Going from a hot to a cold !!

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mackdaddy66

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I think i'm gettin a bead on it i put two o.s. #8 glow plugs in my savage .25 running 20 percent it turned them both white, but i richened the high speed, ok now i put in a r5 cold and that same truck that was idling good with the #8 wouldnt idle with the r5, ok so if a hot plug in effect advances the timing, then a cold plug retards it in esscence, if thats the case i would need to either richen my lsn or lean it. to get that same truck that runs good with a os #8 to run with a r5 cold what carb adjustments would be necessary. i am out of o.s. 8 plugs, and am trying to learn to tune so please explain if you would. i want to tune my own engines. hpi .25 in a savage xl by the way. please explain if you guys would so i can learn its important to me. and thank you very much
 
noone, well ok then, i only had a r5 left so i put that in there today, truck was very fussy but did get it tuned. going to the hobbyshop tomorrow to buy more o.s. # 8 plugs, just hope they last longer than the first two. the .25 engine definately runs better on hotter plugs, just lookin for advice to help me when i am tuning. thanks
 
well, i went out and fired up the .25 hoping i tuned it well, happy to report it run great for the whole tank. the truck isn't as fussy with the 0.s. #8 plugs, but they didnt last long, with the cold plug r5, it quit twice when i first started it but then ran fine. i like the hotter plugs but at $8.49 each, i can't afford to fowl plugs two a day, anyone know a good plug like the o.s. #8, that lasts longer? how bout mccoy plugs?
 
Turning the needles is all about getting the right air/fuel ratio, and has nothing to do with your plug choice. Most big blocks will run just fine on a medium plug. Advancing the timing via plug and/or removing shims can cause detonation, which will reduce performance slightly.
 
well, according to what I've read you are wrong, sorry, on a 2 cycle engine a hotter plug is like advancing the timing, since it has no ignition system. a hot glow plug in esscence advances the timing, a cold one would retard it. you would have to understand what a hotter glow plug does so you could then understand how to adjust the needles accordingly. the way i understand it its more of getting the right air-fuel mixture at the right time. all has to work together. cause no ignition source no explosion.

---------- Post added at 8:49 PM ---------- Previous post was at 8:42 PM ----------

also, a hotter plug will hide a bad tune, or give a lil extra power to a worn out engine, i now see why guys like hotter plugs, when i switched to the r5 cold the truck that idled greast got fussy, quit a few times, but i am still learning, i just think that its not just about turning needles, its the right air-fuel mixture at the right time. thats what i want to learn. I've called my father a dozzen times, he says i'm on the right track. still, i got lots to learn i know that but my lil .25 idles and runs really good after tuning so i'm learning
 
Y ou have thing a bit off. your theory of advanced and retard timing is correct, however this relation between timing has nothing to do with mixure settings. All engines are gonna run ideal at about 1 part fuel to 14 parts air. therefor needle settings are only needed to compensate for atmospheric changes and air density.

Timing is a whole diferent issue. In general the temperature of a plug is related to the "temperature" of the fuel being burned. A hot plug and 20% nitro will give you about the same timing as a cold plug and a hotter (30%) fuel.
 
I see your point, my engine hpi .25 running 20 percent seem to run better on a hotter plug at first, it wasn't as fussy when i first started it as it was with the cold plug, with that said once it got a lil heat in the engine it ran fine with the cold plug. the only problem i had was the hotter plugs went bad very quick and my r5 is still fine. is there a COMPROMISE if you will between a o.s. #8 and a hpi r5 cold that may give me a smoother idle and last a while since glow plugs are kinda high? maybe a medium cold plug????

---------- Post added at 11:44 PM ---------- Previous post was at 11:37 PM ----------

keep in mind i am a basher and what i want is a glow plug that makes the engine less fussy like the #8 but lasts longer like the r5 hpi cold. if they even make such a plug. also i am going to drop from 16% oil content to either 12 or 14. i think the high oil content is definately making my engine a lil sluggish. any and all input would be appreciated as i'm going to the hobbyshop tomorrow. thank you and i really am trying to learn to tune, just gotta hang in there, trial and error my father says. I've got my truck runnin good now but i want to understand more so i can tune better. thanks
 
hey one more thing tower hobbies says hpi recommends r4 or medium cold plugs for their .25 engines, i am gonna buy some medium cold and see how that effects my engine. this "stand-in" .25 has been the perfect mill to learn to tune on, and they say to get in there and do it is the best way to pick it up. peace out !
 
