Nitro Engine Overheating

[danl]

Hello All,

I'm back into nitro after 30+ years away. I have a Kyosho Inferno MP10 readyset with the .21 Hyper engine. I also picked up a HoBao Hyper SS with the .28 Hyper 6 port engine.

I broke in the .21 and while it gets as hot as 280F on the top of the glow plug I can mostly keep it in the 260F range. I put in a P4 glow plug compared to the P3 it came with stock. I also run it as rich as I can without it choking out when going full throttle.

I got the .28 broken in but I can easily get it above 300F on top of the stock P4 glow plug. Note this is the hottest portion of the engine, other areas are low 200F. It is much more rich than the .21 and blows a solid stream of smoke at mid or full throttle. It will get so hot that it seems to vaporize the fuel in the crankcase and hold a super high choppy idle. I then know it is time to let it idle and cool off. I've gone so far as to bring a handheld fan to cool it off when this happens.

This is all concerning to me as I have it set super rich. I am going to try a P5 glow plug but am not expecting much. I would add some head shims but I think it is something more fundamental. I think my tuning is on as it blows great smoke, accelerates out of a corner well with even more smoke, and holds an idle for more than 30 seconds....easily.

I haver tried trimming the body around the head a lot more. I have also removed the body compleatly. Neither solved the problem. Does it need more break in? I have about 1/2-2/3 gallon through it now.

It is mid 90 degrees here now. I also spend a lot of time full throttle on my makeshift course. It is basically a figure out spread out over 100 feet so that I can practice initiating turns, holding the turn, and coming out of a turn.

My thought is that I am just driving too aggressively for a nitro engine in this weather. But if that were true, then why does my kyosho with a .21 run almost 50 degrees F cooler and I can run it as hard as I wish?

 

[tudordewolf]

If the rest of the engine is in the 200's you might be ok, does the cooling head "sizzle" when flicked with drops of water?

Could it be something external to the engine, like drag in the drivetrain causing it to run under mor load? For that matter, are they geared the same?

A .28 will produce more heat than a .21, but they have about the same crankcase mass & cooling head to get rid of it with.

 

[danl]

Thanks for the input.

The cooling head isn't close to sizzling when I put water on it. It slowly evaporates. The cooling heads are pretty big, so that top fin might not be representative to the temp deep down near the glow plug that I can read 300-320F with my IR temp gun. It just seems "hot" to me, because the idle becomes choppy and it is hard to restart if it stalls.

I cannot find any binding in the drivetrain. The car is new, not that it matters as something could still be off. However when I spin the wheels by hand on the stand, they all move freely. I can get a couple seconds of coast down if I spin a pair of wheels quickly. It is the same as the coast down I get in my Inferno.

The HoBao is heavier than the Inferno. I guess I could swap engines and see if it follows the engine or the chassis.

What I may try next is to only run the HoBao in cooler weather for the next 1/2 gallon of fuel to see if that is enough to loosen it up that it has less friction and thus less heat. It only seems to get hot when I'm really ragging on it. I could probably drive it around all day in 95 degree heat at half throttle.

 

[tudordewolf]

Thanks for the input.

The cooling head isn't close to sizzling when I put water on it. It slowly evaporates. The cooling heads are pretty big, so that top fin might not be representative to the temp deep down near the glow plug that I can read 300-320F with my IR temp gun. It just seems "hot" to me, because the idle becomes choppy and it is hard to restart if it stalls.

I cannot find any binding in the drivetrain. The car is new, not that it matters as something could still be off. However when I spin the wheels by hand on the stand, they all move freely. I can get a couple seconds of coast down if I spin a pair of wheels quickly. It is the same as the coast down I get in my Inferno.

The HoBao is heavier than the Inferno. I guess I could swap engines and see if it follows the engine or the chassis.

What I may try next is to only run the HoBao in cooler weather for the next 1/2 gallon of fuel to see if that is enough to loosen it up that it has less friction and thus less heat. It only seems to get hot when I'm really ragging on it. I could probably drive it around all day in 95 degree heat at half throttle.

If the engine isn't getting too hot it sounds like you're alright, maybe a little fiddling with the low speed needle to tame the idle?

The glow plug wire is incandescent and directly connected to both parts of the glow plug (body and post), so additional heat is constantly being conducted into those components, the plug itself will run a bit higher than the rest of the head.

A P5 plug and head shim might do the trick, if at max revs your ignition is too early, that could be overheating it.

 

[danl]

I'll try a P5 plug and see how that helps. I'll look into finding some head shims as well but I may need to order from HoBao directly which may take more time than just trying out a P5.

 

[easy rider]

On the hyper engine, how’s your idle? How does it drop back to idle after wide open throttle? Idle gap good?