RC Model Reviews

What happens if you run hot plug in summer? How do you know it's an issue?

I run hot plugs all year round because I use relatively low (5%-10%) nitro in my engines.

Unless your engine is detonating or regularly blowing plugs, hot should be fine at any time of the year.

Thanks

What the kiwi said, 2nded.

Its an idea to keep lets say a #6 and a #7 in the toolbox. You may find that the #is a little hot for really warm summer days like we have here in SA.
I keep M5, M6, M7 ModelTechnics plugs in the box as well as OS#6, 7and #8 in the box. Through winter I used a #6 or M7 but now with warmer temps the #7 (M6) and #8(M5) are getting some air time.
When I purchased my OS46AX it came with a #6 in the box. I recived my OS91FX today and in the box is a #8 as a running in plug. This seems to bearout the thinking that a bigger engine retains heat better therefore a colder plug is more suited.

This is for fuel with 5-7% nitro and 15-17% oil.
If you use a fuel with less oil then again you will have easier firing and a colder plug may work better.

The OS plugs are pretty damned good... I fired up the club-trainer yesterday for the first time in months and noticed that it was dropping a few RPMs when I pulled the glow-heater.

It's a TT42GP with an OS#8 plug in it.

I replaced the plug (with another #8) and it ran absolutely perfectly from that point on. The annoying thing is that the plug I replaced has only been in that engine for 6 years and has only clocked up (probably) 100 hour's flying time.

Not too bad I guess -- except that the plug in my HP21VT is almost 30 years old -- and still glowing strong.

I beat the snot out of a Merlin 2003 using it in different engines with lots of different setups and it took me 2 years to blow it out. And that might have been because I over amped it with the glow panel.

I have just started using OS-F plugs as I was having difficulty with my OS 20 four stroke and a clubmate gave me a new OS-F and it worked a treat . I ordered a couple more to replace the one I was given and read that OS-F pugs work well on inverted engines . So I put one in another model that has an ASP 21 that has never run right and Bingo , it now runs perfectly . Can anyone tell me why ? I'm guessing that maybe a slightly higher compression but I don't know . Also , Why is it that engines don't like being upside down ? Anyone like to enlighten a relative beginner ?

If an engine doesn't like being upside down it's usually because the fuel-tank is too high.

Because the carburetor of an inverted engine tends to be much lower than that of an engine mounted upright, its very common to find that the inverted engine runs rich at idle -- making it impossible to get a reliable low-speed idle without the engine cutting when the throttle is opened.

This is why a hot plug like the OS-F can help, it allows the engine to tolerate the much richer mixture that comes from having the tank higher than the carburetor.

The best solution however, is to try and lower the tank.

I had this problem with my P51D Mustang with ThunderTiger 91FS engine. I ended up replacing the standard tank with a smaller one that could be mounted lower in the fuselage. Now it idles like a dream, as you can see at the end of this video:

P51 Mustang wheels-up touch and go

Thanks for that Bruce . Fortunately I prefer vintage models which tend to have upright engines and as the Kiwi Cavu is now running ok with the OS-F plug I think I'll leave it be , it's been on the operating table plenty already . The model I have just started building is a 1/4 scale Fairey Tipsy Trainer which I also have a Thunder Tiger 91 to go in so I will be wary as to where I stick the tank . Cheers.

I don,t think I ever met a glow plug I didn't like. Previous post pretty much nailed it. Al Kelly is a great guy. I've known him for thirty years and his Merlin glow plugs are as good as any currently available. Al used to manufacture the best composite propellers available. Glow plugs are a way of adjusting the timing of your engine. A hot plug advances the timing. A cold plug retards the timing. Too hot and you can get overheating, distorted or burned out element and detonation. Too cold and you will probably have poor throttle response . Air temp, humidity, engine design and nitro content all contribute to the correct plug to use. Just because everybody in your club likes OS 8 plugs doesn't mean you have to use them too! My .46 fx likes Powermaster YS 20/20 fuel and an OS 6 (old A3) plug. Experiment and use what works best for you