I run OS LC4 medium plugs with 20% nitro 14% oil. I can usually get a gallon or 2 of fuel out of one before I have to change it.
 
hey thanks, now if hobbytown usa carries that plug i'll try it. 14 % is about what i want to go to, last time i was there they were out of my usual so i bought wildcat eliminator 20 % with 18 % oil content, i think its makin my mill sluggish, i thought about buying some 10 % oil content and diluting it, but i think i'll get some byrons 20 with 12 or 14 % oil, save the oilly stuff for break in maybe.
 
I ordered my plugs from ebay. I got a card of nine plugs for about 36.00 shipped. My closest hobby shop is 60 miles away so it's not very practical for me to run up there every time I need a plug.
 
mackdaddy66 said:
well, according to what I've read you are wrong, sorry, on a 2 cycle engine a hotter plug is like advancing the timing, since it has no ignition system. a hot glow plug in esscence advances the timing, a cold one would retard it. you would have to understand what a hotter glow plug does so you could then understand how to adjust the needles accordingly. the way i understand it its more of getting the right air-fuel mixture at the right time. all has to work together. cause no ignition source no explosion.

---------- Post added at 8:49 PM ---------- Previous post was at 8:42 PM ----------

also, a hotter plug will hide a bad tune, or give a lil extra power to a worn out engine, i now see why guys like hotter plugs, when i switched to the r5 cold the truck that idled greast got fussy, quit a few times, but i am still learning, i just think that its not just about turning needles, its the right air-fuel mixture at the right time. thats what i want to learn. I've called my father a dozzen times, he says i'm on the right track. still, i got lots to learn i know that but my lil .25 idles and runs really good after tuning so i'm learning
Click to expand...

You're the one having problems and asking questions, and all of the sudden you know it all huh? Good luck to ya!
A hot plug will most likely cause detonation.....which can also be referred to as pre-ignition. Run a medium and learn how to tune.
Don't tell me what I have to learn, I get close to a gallon from my plugs every time.
 
Last edited:
page 86, RC CAR ACTION, its about glow plugs and no i don't know it all and at least i am open to discussion and debate, you must know everything. oh, and i am learning to tune. you act like your some genius, i just bet someone taught you. at one point you had to learn too. so i'll go on n ask questions, and you'll go on knowing it all.
 
that's what my wife told me last night ! lol yep, ya know she was right, i didn't ! lol oh, well, if ya can't run with the big dogs stay on the porch, so i guess i'm on the porch! now, about my attitude, right after that cop put me in jail last week he said "BOY, YOU GOT YOURSELF A BAD ATTITUDE" I replied, i know sir but they say theres one in every crowd, well, guess what? had to be me. point to ponder

---------- Post added at 12:56 AM ---------- Previous post was at 12:54 AM ----------

"and as my dear old dad says " horsefeathers"

---------- Post added at 1:04 AM ---------- Previous post was at 12:56 AM ----------

I dont know much, but i can read, i can learn, and i will!

---------- Post added at 1:06 AM ---------- Previous post was at 1:04 AM ----------[/SIZE

---------- Post added at 1:17 AM ---------- Previous post was at 1:06 AM ----------

Now, well, i visited my local hobbyshop and picked up some mccoy mc8 glow plugs and a gallon of byrons 20 % with 12 %oil content, i am gonna keep tryin, of course i will mess up, but you see that is how to learn, jump in and do it trial and error, helps to read articles and have a mechanic for a father, but i gotta walk this road alone and given enough time, i will make that savage sing, does fine now, not perfect but all in all pretty good. peace and no hard feelings guys!!
 
Ok, so you're a know -it-all, congrats for you !!
 
well, if i upset anyone i apologize, didn't mean to upset anyone. peace !!
 

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