Armor-All anti-foam, yes or no?

[Terry Caron]

It does keep foaming down - what's the downside?

[RknRusty]

I think some people tend to use too much. I've heard the formula has changed in recent years, so I can't make any claims for it. I've used the same bottle of Son of a Gun brand since around 1979. I take the cap off of a new can of fuel and spritz it into the cap. Then screw it on and shake it up. If I accidentally use too much, I can shake the cap out before putting it onto the fuel can.

It is said by its detractors to cause a whitish crud on the glow element. I haven't ever had that problem. Once, in 2012 or thereabouts, I had a batch of Sig Champion that caused all of my plugs to turn white and quit working, but after I got rid of that fuel, I never had any white crud again. I put it in every new gallon of Powermaster I use in my stunters. I originally started using it on 1/2A, but since converting them all years ago to bladder feed it's not necessary.
Rusty

[Terry Caron]

I've been fiddling with an old Fox .15 on an old Sterling P-40, standard wedge tank, and it's not holding a setting.
Richened ~800 rpm from peak and it leans again after a bit, so I thought maybe foaming?

[Mike Griffin]

I don't add anything to the fuel mixture I use.  I have found over the years when you start over engineering things you usually end up behind the 8 ball.  Just use good fuel for the engines you are using.  I fly a LOT of profiles and have never had foaming problems.

Mike

[Scott Richlen]

Terry:

You might have a lot of "ifs"  - if you are not using a uni-flow tank you can expect a speed-up, if the tank is not properly mounted you could have vibration and bubbling, if the engine is old and shellacked you could have hot running, etc.  (If I were using an old Fox 15, I wouldn't expect much to begin with.)

You'll probably have to run through a bunch of fixes to find the problem and solve it.  Good luck!

[Terry Caron]

Expectations aren't very high, Scott, but it should be more stable.
I'm running it on the ground so only burning ~1/2 tank; vibration doesn't seem bad; I cleared the fuel line/spraybar.
I hadn't thought, but it's an old shellacked tank so may be internal crud - I'll try another tank and see.

Thanks.

[Dan McEntee]

  When ever I have resorted to using it, I only put just a few drops in a gallon of fuel, and it's enough to stop foaming. I was at the R/C site at Buder Park a few years ago, and a guy was trying to fly a pusher R/C jet, an F-100 I think, and couldn't quite get a good enough needle to get it hand launched. I mentioned the fuel foaming in the tank and suggested the Armour-All cure. he was very reluctant, thinking it would ruin his fuel. I told him if it didn't work, I would give him cash for a new gallon of fuel. I had some Armour-All with me, so gave his fuel the treatment. Just a few drops and shook the jug to show that it wasn't foaming.He started the engine, and it immediately started to run and needle smoother. We could see the tank, and didn't see any foaming like we had before. He got the setting he wanted, but I stopped him and told him to back off a few RPM, and again he was reluctant but agreed, and gave it a launch. It flew out about 20 feet, settled just a tiny bit before it got up to speed and climbed out nicely. The engine ran really nice, and once he got some altitude it peaked out and really sung. I have seen it work in other occasions, but it is one of those things that if a little is good, a LOT more may NOT be. A treatment of a few drops doesn't last the whole jug either. Over the course of a gallon, it needs to be reapplied if you can shake the jug and it foams. In that small amount, I don't see how it can affect the glow plug, as I have never seen any unusual deposits on the plug, but then again, I have only treated fuel when I thought it was needed or there was no other recourse at the field. Like a lot of stuff you read on here, your mileage may vary. Some people can take a simple function and get it really screwed up. In short, I think it works because I have seen it work, but only apply a tiny bit when you need it. Like others have stated, it's better to build a more solid model than rely on modern chemistry!
   Good luck and have fun,
    Dan McEntee

[Terry Caron]

Just in case, I added just a hint to the fuel and it's not foaming.
I've bench-run this engine before (different tank) w/o the instability and it ran well (for a Rocket .15, I suppose - 7x4 MA @ 14.2K on 10%/27%).
The tank change should tell tomorrow.

[phil c]

Armoral can definitely crud up the glow plug.  Too much, more than two drops or just enough to stop the foaming when the jug is shaken hard) as Dan says can cause the problem.  The other  effect seems to only apply to planes flown with a bladder or pacifer pressure system.  As it gets to the end of  the tank the motor tends to richen up. If it gets too rich but doesn't quit it leans out and stops. The hot motor and the cold rich stop seem to be part of what makes the Armoral build up on the glow plug coil. 

The platinum in the coil is a catalyst that fires the charge in the cylinder.  It has to be hot of, course, to work, but glowing white hot isn't necessary.  As the crud builds up it blocks the catalyst and makes the plug act "colder".  It can't fire the charge making the motor run rough and quit.

[Terry Caron]

I cleaned the spraybar, needle and tank, checked everything for leaks and still unstable rpm - never run into this before.
Plug's an OS A5 (now #10), a cold plug - could that be it?
There's no rpm drop when I remove the igniter.

BTW, it's a Rocket .15 and again, I'm ground running it right now, not flying it.

Maybe this should be in Engine Set-up Tips instead.

[Scott Richlen]

About the only thing I can think of is to check to make sure that the engine backplate is not leaking.

Two other things: how is the engine rod?  If it is wallowed out it may cause bad engine runs.  Can you detect any needle valve vibration or leaking?  We used to slip fuel line over the outside threaded section to seal it against the needle.

Do you have any flyers around with engine smarts?  A first-hand look is probably much better than these long-distance guesses.

[Terry Caron]

Thanks for the tips, Scott, no needle leak or vibration and I'll check the backplate and rod.
I have experienced guys available an hour away so if I don't find any of those probs I'll ask them next time we get together.

[Steve Helmick]

Only thing I've ever added is an ounce or two of Randy Aero's "Aero-1" oil additive, and that only to 10-18 Wildcat Premium. Never have run any other "R/C" fuel. Just got a gallon of 10-10-10 SIG at Eugene Toy & Hobby last Friday, which I don't think I've ever run.  Steve