Radio tuning for a more reliable engine

Who wouldn’t want a more reliable run out of their models power plant? There is a simple trick brought to us by the wonders of modern radios that can grant you a little more reliability for the cost of a couple minutes of your time.

Turn on your radio, bring up the menu that deals with servo speed, slow down the movement of the throttle servo, save the change and then sit back and pat yourself on the back for doing one more little thing to keep the R/C gods smiling down on your little pride and joy!

“OK” you say, “So I slowed down the servo, so what? What’s that supposed to accomplish?” Well, here’s the scoop! Contrary to what our egos sometimes like to think our fuel drinking little jewels have a couple shortcomings compared to their full scale big brothers. Carburetors rely on the pressure difference between the atmosphere and the suction of the engine to draw the fuel into the carb and atomize the fuel so the engine can burn it. Engineers have known for almost as long as there have been internal combustion engines that as the throttle was advanced on a running engine the air to fuel ratio leans out momentarily as the forces in the carb can’t respond quickly enough to keep up with the fuel demands of the engine. Traditionally, the answer has been to add an accelerator pump to inject the necessary shot of fuel to get through the lean period long enough for the carb to catch up.

Our little carburetors don’t have accelerator pumps so we are left with two options: Run the baseline air fuel ratio richer so that if the throttle is snapped open the engine doesn’t lean out enough to quit or, open the throttle slowly enough that the carb can keep pace with the demands of the engine, which is what you just did with your radio, sitting in your easy chair while watching The Price is Right. Actually, in practice, most of the time both of these solutions are present to varying degrees to keep the fires lit but slowing down the servo speed a little more is cheap insurance and unless you get ridiculous with it is almost undetectable in flight.

Just in case your radio doesn’t have the capability to adjust the speeds of the servos in the plane don’t get discouraged, there are several vendors that sell speed adjusters that plug in between the receiver and whichever servo you are trying to put the Whoa to.

If you have any questions leave a comment or hit me up at the field.  Happy Flying!