MMP initial power/throttle surge?

[MetalNut]

Hey guys,

I finally stepped into the world of brushless power with my 1/10th rally build. I picked up a Castle MMP with their 4600kv (sensorless) motor. I'm mostly done with the chassis and was testing the electronics. I noticed that, while applying gentle initial throttle, the motor "surges" into higher RPM and then settles down to where I feel it should be at that throttle input. This is just under the load of the drive train, no wheels/tires on the chassis yet. Is that normal? Is this the behavior that people don't like about sensorless motors?

Can any of this be configured via the Castle Link? I'm currently running the stock settings (but BEC set to 6v).

4PL, R204GF-E, Savox 1251MG, 2S Lipo

Thanks!

[ik632]

The Castle ESC tends to do that. You can tune some of it out, but it's just the way they are with a sensorless esc. You'll want to turn up the start power (provided your battery can deliver the current) and that smooths things out, but essentially it's just the way Castle ESC's perform. Since it's in a Rally, you shouldn't be going slow anyway so you won't really notice it once you are running.

[MetalNut]

Originally Posted by ik632

The Castle ESC tends to do that. You can tune some of it out, but it's just the way they are with a sensorless esc. You'll want to turn up the start power (provided your battery can deliver the current) and that smooths things out, but essentially it's just the way Castle ESC's perform. Since it's in a Rally, you shouldn't be going slow anyway so you won't really notice it once you are running.

Thank you for the response! I've been playing with the settings and I was coming to just that conclusion. I just wanted to make sure I didn't have a defunct unit, as I seem to have the luck of getting factory-bad electronics.

I'll try to tune it some more and then just get it dirty

[MetalNut]

Long story short, after trying all possible settings that would minimize the throttle / power surge, I almost gave up. I was getting ready to order a sensored motor and give up on the 1406 with the MMP. But, on a whim, I checked out the release notes for the Beta firmware update that I've been avoiding (I write software for a living, I don't trust my own Beta code )

1.39 Beta:
* Bug fix: Output power could jump inappropriately when motor is having difficulty starting. Could result in ESC damage.

This sounded like EXACTLY what I was experiencing. So, I flashed the ESC with the Beta firmware and... problem solved!. There is still a tiny power surge once the car gets rolling, but it's about 5% of what I was experiencing! So, all my problems were due to a firmware bug and not the sensorless motor.

I hope this helps anyone else in future searches.