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Vehicle warm-up behavior - ScanGauge observations

Discussion in 'Prius c Accessories and Modifications' started by mdgates, Jul 20, 2013.

  1. mdgates

    mdgates Junior Member

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    I drive with a ScanGauge reading battery amps, coolant temperature, and ICE RPM. Here's what my Prius C appears to be doing after a cold start now that it's summer:

    1. Engine off, EV mode for about 5 seconds. I try to get the vehicle rolling so I can shift to N and coast to the end of the driveway / parking lot before hitting phase 2.
    2. Engine at 1300 RPM, not much ICE torque, vehicle primarily driven by electric motor. The battery amps go >100A here if you ask for much power. If you really stomp on the gas pedal, it'll increase engine RPM while still applying max electric power. This phase seems to last about a minute, burns a fair amount of gas and a large amount of battery charge, and is not my idea of hypermiling. I don't know what conditions allow it to move on to phase 3. Phase 2 seems to be skipped entirely in winter.
    3. Regen. The car is driven primarily by the ICE, and battery amps hover around -25A or so to replenish the battery and keep the ICE loaded for faster warm-up. EV glides are still not available.
    4. Almost warmed up, except the car is sometimes hesitant to enter EV mode, making you wait about five seconds before it lets you in. Phase 4 lasts most of my 8 mile commute.
    5. Warmed up. :)

    Obviously, some of the car's behaviors are very frustrating to a driver who's trying to save gas. Does anyone here have good coping strategies, different observations, or methods for modifying the car's sensors' output for thriftier warm-up behavior?
     
  2. winnertakesteve

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    This falls right in line with my experiences. #2 in particular I've noticed driving to the end of my street and having the car favour battery power even with a fair amount of throttle. When the ICE kicks in it really drones for a good couple minutes. The fact that my work commute is under 5km makes it next to impossible to get good mpg numbers since the car is essentially warming up the whole time. My trip information screen indicates I often manage to travel between 40-50% of the route in EV, but still frequently get sub-40 mpg overall, presumably because the engine is at its worst efficiency whenever it is running.

    Kinda sad because the numbers really pull down my overall mpg. I did a number of longer drives outside the city the other weekend, and got my first 60mpg tank. Consequently I'm definitely trying to walk to work whenever possible, but the car is just so darned tempting in bad weather or when I'm running late!
     
  3. drysider

    drysider Active Member

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    You can install (easy to do) an engine block heater in order to start with a warm(er) engine.
     
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  4. Mr Incredible

    Mr Incredible Chance favors the prepared mind.

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    My commute is 4.6 miles. I get between 50 to 60 mpgs. If it were much shorter and I got worse mpgs, I'd still be happy 'cause it would be better than about anything else.
     
  5. mdgates

    mdgates Junior Member

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    Maybe I will. Either way, I want to understand and perhaps modify the car's warm-up logic. I also wonder what the Gen III modders have been up to.
     
  6. winnertakesteve

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    I like to hope I am getting good numbers given the conditions, but 30mpg with air conditioning on its lowest setting still is a far cry from 50-60mpg
     
  7. ztanos

    ztanos All-around Geek!

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    What do you get in any other car doing the same route?
     
  8. winnertakesteve

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    I honestly have no frame of comparison with other vehicles, so I'm being genuine when I say I hope it's decent! It just sucks to be stuck in driving circumstances that return numbers that "look" unimpressive, even if they are in fact as good as can be hoped for.

    I drove for an hour on the highway the other day and got to almost 70 mpg before hitting Toronto and having those numbers tank. The "c" in prius c stands for city, but that city is certainly not Toronto!
     
  9. drysider

    drysider Active Member

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    The engine needs to warm up in order to operate properly. To warm up, it has to run...in fairly low mileage modes for part of the time. It is interesting that you have such a decrease in MPG in the city. My lowest segments are always on the freeway.
     
  10. JMD

    JMD 2012 Prius 4 Solar Roof

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    Why put the car in neutral and coast. That sounds like a non standard start. Who does that?
     
  11. wjtracy

    wjtracy Senior Member

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    ...I am not a hyper-miler expert, but you want to check the procedure...I am thinking letting the car warm up a few minutes is hypermile Step-1 assuming you have the time.
     
  12. drysider

    drysider Active Member

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    And understand what happens in neutral...it can do things you aren't expecting.
     
  13. ztanos

    ztanos All-around Geek!

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    Even non-hybrid cars have to do a warm up cycle... my bet is that your route in a normal car will be much worse.
     
  14. winnertakesteve

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    i'm sure you're right. it's still motivation to walk whenever possible. you can't beat that fuel economy! :p it'd be a perfect bike distance, too, but i'm terrified of biking in downtown toronto.

    all that said, it still does surprise me just how much of a gas guzzler the C's ICE can be in warm up mode on my route. low 30s are more of a worst case scenario, so to be fair, lets say i get 40mpg on the trip. given the in town driving, the car still tries to turn off the engine quite frequently, and the info screen on average reports that half the trip is completed on battery power/gliding. so correct me if i'm wrong, but does that mean the car is only actually getting 20mpg when the ICE is running, since it's only running half the trip?
     
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  15. mdgates

    mdgates Junior Member

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    <-- This guy.

    Putting the car in neutral keeps the engine from starting. An engine has to run to get warm, and the right time to run it is when you need propulsion. Not while you're rolling backwards in the driveway at -2mph, or when you're slowly rolling up to the stop sign at the edge of the parking lot at work, where you will wait for a minute.

    Has anyone else studied the Prius' warm-up?
     
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  16. ztanos

    ztanos All-around Geek!

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    Neutral doesn't keep the engine from kicking on... it'll kick on if you are in park...
     
  17. drysider

    drysider Active Member

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    Actually, neutral does not necessarily mean that the engine is not running. If you shift to N while the engine is running, it will continue to run. Also, there is no regen in N, so you would need to take those energy losses into account. I think that engine life (and probably MPG's) would benefit from allowing the firmware to warm the engine up according to it's own schedule. That being said, a little experimenting is what this board is about.
     
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  18. JMD

    JMD 2012 Prius 4 Solar Roof

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  19. wjtracy

    wjtracy Senior Member

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  20. mdgates

    mdgates Junior Member

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