Introduction to Measurements made on my Prius

Some understanding of the hybrid powertrain of the Prius can be gained by reading Toyota literature.  However, Toyota's objective is mainly to sell you the car, not to explain how it works.  For example, no Toyota publication mentions the "overdrive" mode of operation in which MG1 and MG2 reverse their "normal" roles to increase the speed of the vehicle while keeping engine r.p.m. low.  Toyota engineers have presented papers to the SAE (Society of Automotive Engineers) and elsewhere that give tantalizing glimpses into the workings of the car.  Laboratories such as Argonne National Labs and NREL have also published information in various forms.  But, to really figure out many of the details, I have found it necessary to make my own measurements.  In fact, I "discovered" the overdrive mode for myself by measuring vehicle speed and engine r.p.m. as I drove the car and then performing some simple math.

In this topic area of my Web site, I will present measurements I've made, how I made them and what conclusions I have drawn from them.  I have tried to provide enough detail for you to repeat my experiments if you wish.  Please understand that I have engineering training and can figure out what is safe to do and what isn't.  You use the information I provide at your own risk and I take no responsibility for the results.  The easiest measurement for you to reproduce is the fitting of a battery current meter.  Several people have accomplished this and have found the results edifying.  At the time I first published the design of the meter, the total parts cost was under $25 (US).

You can explore the sub-topics in this area by clicking on their titles in the contents pane at left.  The contents pane will stay with you so you can move between sub-topics or return to this introduction.  To leave the contents pane behind, right click on a title and select "Open in New Window" from the pop-up menu.

Last edited November 10, 2002.  All material Copyright   2002 Graham Davies.  No liability accepted.