Heat

[ilpufxit]

I'm running 5s on a modded MM, I've been trying to finish a 20 minute race in my 8b without overheating the esc. I've tried a 1512 2.5d (2050kv), it's too fast on 5s even at 11/46 esc thermals. So, I thought that a lower kv motor should solve the problem. I ordered a Feigao 11xl (1390kv). I was surprised how fast it is at the same gearing, seems almost the same as the Neu. I was expecting a drop of 660kv would make a bigger difference. It also thermals the esc. Am I missing something? How do I drop the esc temps low enough to race? I can do better on 4s with the Neu, it's a bit slower and cooler. I thought that if I could run 5s and lower kv, I'd get more runtime and less heat but something doesn't equate?? Do I just need a bigger esc? Btw, I ran a Quark 125b on the same setup with the Neu, it lasted a little longer but thermalled before the end of the pack.

[bl-is-future]

Bigger ESC or go to 4s.

Originally Posted by ilpufxit

I'm running 5s on a modded MM, I've been trying to finish a 20 minute race in my 8b without overheating the esc. I've tried a 1512 2.5d (2050kv), it's too fast on 5s even at 11/46 esc thermals. So, I thought that a lower kv motor should solve the problem. I ordered a Feigao 11xl (1390kv). I was surprised how fast it is at the same gearing, seems almost the same as the Neu. I was expecting a drop of 660kv would make a bigger difference. It also thermals the esc. Am I missing something? How do I drop the esc temps low enough to race? I can do better on 4s with the Neu, it's a bit slower and cooler. I thought that if I could run 5s and lower kv, I'd get more runtime and less heat but something doesn't equate?? Do I just need a bigger esc?

what ESC do you have?

[bl-is-future]

very first words "I'm running 5s on a modded MM"

Originally Posted by azjc

what ESC do you have?

if you are racing IMO you dont need more than 4s with the 1512 2.5d, and are you running an external BEC? the MM should be fine on 4s with this done

[bl-is-future]

yep i wound go down to 4s. You will be fine if you have good batteries.

[BrianG]

I would look at the MM programming: What is your timing, punch control, etc set at? 11/46 is pretty low gearing and the MM should have no trouble pulling a buggy around considering the voltage and wind - unless of course the buggy weighs 20lbs.

[ilpufxit]

Timing is set to lowest, punch control disabled. Weight is between 7-8 lbs depending on motor/pack.

There was a guy at my local track last night running an RCPD RC8 with the same 1512 2.5d but he was running a 22t pinion on 4s with a MMM. Mine thermalled, his was only warm after some hard running. Is the MMM just that much better?? I'm thinking yes.

Originally Posted by BrianG

I would look at the MM programming: What is your timing, punch control, etc set at? 11/46 is pretty low gearing and the MM should have no trouble pulling a buggy around considering the voltage and wind - unless of course the buggy weighs 20lbs.

[BrianG]

Well, the MMM does have a substantially bigger heatsink...

I would try to set punch control to the highest setting you can before you notice performance loss. Having that much instant torque is not good for the cells, ESC, motor, or drivetrain. You're just pulling too much current on startups/acceleration, and high current is what generates the heat.

[jhautz]

Have you checked that there is no drag anywhere in the drive train? If you have bad bearings or something rubbing or difs that are shimmed to tight or something else causing drivetrain drag it can drasticaly effect the heat and runtime. I ran the 1512/2.5D on a R1Pro and 5s with no problems at all. I didnt even have a fan on it. and from my experience the Mm can take a little more the the R1Pro because of the R1Pros lack of a heatsink to disipat the heat. Id look into the rest of the setup to see that you arent introducing some other form of drag the MM should handle that no problem with a fan. If not, try the hole mod on the MM case. Drill some vent holes in the MM case so air can get in and aid cooling. SOme have even put holes in the bottom of the case and put a 2nd fan on the bottom as well, but those are ht guys running the crazy hot setups. What you are describing is powerfull, but not insane. Also having adaquest ventalation on the ESC will help alot too. So if yout dont have it put some cooling holes in the body.

[ilpufxit]

Thanks for the suggestions. I've got punch control up to 70% with no noticeable lag, I'll try going even higher. I drilled the esc case and I'm waiting on two fans, top and bottom. I kinda hate to do it but I've seen in 10th scale how much difference the fan made on my GTB. I haven't been out to the track yet to test but I know it's better already.

I put all new wheel bearings in it last week, that helped, a couple of the rears were dry. It seems to roll nice and smooth without a motor in it but I'm still going to double check all three diffs for bearing issues.

I notice that the Neu motor feels like it's dragging much more than the Feigao but I think that's normal. It did make me have to adjust my driving style to avoid flipping backwards off jumps with the Feigao. It's like the Neu has a built in drag brake.

I just ordered a 49t spur and a 10t pinion (both hardened) so I'm thinking that the gearing should be much better. It actually changes the drive ratio (pinion-spur) from close to 1:4 to almost 1:5, big difference.

I'll update after the next track day