Good morning guys, I have another question for you my r/c brothers.
Can you break in your motor off the ground ? :fear: what I mean is, does it have to be on the ground to be broken in? I'm in the house and it might rain all day so I wanted to break in my new motor in my shed today. My shed has many windows and wanted to put it to use. Help me out guys have any of you guys done it before? like on your mount or on a r/c stand that's off the ground. It doesn't hurt to ask right !

To be truthful, the engine should be broken in with resistance, i.e., running on the ground.

I usually have the clutch off for the first run, and stab the throttle a bit.

This is BudBud, this is showing you the idle way.

[youtube]http://www.youtube.com/watch?v=HVD8em6mLiU[/youtube]

I read the HPI directions that came with my RS4, and it said to put the car on a stand with the wheels off the ground. and let it free idle for the first tank.

Notice he is holding the tires, this puts some load (resistance) on the motor. He also checks the temp with a meter.

The risk on breaking-in by freewheeling (on blocks) is overheating. Since its not moving, there is no wind to cool the motor. And without resistance, the rpm will be high. You'll have to tune it just for break-in, then re-tune it for running.

what are you talking about? an idling motor is almost impossible to over heat, in fact its hard to get the motor up to temps when its idling, the faster the better to 200f anything below puts far to much strain on the motor's parts and in worse cases cause the con rod to snap.

Again he does put some pressure on the tires to make the motor work harder to get temps up, new motors need heat fast.

That is my LRP ZR.30 and I actually later used the plate you see in my truck bed to rub the front tires against for added friction load. I have seen engines go both ways, my original modded Picco refused to warm up during break in and I ran the front tires against a foam block to add resistance. While some may argue that we are breaking in the rod bushing and multiple other parts in the engine, truthfully though, the only thing that we are breaking in is the aluminum piston in the hard chrome sleeve. It is true that eventually, especially with the aid of dirt, we can wear the sleeve. But in a quality engine, that sleeve is so hard, it is difficult to cut with a file. The piston in the other hand is relatively soft.

My problem with the rich idle break in and running is that the piston never gets hot enough to get tight in the sleeve, so we are doing nothing for break in except pushing a lot of fuel through our engines. Then the first time we get out and start running, the piston gets hot and sometimes actually sticks in the sleeve, which is very hard on the connecting rod.

I like to make sure it gets over 230, preferably 250 for a Picco, and then cooled back down below 160 to 180. Several cycles through this range will also the piston to expand and get tight, then cool off with lots of lubrication.

I know most of the manufacturers recommend some long cold break in, they are simply trying to protect themselves from warranty work. Ask 30 people and get 30 different opinions, maybe all of us have a valid point. Some engines will get very hot just idling with no load, some will not get warm running a moderate rpm against a load, like this LRP for instance. It was hard to build heat in that engine and it still runs cool. Glen

That isn’t quite correct. The piston doesn’t “get hot” and expand into the sleeve. The upper portion of the sleeve expands to fit the piston, the piston doesn't expand to fill the sleeve. If an ABC engine piston seizes it is because the sleeve hasn't expanded enough.

The high silicon content of the ringless aluminum piston allows the piston to expand at a slightly slower rate and to a lesser extent than the plated brass sleeve surrounding it. (of course non-ABC/ABN/AAC engines are different) The whole design and operating principle of the ringless ABC type engine is such that the upper portion of the sleeve expands at operating temperatures to form the tight yet free running, blow-by free combustion chamber. The pinch is almost gone at operating temperatures. This is why there is a much tighter pinch felt when turning the engine over cold. (doing this should be avoided especially with an engine that hasn’t been broken-in)

These ABC type engines are also called “tapered bore” engines because the cylinder sleeve has a slightly smaller diameter or bore at the top of the cylinder than at the bottom of it. The reason for this is because the upper part of the sleeve which is above the transfer and exhaust ports operates at a much higher temperature than at the lower part of the cylinder. The top of the cylinder therefore has a slightly smaller bore than at the bottom to compensate for this expansion when the engine reaches operating temperatures.

Besides the fact that the piston is unable to expand more than the surrounding sleeve, it is also constantly bathed in a fuel/air mixture on the underside (as well as the areas exposed to the transfer ports) which cools it quite a bit. The piston is unable to attain hotter temperatures than the sleeve. If the piston did get hotter and expanded more than the sleeve then the pinch would increase not decrease when the engines run. There isn’t a circumstance in which the piston could expand only once in a while to seize the engine.

The object of the break-in is to avoid damaging or wearing out the critical and delicate upper cylinder piston/sleeve fit while at the same time stress relieving the parts through heat cycling the engine.