Power drop at WOT on 6s with MMM geared for 90mph...

[BrianG]

Did you calibrate the new MMM to the receiver? It may just not be seeing quite full throttle. After I do this, I usually bump up the throttle EPA a few % points. It doesn't make it go any faster, but will compensate for any value drift in the throttle potentiometer.

Take a look at your battery connections. After repeated plugging/unplugging, the contacts can get pitted from the initial arc. After a while this, and any "soot", results in higher contact resistance, and more voltage drop at higher currents.

As far as the decreasing speed: Motor speed is a function of battery voltage, so if the battery voltage falls after several seconds, the total RPM will drop as well.

After doing a number of speed runs, I would look at things like tire balance, bearings, etc. Those things can affect speed at the levels you are running.