How The Prius Stays So Efficient

"The Toyota Prius is packed with some pretty high-tech stuff, but at the heart of the Hybrid Synergy Drive (HSD) is a simple little device called the Power Split Device, or PSD. The PSD is a planetary gear set that removes the need for a traditional stepped gearbox and transmission components, and also the familiar rev-lurch-rev-lurch of acceleration in an ordinary gas powered car. It acts as a continuously variable transmission (CVT) but with a fixed gear ratio.

If you have no mathematical or mechanical understanding of hybrid technology or even regular engine components, this will help you get a feel for how the PSD allows the car to use power from an internal combustion engine (ICE) , as well as 2 electric Motor/Generators (MG1 and MG2), all spinning at different and variable speeds. The PSD even allows the smaller of the two Motor/Generators, MG1, to act as a starter for the ICE, thereby eliminating another component of a traditional gasoline engine." (Full Story)

[Image via cleangreencar.co.nz]