COntrary to what people think they know about Nitro.....
Higher NItro, means a COOLER runnig ENGINE....

One of the RC care mags did a entire workings of it.....
Simply.:
Higher nitro= richer setting to offset the increased oxygen
richer needle means more fuel run through the engine (nitro, oils, alcohol)
='s cooler running engine.....

Now, extra stress on the engine? That is a different story.....

The colder plug is used to offset the increased TIMING associated with the HIgher combustion properties of the
higher percentages of NItro/oxygen..

Too hot and you get KNOCK (The fuel, ignites when the pistion is going on it's down stroke or just comming on it's way up)
Depends on how much the timming has advanced
...... If it isn't KNOCKING..... and there isn't any pitting in on the inside of the head of the engine,
and you are not burning out glow filiments regularly you should be just fine!....

Justin

Justin,


Why don't you just run your own family car on nitro!?

It cools your engine, so you don't need the radiator, the coolant, the water-pump...
Power will be up too...

The 'fuel' will cost you $50-100 per mile??? So, its a hobby... Who cares?... No?


Let me say this as explicitly as possible: Glow engines run on methanol and are designed to do just that. ALL OF THEM SHOULD BE!
Nitromethane is just a fuel additive; used in small percentages to improve a glow engine's handling qualities and marginally; its power.

Nitro is not the fuel and despite the fact that some less knowledgeable people call them 'nitro engines'; they are not.


Methanol is expensive enough (at 8-10 times the per-flight cost of gasoline/petrol). Nitro can get this figure up to 100-200 times the cost of gas...


Do you want to change RCU membership to the; err...~3 who can finance running all nitro, all the time?

The AMA should limit glow-fuel to 5% nitro and all sanctioned competition events to FAI fuel; just as it was in earlier years.

Naohito Yamada; are you listening!? No nitro!
Can you redesign all your engines to use FAI fuel?

.................................................. .................................................. ...............


Chris,


Your engine's capabilities seems far and beyond those of other OS.46AX engines; more than mere ambient conditions can explain.

Please see [link=http://www.jettengineering.com/accy/jettstream.html]Dub Jett's OS.46 numbers[/link] at the bottom of the page.
These may be for an FX, but according to full reviews in R/C magazines, the AX numbers are very close.


Would you care to share the techniques you use, so we can all enjoy your advantage?

Quote:

ORIGINAL: kochj

One of the RC car mags did a entire workings of it.....
Simply:
Higher nitro= richer setting to offset the increased oxygen
richer needle means more fuel run through the engine (nitro, oils, alcohol)
='s cooler running engine.....

Now, extra stress on the engine? That is a different story.....

The colder plug is used to offset the increased TIMING associated with the higher combustion properties of the
higher percentages of nitro/oxygen..

Too hot and you get KNOCK (The fuel, ignites when the piston is going on it's down stroke or just coming on it's way up)
Depends on how much the timing has advanced
...... If it isn't KNOCKING..... and there isn't any pitting in on the inside of the head of the engine,
and you are not burning out glow filaments regularly you should be just fine!....

Justin,


I have not read the article you are referring to, but I can tell you that many general audience publications, do such bad job of explaining...

In an attempt to make their article easier to comprehend, they exchange accuracy, with vagueness and facts, with assumptions and beliefs...


When you take the oath in court, you swear to tell the truth, the whole truth and nothing but the truth... not to say it in more comprehensible terms, which may compromise this truth...


You seem not to have the issue in clear view...


The destructive term is 'detonation'.

In normal operation, ignition is initiated before TDC, the propagating flame-front consumes all the air-fuel mixture and maximum pressure is achieved after TDC, as the piston is descending and the combustion volume is expanding.

Detonation occurs when ignition is initiated too early; causing the flame to begin propagating normally, but the maximum pressure in the combustion chamber occurs as the piston is still rising and the combustion volume is becoming smaller. This extreme pressure causes the remaining, unburnt mixture to spontaneously detonate, all at once; instead of being burnt normally.

In extreme cases, such as model four-stroke engines, this 'hammer-blow' on the rising piston, causes it to stop and reverse, throwing the prop, flattening the spinner and possibly even perforating the piston, causing the crankshaft to shear, or the con-rod to buckle.

In less extreme cases (most two-stroke engines), it is called 'a lean-run'.


What the car mag people forgot to tell you, is that with everything else given (i.e. prop-load, glow-plug, fuel, ambient conditions and C/C temperature), the only control that you have over the ignition timing, is the settings of the fuel needles...
Say, what? Yes! What determines how early the mixture will ignite and how fast the flame will propagate through the mixture, is the fuel-air ratio.


A hotter, leaner mixture will ignite earlier and the flame will propagate through it faster, than a richer mixture.

So, turning the needle is exactly analogous to changing the ignition advance.


Nitro needs to have a lower C/R to run properly, than if the same engine was being run on FAI fuel (20/80). But if you cannot decompress the engine (i.e. add head shims), you need to open the needle more. Not only to let in more fuel, that the oxygen brought in by the nitro could oxidize, but also to delay the ignition, to compensate for an excessively high C/R...

Nitro is much less potent, about half weight for weight, compared to methanol. It only increases power because it needs to come in at much lower stoichiometric ratios (2.5-0.5:1, compared to methanol's ~6.5:1 best-power ratio). So, you need to burn a lot more nitro, to get a little more power.

And as to having the glow-element as an indicator of ignition knock; it is a good indicator of the combustion temperature, which is also much higher during detonation...

Hi!
You are right kochj!
Using small amount of nitro will make it possible for a glow engine to run cooler!
That's a fact every experienced R/C flier knows ..or should know...!
The reason behind this is that small amounts of nitro ( 5-15%) will make it possible to set the high speed slightly richer and still get the same rpm as with 0% nitro.

Thanks...
That is all I was trying to say!.....