Gas engine question
 

Hey guys, after being in r/c for almost 40 years, I'm going to try my hand at flying. Have the Phoenix 5 on the way and the Spektrum DX5e Tx. Plan on getting the Eflight Apprentice 15e BNF to start with. Now eventually I want to strictly use gas engines. I've always had large scale cars, trucks, and boats all with very high rpm gas engines. Now my question is after reading some about gas engines for planes, why does it take GALLONS of gas to break in one of these engines? Every gas engine I've used from 23cc to 29cc has fully broken in inside of a 1/2 gallon of gas.

It doesn't take multiple gallons of gas to break in a plane engine. 2 tanks through a ringed engine is enough to seat the ring and get it ready to fly. You will see improvement in the power and idling of the engine for the next few tanks though.

Oh ok. I was getting stumped about it from all that I've been reading. Yes, I can definitely understand how performance would improve over use.

In my experience, they are all different. I'm going to agree with jester though, generally speaking after a couple of tanks the engine is running reliably enough to fly, for sure. How long the engine takes to fully break in is questionable. You will notice smoother transitions and more power the more the engine is run, I would presume once improvements in these areas stop, the engine is then considered broken in.

If you compare an airplane engine which runs for 10-12 minutes maybe 3-4 times a day, as compared to say a weed wacker or chain saw which runs sometimes for hours at a time, it may make sense that the airplane engine will take longer as in more days to break in. Just a thought

On to your venture into flying! Welcome, you are going to love it! Good choice on using a simulator and the apprentice is truly a wonderful flying airplane.

Thanks AB!

Best way is to run a little extra oil then break it in in the air. This way you are varying the throttle up and down with a bit at full throttle. Much better air cooling by flying it.
Lean it out to max rpms then back off until just before it starts to stutter from being rich.

That's for glow engines. I've never tuned a gas engine that way. I've done it like this for years...after running a 1/2 gallon through it, run it at WOT, kill engine while holding WOT, bring it in, pull the plug and check the color of the insulator, richen or lean it from there, repeat procedure until the plug is a medium brown color. Done.

Yea, running a gas engine that rich doesn't do anything other than prolong the break in, it's got to reach operating temp. Tune it to max rpm then back it off 2 or 3 hundred, adjust the low end for good transition.

Go fly

Be prepared to tweak the top end as the ring seats

I didn't mean run it rich, rich. Just peak it to top rpm , then back it of till you just hear it slow down. It's still in two cycle mode.
Ran a small motor shop for 35 yrs and converted many chainsaw motors for air use.

Most engines "fully" break-in after a gallon or so of fuel and as stated; can then be more precisely tuned with better idle , smoother transition, and higher rpm's.
The smaller displacement abc gassers however do take a very long time to fully break-in. I have several 10cc engines and each one took 2+ gallons before it really came alive and could be finely tuned.

I've never tuned an engine like that. I always go by the plug color. Even back in the day when I was drag racing, that's how I adjusted the carb. But if that's what works for you, knock yourself out. Always more than one way to get things done.

I guess you don't understand too well. We're talking about engine break in. Once it's broke in, then I go by the colour of the plug.

I was originally asking about break in time, not procedure.

They all will require a few "tweeks" as they progress, usually minor. There are several folks who fly locally who can not leave the needles alone and they are the ones who have lot's of problems, mostly self induced in my opinion!
When you have it reliable fly until the tune is obviously in need of change, usually leaner in most cases. Fly again until changes are needed again and repeat.........if you feel the need to be constantly tuning then you are over-thinking
the process. Once you find the sweet spot leave it alone. I have large Chainsaws that have gone for years w/o carb settings requiring changes.......... Big Weather changes may alter things a little, but not a great deal.

After I get the carb adjusted correctly, I use a mixture screw clamp to keep them in place.

Can if you want, never had a problem if the springs under the needles are good.

Well, maybe on the plane engines I wouldn't need the needle clamp being that they turn such low rpm. The engines I've had in various cars and the one in my boat are all in the 18,000 - 19,000 rpm range. Those engines needed the mixture screws either clamped or fitted with short pieces of fuel line to keep them from turning. The springs just weren't enough.

Think you are good as far as planes go!

Well shoot I thought the subject was about typical airplane gas engines most will never see much more than10,000 and many more a little less in a static ground check when propped with an appropriate flight prop.

These engines are not boat or car racing engines and unlikely to ever see 18, 19000 RPM.

Gizmo-RC is correct the springs work quite well and nothing else is needed.

John

I'm well aware of that sir.

Hey, that's how I used to do my drag car...That's a extremely good way to sat air/fuel perfect