22 mph on a 48v system - particularly a fat geared hub - is about right. You could take it up to 23 or 24 given the right circumstances, but your bike is performing about where it should be for a 48v system that is also probably pretty heavy given its got the weight of two motors, and probably a pretty big battery to boot.
A 2wd bike is not going to go twice as fast. You'll get a little more speed out of it, but only a little. My 35a, 52v fat 2wd is good for about 31 mph on a single motor. Two motors: 34 mph. And that will drop right off as the battery runs down. 2wd is about the benefits of distributed traction, not higher speed. It also makes the motors run a LOT cooler than just one would, but thats not something anyone asks for when they are thinking of a 2wd bike. Its just a noteworthy side effect.
For what its worth, its the voltage that decides your top speed, not the controller amps. The amps determine the strength of your acceleration. To use more broadly understood terms, here's a good (if technically inaccurate) way to think of volts and amps: Volts are horsepower. Horsepower increases top speed on a car. Amps are torque. Torque on a car determines how fast it accelerates. As the old saying goes: Horsepower sells cars, torque wins races.
If you have 19a controllers, and those controllers measure that '19' as a peak value, then you probably have an 8 or 9 amp continuous output rating on those controllers. Which ain't much. You've got a bike that is made to give you mild awd benefits and its never going to be a speed demon unless you start replacing parts like the battery and the controllers... which is going to get really pricey considering a battery that can handle that - two 35a peak controllers so a BMS capable of about 80a continuous is in order - has to be custom made. The controllers alone are about a hundred bucks each.
Probably better to just be happy with what you have, or sell it and build something truly fast.
A big bruiser geared specifically to be pedaled hard at 32-34 mph, this is my commuter workout-workhorse. Don’t want to sweat? Just relax and pedal easy… at 28 mph.
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