Hi, I am new to this site and getting back into R/C after 30 years. I have a question: New engine breakin in when weather is freezing. Is it ok to break in an engine or is it better to wait until Spring when the air temp. is warmer. My initial thought is wait , what advice can you give me.
Thanks

humm never thought about it umm id call up the engine mfg and talk to them also ask what operating temp it needs to be at and get a temp gauge and make sure you get it up to that temp..

Flying Freak is right, the engine needs to get up to operating temperature in order to break-in properly. If it's too cold outside the engine won't get up to the proper temp. If you must break it in then you can wrap the head of the engine with aluminum foil which will hold some heat in and allow the engine to heat up properly.

Ken

Forgive this simple question (I'm not a motorhead by any s stretch and am curoius) but wouldn't just idling the engine for a few minutes warm it up sufficiently to begin the break in process? How does the outside temperature affect the breaking in?
I'm assuming the plane is kept in a relatively warm garage, etc and the breaking in time would be outside where it is colder. I know you would need to adjust your needles some due to the change in air but wouldn't the engine warm up enough just by idling?

Not necessarily. As I said, the engine needs to get up to operating temperatures. Depending on how cold it is outside the engine may not get up to the proper temperature as the outside air keeps the engine cooler than it should be while running. This could be bad because if the engine isn't hot enough during break-in the parts will not wear in properly, then when the plane is flown the engine can wear abnormally because it was never broken in properly.

Ken

Kinda glad for this post too because I'm in the middle of breaking in my new Saito 125. I'm doing it in my garage with with the exhaust pointed out the window,lol. Still I noticed that with the first few 8oz tanks I ran through it at idle or just barely over,the motor never heated up much more then room temp. Now that I've got about 6 or more small tanks out of it at an extremely rich mix I'm starting to rev her up more to sometimes 6 thousand rpms for a few seconds at a time to try to get some heat out of it. It still doesnt heat up much at all. Its still no problem to hold your hand on it after the run. The pipe gets fairly hot,but thats it. Is what I'm doing ok? And now that I've got about eight,8oz tanks through it at colder temps,when can I start to think about taking it wide open for a bit?

Ken: I respect your reply. I figured the the warmer temp for break in would be the right decision. Thank you for your input. I'll wait.

Jester, extremely rich will also result in colder engine temps, remember.
But I don't know by how much, I admit.

Let's elaborate on the question a little bit and ask: "Just what IS standard operating temp of the cylinder head?"
Then consider the difference between 80 deg outside air and 20 deg outside air.
What percentage difference is the delta T?

I don't know the answers, I'm just asking out loud.

Of course its the fast air passing by the engine that cools it at any air temp. So would putting the prop on backwards (using well secured plane or break in mount) help some? I would think a 50 degree day wouldn't matter much but a 10 degree day would be a different story. SAFETY FIRST

This isn't going to help very much but the standard operating temp of an engine is whatever it gets to if it's tuned correctly (somewhat rich from full peak) and there's sufficient oil in the fuel. Other than that, there's nothing you can do about the temperature. As a guide though, one of my engines runs at about 300F when fully peaked, around 295F when richened a little and I've had it down to 145F when run slobbering rich almost to the point of cutting out.

As for running in an engine when it's very cold, cold for me is when it gets below maybe 50F so I've got no experience with what some of you guys call cold . But seeing I like to experiment, I picked out one of my engines that has a very nice pinch at 65F without the plug fitted and put it in my freezer for some time. I got it's temp down to 23F and rechecked the pinch. Surprisingly it had lost all its pinch! This is the opposite of what I expected but I've found some strange things with ABC engines . Letting it warm up again to room temp restored the pinch.

This is the same engine I experimented with when it was new by running it extremely rich to see what sort of damage would be caused by not letting it heat up to normal temps. I ran it for 45 minutes slobbering rich (that 145F temp) then stripped it. There was no damage whatsoever and the piston looked brand new. I had to lean it out into a 2 stroke to get it to run in. The write up I did here in RCU about this experiment caused huge controversy . Personally I wouldn't hesitate about running in an engine with very cold air temps.

As for airflow, this of course has an affect but after another experiment (also detailed in RCU) it seems that with the pitches and revs we use then we don't get anywhere close to having too little airflow. I compared the temps on an engine using both an 8" pitch and a 3.75" pitch props and the temps were identical. And at one stage I put the fine pitch prop on backwards. That's an old trick used by CL fliers sometimes to slow a plane down if there's no suitable prop handy.

I really doubt that running in colder weather will do more than cause a prolonged break-in period, as explained by several previous to me. A cool well lubed engine will not seize or damage it's self, I have run a lot of newer engines in some really cold conditions and never hurt one, ever.

I used to live in Bellingham,Wa and I remember the long winters and the engine break ins in the cold weather, well if its too cold like in the low 50's, dont even try to get out in the cold you are going to end up leaning your engine too much and that will be the end of it, there is nothing wrong on waiting till you get a warmer day at least 65f or try it in your well ventilated garage!! dont rush it,
fernando