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View Full Version : Mamba Max problem running a 13.5 motor


GSMnow
07-10-2009, 02:27 AM
I am having a serious problem. I know others on this list have tried running sensored motors on their Mamba Max ESC with varying results, so I figured I might get an answer in time. Basically, I am curious who is having the best performance with a high turn count (13.5) sensored motor on a Mamba Max. What firmware are you running and what settings are working for you. I put my Losi 13.5 motor on my Mamba Max and the performance (ONCE ROLLING) is fantastic. The acceleration and top speed are right where I need to be, but it is HORRIBLE at startup. I am not taking a stutter before roling off, I am talking will not roll. It hanks, groans, jerks forward and back, you name it. And it pulls OVER 100 AMPS doing this. I have version 1.21 beta in my ESC right now. I think 1.17 was better for low speed running, but I am nervous about trying it. I may also try gearing it a bit slower. The top speed really is amazing for a 13.5 so I may just be asking too much. I tried all 3 start power settings and they all suck, with high being the worst. The motor also got quite hot when it stuttered, but the ESC and battery seem fine. After just 2 minutes of a few start attempts, it was over 150F on the motor can, but the ESC was only 93F and the batter was at 78F (ambient). This is a 5000 35C Reedy pack, so it can dump the amps without breaking a sweat.

I am entered in the Hot Rod Hobbies Shootout this weekend. It turns out that pretty much all the entries in 4WD Mod are very serious sponsored racers, and I really don't want to just be a road block for them. With my Mamba Max 5700, my car is easilly as fast as them anywhere on the track, but my driving is just not up to that pace, in practice this morning I only got in 6 laps before I took out a front A-Arm trying to keep up with the others. So it was suggested I run in the 13.5 Super Stock 4WD class. This is not a bad idea. The pace is a bit slower, and almost none of the big name hot shoes are entered there, so I won't be a hazard. Too bad, I only have one sensored ESC, and I have that in my truck where I feel I will be more competetive. I finnished putting the 5.5 bullets on all of my brushless motors and tried a few tests, only to find I may be SOL. If I can just find a way to make sure it gets roling I will be good to go, but as it is now, it is not reliable enough to have on the starting grid. I may be okay for qualifying as long as it is IFMAR start, but for the main, I will be lucky to get going on the horn. It really is that bad.

Please help!!

GSMnow
07-10-2009, 04:04 AM
UPDATE

I downgraded the firmware to 1.17 and it is a little better. It just might be good enough to race on, but I would say there is still a 1 in 10 chance it will not roll off when I pull the trigger, which is a huge leap better than the 3 out of 4 times it would just stutter on the 1.21 firmware. It also seems to be running cooler, but as it is now dark it is much cooler out as well, so that may not be an accurate reflection. I am still on low start power on 1.17 and I am a little nervous about trying higher. WhenI had a rock in the gears with my 5700, it stuttered like this and cooked the ESC. But so far I have not seen the ESC get over 125F. I know the series R of this motor is way higher than the 5700 though, so the stall current should be much lower, which may be why it won't start the car roling.

kufman
07-10-2009, 05:33 PM
I made my 13.5 work very well.... just never on the Mamba controller :-( I ended up buying an RS-Pro for spec ROAR motors.

GSMnow
07-10-2009, 06:31 PM
A guy is loaning me a Novak 13.5 motor, and it does start much better than the Losi 13.5, but it sure does trade off some top end. I literally can't gear it fast enough. I have great low to mid speed, but they are running past me down the straight. On the good side, besides the much better start, (it still will stutter one out of 5 times) also clears both triples with no trouble at all. Too bad I broke in the first round of qualifying. My lap times are about 2 to 3 seconds off where I think I should be. Check us out at LiveRC.com, runing now. We just completed round 1, Round 2 will be starting soon. I am not up again until heat 25 in my truck and heat 30 in my 4WD.