Fuel Age and % Nitro

Hi Darren, as I wrote you in my email, the following may be the reason for power loss especially in beautiful Thailand where you fly:



Apart from methanol and nitro evaporation, sometimes the fuels get saturated in water especially in humid countries like Thailand. Glow fuel is hygroscopic and tends to absorb humidity of air in the short time and multiple occasions you open and close your can for refuelling. If this is the case, the only way to help is replace fuel with fresh blend, unless some desiccant is found that does not combine with fuel...but I would not try that.

Another reason of power loss maybe varnish deposition on cylinder wall, another symptom of humid air, that carries water and promotes varnish formation. I would expect this to be the case in Thailand.

Remove the glow head and turn the prop around. If you feel irregular resistance when the piston moves before and after the top dead center, that is an indication of too much varnish, that is also visible as a brownish discoloration of cylinder wall.


For varnish removal, I do not use the the devarnishing brush. You may want to follow this:


Remove cylinder.

Soak a cotton earbud in cold grease remover fluid used in the kitchen and swipe the cylinder wall with the bud multiple times until earbud turns brown. Repeat until last bud remains white and cylinder is visibly clean. This won't take more than 2 buds.

Wrap next earbud in a piece of aluminum cooking foil and move it around the cylinder. Aluminum will not scratch cylinder but will remove the remainder of varnish.


Wash cylinder in water or some solvent  to remove grease remover and varnish fragments, then oil and put it back on engine. Check if piston movement is easier. Older cylinders may be taper bore that shows some normal resistance near the TDC, but they also get stuck in varnish sooner...so some result of devarnishing will surely be tangible.

I just did this devarnishing with success on a COX049 that had too much varnish on its cylinder, most likely due to my flights in early spring with high relative humidity in our otherwise continental climate in Hungary.

I trust it helps you too.

Hi Iceberg,
Most of my Cox .049s have run on %15 Nitro.
The mix I get is 18% oil, 1/2 castor. I add some extra castor to bump it up to %20 oil.
I am not breaking speed records here, just having fun.
%25 Nitro did not make much of a difference. %5 Nitro did.
Here is the problem...
The methanol part of the fuel sucks up moisture. Whenever it can.
I can say this sucks, without getting kicked off this Cox forum.
Old fuel,
Is old fuel.
Same with Acetone, leave the cap off, it is water tone.
The only way to burn old fuel,
Is to mix it with fresh stuff...
Your results will vary,
Take care,
Have fun,
Dave

HalfaDave wrote:The methanol part of the fuel sucks up moisture. Whenever it can.

I don't say this proudly, but my fuel is at least 5 years old stored in a dark corner of the garage but still works OK, but we have very low humidity here in eastern NM, sometimes as low as 7%, usually below 20%. This is why evaporative (swamp) cooling works very effectively. (Psychrometrics (spellchecker changed it to psychometric, root psycho, crazy ) science - when you add water moisture to the air, it drops the temperature of the air. The lower the humidity, the more effective this type cooling works.) This may explain why my fuel still works.

HalfaDave wrote:I can say this sucks, without getting kicked off this Cox forum.

We have emogies such as           and you are worried about the word, "sucks"?  
 

I have a little story.   Back in the early 2000's at Cannon Air Base, one late afternoon, I was doing some research looking up metering devices on a website called "flowcontrol.net". (I don't know what's there now, but back then 20 years ago, they had all sorts of valuable engineering science info on material properties, equations, viscosities, pump and fan curves, available transducers for measuring flow, temperature, force, etc.)

When I entered the URL to go there, immediately I received a full screen big lettered pop-up from Air Combat Command! "You have entered a Pornography Site! Your IP address has been recorded!"  

I was tired and frustrated, so, I HIT THAT URL a dozen times before packing up and going home.  

Next morning, I clicked the link, and it opened the site as usual.

I think that I.T. had their watchdog settings set too high, site probably had words such as "suck", "flows", "blows", etc.

Hi gg,

Back in 'the Days', we got metal can pints of Cox fuel from the local hobby shop.
Red label was 'Hot', green was 'medium'.
We took them back to get them filled up again.
No tachs or mention of nitro content.
Just went flying.
With fresh fuel.
%15nitro and %20oil works for me.
If you cannot smell castor oil,
You are not running Cox engines for long.
Your results may vary,
Take care,
Have fun,
Dave

HalfaDave wrote:If you cannot smell castor oil, You are not running Cox engines for long. Your results may vary.

They ought to make a cologne called, "Klotz Benol".

Hi Darren, I never leave the cap off of my fuel containers for any longer than necessary. I probably use LESS FUEL than most of us.. and as a result; I have some really old fuel.. but I don't seem to have any problems with it going bad.  

I doubt that the brand of fuel matters too much.. as long as it's the correct blend for the engine that's using it. That said; I run Sig "Champion" 25 and 35% nitro 1/2A glow fuel in my Cox engines.

