MP III Internal Controller Speed Limitations

[Triac]

Hi all,

I have recently completed a MTB conversion with a rear mounted Magic Pie III.
It’s a fantastic piece of equipment & I have been very happy with the motor power output, it has just cracked 250km of total run distance.

However, as with any motorised vehicle its not quite 'fast enough'.
I would like to find out if anyone has been able to eek out a little more top speed from the internal controller.

Currently I am running a custom 36v 15Ah (40152) headway pack with a modified Turnigy whattmeter.
I can happily sit at 32km/h all day on flat road @~400w. But would really like to get up to 40km/h, as this is about the limit of which I can still 'pedal assist'.
The battery pack has more then double the juice required for my daily commute, so the extra watt hours is no issue.

I have already cracked open the controller and had a play with shunt modding (I am very familiar with the consequences of this). 
I now have around 25% more current available & the pickup is amazing (pumping around 3Kw peak). However the top un-assisted speed is still bang on 32km/h.
This leads me to believe that the controller is holding back, since it knows exactly how fast the wheel is turning in order to correctly phase the windings.

I have also played with the usb programming interface & had a bit of a hex edit of some data files, but to no avail. I believe the speed limit must be coded into the controller IC.
I am yet to fully strip down the controller and identify all the IC’s, I was hoping someone may have already done this for me

I figure fudging the wheel speed will be quite difficult due to the nature of 3 phase control.
One possible option would be to ‘over clock’ the processor (depending on how timing is achieved) this can be done by swapping out the xtal or ceramic resonator (though very strange things may happen).

Has anyone been game to give it a go?
I may end up buying a spare controller to experiment on, as it may end in tears…

Any info would be much appreciated!

Here is a pic of the bike:


Cheerz
-A 

[truly_bent]

Hi -A and welcome.

That's a sweet battery pack setup you've got there. Did you design that enclosure yourself or is it an "off the shelf" item?

I'm pretty sure you're going to have to up your voltage if you want more speed outta the motor. The rule of thumb being that voltage determines speed while amperage determines torque. For example, I'm running 48V and I cruise unassisted at somewhere around 45kph; generally a little better.

Having said that, my third party controller has an "overspeed" option. I can (and do) set my top speed for 112% (which is the max setting). Since I've never run a GM controller, I can't give any comparison though.

Overclocking the microcontroller is unlikely to produce any improvement, even assuming that board timing issues or overheating it's wee brain don't kill your efforts first. Since the FET firing timing is based on positional feedback from the hall effect sensors, the best that overclocking would do is to allow the controller to see the feedback pulses a microsecond or two sooner. I think the net gain would be too small to quantify.

I've seen others asking for the MP controller schematics and I'm pretty sure they haven't been released. Some speed fanatics over at http://endless-sphere.com/forums/ might have gone to the trouble, but I doubt it. Those guys are more likely to dismiss the GM controller as an unworthy candidate for power mods and use some other tire shredding option. But, don't take my word for it.

[Triac]

-truly_bent

Cheers,
I figure the internal controllers are not to popular with mods, due to the lack of space.
Though looking at the rated FETs this thing has pretty serious power capabilities.
It is interesting that upping the voltage is the only way people appear to be able to get more 'speed' out of the controller.
I would have liked to go 48V, but space constrains/weight were a bit of an issue.

Yes the battery enclosure & dash are custom jobs, the batteries only just fit inside the frame of the bike, no chance of adding more unless going a full re-design.
I am planning to add a rear carry rack which will house the charger,  tools & spares in another sealed enclosure, I am not too keen on adding much else, as the conversion is already up to 25+Kg.

-A