With the voltage set at default of 48 volts nominal, the low voltage cut-out is defaulted to 45vdc.
The
Undervoltage protection value (V) on my Magic Pie controllers all default to 42V:
Have you increased yours to 45V, or have GM changed the default values?
Typically more voltage is the cure for torque.
I am not so sure about that, as speed is proportional to the voltage, and torque is proportional to the current.
The following figures were taken from GM's Magic Pie dynomometer results for both 36V and 48V tests:
23.15Amps @
36V = 27.2Nm of torque @ 202rpm
23.16Amps @
48V = 27.4Nm of torque @ 280rpm
Although the torque and current are very similar for both voltages, producing this torque at a higher voltage
(and higher rpm) produces more power.
I modified the internal controller on my original Magic Pie by increasing the thickness of the current sensing shunt, and this resulted in
~93Nm of torque @ zero rpm whilst drawing
65.94 Amps from a
25.9V 7S LiPo pack.
Check out
this post for further details of how I measured and calculated the stall torque.
The modified controller produced even more torque when it was pulling
97.75 Amps from a
51.8V 14S LiPo pack:
Although the voltage sagged to ~45V under maximum load, it was still drawing a massive
4396.7 Watts of power from the battery pack.
At 97.75A, the torque was so strong that it would easily lift the front wheel when I tried to pull away from a standstill on level ground with full throttle
(without pedalling), and I could not pull away uphill using full throttle continuously
(again without pedalling) without the bike instantly flipping over backwards.
Basically, if you want a higher top speed, you need a higher battery voltage, but if you only want more torque, you only need to increase the current going to the motor.
Unfortunately, it is not possible to easily modify the controllers on the MPIII, MP4 and MP5 like it was on the earlier MP and MPII internal controllers.
I now have my Magic Pie controllers set to the maximum battery current
(30A) for maximum power, and I also have the Phase current set to the maximum
(70A) on MP4 and MP5 controllers where this setting is available.
If you really need more current than the factory controller can supply, you will have to swap to a high current external controller, and possibly a battery pack with a higher current output to suit.
Alan 
