RcDude21

Hi guys, I recently got a new 1/8 scale truggy, it is my first nitro but not my first rc. i live around 7800 feet and i'm having quite some trouble tuning any pointers on tuning or fuel or basically anything would be very helpful. as I am new to nitro i will need to learn most of it, thanks!!

Maxximize

Welcome to the world of nitro!

High elevation can cause some issues. Iirc, you have to tune leaner than normal to compensate for the thinner air. I start by getting the idle gap set to around .5-1mm (A small paper clip makes for a nice spacer), tune the low end using the pinch test, then do the high end. Start with factory settings for the engine and use small 1/16 turns. Clockwise for leaner, counter for richer. Factory settings are generally very rich as it is set for break in, so you usually end up leaning it out. The pinch test will get you into the ball park, then you can fine tune it from there.

Basically you get it warmed up, pinch the fuel line right by the carb, then listen to it as it dies out. It should rev slightly higher, then die after a few seconds. If it revs way up and dies, it's too rich. If it dies right away, it's too lean. From there, you can fine tune it by letting it idle for about 10 seconds and then gun it. It should take off quickly with little to no hesitation. Also, monitoring your temps with an IR gun is very helpful. A well tuned low end will cause the engine to begin cooling down slightly at idle.

Once the low end is set, you can do some speed runs to tune the high end. You're looking for a good, thick trail of smoke, and not too high pitched for exhaust sound. Really high pitched sound and thin smoke trail = lean. Too lean and it will fall flat on it's face when you floor it and try to cut out. Too rich and the engine will spit and sputter before it revs up and feel genarally sluggish, and it will also keep revving after you let off the throttle. Again, use an IR gun and try to keep it at 180-230 degrees or so. If it's a little hotter, it won't hurt it. I hit as high as 250 degrees on a hot day with the body on my Mad Force. Just don't let it get too much higher than 250 degrees or so.

For visual and audio reference, search youtube for pinch test and high end tuning. There are quite a few good videos there. It will take some practice, but stick to it and before you know it you'll be able to tune any engine in minutes.

For fuel in my big blocks (.21 and larger) I use Bones Brew 30% with 10% oil. It is some excellent stuff! For small blocks (.20 and smaller) I use Byrons Race 20%. Big blocks generally like more nitro content in my experience and will run and tune better with 25%-30% nitro and 10%-11% oil. Byron's race uses 11% oil, and is also some great stuff if you can get it locally.

Also, don't overlook your air filter! Clean it every few runs and re oil it. If you run dusty, dirty environments, clean it every 3 runs or so.

RcDude21

Thanks! I will give that a try, but another question, if you get the right air/fuel fixture for altitude wont it not have enough oil and run way too hot? also, last time i drove if you floored it at idle it would hesitate really bad and not even rev at all, unless, when I gave it 1/2 throttle or less it acclereted ok, what does that mean.

Maxximize

That is a possibility yes. But as long as you're running a good brand of fuel (Byron's, Bones, Odonnell, etc.), and your temps are good on your temp gun you should be fine. I personally run Bones Brew 30% nitro with 10% oil in my trucks with engines .21 and larger with great results in all temps and environments. You have to order it online, but the price is very reasonable. My back up to Bones is Byron's Race Gen 2 30%. When checking the temp, point the gun right at the glow plug from the top of the engine, that will give the most accurate reading. Most manufacturers will give a recommended max temp. I just try and keep it between 180 and 250 degrees for all my engines. Be careful when running in cold temps, an engine that is too cold will wear out quicker. I use the elastic part of an old sock I cut off to wrap around the head if temps are too low.

The nitro methane and methanol in the fuel also aids in cooling, so a higher content of nitro will help big engines run cooler at leaner mixtures. Small blocks (.20 and smaller) seem like lower nitro content in my experience. Byron's Gen 2 20% works well for them in most conditions.

Another thing I forgot to add earlier is glow plug selection. Generally speaking there are 3 types, hot, medium, and cold. I usually just stick to medium plugs, OS #8 and McCoy MC-8 work best for all around running in most engines I've ran.

It sounds like your engine is running too lean on the high end. Richen it about 1/16 turn at a time and keep re testing.

RcDude21

Ok, thanks all this info is very helpful! I'll get some bones brew and try to figure it out, thanks!

RcDude21

also, looking at engines i see stuff like two port, six port, five port, seven port, what does this mean?

Maxximize

No problem, happy to help. Nitro can seem daunting with no insight into anything! Feel free to play around with different brands of fuel too if you like. You will usually have to re tune slightly when switching brands though even if the nitro and oil content is the same.

The transfer ports for a nitro engine are fuel/air intake ports machined into the cylinder sleeve. The fuel and air in the crank case enters the cylinder through them when the piston is at bottom dead center. They are closed off by the piston when it moves upward. Some have different angles cut into them to direct the fuel flow into certain areas of the combustion chamber. A boost port for example directs fuel upward toward the glow plug. The way they are positioned and the number of ports is used to change the timing of the engine and to create more low or high end power output. The exhaust port is usually not counted.

The number of ports is not directly related to power output, though. I have seen 3 port engines out run 7 port engines before. OS has made excellent 3 port racing engines for years and won world championships with them.