I was in the market to get a hub motor conversion kit for my Trek 7500, but found it pretty hard to judge in advance how powerful, how fast, how torquey etc. the various hub motors are. I wrote to most of the vendors on the net (including many on Ebay), and a few of them sent me data sheets for their motors.
I found that all the data sheets I could get, only list full-throttle performance. Since I was mostly interested in 48V 1000W motors, that's what I mostly asked for, though I got one for a 36V motor too. Also, the data sheets seem to only list performance at the higher RPMs, which you would get at 30mph or faster with a 700c wheel.
They were a little cryptic, since they listed Efficiency, RPM, Watts in, Watts out, etc., as a function of torque. So I picked off a number of data points, and re-listed them here, as Torque, Efficiency, Watts etc. as a function of RPM at full throttle.
At the highest speed, that's what you get with no load: Lift the wheel off the ground and open the throttle wide, and the wheels spins freely, without pushing anything in particular.
At less than top speeds, that's what you get on a very slight downhill slope, or on level ground, or going up a long hill, all with full throttle all the way.
These charts don't tell you what the motor's performace is at part throttle, which is actually where most e-bike riding is really done. Your e-bike might be able to go 30mph at full throttle on level ground, but that doesn't mean you keep it blasting along at full throttle every minute. You probably back off on the throttle and go maybe 20-25 mph, or less, most of the time, right?
Still these charts give a hint of what the motor can do, which one is more powerful, which uses more battery power, etc. I'd like to get data for part-throttle performance too, but haven't seen any yet. I may have to build a dyno and test motors myself... with all the spare time and money I have (yeah right).
I also looked thru many websites and Ebay ads, and made a list of what features and toys each one offers with his motor (charger? Battery bag? thumb throttle? etc.).
These charts helped me when selecting a motor (I went with the 48V 1000W from YXM Corp in China, now we'll see how their delivery and after-sale service is). Hope they help you, too. Every little bit, is better than no info at all. Click the thumbnails below to get the full-size chart.