my 9920+9L setup still good?
 

Hello, I purchased my 9920 (at the time it was 9918, but the name changed, but they are the same exact controller from what i've read) and Feigao 9L brushless motor about a year ago from rc-monster.

I'm running it on 14 cells (GP 3300), with stock diff and tranny, with a spur/pinion of 70/16.

I've been doing some reading around today, and I've seen people talking about not using the L series, but rather go with the XL series of motors. I also used the R/C Calculator, and with my motor on 14 cells, it warns me about that cell-count, saying the motor could overheat.

Is this a bad setup? Should I replace the motor with something else? I do notice the motor gets hot pretty quickly; gets to > 160 F in like 15 minutes of normal bashing and the occasional speed runs. Also, some of the shrink wrap on the 9920 is starting to shrink around the heatsink.

Thanks!

for a while the 9920 and the 9L was the standard setup. I think most have found that the bigger XL motor is better suited for the MT size vehicles. Your setup is still fine. Nothing wrong with it. Its still a fast setup. The 9L on 14 cells is about the limit you want ot run.. If both you motor and speed controller are getting hot you are probably running to high of a gear ratio. Try dropping a tooth or 2 on the pinion and see if that helps. If not maybe a fan on the controller and/or motor might help you keep the temps down.

Although, 160 really isnt overheating the motor, and as long as you arent thermaling the ESC you are probably with limits.

Thanks for the reply!

I'm really paranoid with the motor. I've heard that above 170 F you risk degrading the magnet. I tried the fan setup, but it caused too much interference (even with my FM radio... *sigh*)

Do the XL motors run more efficiently with MT's? What would be comparable to the 9L on 14 cells? Or would i have to run more cells, and still get better efficiency?

Also, i think my 9920 MIGHT be overheating... it *kind of* suffers from that infamous brake-fade once it gets hot. I mean *kind of*, because the brake only fails when at 100% (being gentle on the brakes, however, and they work fine... oddly)

XL motors are longer and have more torque and can handle heavier loads better. Your 9L has a kv of 2418. There isn't an XL with that exact KV, but the 6XL and 7XL are close. I'd go with the 7XL out of those two. And if you think you lost too much speed with the 7XL (lower kv), you can always gear up a tad to regain it since the motor is stronger.

ESC overheating is usually caused by overgearing. Try gearing down a little.

I think he is having more of a motor over heating.
Not really an esc heating issue.
7xl don't sound to bad to me.

The 9L on 14 cells is never going to be cool running. Its over 40K rpm at that voltage.

The ultra condensed motor wind selection guide.

1)Choose your voltage (14 cell = 16.8 nominal volts probably more like 16.2 under load)

2) Pick a motor with a kv that based on your voltage will run between 35K rpm and 40K rpm. closer to the 35K for better run time and cooler temps and closer to 40K for more top speed but higher temps (like you are seeing now)

I just mentioned the ESC thing because he was saying something about brake fade...

Thanks everyone! I'm going to look into that 7XL and other possibilities. Thanks for the info!

I know the 9L on 14 cells is scary fast =D