C-max EV mode

[MomsHugs]

Wow... just wow! This thread is full of great under-the-hood explanations. Understanding how things work helps me drive my C-Max right to hopefully achieve 45MPG like you all do. :worship:  I appreciate your help. :flirt:  Thank you so much!  :love_shower:

[nsteblay]

Actually the 2013 C-Max hybrid FE in fuelly hasn't improved over time. It's fallen.  You need to filter the recent fuelly data for the C-Max as Energis are now included in the overall average.  The 2013 C-Max hybrid peaked last summer at IIRC at over 40 mpg maybe around 41 mpg (I think I may have a snippet of it somewhere).  The 2013s Hybrid appear to be under 40 mpg now.  Here's a link where I downloaded the fuelly data in May 2014 and computed the standard deviation of the Hybrid at about 4 mpg (I excluded several low mileage C-Maxes that were not Hybrids but it hardly made a difference). 

 

I do agree that the characteristics (constraints) within the algorithms of the two cars have to differ based on physical characteristics of the vehicles and thus affect operations but the higher road load of the C-Max will limit the FE of the C-Max to a number significantly less than the Prius. But again there's nothing that I can find where the theory behind the algorithms differ.  I would say the C-Max  drivers have a better chance of reaching the 47 mpg in mostly city and suburban driving where year round ambient temperatures are mild.  Higher speed driving of the C-Max will have a greater affect on FE as the RLHP increases rapidly compared to the Prius. Also, air density play a significant role in FE as ambient temperatures vary. That can't be overcome but for moving to a warm climate.

I generally agree with your analysis.  The physical characteristics of the Prius has a tremendous amount to do with it getting more consistent and better gas mileage.  My mileage has definitely improved as I've learned to drive the CMax as many would attest on this forum.

 

Having driven the Prius though I believe there are some significant differences in how they've implemented the Power Split architecture.  I can't speak from an engineering perspective but from my driving experience only.  The Prius seems to strongly govern how you can accelerate.  When I drive a Prius I feel like I'm driving an appliance not a car.  

 

I've perused the Prius forums and found plenty of technical information regarding Toyota's implementation of the Power Split architecture.  The descriptions of the driving modes are different from Ford's descriptions and I am sure the planetary gear systems, electric motors, gas motor, computer modules and embedded software are different in their specific configurations and implementation.  There is more than drag coefficients going on regarding the differences experienced between the cars.

Edited August 21, 2014 by nsteblay

[plus 3 golfer]

My point though is it's the drag forces acting on the C-Max that lowered it's FE from 47 mpg to 40 mpg EPA combined rating.  The energy to overcome these forces comes from the fuel .  There are no tips, tricks, algorithms that can overcome these forces.  

 

Ford made it clear from the beginning that it designed the C-Max to drive and feel like a normal car (would have to look up there exact wording).   Toyota apparently designed the Prius for FE (low Cd, weight and likely constraints on operations).  Change the Cd and add weight to the Prius and the Prius EPA rating would fall.  If fact Toyota did that with the Prius V for a 42 mpg overall rating compared to the Prius hatchback rating of 50 mpg overall;  Add more weight to the Prius V and increase Cd slightly so that the Prius V and C-Max have identical drag forces and the Prius V FE would likely drop to the same as the C-Max 40 mpg overall rating.  By looking at the curves above on RLHP, it's easy to see why the FE dropped.  The effect of external influences like temperature will have virtually the same affect on the Priis and the C-Max.  

 

Here's a paper on the hybrid power split transmission with 5 modes of operation - the names may be different but the functions appear to be the same for the C-Max and Prius.

 

Comparison of Hybrid Transmissions.pdf