I'm looking for more technical specs that what I can find in the available TIS literature and PC technical threads on the following topics. The focus is on the 3rd gen Prius, and more specifically the 2012 liftback, if the answers vary amongst the various models/versions like the Prius c/Prius V/Prius Plug-in/regular Prius etc. 1) ICE Compression and Expansion Ratios. As per Prius specs (Toyota Prius - 2012 Performance & Specifications) the ICE is listed as having a 13:1 compression cycle. Given that the Atkinson cycle has different compression and expansion ratios, what are the individual figures for the compression and expansion ratios? 2) Traction Motor Power. As per Prius specs above, the max power of the ICE is listed at 98 hp, traction motor at 80 hp traction battery at 36 hp, and net hp at 134. If the total max system power is just ICE+traction battery, as shown by the above figures, why is the traction motor rated at more than 36 hp? Is the extra hp used purely for regen braking and dumping the regen power into resistors? Also, is the traction battery hp same for both sourcing and sinking power? 3) Regenerative Braking Efficiency. How much energy is recovered by regen braking? There is a brief discussion on that topic in this thread, with the estimated recovery at around 30-40%: Just how lossy is regenerative breaking? | PriusChat Are there any actual tests for measuring the energy recovery under different speeds/braking conditions?
re: 1) The Prius actually has only a "psuedo" Atkinson cycle. It achieves this by keeping the intake valve open for the first part of the compression stroke, thus making the power stroke longer than the compression stroke. A true Atkinson engine requires the use of a specialized linkage. See Animated Engines - Atkinson And, unfortunately I do not know the effective ratio of the compression and expansion cycles for the Prius.
