I was looking at the EPA road-load HP values listed for the 2014 PiP and the 2014 Prius and noticed that, at 50 mph, EPA indicates 8.7 HP for PiP but 9.1 HP for Prius: This slight Road Load HP (RLHP) difference really shows up at speeds below 17 mph, as shown by the HP ratio (PiP/P) going above 1.000 (black line; righthand axis):
Honestly, I don't know. The EPA PiP test weight is 3500 lbs and the EPA Prius test weight is 3375 lbs, so there's only 125 lbs difference. Sorta looks like the PiP needs more HP to get started, but past 17 MPH, it actually needs less HP...up to their max speed of ≈105 MPH, where their RLHP become roughly equal again.
Good lord! This car weighs 3400lbs!? A Corvette is lighter! I'm stunned Chevrolet hasn't made that a hybrid yet. All the exotics are heading in that direction.
EPA "test" weight is NOT the same as "curb" weight (all fluids fully topped, no cargo or driver). It's basically the mfgr's "estimated" weight of curb+driver+some cargo, ie: a slightly loaded vehicle, but not 100% loaded to maximum capacity.
No, the Toyota document to EPA lists the same P195/65R15 89 AS tires for all three test vehicles (2 base PiP; 1 advance PiP).
The 15-May-2013 Toyota document to EPA only covers the 2014 Plug-In Prius vehicle, not HV vehicle. Tire data is located on page 39 of 48: http://iaspub.epa.gov/otaqpub/display_file.jsp?docid=32267&flag=1
This document refers HV Prius with some 215 17" rim fitted http://iaspub.epa.gov/otaqpub/display_file.jsp?docid=32264&flag=1 Maybe the source of the road load values comes from these tests...
Of course the PiP is a heavier car, does it ride lower? From what I understand the only two things that can affect road load HP would be aerodynamics and tire rolling resistance. Frictional losses from the wheel bearings should be the same between the two of them.
Curiously, that second EPA document shows same 9.1 RLHP @ 50 mph and same ABC-coefficients for both 15" and 17" rims, which to me, indicates Toyota did NOT actually test 17" rims.
Well, the rims are different. PiP has a full alloy premium aerodynamic wheels (without covers). Perhaps, they are lighter? Is it enough for the 0.4 HP difference?
A) Lighter wheels would require LESS power (rotational inertia) to get turning... B) Better aerodynamic wheels would create LESS aera drag... However, the PiP's higher RLHP below 17 MPH does NOT compute; but, I'm at a loss to explain why.
With recent Ford lowering MPG of it's cars, it reminds me of this thread. I think we should discuss more about it. Why is PiP's RLHP lower than a regular Prius. PiP's highway MPG is 1 higher. Is it the reason?
SWAG on my part, but maybe Toyota has "reprogrammed" the PiP use of EV at < 17 MPH in attempt to "squeeze" more EV time? The consistently lower RLHP > 17 MPH would seem to indicate better aerodynamics, which, respectively, effects drag and HP as squared- and cubic-functions.
