"Taters" is short for potatoes...presumably because they look like tiny little potatoes growing on the coil. I've never seen them myself though.

Dar,

Taters = potatoes...sorta what these build-ups look like when magnified.

George

Edit: Sorry, Downunder. Didn't notice that there was a second page...Looks like we agree.

OK, Brian, George.

What about that skin disease?! Never mind...

About two years ago I started a thread about that scale like 'growth' on the glow element.


It was said to be a result of an additive in some fuels, or some after-run oil. I saw it with Morgan Omega fuel in an OS.46FX, but I never saw it with Model Technics Duraglow.
I used Hobbico after-run oil exclusively, with both fuels.

I have a C6S plug in an MVVS .49, that has been there since it was new (over 70 hours), yet has no sign of 'taters', or any decline in performance, yet.

I seem to remember from years ago in another forum (SSW) that Byron fuel was renowned for causing taters. I think there was another fuel too and Cruel Power rings a bell.

Keep going with that plug in the MVVS, I used the same plug (whatever it was) for hundreds of hours in an Enya 45

Not all glow plugs are created equal. Cheap ones are plated ( would you rather have a solid gold watch or a plated gold watch. and better ones are mixed alloy. Another words some platinum is mixed inside and out , not just outside plated. Just because advertized it may say 100% platinum could mean of the platinum portion used it is 100% pure. Just like if I grabbed a fuel bottle that said 99.97% pure methanol would kind of look like there is only .03 oil content. But it just accounts for the meth portion. If there is excessive carbon I'd look for fuel brand or running a little to close to lean setting and burning up lube oil too.

There are no plated plugs and there are no 100% platinum plugs. If you say there are, how about an exacmple of each??????

Well, tested. The plug was no issues. The old plug still give 9300rpm as brand new one. The new one seems to give a feel of a bit more responsive feel. I richen the needle by half a turn with the new plug and it still give 9300rpm and spool up with no hesitation. The old plug will slowed if I richen the needles. I guess the element is somewhat lesser of performance when the condition is more richer, eh?

This thread is getting so long I don't remember if this has been covered. If so, apologies.

Engine timing adjustment is a function of prop, fuel, glow plug, and compression. Change any of these and engine performance will change.

Assuming the prop is sized for the plane, you don't want to vary the amount of head shims, and you are using the fuel you want to use, the only thing left is the plug. I would suggest trying some different heat-range plugs to see if the timing is off a little...or some different fuel.

Taters: If memory serves, these are caused by impurities in the fuel, such as too much silicone (for foaming).

George

George,


One more thing affects the engine's ignition (actually maximum combustion pressure) timing and it is the mixture strength.

Since this was widely elaborated in some other recent threads, I would not go very deeply into it again here.

In short, leaning the mixture advances the ignition timing and vice-versa.


So, if you have slightly too much compression, slightly too hot a plug, slightly too much nitro, and/or slightly too heavy a prop, you could prevent the onset of detonation, by richening the mixture.

...The cost is a marked increase in fuel consumption, which is why mid-large engines that are incorrectly installed with an OS A3 plug, become fuel guzzlers...


Getting an engine to run properly requires that all the parameters be optimized. Getting just the highest RPM is insufficient.

Where did that little tidbit about A3 plugs come from?? I have used an A3 an Enya#8, an OS #8 as well as a Fox and K&B plugs in my OS61FSR. The difference in fuel consumption is negligible

You all has been very helpful in providing the insight. At any rate, the overall performance has drop since everything else remain unchanged with the exception of fuel. I may have not richen it adequately when I move to 15% and this may have overheated the engine. So my top end with the same prop ie 15x6, was only 9300rpm. It used to be at least 10000. The differences are so vast that I lost the following:

I used to be able prop hang the Velox with 7.5lbs AUW, and have slow vertical on 5% with 15x6. With 15%, the power is crazy! The vertical punch is very strong. It can even spin 16x6 with ease and able to knife edge loop with ease.

Now even on 15x6 with 15%, it barely able to hover at WOT. So something has happened around the last 2 gallons when I first moved to 15% cool power. Totally forgot to richen it a tad more with syn fuel. I lean them out and richen it as in Castor based. I should have richen a tad more...sigh!

I have not dismantle the head to check for cylinder and ring for scarring. The idle still perfect, start with a snap, and transition is superb,,,,,,just no top end.

And recently with a direct nose in, I wonder if the bearing and crankshaft have any damage though it ran last 2 weeks with no excessive vibe. If I were to replace the ring, cylinder liner, bearing, etc. Heck, I might as well get a new engine. The 120AX only cost like US225 though the magnum/asp 120 can be had for US150 locally.

Dilemma dilemma dilemma....

Did you check the head bolts? loosing 700RPM is major on same prop ,plug brand, fuel. Check muffler tightness and make sure nipple is not plugged.

I was scrounging around in my box for a spare plug after I blew one in my TT46Pro.

First to hand was a used Fox Miracle plug (I've used these in the TT46 before and they're okay).

I popped it in and fired up the engine.

It gave all the symptoms of running very rich -- lots of smoke, revs dropped at idle when the glow battery was removed, and a hesitant transition.

I did a few flights like this then tried to lean the mixture a bit -- but the engine would not peak -- just start dying off if I wound the needle in at all.

I figured this plug was proabably the problem so I replaced it with a brand-spanking new OS#8.

What a difference -- without changing the needles the engine was back to normal. Idling like a swiss watch, brilliant transition -- and much less smoke. In fact I richened the needle about quarter of a turn (to get around 200RPMs down on "peak" and it still wasn't smoking anywhere near as much as it did with the old plug.

I guess the Fox was not providing sufficient catalytic action to promote rapid/full combustion of the air-fuel mixture and the result was that the engine appeared to be real rich -- when it wasn't.

Open up the head and look for any scaring or damage. I have not seen any other than the usual blackness associate with the combustion chamber. How do you know if its scarred? I did not see any obvious scratches. Look normal to me though.

Sigh!!!!!!