HELP! HPI K4.6 not reaching normal temp(always below 185)

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G

ggomez

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I broke in the engine & ran 1 gallon through it on my Warhead. The HPI K4.6 engine was running fine & reaching normal temps (230-260) on the Warhead.
I installed the engine on my savage & now I can't get the engine to go over 190 even after running through 2 gas tanks without turning off the engine.
I have tried leaning the high speed needle more & more but I still can't get the engine over 185. I use OS8 gloplugs so I went back to the factory HPI K4.6 glow plug that came with the engine & i was able to get it to 220 after leaning it more & running almost 1 tank. The few times that I am able to get it over 200 I have to run 1 full tank to get it over 200 & I feel that I'm leaning the high speed too much & the engine sounds like it's reving extremely high when I go full throttle, but there is a trail of white smoke & the engine feels like it has power. OH & I can't get a smooth idle, it usually turns off after rough idleing for 30 seconds. Below are the details.

Savage/HPIK4.6/Fantom pipe/HPI aluminum clutch shoes/Big Fat cooling head/
MGT wheels&tires/Robinson Racing combo/3speed tranny
 
check you lsn. and see if it walked in. other that got me but i do like the 200 degree temp and making power.
 
I bought a OSA5 glow plug & it made a world of a difference. Without playing with any needles it idles like a kitty just purrs & doesn't act like it's shutting off for over a minute or two. I started leaning it & I noticed a performance/temp increase immediately & when I richened it I also noticed a performance/temperature decrease immediately. YEAH! baby I like it like that. With the OS8 glow plug I leaned it &richened it & I didn't notice any performance or temp increase/decrease. Everyone was telling me to just keep leaning it, but I was nervous about leaning it more & more because I didn't see very much performance / temp difference after leaning it or richening it. There was nothing wrong with OS8 glow plugs, I tried a new OS8 & another OS8 & they both made my savage rough/iratical idle & temp/performance didn't increase by leaning. I guess the moral of the story is "the glow plug you used on 1 engine for months might not work on your new engine this season, and I stilldon't understand the different theories about glow plugs cold/hot/med/warm/chilled/ everyone tells me something a little different.

Can someone explain the technical details of how the glowplug theory affected my Savage?
 
What % of fuel are you running?..the "8" is a medium plug and the "5" is a cold plug..the cold plug will run better with a higher percent nitro and the medium would like 20% to 25% or so.i have a post here on nitro and plugs.......under "glow plugs"

-Joe
 
the os8 plugs are shorter in reach than the stock hpi plug is. fact is the os8 plug is shorter than most plugs and was really designed to be ran in os engines only. they work in other engines fine but others don't like it. i myself have tried to run them [when the lhs only has the os8s and nothing else will work] . the 4.6 engine likes a colder plug[most big blocks do like colder plugs. but there are some that like the hotter ones] the reason the longer reach is needed is the combustion chamber is designed to have a certian ammount of compression. the shorter plug[the os8 is almost like 3 threads shorter on reach] dosent provide the correct ammount, it actually decreases the compression. which will make the engine run rich and need to be leaned way out to get it to make power. you probally only noticed a problem after the breakin and you were tuning for performance[ i use a hoter plug for breakin sometimes ,then change after breakin is over- but it needs to be the correct reach plug]. these engines are so small that they are really effected by changes like that.also the hotter plug advances the engine timing making the fuel burn and detonate early which will damage the top of the piston. so running the wrong plug will give all kinds of running problems under the right condtions. the stock hpi plug is the best to run in the 4.6 engine and the mccoy cold plug works well too, also the ofna 51007 works too[ the 51007 is actually the exact plug that hpi uses in the 4.6[thats what an hpi tec told me.]i would do just as you did and continue to not use the os8 for it and stick with the colder longer reach plugs. the engine will actually make more power with the right compression.oh yea the engine was probly running good in the warhead because you were still in breakin rich settings and then when you tuned for performance you were ok in that truck setup because the warhead uses a header tank and dosent have the half tank lean problems like the stock savage has.the half tank lean can compound a poor engine set up also the warhead probally has diffrent gear ratios too.
 
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oh yea. the plug /nitro combo that works for me in hot south fl dosent always work for others in higher altitudes.in my sts engine i run a mc59[hot plug] and i run 20% nitro. my sons .21 engine we run the same fuel but use the cold ofna plug. his engine wont run the os8s. the other 28 engines iv had all liked the cold plugs nomatter what nitro% i used, the sts is the only engine iv got that dosent like cold plugs.my buddys truck[titan twin] has 2 force .26 engines in it and it uses os8s and dose fine ,but it runs a lot better with the colder plugs with the longer reach plug. its a learning thing to figgure out what combo works the best for your application.
 
Thanks JStorm

That was very informational.
You put it in simple plain english without any mysteries.

This is what most people just tell me
"turn the needle to the right & if it gets worse then turn it to the left"
 
I use traxxas top fuel(20%), and mc59/s in my savage with the k4.6, and it has awesome power, runs pretty cool(235 f). I have even let it idle for extended periods of time(10min+), and it never stalled, I monitored the temp, and it never went over 240 f. my old nitro star s25 was a pain from day one, didn't like idling, hard to start, and very hard to tune.
 
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