Engine basics > Engine set up tips
Engine tuning tips
David_Ruff:
I will ask my dumb question here about the 4-2 break. What causes the break? Is it the leaning of fuel mixture? If so, how does that happen? In a perfect world the fuel mixture should not change with a fixed system?
RandySmith:
--- Quote from: David_Ruff on February 08, 2014, 06:39:22 AM ---I will ask my dumb question here about the 4-2 break. What causes the break? Is it the leaning of fuel mixture? If so, how does that happen? In a perfect world the fuel mixture should not change with a fixed system?
--- End quote ---
Hi David , it is a combo of things, load and mixture, the fuel head does change, as well as load when the airplane is in maneuvers, to see for yourself, run an engine on the bench, set it just in between a 4 and 2 cycle, raise only the tank up higher, then lower the tank only lower than the engine, you will see the engine go richer and leaner. you just changed the mixture.
Randy
Andy Bush:
This info is the best!
I never realized how little I know about this hobby...here's my stupid question!
What is meant by the 2-4 cycle reference? The same as for lawn mower engines, for example? Or is it just a reference to the engine running at different speeds?
Andy
RandySmith:
--- Quote from: Andy Bush on May 13, 2015, 06:13:44 AM ---This info is the best!
I never realized how little I know about this hobby...here's my stupid question!
What is meant by the 2-4 cycle reference? The same as for lawn mower engines, for example? Or is it just a reference to the engine running at different speeds?
Andy
--- End quote ---
Hi Andy
When you richen the needle setting on a 2 stroke model airplane engine, it will drop its sound tone,go into a misfire every other evolution and will be in a "4 cycle", when you lean the mixture out it will sound like it cleans up , normally sound like it just "jumped" into a faster RPM, and is now in a 2 cycle mode ( firing every revolution} higher the 4 cycle sound lower volume/pitch , the 2 cycle sounds higher volume/pitch.
You can may times hear this if holding the plane while running, and turning the nose of the plane up and down.
Randy
RknRusty:
Am I correct in my thinking that when it's right on the edge, the RPM stays nearly the same as it breaks back and forth from 4 to 2? Yet the torque must increase when it breaks into 2 stroke, giving it the ability to climb with more authority?
Rusty
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