4 cycling

[rc modifier]

hi guys
Please help me if you can.
I startded a thread in the begginer area for fuel planes.
Somebody mentioned that if you are running too rich your 2-stroke could be 4 cycling (firing on every 4 stroke) now im not sure what that means exactly is there a sound that is tell tale of this?

[Clancy Arnold]

Many fliers in Control Line Stunt run their engines in a 4 stroke setting. When the nose is pointed up the engine leans out and goes into a normal 2 stroke run, then when the nose is back level the engine goes back to 4 cycling. They refer to it as 4-2-4 breaking. The RPM changes a few 100 RPM but the sound is very distinctive.
Clancy

[rc modifier]

Thanks Clancy, was usefull but doesnt it hurt the engine?

[donnyman]

rcmodifier

In response to does it hurt the engine ......... no!

I have engines I used in the fifties that still run fine, the reason I used the technique mentioned was to maintain constant flight that wasn,t particularly fast ( appearance of manuvers) with the nose of the plane pointing up the engine would lean out enough to get that extra power to pull through upline or vertical manuvers. If you are new to this in time you will be able to detect rpm difference with just the sound of the exhaust, rich running sounds like what i call blubbery, lean running is high pitched and sort of a whine (bad news)

the blubbery range is refered to as four stroking and is the result of too much fuel flow.

this subject can get real technical and each person has their own feelings about it. try to find a oldtimer to give you a demo. Happy flying ....DONNY

[rc modifier]

Hi donny. Thank you for the reply. I havent heard a whining rpm so i dont think im running lean. Also the transition from low to hi aswell as the transition from hi to low seem very good. Over the weekend i took the calmato to the field but not to fly, just to run fuel through the engine. Everything seemed good and ready to fly. It did seem to get smoother as the day went on. So thanks again for the help, everyone. Mod

[downunder]

It's kind of hard to explain in words what the difference in sound is between 4 stroking and 2 stroking but if you've ever heard an engine running (especially in RC) then that's the normal 2 stroking sound, sort of a high pitched steady scream. When you richen the mixture enough the revs (at full throttle) start to drop and it can end up sounding something like a Harley motor bike :). Most engines will start to do this at around 2000 revs or so below peak on a normal sized prop. It really is a 4 stroke because the engine regularly misfires on every other stroke. Strangely though the engine doesn't suddenly lose half it's power because the actual firing stroke is more powerful than the normal 2 stroke firing which is why there's not a great difference in revs.

It does no harm to the engine at all.

[RedStarArmy]

I've read that 4 stroking a 2 stroke during break in in some instances can astually damage certain engines...has to do with the lack of heat produced, or something to that extent..just something you may want to look out for.

[rc modifier]

I saw a video on you tube with a buy breaking in the same engine.it sounded like mine but it seemed very rough on the plane. It seemed to jerk the plane.mine did this but then smoothed out, is this an indication of been run in? Other question.wont you battle to start the engine if its too rich?

[donnyman]

RC MOD...
your question cannot be answered as a flat statement because to many unknown parameters are involved. a engine Can run rough if too rich, and be hard to start.

Too much fuel will tend to cool the glow plug and hinder IGN/combustion (simplified answer)..........Donny

[RedStarArmy]

I saw a video on you tube with a buy breaking in the same engine.it sounded like mine but it seemed very rough on the plane. It seemed to jerk the plane.mine did this but then smoothed out, is this an indication of been run in? Other question.wont you battle to start the engine if its too rich?


As long as it's not 'overly' rich, it should start fine, as long as you give it a good prime and use proper techinque. To fully run in an engine 'usually' takes about a gallon of glow. But after the first few tanks, feel three to take it up in the air for the remainder of the breakin, just run it a bit richer than you normally would..after that..tune the high speed needle to max minus a couple hundred rpms.

[rc modifier]

Thanks for all the input guys it has mostly resolved my guestions.

[Pinecone]

Engines with lapped pistons need to be broekn in starting very rich. Not many engines made like this any more.

Ringed motors need a fast 4 cycle, just into 2 cycle to give some combustion pressure behind the ring.

ABC/AAC/ABN/AAL, etc motor, need to be run fairly close to right on to get the heat in the piston and cylinder.