HPI S-25 engine heat problem

[speedticket75]

about 240-250 dedree is the ideal temp for the hpi s-25 engine......Heres the problem........The engine was broken in properly & took 2 more tanks of fuel than what was called for to finnish the breakin.......There are no bubbles in the lines or cracked lines & no air leaks anywhere in the engine or lines & filter is new & the fuel filter too.....The problem is the thing runs about 285 degree no matter how much I open the high & low end needles.......I have them both set at 3 1/2 rounds open from the closed possition........What should the high & low end be set at so the engine will run about 240-250 dedree ???? Dont wana burn up another engine because of running hot....

 

[SkyMaxx]

Before you panic...do you have some decent smoke coming from the exhaust (bluish in tinge and not overly heavy...just kind of a steady stream that gets heavier when you lay on the throttle)?

The reason I ask is that you might have had it tuned just fine.

As for the needle settings, I'd start by getting the engine back to the factory presets and tune from there.

Note, some engines burn hotter than the book says it should and run just fine (for instance most TRAXXAS engines burn on the hot side...whether they run fine or not is subject to interpretation.)

 

[NCNitro]

I had the S-25 in my SS for two years before the pull start broke. I took it out to put an Ofna/Picco .26 in it that a buddy of mine hooked me up with. It ran great at about 260-265, and was still running strong when I removed it, well other than the pull start, lol.

 

[SkyMaxx]

Also, not certain where Kilgore, TX is but in general Texas is pretty hot...and you might simply be seeing the affects of Texas heat and engine heat...

 

[speedticket75]

yes there is a blue grey like smoke comming from the exhaust & oil gets all over the right side of the savage (moastly on the passanger side rear arms)....but......i dont think the cooling head arta smoke (more like steam) when the thing gets up to 280 deg......The engine dont run hot when I'm just driving but it does when i run it in third gear for long.....What do I adjust for that ? The needle on the end of the sliding throttle or the big needle that sticks allmoast straight up ??? Can a glow plug affect how hot the engine gets ? What would be the correct glow plug to use ? I must sound realy dumb but just got into the hobby......I'm used to nitro plane engines & dont have to worry much about those getting hot because the air from the prop keeping them cooled down.....

 

[olds97_lss]

With a BB (big block) running 20% nitro, you want a medium/cold plug. Running too hot of a plug causes early detonation which makes the engine fight itself. The fuel/air mix in the cylinder is exploding before the piston gets to the top of the stroke, which makes the engine want to fire in reverse. Momentum keeps it going in the right direction, but it's constantly under strain.

Try an OS #8 plug (medium-hot). Kind of pricey, but I had a similar situation with my OS 21 RG in my savage. Didn't run quite right and ran hot... I didn't know any better and I was running an OS #3 (hot) plug. Then I switched to a #8 and the engine liked the timing better. Gave me much more power and ran cooler.

I tried running an OS A5 (cold) plug like the manual suggested, but it ran like crap, so I tried the next one up (#8) and it has run great ever since.

 

[speedticket75]

Thanks.....that may just be the problem.....I'm using a 3 right now.....didnt run hot before i changed plugs......i didnt even think about that....been goin beserk like a trapped up cat bouncing off car winders looking fer a way out.....on the plugs, is it the lower the # the hotter the plug or what ? just making sure

 

[redneckracer1979]

The S25 runs hot also. My S25 likes to run between 270 and 300 and I have 8 gallons on it and still going strong.

 

[speedticket75]

what would be the size # of a medium-cold plug ??? #3,4,5,6,7,8 for the hpi s25 engine ?

 

[DoDaMan]

Pretty sure its an OS 8

 

[olds97_lss]

what would be the size # of a medium-cold plug ??? #3,4,5,6,7,8 for the hpi s25 engine ?

Actually, the A5 is medium-cold... but I've had better luck with the #8.

http://www.osengines.com/accys/glowplugs.html

 

[speedticket75]

I put a r4 plug in.....it sposta be a medium/cold plug.....it brought the temp down to about 270