fyi torque for android will give you lots of nice numbers and they have special pids for the prius
http://ecomodder.com/forum/showthrea...4-a-25216.html
And it is insanely cheap if you have an android already, I spent $17 on software and adapter. It has torque/rpm for mg1,mg2,ice and all sorts of things (check out the spreadsheet of custom prius pids), I even use it to tell me the brake friction pad horsepower so I get a feel for how much I can brake on regen alone.
But yes, under acceleration/high current it certainly feels "lossy". And all that mechanical to high current electrical, to a buck/boost/inverter to mechanical, it would not suprise me. It is basically a glorified torque converter, and mg1 always needs or generates power to oppose engine torque to get any useful work out of the planetary gear carrier.
I have not gone 100mph, let alone looked at the power demands, but will let you know if I do
But do check out the custom prius pids on a link in that link, good stuff.