ENGINE TUNING BASICS FOR GLOW HELI ENGINES
TUNING IS EASY ONCE YOU HAVE THE BASICS DOWN
Fuel Lines: You need a simple plumbing setup,thats tight,doesnt leak,and is free of extra crap like valves and connections.A fuel filter is a must,try to use one with a plastic mesh screen to keep junk out of your carb,metal screens can deteriorate,and pieces of it can score your cylinder walls.
Connections: Try to keep it simple,the less fittings the less places the engine will have to suck air.A fuel system that sucks air will not cure itself and will drive you crazy,keep the fuel lines confined to the tank,header tank,and muffler pressure line if applicable.
Muffler pressure line: Tap into the system at the end of the muffler or the side of it,using a tap in the header allows air to rush past it and wont pressurize the system.YS Engines do not need to get pressure from the exhaust to feed fuel to the carb.
Clunks/Pickup Lines: Lots of folks have problems with this believe it or not,usually the line is too long or short,and worse the clunk sucks the side of the tank and wont ALLOW ENOUGH FUEL TO GO THRU THE LINES causing a starving condition.The clunk line should be able to barely get to the corners of the tank and not get hung up on the walls period.Header tank clunk line should be the same,and both should be able to pick up fuel while the machine is either upright or inverted.
Fuel: Should be fresh and free of moisture,kept tightly capped,use a filter on your linr going to the fill point on the machine for extra protection.
Adding a filter to a muffler pressure line can help keep unwanted out of your fuel tank too!
Glow plugs need to be changed every couple gallons of fuel at the least.A old or wore out plug will keep an engine from running at its peak,Enya 3's,OS 8's,KnB 4520's all work good in most engines,use what the manufacturer recommends for starters....AND DONT BE A CHEAPSKATE,A BAD PLUG CAN CAUSE A FLAME OUT. INSTALLING A NEW GLOW PLUG IS CHEAP INSURANCE.
A Plug thats been in a lean running engine will have the element drawn out of the plug, replace it
A Plug in a rich running engine will be black,dark wet and even gummy sometimes,replace it.
A Plug in a well set engine will have a slight tint to it from the color of the dye in your fuel and wont show the above symptoms,it will be slightly bronzed with hardly any residue present,and may have a little bit of black near the center.
Lets Start it up!
Go thru this procedure after you have properly set up your pitch curves,if your not sure about the pitch curve and its setup get help from an experienced pilot.
The info here is here to give you someplace to start.Make sure all fasteners are tight,muffler is secure,radio is functioning properly,and theres no loose connections in the fuel system.Its best to get a engine running on a muffler before you go to a tuned pipe setup,Tuned pipes can be tricky,but have theyre advantages.Setting up a tuned pipe is a science all to its own,I wont cover that here,meet me at the field for help with pipes.
LOW END ADJUSTMENT
Fuel it up,hook up your glow driver and start the engine.Bump up the idle to keep it going without engaging the clutch.
Pinch test: Pinch the fuel line going to the carb and count 4 seconds,when you hit 4,thenengine should pick up slight speed,if it does,your very close on the low end or idle screw adjustment.
If it keeps running after 4 secs. it may be a tad too rich,if it quits before 4 secs its too lean.
If its too rich use a small screwdriver for OS's or use the low needle on a YS,lean it out,by turning the screw/needle clockwise a couple of clicks or an 1/16 th of a turn.
Do the opposite(counter clockwise) to RICHEN it up.
If you turn it too far in or out by turning in large increments youll be there all day trying to get it right,have patience and adjust to pass the pinch test.
Mid Range Adjustment
If your using a YS do what the manual says,the YS engines need to be broken in properly for best performance
OS Engines: On a three needle carb I usually go out 1/4 of a turn,pick it up in hover and tune slowly till it runs crisp and consistent,usually in 1 or 2 click increments.THe midrange needle on a OS will drive you crazy if you open it up any more than 1/4 turn to start,its more for tuning for hovering and hover manurevers found in a contest schedule.
THE HIGH NEEDLE
Again with the YS use manufacturers settings.
On a new OS start at 1 and 3/4 turns out from fully closed.
Pick the machine up into a hover,you want to have a steady stream of smoke coming from the exhaust,and a steady headspeed.
If the Headspeed starts to increase after hovering for a minute,and continues to do so,land the heli and come out on the high needle 2 clicks.Continue to do this until it hovers smoothly,no gurgling sounds,smooth and crisp.
If The Headspeed just wont come up,and the heli is hard to get off the ground,and its blowing a ton of smoke,it may be too rich,land it and turn the screw in 2 clicks at a time until it flies smooth and crisp.A OS will usually be at 1 and a half to 1 and 5/8'ths out on the high needle,outdoor temperature,elevation,and type of fuel being used all affect a engines performance.
By the time you get into forward flight,youll have a good idea as to how your machine is actually running mixture wise.
Pitch Curves changes will change your headspeed as will carb adjustments,LEAVE THE CURVE ALONE UNTIL YOU GET THE ENGINE RUNNING RIGHT,THEN TWEAK IT.
Fly the machine in fast forward flight,if the machine starts to go lean it will lose power,when you land it it will go rich again(in a good way) richen the high needle 1 or 2 clicks.Its flying lean.
If youre flying in fast forward flight and it goes lean ,and you land it,and it still continues to lose power while hovering,its running hot or overheating.Once a heli starts to overheat it doesnt stop until it quits or seizes.This is why learning to do autos is important hehehe.
If the heli is overheating you may be running too much pitch,have a accumulation of dirt in the fan shroud(rare)or may be running the machine way to lean period.Too much pitch will put a real good load on a engine,as will hovering inverted.Running a heli slightly rich is a good way to keep an engine from overheating.Easy way to overheat an engine? run too much pitch,and run it real lean.
More to come!