Here is a new one to me. The instructions to my OS FS A .56 state, "Do not close the needle valve and mixture control valve too far as this will cause a lean setting and overheating of the engine. This can, in turn, create nitromethane oxide leading to internal rusting of the engine." So, that being said, does it mean if ya run your four cycle engine on the rich side, no rusting will occur? interesting.

LOL. That's a new one!

Made me giggle. Sounds idealistic.

Jim...

Last I checked, burning nitromethane leaves a residue containing nitric acid. This in addition to a little moisture from combustion and you have a recipe for disaster.

I used to have that problem with piped 60's the bearings would rust bad.

Jim...

Yeah... Nitro is a bit of a catch-22.... Its really weird though - I use 20-30% nitro in my car engines (at 10-11% oil mine you) and never have problems with bearings, but it seems airplane engines have more problems with bearings rusting. FWIW I haven't had any bearings rust or need replacement after replacing the OEM bearings yet. Knock on wood I guess.

Probably supposed to be "nitric oxide" which
can lead to nitric acid formation.

Jenny

One would think a "reputable" company such as OS engines and their "reputable" distributor would have proofread the manual. I wonder if Bill Baxter will chime in and set the record straight.

Only burning nitro with less than 20% methanol will leave any nitric acid. And even then it disapates and burns off on its on. That is the reason the dragster racers have built in filters with acid neutralizer in their helmets. If the nitro percentage is high enough to have huge flames from the headers you probably have some nitric acid. Such as with the dragsters and funny cars. But the nitro motorcycles use much less nitro and have no flames. The nitric acid will be neutralized from the hydroxide (HO) left from the methanol exhaust.

Got any reading material you could suggest that talks about this? I'd like to research it further, preferably not on the internet.

Don't remember, but there is some chemistry sites that will break down the reactions for both nitro and methanol. Some will show for both rich and lean. Also I think some drag racing sites has info. Maybe look it up later. Some of that was top of head memory, so don't recall where from..

Burning hydrocarbons is not as straightforward
and simple as it seems. There are multiple
intermediate reactions and incomplete combustion
to consider. As a result there are many different
chemicals in the resulting exhaust in addition to
carbon dioxide, water and nitrogen which are
the primary exhaust components from burning
glow fuel.

Jenny

Nitromethane by itself is very acidic.However, It makes its own Oxygen when ignited.Oxygen will destroy almost any kind of metal,except for your precious metals,(gold,platinum,silver, chrome,aluminum,(which is't precious) you get what I mean. Anyway, Why would you want to run any engine lean except for: Dragsters,Pylon raceing, and combat. You will only get 2-3 runs out of any engine if you lean out your engine to the max. Otherwise,go easy on your motor. Unless you have unlimited funds! Ha.

There is no benefit to ever going lean in any engine. Racers look for peak RPM, which isn't a lean condition at all. They occasionally miss the peak and wind up lean, but there is no harm to be done making maximum power with an engine.

Nitromethane is pH neutral actually (7). Methanol however is corrosive by itself (to aluminum) and seems to be moreso when it has some absorbed moisture.

http://www.sciencelab.com/msds.php?msdsId=9927374

Exactly, the water and the O2 that nitro makes is corrosive. On alluminum,and especially on your crank and bearings,which are steel. Damm,I have to learn how to spell alluminum Ha.

My appoligies, when I quoted "precious metals"Aluminum is affected by Nitro. Sorry for my mistake concerning this.

Yes, Your right,there is nothing wrong with getting the maximum out of your motor, but there is a fine line between maximum performance,and overkill. In this hobby, there is no reason to max out your engine unless your racing and and there is a bet to settle Ha

If there is copper in the aluminum alloy, then you may have to be concerned, but otherwise nitromethane poses no imminent risk to aluminum or steel for that matter. Not in its unburned form anyway. Methanol is far more caustic to aluminum than nitromethane is. The risk lies in the combustion byproducts/residues left behind can be a problem. This is why it's so important to run the engine dry at a modest rpm to evacuate as much residue (unburned fuel) as possible. THAT is the key. Leaving any unburned fuel residue in the engine will attract moisture and rust/corrode the internal parts.

I tune all of my engines for maximum power in the air. This is an area where I think there is widespread misconception. There are guys who don't understand how our engines unload in the air who tune for max RPM on the ground. Some of them are racers. They go through engines quickly and have lots of deadsticks. But that's not tuning for maximum power; that's running lean in the air and ruining your engine. There are other guys who think lean=more power and rich=more durability which is also false. Peak tuning is more power, and keeping the RPM's down and keeping the engine cool is durability.
What I do is experiment with various rich settings on the ground until I find the one that gives me the maximum RPM in the air throughout a flight. It's easy enough to hear what the engine RPM is doing after you've been at this for a while. I find out how rich the engine needs to be on the ground to still be peaked at the end of a tank of fuel, and that's how I tune it from there on out. Every plane, engine, fuel, and prop combo is different, so it take a little time to get it right for everything you fly. The old rule of thumb of tuning 500 RPM rich on the ground gets it pretty close to peaked in the air on most engines, but not always. The point though is to find out what your particular engine and plane needs and set it to run its best.

I always heard it was 300 RPM, but no matter. Are you mostly talking about 2 strokes or 4 strokes? Or both? I don't think you can come up with a rule of thumb for 4 strokes where they aspirate efficiently in the air. By the time you test fly it, land and tweak, and take it back up to confirm there's no telling what how rich you are past peak unless you are using telemetry and using the same engine heat levels.

I've never used a set number of clicks or a set number of rpm to set the needle by. I set the needle by pinching the fuel line and to get a noticeable change in rpm. Ive found some engines are too lean at the typical settings, but setting by the pinch method puts it in its happy place - which ends up being 500-800rpm rich from peak. On 4-strones, I use a tach only to set the needle. Start over-rich with misfiring, lean it until it just cleans out and runs smooth. Ends up being about the same rpm rich from peak as with 2-strokes.

This still doesn't answer the question if nitromethane oxide is formed by over-leaning the needle valve.

Actually aluminum is unharmed by nitro. It's the methanol that attacks aluminum. The oil in the fuel prevents that to a great extent.

This is what I do one click at a time slowly. I don't know why this is not in the instructions.