1. Attachments are working again! Check out this thread for more details and to report any other bugs.

ICE run-time and efficiency questions

Discussion in 'Gen 2 Prius Fuel Economy' started by Jim Caldwell, Mar 3, 2017.

  1. Jim Caldwell

    Jim Caldwell Member

    Joined:
    Mar 22, 2015
    144
    26
    0
    Location:
    Mathis
    Vehicle:
    2014 Prius
    Model:
    IV
    I have a 2009 Prius sedan, it has 100K miles now. We have been driving at 70-75 mph. almost all of its miles are hwy miles. You get run over in Texas if you drive slower than that. As far as I know, it had the factory low rolling resistance tires on it when I bought it at 50K miles. I think the brand name was Yokahama I replaced these Yokohama tires recently (like 8k miles ago). The special LRR tires were going to cost about $1000, so I just had high-end Continentals put on. The mileage dropped from about 44.5 to 40.5 MPG with the new set of tires. I keep them at about 40 PSI.
    Of course the ICE is running 100% at our usual hwy speed. I am assuming the high hwy speeds we drive and the new tires is why we are way, way less that 50 MPG + many Priuus owners say they get As an experiment, I drove 60 miles at a constant speed of only 60 MPH . this brought the MPG up from 40.5 to 46.5 MPG.
    Later, I went some miles on flat ground at 40 to 45 MPH. It wasn't until I slowed down to about 42 that I saw the ICE beginning to cycle on and off. Is this normal? Or does the car have a problem with efficiency, like a problem with battery pack, making the ICE run more than it should?
     
    #1 Jim Caldwell, Mar 3, 2017
  2. kevinwhite

    kevinwhite Active Member

    Joined:
    Jun 10, 2006
    331
    199
    0
    Location:
    Los Gatos Ca
    Vehicle:
    2017 Prius
    Model:
    Four
    Your experience and mpg sound entirely normal.

    On the Gen2 Prius the engine is always rotating when the car is above 42 mph.
    (Except for special conditions if you put the car in neutral when it is below 42mph then speed the car up by going down a hill!).

    The motor generator MG1 that is part of the HSD has to rotate at high speed if the engine is not running - at 42mph it reaches its maximum safe limit so above that the ICE has to run - usually at 960RPM if it is not required to produce power or absorb power by engine braking. Although the ICE is rotating it may not be consuming gasoline.

    The speed at which the engine is required to run has gradually been increased with each generation - I recently got a 2017 Prius and see that the ICE can be off up to about 60-65mph.

    kevin
     
    #2 kevinwhite, Mar 3, 2017
    Data Daedalus, jerrymildred and valde3 like this.
(You must log in or sign up to post here.)