Beginners Guide to Nitro Engine Tuning
Idle Screw
When tuning a new Nitro RC Engine I always start with the idle screw, I like to set it a little high while I'm dialing my RC Car in, as it'll help stop the glow engine from stalling. All the idle screw does is prevent the throttle from closing, if you tighten it the minimum throttle closure will increase, if you unscrew this the throttle will be allowed to close more, too much and it'll stall as the engine is starved of fuel. if your car wants to move at idle then your idle screw is set too high.
The Low Speed Needle
This controls the air/fuel mixture at low revs, if your battling to get the car to start this what you need to adjust. Clockwise will lean the mixture while an anti-clockwise turn will richen the mixture. The low speed needle can be very sensitive to changes made, and once you get it right you won't need to change it again.
The High Speed Needle
This controls the air/fuel mixture at higher RPM than the low speed needle, this is the needle you will need to adjust every time you go to the track as the optimum will be different depending on the environment. A clockwise turn will lean the mixture while a counter-clockwise turn will richen the mixture. If your not sure always run your RC Car too rich. as this will ensure that the engine is getting enough lubrication and cooling.
How To Tell If Your RC Nitro Engine Is In Tune
To be honest this is the tricky part, it's one thing to work out how the needles work, but another thing entirely when it comes to putting that knowledge into practice. Only trial and error will help you get this right. But if I could offer some tips and tricks to tuning your RC Nitro Engine, they would be:
- Learn what a Nitro RC Engine sounds like when it's in tune
- Watch the smoke
- The perfect tune for a beginner
Sound is one of the best ways to tell how the engine is doing, after a few runs you will most likely be able to pick up a problem by the sound of the engine. Other than a drop in performance, the note the engine makes is often the best way to tell how it's going.
If your tune is rich then there will be a lot of smoke and unburnt oil being expelled from the exhaust, it's critical to watch this, as an engine leans out as it warms up, so a good tune now, might be way to lean after another 5 laps.
Your RC car should idle for about 30 seconds to a minute. A rich low speed needle will fill the combustion chamber with fuel, this is a good thing as it means when we're not revving the engine it's be cooling down while it idles.
Your RC Car should be able to go from a standing start to full throttle without stalling. If you let it idle for too long it will stall when you do this, but generally it should be able to idle for 10 seconds and still pull off quickly. depending on how it stalls you can tell whats wrong with the tune, but for a beginner just richen of lean out the mixture 1/8th and try again, then ask yourself "Did the problem improve or get worse?"
Your Nitro RC Car should not overheat. A good test is the spit test, by putting a drop of liquid on the head of the motor it can give you a very good idea of how the engine temperature is doing. The ideal temperature is about 100° C or 120° Fahrenheit, which is when water starts to boil as sea level. So if the drop of liquid simmers, then your temperature is good. If it evaporate instantly then your running too hot. Richen your mixture to fix heat problems.
If you can't get it right. There might be an air leak somewhere in your fuel system or carburetor, if this is the case then there is no way you will ever get the RC Nitro Engine into tune, you'll need to locate and fix the leak before you continue.
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