glow plug

tdogg

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Hi guys i have a savage 3.5 and know abit about tuning but will a hotter/colder plug effect the tuning
 

tdogg

Member
Messages
6
Location
Western Australia
Thanks mate was exactly what i needed to know they gave me a r5 for my hpi savage 3.5 which was making it run too cold but the os 8 works good was thinking the os 7 would be better i used to run it in my lrp 28 could also be why i cant get the engine temp up to 220 any thoughts?
 

X

Conspiracy of One
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Yea, a cold plug should 't be used unless you are running 30% or greater nitro. Or a big engine. Running a hotter plug will certainly help a little with your temps. Also, are you tuned for power (past break in) ? If so, perhaps you could try leaning out the HSN a bit.
 

tdogg

Member
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Location
Western Australia
Thanks x i ran it too lean trying to get the temp up ill see what happens when i put a 7 glow plug in it I'm running 20% nitro in my savage 3.5 with the stock engine size 21
 

tdogg

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6
Location
Western Australia
Can usually tune an engine no probs but i think the glow plug is throwing it out didnt help using a cold plug on a offroad haha
 

olds97_lss

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Plug temps really only change the engines timing. Higher nitro fuel detonates easier, so usually with higher nitro (30%+), you run cold plugs to avoid having it detonate early in the rotation.

20% usually works well with medium/hot-hot plugs.

I use medium plugs with 25% nitro and it does really well.

Too cold of a plug and it fires as the piston is at he very top or going down in the stroke. So, you lose power and it runs cool since it's spewing most of the bang out the exhaust. Too hot of a plug and it's firing as the piston is coming up the stroke, which causes it to fight itself, tends to run hot, give poor power and pit the piston top/head button. You want the fuel/air to detonate just as the piston is about to get to the top, then you get the most burn time for the fuel and it doesn't fight itself.
 

Nitrodannyboy

Member
Messages
24
Can usually tune an engine no probs but i think the glow plug is throwing it out didnt help using a cold plug on a offroad haha
I just picked up the savage 21 3.5 engine today and put a traxxas glo plug in it. and the piston was making physical contact with the glo plug. I stopped it right away before it fired over. But does the savage 21 engine take a shorter glow plug if so what thread? 4? 5? Idk I'm upset, my slayer ran great now I'm stuck with this and don't know if it takes specialty plugs or parts?
 

francis Labarbara

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456
Location
West Virginia
LOL Try an OS #8 glow plug. It is the Traxxas plug that is longer than usual. Or a OS R5 or R7. Or the many equivalents. The Traxxas glow plug is an LC4 equivalent. don't get hung up on the Air designation on the left. All the car engines I own (LRP, Kyosho, HPI, Ofna) will run on a #8 except my Traxxas Slayer.
glow-plug-chart.jpg
 
Last edited:

olds97_lss

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If your running 20% nitro fuel, then the #8 is probably ok for you in a big block. If it's a small block (less than .21), the hotter A3 may work better for you.

I run medium plugs with 25% nitro. Higher nitro works better with cooler plugs as it's more susceptible to combustion under pressure and a cooler plug helps with the timing of that.
 

JVT73

Well-Known Member
Messages
289
Location
Pennsylvania
I just picked up the savage 21 3.5 engine today and put a traxxas glo plug in it. and the piston was making physical contact with the glo plug. I stopped it right away before it fired over. But does the savage 21 engine take a shorter glow plug if so what thread? 4? 5? Idk I'm upset, my slayer ran great now I'm stuck with this and don't know if it takes specialty plugs or parts?
Just a thought, have you taken the button head off to check and see if the brass shims are in place. I know some guys that mess with or remove these trying to bump compression. If it were me, I'd check that engine out.
I run a LC4 in my Savage x 4.6 & it works great.
 

Vmansavage

Well-Known Member
Messages
255
Location
Cumberland MD
Hi I know this is an old post but what I have read is I should run the #8 i am running hpi r5 now using 20% nitro does outside temp come into the equation as well usually run in outside temp of 75°F to 95°F just want to get the most out of my stock sav X and XL stock engines thanks for any help
 

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