1QwkSport2.5r

Since I'm going to start mixing my own fuel, the idea of cheaper FAI fuel is of high interest. Everyone says to run a hotter plug, but hotter vs. what. I run McCoy #59's in all of my engines and I went looking today to find a hotter plug as a backup when I fire up the FAI. Is there a plug hotter than the MC59? What does everyone else use? Its still pretty frozen in Minnesota, so burning any fuel probably wont happen for awhile yet..

I'm probably going to run the FAI fuel when I'm out "bashing" around. If I get into any sort of racing I'll use some nitro in the mix.

My first batch was going to be a quart "test" bottle. 20% castor, 3% acetone, 77% Methanol, and a half drop of silicone oil for foam control. Test mule is a TT .46/Jett muffler

pe reivers

nice mix.
Raise engine compression ratio until you start burning plugs every five flights or so. That will get you best power without nitro.

carrellh

Consensus on glow plugs? Not likely.
Based on the part descriptions at Tower, it is possible the MC-55 is hotter than the 59. They list a phone number for McCoy: 909-982-3888

From Tower tech notes:
This is the McCoy MC-55 glow plug without idle bar for low nitro and FAI use.
and
This is the McCoy MC-59 Standard Long Plug (No Idle Bar) with a Hot element that's designed for use with Low to Medium Nitro Fuels, perfect for Helicopters.

downunder

Although it's best to use a hot plug for FAI fuel I wouldn't get too concerned about it until you find out how the engine runs with whatever you have now. By "runs" I mean how well it idles and transitions. My only fuel is FAI but I mainly fly CL so idling isn't a problem however my son flies RC with the same fuel and we never get particularly concerned about plug heat range although we tend to buy a hot plug when needed.

Raising compression will certainly help to make the most of straight methanol but the amount needed requires a lot more than just taking out a few shims. Compression needs to be up around 13.5:1 which invariably means some head machining is necessary. Plus a lot of careful measuring .

Chances are you may be quite surprised how well the engine runs on FAI fuel. My ST45 turns an APC 10x6 at 14,600 revs with 25% castor and my OS 61VF has the most amazing transition from idle to flat out that I've ever seen, it's almost instant with a 12x6 prop.

iskandar taib

My Feedback: (5)

Hotter plug? Try one of the four stroke plugs - Fox Miracle, O.S. F, McCoy 4 Stroke, etc. I remember trying a Fox Miracle in a Fox Combat Special (Mark IV) - you could tell the difference turning the engine over by hand with the plug driver connected. Talk about a bump!!

Iskandar

fiery

My Feedback: (2)

Agreed

Just tried a McCoy MC-4C plug (nominally a "4 stroke" plug, though it is a standard long reach configuration) in an old Taipan glow engine. It loved it, more so than a standard "hot" plug.

1QwkSport2.5r

AFAIK, All McCoy Glow plugs are long-reach plugs. The MC4C plug is the hottest plug they offer, I believe. Only slightly hotter than their MC59 which is quite hot in itself. I have been using an MC59 in my Enya SS30, I just added an extra copper washer to shim the plug out of the chamber a bit more. All the rest of my engines use long reach plugs and perform wonderfully on the 59's even using 80/20 true FAI fuel. My Super Tigre S90K ran fine on my homebrew FAI fuel once I added some acetone to it on the same 59 plug. If I didnt want to add acetone, I'd probably go one step hotter with the plug to keep the idle a little more stable.

I haven't tried mixing up some kleanstrip brew yet though. I wonder if a 59 can hack it...

KeroPower

I just use the OS #6. My Fox .40 R/C runs perfectly on FAI with that plug.

1QwkSport2.5r

I tried an OS #8 & #6 glow plugs in a couple car engines I had 10 years ago and they ran horrible. The short reach influenced compression to a noticeable degree in my test engine at the time. Traxxas glow plugs ran better. I switched to McCoy 2 years ago and have never looked back since.

So many people put OS on a pedestal, a benchmark if you will, and I just don't see them being that great. I myself won't buy anything with the OS name on it. Especially when their glow plugs are $2-3 more expensive than any other brand sold locally. Their engine prices are outrageous. I'm happy with what I use.

KeroPower

I agree completely. OS products are WAY over priced. I mean $150 for the .25 AX, that is insane. The OS plugs I have were not purchased locally. I usually through a couple in the cart whenever I order something from Tower. Locally, they are expensive.

The last (also final) OS engine I bought was the humble .25 LA. I bought it from the hobby shop next to the AMA field in Muncie, Indiana (I visited a few summers ago). I will admit though that it works as well today as the first time I ran it three years ago.

Currently I have gone all American made engines. A Fox .40 R/C, Fox .25 R/C, Fox .25 C/L,and a Fox .15 C/L. So far they have all been great. I am thinking about trying K&B next.

Fox Hot 0% Nitro plugs do not work well at all with FAI fuel.

1QwkSport2.5r

I'm going to trade my now worn fox .40 for a new fox when I get around to it. I like to support the US but the engines ive acquired lately have been too good of deals to pass up. Enya .30, ST s90, and TT .46 awhile back. I have 2 k&b's but they need help in the form of new carbs.

I'm sure OS was the sniz back in the day, but there are better and cheaper options out there that last as long or longer and give hassle free operation.

I've heard that new fox carb is really a nice piece, any comments on it?

Sport_Pilot

Hot plugs!  Enya 5, OS A3, Fox Miricle, OS F, and the hottest plug I have seen is the Thunderbolt 4C plug.

1QwkSport2.5r

My Ol' Faithful MC59's work valiantly with FAI fuel. With 4-5% acetone the idle is near perfect as compared to 5% nitro/no acetone in my ST S90K. To note, the Exhaust note has a nice "snap" to it on FAI that it doesnt have with 5% nitro.

Fox Miracle plugs are medium/hot plugs I think.... Not quite as good of idle as the MC59, but better than the K&B 1L. I have some Traxxas medium plugs, 1 Duratrax LR3 (which is as an OS LC3 I think), and a few other no-name plugs. None of them run as well as the MC59. I thought about getting a MC4C, but I dont need it.

Enya and OS plugs are not long reach. All of my engines use long plugs except the Enya 30SS bb I have. I use a long plug with 2 washers in this engine. 1 1/2 gallons of break in on the same (originally used) MC59 and she rips real nice (and loud)...

I dont think the Enya will run on FAI as well as the Super Tigre though. Nowhere near the same compression ratio.

fiery

My Feedback: (2)

I run an Mc Coy MC 59 glow plug in this old Sanye .46 engine, with nil nitro fuel.

Lube is 10% first pressing castor oil, 10% Klotz KL-200. Balance methanol.

The thing runs really well. The engine is in good shape. Prior to insallation in the aircraft I replaced the piston and liner with a new set.

It has never quit in the air. Idle and transition are perfect on the MC 59 long reach plug. Not so on a more highly regarded plug from a Japanese manufacturer.

1QwkSport2.5r

Thanks for sharing that. The MC59 is been my go-to plug for the past 5 years. When I ran 80/20 FAI fuel in my ST S90, it ran fine on a MC59 plug. It lost about 800rpm from 5% nitro, but it ran well and throttled okay. This was true FAI, 80% methanol 20% castor. I now have a good stock of Enya #3 plugs of which are a good and hot plug as well. I'm sure these would work as well or better than the McCoy MC59 plugs.