One of my engines will not stop overheating.
07-25-2017, 05:43 PM
#16
In other news, I decided to try a lower shim-stack again (0.6mm vs. 0.8mm), this time leaving the hot glowplug installed instead of going back to the medium glowplug I was using before. The engine seems to like that combination a LOT better; I got significantly more power without the engine getting hotter than 260F. Granted, the weather is also about 15F cooler today than it was the last time I ran this truck, so when it's hot and disgusting again I might see temps closer to 275-280F, but that's still better than 290F.
Apparently I was on the right track when I switched to the hot glowplug to advance the ignition timing, but I should've tried that before lowering the compression. Lesson learned.
Apparently I was on the right track when I switched to the hot glowplug to advance the ignition timing, but I should've tried that before lowering the compression. Lesson learned.
07-25-2017, 07:55 PM
#17
...so, I may be an idiot. I made another change last night that I forgot to test separately from changing the shim-stack. I took the cylinder-head and the heatsink, and I lapped them together using polishing paste to make sure they had maximum contact with each other, then I cleaned them thoroughly and used a little CPU heatsink paste between them during reassembly. So I don't know how much of the lower temperature is because I lowered the shim-stack while retaining the hot glowplug, and how much is because I improved the thermal interface between the cylinder-head and the heatsink.
Oh well, either way it seems to be performing better, that's what matters.
Oh well, either way it seems to be performing better, that's what matters.
07-29-2017, 07:54 PM
#18
Well. As luck would have it, I came across an aftermarket heatsink on eBay that was billed as fitting HPI .18 engines, and they weren't lying.
The thing is huge, but it does fit with a slight modification to the body shell.
Before installation, I smoothed the contact surface (dry sanding, then wet sanding, then polishing) to make sure it had the best possible thermal conductivity, because the original surface was rough.
My HPI T3.0 runs like a completely different engine now. Even after leaning the fuel mixture slightly, it still runs 60°F cooler than it used to, with a max temperature of 230°F instead of 290°F, and it starts pulling hard when the cylinder-head is still down around 180°F. The cooler temperature should help the engine last a good long time, and being able to run a leaner fuel mixture means it really hauls ass now; it's still not as powerful as the Losi 3.4 in my other HPI Bullet, but I'm impressed nonetheless. The heatsink was totally worth the $20 I spent on it.
The thing is huge, but it does fit with a slight modification to the body shell.
Before installation, I smoothed the contact surface (dry sanding, then wet sanding, then polishing) to make sure it had the best possible thermal conductivity, because the original surface was rough.
My HPI T3.0 runs like a completely different engine now. Even after leaning the fuel mixture slightly, it still runs 60°F cooler than it used to, with a max temperature of 230°F instead of 290°F, and it starts pulling hard when the cylinder-head is still down around 180°F. The cooler temperature should help the engine last a good long time, and being able to run a leaner fuel mixture means it really hauls ass now; it's still not as powerful as the Losi 3.4 in my other HPI Bullet, but I'm impressed nonetheless. The heatsink was totally worth the $20 I spent on it.
07-30-2017, 04:56 AM
#19
Well. As luck would have it, I came across an aftermarket heatsink on eBay that was billed as fitting HPI .18 engines, and they weren't lying.
The thing is huge, but it does fit with a slight modification to the body shell.
Before installation, I smoothed the contact surface (dry sanding, then wet sanding, then polishing) to make sure it had the best possible thermal conductivity, because the original surface was rough.
My HPI T3.0 runs like a completely different engine now. Even after leaning the fuel mixture slightly, it still runs 60°F cooler than it used to, with a max temperature of 230°F instead of 290°F, and it starts pulling hard when the cylinder-head is still down around 180°F. The cooler temperature should help the engine last a good long time, and being able to run a leaner fuel mixture means it really hauls ass now; it's still not as powerful as the Losi 3.4 in my other HPI Bullet, but I'm impressed nonetheless. The heatsink was totally worth the $20 I spent on it.
The thing is huge, but it does fit with a slight modification to the body shell.
Before installation, I smoothed the contact surface (dry sanding, then wet sanding, then polishing) to make sure it had the best possible thermal conductivity, because the original surface was rough.
My HPI T3.0 runs like a completely different engine now. Even after leaning the fuel mixture slightly, it still runs 60°F cooler than it used to, with a max temperature of 230°F instead of 290°F, and it starts pulling hard when the cylinder-head is still down around 180°F. The cooler temperature should help the engine last a good long time, and being able to run a leaner fuel mixture means it really hauls ass now; it's still not as powerful as the Losi 3.4 in my other HPI Bullet, but I'm impressed nonetheless. The heatsink was totally worth the $20 I spent on it.
03-16-2020, 04:48 AM
#22
Probably from an RB .12 or .15
https://www.modellsport.gr/index.php...roducts_id=428
If you know someone with a lathe you can make one by your own.
https://www.modellsport.gr/index.php...roducts_id=428
If you know someone with a lathe you can make one by your own.
03-17-2020, 01:58 AM
#23
It does look similar to that heatsink, but it doesn't have the cutouts on the sides to access the engine-mount screws. It also looks like a HPI 4.6 heatsink, but it's slightly different from that design too. It must've been a no-name factory special.
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