I also buy my fuel in QUARTS.. as opposed to gallons, which avoids Hazmat shipping charges. The Sig quart containers are a translucent HDPE plastic with a plastic screw-on safety-cap.

You may want to try transferring any new/fresh fuel into pint or even half-pint containers. Let's assume that we buy a "gallon" of fuel from the local hobby shop and use that gallon container exclusively.. until it's empty. Maybe we even have it capped with a fitting for a fuel-pump for convenience. This is NOT a good idea for someone who runs small displacement (IE: 1/2A) engines. Even if we run our engines frequently; it's going to take a while to use-up a gallon of fuel. Once we reach the half-way point in that gallon; there's now two quarts worth of air-space in the container that can absorb moisture.

You can source a few smaller containers.. which will help to keep your fuel fresh as well as allowing for custom-blending small batches.

As I recall the Cox "sport" engines like the Babe and Golden Bees, Pee Wee etc. are specified to run on Cox fuel in the blue can which was 15% nitro. Contest engines of the TD series were specified to run on Cox racing fuel in the red can which was 30% nitro.
I used to run my Cox TD 049's in 1/2A Free Flight power on 45% nitro which would just stay in solution on cold frosty mornings.
If your Cox engine is down on power after a layoff it could be water from the air that has dissolved in the methanol in the fuel, but it could also be that the cylinder bore has coated itself with the shellac like varnish or the castor oil has congealed in the main, big and little end bearings. I always dismantle the engine fully in that event using special tools I have made to avoid damaging or marring the components. My favourite cleaning method is to soak the parts in proprietary paint stripper containing 83% methylene chloride and 17% methanol for an hour or two depending on how bad it is, cold water rinse in a sieve under a running tap (faucet) then switch to running hot water, shake off excess and lay on paper towel to dry. Reassemble the engine dry then oil with automatic transmission fluid internally and externally to prevent corrosion and bag up in a zip loc bag.

aeroland wrote:My favourite cleaning method is to soak the parts in proprietary paint stripper containing 83% methylene chloride and 17% methanol for an hour or two depending on how bad it is,  cold water rinse in a sieve under a running tap (faucet) then switch to running hot water,  shake off excess and lay on paper towel to dry.

If engine / components are powder coated, would such a method remove the powder coating? Are the plastic carb bodies safe or to be removed? Or, this is only meant for the cylinder and piston?

Yes, paint stripper will remove powder coat on engine parts. as it will remove fuel proofer and any traces of dope that gets on some engines during model finishing. Does not attack anodised finishes.
Cox used nylon tanks on the Space Bug Junior and Delrin carburetor bodies of TD engines and the 010 and 020 tank assemblies too. Those materials do resist paint stripper but I tend to remove plastic parts and wash them in dope thinner in case some bright spark adds something to the paint stripper without declaring it. Delrin has good resistance to aromatic solvent type chemicals and is widely used in automotive fuel system component parts. Delrin however is attacked by chlorine and I am pretty sure that is why you sometimes see TD 010 and 020 engines with tank feed pipes attacked from free chlorine from the PVC fuel tubing. Best to always remove the fuel tube from those engine's tanks before storage.
Need to keep paint stripper off your skin or else a painful burning sensation will result. ALWAYS wear eye protection too. Also don't contaminate it with water or aluminium parts will develop black surface corrosion requiring resurfacing to remove. Clear, green and red plastic tanks on English diesels like ED's are made from cellulose acetate (I believe) and certainly will get attacked by paint stripper or dope thinner. Mills .75 tanks were made from acrylic and if cleaned with alcohol will eventually develop solvent stress cracks. The Mills 1.3 tanks were moulded in nylon and can be solvent cleaned.

Hi Roddie
Thanks for that. I bought a quart of methanol and added 10% as I feel the fuel evaporated about that much. I live in a terribly hot City here in Bangkok and constant on and off AC has taken its toll on the fuel. I ran the fuel with a 10% methanol addition last night in my.15 med as well as one of my TD .09 and it ran super good. I might look closely with the new fuel and see if possibly my old batch might need even another 2-3% of the methanol. But good news as really improved.

Thanks Roddie appreciate the comments.
Darren

Iceberg wrote:Hi Roddie
Thanks for that. I bought a quart of methanol and added 10% as I feel the fuel evaporated about that much. I live in a terribly hot City here in Bangkok and constant on and off AC has taken its toll on the fuel. I ran the fuel with a 10% methanol addition last night in my.15 med as well as one of my TD .09 and it ran super good. I might look closely with the new fuel and see if possibly my old batch might need even another 2-3% of the methanol. But good news as really improved.

Thanks Roddie appreciate the comments.
Darren

Darren, you talk about adding Methanol. I assume you mean Nitromethane.
Rod.

Read #14 over at RC > https://www.rcgroups.com/forums/showthread.php?1950999-How-can-I-remove-water-from-my-nitro-fuel   OK mite want to go to 2nd page talking about filtering .

Saw this while shopping the other day at Albertson. This pilot needs high nitro just like the Cox engines.