. If you have a temperature gun, now is a good time to check the temperature of the engine. During this 5 minutes of running you should be observing a fair amount of visible smoke from the exhaust. If you do not see anything coming from the exhaust you are running way too lean.
Stop the engine and let it cool for about 15 minutes. What we are doing is "heat cycling" the engine. During the cool down time be sure the piston is towards the bottom of the stroke. You can do this by turning the flywheel by hand about t turn from where you feel the most resistance. We do this simply to keep the piston out of the "pinch zone" located at the very top of the stroke. If your engine stops with the piston at top dead center, a lot of stress will be put on the piston and the liner of the engine and we are trying to avoid stress.
After the engine cools, start it back up and run again, this time for 10 minutes or so. Stop the engine and let it cool. Do not forget to check the engine temp again if you are keeping track of your engine temperature (recommended).
Now we are getting close and you should have to refuel if you have not done so. This time after we start up our engine, we are going to re-tune it. You may not have to make any adjustment, but if you had your engine very rich, you may be able to lean it up a bit.
Now we will continue to run our vehicle for a full tank of fuel avoiding full throttle. Go ahead and take it down the sidewalk a bit and "burp" the throttle a few times, just do not open it up yet. Keep track of your engine temperature, you may be getting up over 200F now and that's OK.
Once you have exhausted your fuel supply, let the engine cool again. Now you have run your engine with care for about 30 minutes of run time. The next time you run you should be able to get a bit more aggressive, but do not over do it! Your engine is not fully broke in until you run about a gallon of fuel.
Why do all this? Most Nitro engines that break a connecting rod do so during the first gallon of fuel. It is often caused by improper break in and high stress on the engine as a result. But more often improper break in, or worse – no break in, results in un-even wear on the piston and piston sleeve resulting in poor engine performance and reliability.
Good luck and may you have many, many hours of un-interrupted fun with your Nitro vehicle!