The one thing that sold me on this Empulse was that not only would it go Interstate speeds if necessary, go the range that I need it to, look kick-a around town, but primarily that I wouldn't have to learn how to shift gears like standard motorcycles.
Theoretically you could unbox the Empulse, put it in an intermediate gear (say 4th), charge up the bike, and
never touch the clutch or shifter again in your life.
Take a look again at this chart of an Enertia 3.1 with a simulated IET, and the power at speed available in each gear. 4th gear is geared essentially the same as the actual Enertia's direct drive, and so it is a useful comparison point.
[smg id=283 width=500]
Below 20 mph, the actual Enertia's motor is operating below its power band in a torque-limited regime. IET can increase the gearing ratio, increase motor RPM into the peak power band, and improve wheel torque/power performance by 30-40%.
From 30 to 50 mph, the actual Enertia is operating inside that peak power band. IET has very little benefit here.
Beyond 50 mph, the actual Enertia's motor is operating above its power band and swiftly falling off in power output as RPM increases. IET can decrease the gearing ratio, decreasing motor RPM back into the peak power band, and significantly increase both performance and maximum velocity up to the point where the bike becomes drag-limited (likely 70-75 mph).
A gas bike needs a clutch to get the bike moving from a dead stop, and it needs a multi-gear transmission to enable it to operate within a fairly narrow power band.
An electric bike will produce 100% torque from a dead stop, and has a much broader power band. The Enertia above produces 80% peak power from approx 25 mph to 55 mph .. a gas bike with similar gearing would produce 80% peak power from say 45-55 mph. There's substantially less need for a multi-gear transmission on an electric bike -- thus making it a worthwhile exclusion on a commuter bike or low-cost bike -- but it does improve performance at the low and high rpm ranges.
I really thought that one of the plus sides of being an electric vehicle was that it required a fraction of the parts of its ICE counterparts. Doesn't a transmission just add complexity to a streamlined, simple, revolutionary device?
IET adds complexity, weight, packaging, and cost. It decreases range through additional weight and presumably slightly lower efficiency than direct drive. It can increase efficiency through operating the motor at a more efficient RPM, if the motor has a low efficiency range that the motor typically operates in. It can significantly improve performance at low RPMs below peak power and at high RPMs above peak power. And if you use that significantly improved performance then your range will plummet ; P
