8L Heat issues, suggestions?
 

Hi, I've got an 8L and Mtroniks Truck combo running in my Emaxx, and it runs nice and strong - geared 18/66, I'd estimate 35-40mph, closer to the 40 I reckon. But it has a heat problem. Its fine when the weather 35F but now its crept up to 55F upwards its coming off a run too hot for me to hold a finger on for even 2 secs.

It does this if I run in either 1st for a run, or 2nd for a run, even if I'm keeping to low speeds, like just doing a couple of small ramps on my garden. The tranny is stock except for a Robinson Racing slipper kit.

Does anyone have any suggestions on keeping the heat down? I tried gearing at 15/66 and it gets just as hot. My stock front and rear gearboxes seem to have a fair bit of resistance in them, is there a way to reduce that? I thought of putting a fan over the endbell, but its not going to cool the rotor too well is it. I also thought of getting a 7XL but I don't want to loose the top speed I'm getting now.

Cheers.

hi there, first off, do you have a heatsink motor clamp? This will reduce temps, also , and fan on top of the motor will cool it down some. Gearing it down WILL NOT reduce temps, gearing up will, if you get a 7xl , you can get similar top speeds as your 8l, all you do is gear up . Hope this helps

Gearing it down will reduce temps if it is overgeared. Gearing it up will make it better if it is under geared. If you can make sure the timing is right on the esc as well. I have had the timing off and made motors run hot. The drag in the driveline will make it run hot to. I have seen over tighted rims make it bind as well. How many cells do you have running on it?

I'm confident gearing down isn't going to help as I've tired that. I'd try gearing up but I have been advised to gear this motor 16/66, and I'm already running 18/66.

The timing on my ESC is at 0 degrees, would you recommend adding some? I can go up in 6 degree stages up to 18 degrees.

I've checked all the wheels and they're not overtightened to the point of binding, nor is there excessive driveline binding compared to every other MT I've fiddled with, just feels like loads compared to the trucks I'm used to (RC10T/T2/T3 series).

I'm running 12 cells, using GP3300 and brand new GP3700's. Definately comes off hotter with the 3700's.

I'm not using the heatsink clamp as I've not ordered anything from Mike yet, but if I switch to a 7XL I will likely pick one of these up.

Well my brother had an 8L. It was hard to keep his motor cool. The 16 66 gearing sounds right. A heat sink clamp will help right much. If you have a temp checker that is the best way to check the temp. I think they supposed to run a little bit of timing. I can't recall how much though. I will try to flip thru one of my books I have and see. I will let you know from there. Gear your truck at 16 66 and put 2 steps of timing in it and test it out to see if it is cooler or hotter.

Okay then tomorrow I'll try it with 6 degrees of timing. I will most likely buy a heatsink clamp, till then I'll try and dig out one or two small ones from my touring car days and fit them.

16/66 gearing sounds a bit..low? The stock electronics on 14 cells will hit the same sort of speed (of course without the great acceleration). I will see if I can find a 16t pinion out, not sure if i have one. Thing is though is I'm really happy with the top speed, and acceleration it currently has, so gearing down is a last resort for me.

Any additional help or advice will be greatly appreciated :) Thanks for the suggestions already.

fan over/on motor and heatsinks.

justin

Stock evx and titan only turn 1200 or so kv. Your 8l is turning 3000 kv. So gearing it down to match up to same speed would be alot lower. since the motor is turn like twice the rpm.

I am thinking the hacker and feigao type motors like about 15 degrees of timing. I am not sure on this though.

The factory setting of the BK controllers is 15 degrees timing.

How heavy is your e-maxx?

And, yes try 7XL on 12 cells... you can crawl after it! Guys do you care about Kv ratings or what?

Timing, how much efficiency in % you will gain on average playing with timing?

If you under 11 pounds install 9L and good heatsink. Timing will be later when overheating would be solved.

Artur

P.S. 8L and 16/66 are wrong numbers, unless you have custom diffs., spur should be 72 or 70 at least. You killing motor...

I've always been told 2 pole motors don't like much timing - to be honest I've only tried more than 6 degrees timing on a motor once, on a 540 6s, and it didn't much like it - it ran hotter and lost some bottom end, maybe because my batteries. Will experiment a bit tomorrow though.

Maybe Mtroniks set 12 degrees timing from the factory, and this is why I felt a small loss in power when I set it to 0? Didn't know BK set such high timing by default.

16/66 is about 20:1 in 2nd gear? The tyres are stock (5.75 inch), the motor assuming the battery voltage doesn't drop too badly (gp3700's) will be turning ~40,000rpm, which ends up around 33mph? The gearing I'm on now is 37mph by the numbers. This isn't unreasonable? My friends emaxx with stock electronics on 7 cell gp3300 packs must be doing 30mph easy.

The emaxx is 95% stock so stock weight..not too sure exactly to be honest.

Torque > timing > RPM

Less timing more torque, less RPM; more timing higher RPM, less torque

Try 70-72 spur and you will be surprised. With 66 spur your motor doesn't reach its RPM, and I bet your batteries are getting hot as well.

Artur

P.S. Just in case http://www.hackerbrushless.com/cars/otd/emax_otd.shtml C50 has the same Kv as 8L

Actually the temp on the batteries are fine, only ones that get hot are my old 2400 stick packs. My GP33's and 37's come off only warm. ESC only gets warm as well. I'm fairly certain its not overgeared.

I still don't want to gear down unless its the only option..I don't even know if I can get a 70t spur for my Robinson racing slipper. The cars performance is too good for it to be overgeared.

actually i think it is overgeared somewhat. i had a lehner xl3100 (very similar specs to 8l) and a robinson slipper on my mostly stock maxx and it seemed to like a 13 or so.

You really need to get some different pinions there to experiment.