Install dash light to show when ICE is on / off ?

Discussion in 'Gen 2 Prius Accessories & Modifications' started by cDxA, Feb 2, 2026 at 2:54 PM.

  1. cDxA

    cDxA Junior Member

    Joined:
    May 16, 2025
    40
    7
    0
    Location:
    Texas
    Vehicle:
    Other Non-Hybrid
    Model:
    N/A
    Imagine an LED that comes on when the ICE does.
    Install it in front of you on the dash.
    Just bright enough to not be distracting.

    Why not just look at the screen ?
    Well, because I like to focus on driving instead of the screen.
    My screen is also all clouded up and cracking inside.

    How hard would it be to find the wire going to the ICE that is powered on and off and splice into that with a low wattage LED ?

    Could that brick the car ? Also, as with everything, it's never that easy.
     
    #1 cDxA, Feb 2, 2026 at 2:54 PM
  2. ChapmanF

    ChapmanF Senior Member

    Joined:
    Mar 30, 2008
    27,802
    18,379
    0
    Location:
    Indiana, USA
    Vehicle:
    2010 Prius
    Model:
    IV
    well, that depends on whether there is such a wire
     
    #2 ChapmanF, Feb 2, 2026 at 3:10 PM
  3. Brian1954

    Brian1954 Senior Member

    Joined:
    Jan 31, 2021
    2,329
    926
    0
    Location:
    South Central PA, USA
    Vehicle:
    2011 Prius
    Model:
    III
    #3 Brian1954, Feb 2, 2026 at 3:17 PM
  4. PriusCamper

    PriusCamper Senior Member

    Joined:
    Mar 3, 2012
    12,927
    5,252
    0
    Location:
    Pacific Northwest, USA
    Vehicle:
    2007 Prius
    Model:
    Two
    Monitoring your engine RPMs via an OBD2 reader and an app on your phone will give you lots more info about your engine running or not then a light will.
     
    #4 PriusCamper, Feb 2, 2026 at 3:54 PM
  5. fuzzy1

    fuzzy1 Senior Member

    Joined:
    Feb 26, 2009
    17,775
    10,546
    90
    Location:
    Western Washington
    Vehicle:
    Other Hybrid
    Model:
    N/A
    Imagine an ODBII-port tachometer.





    As mentioned by a previous member, most of these devices supply plenty of other datapoints too.
     
    #5 fuzzy1, Feb 2, 2026 at 4:28 PM
  6. cDxA

    cDxA Junior Member

    Joined:
    May 16, 2025
    40
    7
    0
    Location:
    Texas
    Vehicle:
    Other Non-Hybrid
    Model:
    N/A
    Thanks.
    I know these supply lots of useful data, but what I am needing is a way to look straight ahead at the road and know if the car is in ICE or not simply by seeing a light in my pereferal vision.
     
    #6 cDxA, Feb 2, 2026 at 6:36 PM
  7. dolj

    dolj Senior Member

    Joined:
    May 14, 2012
    8,477
    4,301
    0
    Location:
    Wellington, New Zealand
    Vehicle:
    2007 Prius
    Model:
    N/A
    Why?

    What benefit do you perceive you will get from having this information?
     
    #7 dolj, Feb 2, 2026 at 8:17 PM
    Brian1954 likes this.
  8. PriusCamper

    PriusCamper Senior Member

    Joined:
    Mar 3, 2012
    12,927
    5,252
    0
    Location:
    Pacific Northwest, USA
    Vehicle:
    2007 Prius
    Model:
    Two
    Many apps like "Car Scanner ELM" have a heads up display setting so your phone will reflect the screen on your windshield so you can look straight ahead at the road while keeping your RPM at 3500, which is the most efficient RPM to use when climbing mountains and doing freeway driving.
     
    #8 PriusCamper, Feb 2, 2026 at 8:23 PM
    cDxA likes this.
  9. ChapmanF

    ChapmanF Senior Member

    Joined:
    Mar 30, 2008
    27,802
    18,379
    0
    Location:
    Indiana, USA
    Vehicle:
    2010 Prius
    Model:
    IV
    I'm not sure I follow. This being the gen 2 forum, we'd be looking at the left plot here:

    [​IMG]

    What jumps out at me is that the desirable 230 g/kWh region is skinny perpendicular to the RPM axis, but long perpendicular to the torque axis. The region extends from ~ 2000 RPM up to just below 4000 RPM, but only a narrow range of torque, just under 80 to just over 100 Nm.

    That suggests to me an efficient power-management strategy would be to try to match whatever power in kW the mountain or freeway is demanding by aiming for an engine torque in that sweet 80 to 100 Nm range and letting the RPM fall where it may in that 2000 to nearly 4000 RPM window. (As the heavy path in the plot shows, that's pretty much the strategy the car is programmed to use.)

    3500 as an upper limit to shoot for makes sense; it is pretty close to the rightmost end of that most-efficient region, so if you do catch yourself exceeding 3500 on a freeway or mountain climb, it might pay to back off some, if the conditions allow it.
     
    #9 ChapmanF, Feb 2, 2026 at 9:11 PM
  10. fuzzy1

    fuzzy1 Senior Member

    Joined:
    Feb 26, 2009
    17,775
    10,546
    90
    Location:
    Western Washington
    Vehicle:
    Other Hybrid
    Model:
    N/A
    3500 RPM for ordinary non-mountain-climbing freeway driving, without large aerodynamic drag bundles attached externally, will bring far more speeding tickets than I can afford, even in this modern low-enforcement environment. When traffic and road conditions allow one to use such speeds at all.

    I believe existing MPG-vs-speeds graphs show better MPGs at speeds achieved by considerably lower RPMs.
     
    #10 fuzzy1, Feb 2, 2026 at 9:57 PM
(You must log in or sign up to post here.)