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The efficiency of electric motors is very flat across a very wide RPM range. For example, the Illuminati Seven has a 5-speed Suzuki/Metro transmission, but they found out that they can run very well in just 3rd or 4th gear. So, they put in 3rd to get more acceleration, or 4th to get more efficiency. Having a continuously variable transmission (even with a narrow range) would help an EV wring out the last bit of efficiency, but the difference is relatively small.
Back on topic, electric motors are a great model to study for efficiency -- much of it comes from the nearly perfect geometry of the force vectors relative to the rotation of the armature.
On the "Blanchard Cycle" proposed open source design, I realized that it has a power stroke (in each pair of cylinders) that is 270 degrees out of every 360 / revolution. Compared to a typical 4-stroke that has only 90 degrees out of every 720 degrees, or every 360 if you have two cylinders. So, from that standpoint, all else being equal, it would be producing 3-6X more torque, and it could be nearly that much more efficient, too.
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