ORIGINAL: ShoestringRacer

There are two problems with what you suggest, at least when talking of nitro engines installed in RC vehicles (as opposed to airplanes). 1) the engine is not getting any cooling airflow and 2) the engine is not under load. An uncooled and free revving nitro engine will at least suffer piston/sleeve damage and/or likely connecting rod, wristpin and crankpin failure.

That said nitro engines can certainly last longer than 24 hours, and I'm sure many have. Many large displacement nitro 2 stroke airplane engines aren't even fully broken in until a couple of hours, and older lapped iron or steel piston with iron or steel cylinder engines took even longer to beakin. I have never kept a log of my airplane (or car/truck) nitro engine runs but a good ABC engine run properly from the first start can have a long life.


Running a nitro engine non-stop for extended periods of time will actually cause less wear than going through repeated start and stop (heat and cool) cycles. But it has to be run at WOT. And it HAS to have a load and it HAS to have cooling. It sounds counter intuitive, but WOT will have less wear on the piston and sleeve. If you ran the engine at idle, even with proper cooling airflow, the piston and sleeve would last no where near 24 hours, only a fraction of it. (prolonged idling will kill any ABC type engine's piston and sleeve regardless of other conditions) The most wear comes from changing conditions in an engine (any engine for that matter) i.e., starting, shutdown, temperature swings, power setting/RPM changes. Constant state running is the least detrimental. And with ABC, ABN, and AAC type tapered bore (ringless) nitro engines, the most longevity will come at wide open throttle with proper cooling and proper HSN setting.

If you were to put a nitro engine on a breakin/test stand with a properly sized propellor for its displacement (which gives cooling airflow and puts a load on the engine), with a proper high speed needle setting at WOT it will run and run and run at WOT provided it has continuous fuel. Why someone would want to do that for 24 hours continuously I don't know but the point is continuous running (only if NOT done at idle) under proper conditions is no big deal for an engine. (look at automotive and diesel engines tested in test cells, they have fuel, coolant and a load; it doesn't matter how long they keep running. and while you can't compare 2 stroke nitro to diesel some diesel engines are rarely shut down like generators)

Actually when nitro engines first appeared decades ago they didn't have any throttling or idling ability (no carburetors on them). When they started up they were at WOT instantly. Throttling an ABC type engine is actually detrimental to their longevity. The piston and sleeve fit is designed to run at WOT and any throttling just reduces temperatures which leads to a tighter piston/sleeve fit which leads to wear.