[RAMJET]

If you have changed nothing and the engine is not running as it did something has changed, going to a different plug should not be necessary unless the first plug you used was to cold for your application (you let it idle a lot or run rich). Check the plug to see if it's fouled ,if it is you could try a hotter plug to resist fouling in the future . problem with running a hot plug is though it may help keep the plug from fouling when idling on the flight line it could melt a hole in your piston if when you do fly , if you fly it hard . My advice would be to set the plug for your type for flying (if you fly hard /hover ,use a cold plug) if you just putter around( use a hot plug ). and avoid any long periods of idling with 2 cycle engines because it will give you false readings on your plug . to check your plug color , put in a new plug and run your engine at the RPM you normally fly for a couple of min then pull the plug, should be light brown . cheers Roger

Originally Posted by mrrandyman

Thanks for the info folks.
So here is another question. If say a Gas engine seems to be not performing as well as it should would changing the Sparkplug out with a different type improve the performance?

I say that given that everything else is connected/Clean with no obstructions and the fuel is fresh and mixed properly.

[mrrandyman]

Thank you for all the input.
I should have just asked if installing a different plug would result in better performance out of a given gas engine.
I will stick with what is advised rather than take the chance of blowing an engine.
Other than the one gas engine I sent in for service I have had no real issues other than the length of time they seem to take to break in to obtain optimal performance.

[floyd]

You can cross reference plugs online and get the same heat ranged plug in a different make. You have to remember what Roger touched on, up in Canada running any engine is different than in the States. I had to order in my Bosch plugs, but they cost the same as the NGK did. I had a Supertigre 90 that took over four hours to break in before I could get a satisfactory needle setting to fly. The ring was so hard, but that's a good thing for wear. I've seen the same with Saito's that needed a longer run before you could get a good needle setting to fly. Almost the same as guys I've seen tuning a 2-Stroke with a #8 OS plug in it, Its an endless ordeal with the same dead stick result.
Cheers Floyd

[Flypaper]

Rule of thumb is to run as hot a plug as you can before detonation. As you know, the number on the plug designate how hot it is. Best way is to go by the mfg. of the machine as to what plug they recommend.

[floyd]

Originally Posted by Flypaper

Rule of thumb is to run as hot a plug as you can before detonation. As you know, the number on the plug designate how hot it is. Best way is to go by the mfg. of the machine as to what plug they recommend.

I agree with the first part of your comment. But if your engine comes from the southern States the climate is a lot different than what we have in Canada. The plug they tested in the engine may have ran fine down south, but may not be the best for a Canadian climate. Just like the OS#8 plug running fine down south, but it doesn't run very good up in Canada. Cheers Floyd

[Flypaper]

Was just a recommendation to be on the safe side. If it does foul plugs from running too cold up here. go to a hotter plug.

[RAMJET]

Flypaper I am not sure if you are talking about glow engines or gas engines , a too hot plug in a glow engine could cause detonation . Too hot a plug in a gas engine would more likely cause preignition because the plug heat range does not change the timing on a gas engine so it will have little bearing on the pressures or heat in the chamber. Preignition in a gas engine is when something in the chamber gets so hot it lights the mixture before the spark plug fires but the mixture burns like normal , timing is advanced greatly though causing extreme heat . This condition will melt pistons, burn valves (that is why you never hear you dirt bike rattle like a detonating car before the piston melts) it was suffering from preignition. Detonation occurs after the spark plug fires, the flame front is burning normal until the pressure gets so great it surpasses the ability of the fuel to resist exploding (detonate) this condition will cause cracking and breaking of parts and has a distinct rattle . like I said deeeeep rabbit hole. and this is only scratching the surface LOL cheers Roger

[mrrandyman]

Looks like I started something here.
I'm only speaking of possible improvements in our Aircraft engines ( Gas ) that is.
My goal is to learn as much as I can from your knowledge so that I can better understand how to maintain and possibly enhance my future use of these engines.
It would be pretty cool if we could hook up our engines to a computer to fine tune them.

[floyd]

Here's a comment I posted on another RCCanada thread regarding burning gas in a glow engine with just changing the plug to a G5. Gas engines are very finicky to run properly as the post describes. Judging by the amount of crashes I've seen with gas engines its not as easy as it looks to set one up and keep it set up. Just like in the spring and fall I have to change the needle settings on my glow engine to compensate for the temperature differences. I think gas engines are still in learning mode for most people. Cheers Floyd.

Now then you cannot just stick the G5 plug into any glow engine and have it run properly as a gasoline engine. Many glow engines have too high of a compression ratio and may wind up with pre-ignition or detonation occurring. You may be able to use high octance aviation gasoline to compensate though. But using some head shims may be better. Also the regular RC glow engine carburetor is calibrated for methanol fuel and is designed to run a more rich air to fuel mixture. You will likely have to do something about that. Methanol will still combust inside a glow engine with a wide range of air-fuel mixture ratios. But gasoline only works within a very narrow range, which is why they have fuel pressure regulators, etc in the carburetors to help them work right. Some gas engines such as the NV-Engines GX-40 .40 gas engine changed a lot of things inside the engine too. A different combustion chamber shape, porting, piston, etc were all changed.