Plug Grow Warts...Why???

I have a nagging problem. I fly on a plug for a while, it doesnt matter what brand or type or heat, and it will grow a build up of carbon between the first coil and the side of the plug where it is attached. It is quite frustrating. I have been batteling this now for about 3 seasons. Sometimes it does it in 50 flights sometimes in 10. I can just wipe off the peice and fly it some more butthen after a while it gets hard to needle and you know it is time to change. I usually dont do that unless I am in a contest or only need another 1 or 2 flights.

Anyone got any ideas why this happens.

I run the OS 4cycle plug. It gets expensive after a while. But it does happen on all the different plugs I have tried.

I find this only to be a problem in my PA motor. Do you all think it is my setup causing the buildup? I run the PA in an almost constant 4s. Brett does too I wonder if he gets the same problem.

I run sig fuel 10%-15% Nitro. 20% oil half and half.

Any ideas?

DMoon

PS Tried the Aero one additive. Didnt change a thing or make it run any different. Still grew warts, same amount of time too.

You mean "taters" - they are black on the surface, but if you scrape off the surface, they are tan/gray underneath. The combat guys named them "taters".

Don't know for sure, but it's something from the fuel (likely silicone anti-foam agent) polymerizing under the heat. SIG is really prone to this. Powermaster seems to be almost immune, according to David.

Some engines are worse than others, too. The setup doesn't seem all that correlated. My engine, for whatever reason, doesn't tater up as quickly as say, David's #1 engines.

I don't know if the type of oil makes a difference, but SIG uses Klotz while Powermaster and Rich's Brew, for instance, use Ucon oil. I know the defoamer I had gotten from Red Max would not work on the Ucon oil fuel. Don't know why. But they could be using something else in the fuel.

Matt was having trouble for a while in blowing plugs on short notice, also. But he was using the same fuel (got 11 cases at one time) so one wouldn't think that would be the problem.

Leonard Neumann

Well maybe then I will try me some Powermaster and see what happens.

DMoon

Doug, try soaking the "all tatered up" plugs in Carb Cleaner. Also try Techron, the detergent additive that Chevron and Texaco use. Chevron dealers sell it. Something should remove these "taters" chemically. I would not heat any of these chemicals. The crock-pot/antifreeze cleaning plan might just work, too. Our closest dealer with useful fuel carries Powermaster, and I haven't had a problem with taters, with 4 gallons through the LA .46 on one Thunderbolt. I do have a problem with Onion Rings, tho;-) Steve

this sounds like a different problem, esp. if the deposit is soft enough to scrape off. Could it just be carbon buildup?

No (at least I don't think so). The tater has a carbon outer surface, but the inside is a sort of tan, and looks *exactly* like the one I saw on a combat plug back in the 80's. It's not all that soft - it can be scraped off, but only with some difficulty.

There is an interesting piece in the July 1987 Model Aviation (p 44) that shows cut-a-ways of a couple of plugs, and photomicrographs (shot through an electron microscope) of a plug coil that would nor idle anymore. At 500X, 2000X and 5000X, the damage to the wire is dramatic. An x-ray image of just the carbon deposits on the wire is even wilder. This is worth a look if you have access to the magazine. I would offer to copy it, but can't guarantee that the photos would be any good. But it gives a good idea why plugs get cantankerous at times. It also makes me wonder at claims of 15,000 flights on one plug, etc.

Apparently, the layer of carbon blocks the fuel from getting to the platinum that acts as a catalyst to light the fire. Plus the wire itself erodes drastically. You can see the holes in the photos.

Come to the meeting Thursday and I will give you a copy of the above mentioned article.

DMoon

I remember that article. Maybe one of your illustrious chaps would be willing to scan the pictures and post them here.

Leonard Neumann