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Driving technique before car is warmed up

Discussion in 'Gen 2 Prius Main Forum' started by lorkp, Jan 13, 2007.

  1. lorkp

    lorkp New Member

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    What is your technique for driving the Prius before it's fully warmed up (i.e. pulse and glide is not available)?
     
  2. Skwyre7

    Skwyre7 What's the catch?

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    <div class='quotetop'>QUOTE(lorkp @ Jan 13 2007, 03:20 AM) [snapback]375098[/snapback]</div>
    I just drive it like normal. I don't accelerate quickly and I coast when I can. An engine block heater and blocking your grill would shorten this warm up time. Oh, and don't use the heat at first (unless you have to defrost your windows).
     
  3. seasalsa

    seasalsa Active Member

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    Just drive normally. Do not turn off the heat! That defeats the electric heaters that are meant to give you some heat until the ICE is warm.
     
  4. chogan

    chogan New Member

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    <div class='quotetop'>QUOTE(lorkp @ Jan 13 2007, 03:20 AM) [snapback]375098[/snapback]</div>
    I agree with the previous post -- there is little you can do. But I'll describe what I do anyway.

    I installed the CoastalTech EV mod for Christmas.

    There are two things I do with it.

    First, I start up in EV mode. I EV (slowly) out of my neighborhood on startup, and run the engine ICE only when I've reached the main road. I do that because once you start the ICE, it'll run for a minimal warmup period regardless. (Seems like about a minute, but VA has been exceptionally warm this winter.) So, I prevent the ICE from starting until I'm ready to use it for propulsion.

    Second, after startup, I use the EV switch to try to mimic what the Prius would do if warm. So, if I'm at low speed, where I wouldn't normally need the ICE, and it continues to run, and I suspect it's just for heat -- then I try to toggle it off with the EV switch.

    It works somewhat. It has limitations -- sometimes the car insists on running the engine anyway, and it only works at slow speed.

    Nevertheless, it eliminates the initial 25 mpg bar I used to get on most days, though of course I pay for the electricity with lower MPG later as the car refills the battery.

    It's worth it for us because my wife and I do a lot of short trips, and for that kind of driving, the startup periods constitute a large fraction of total miles and they are murder on the mileage. It seems to help the mileage, but with the warm winter we've been having, there's no way for me to tell how much. All I know is, we haven't had a tank below 47 MPG this winter, which is excellent winter mileage for us.

    The only other thing I do, in cold weather, before the engine is warm, is that I don't use the cabin heat (when driving alone). If I'm particularly bored, I manually synch the heat with the ICE -- turn the heat on only when I need the ICE for propulsion. (That one's not a game to play in traffic, though.) At the min, shut off the heat at stoplights, if the engine continues to run at stoplights. That one you can do fairly safely. Wish that was a programmable mode on the car, actually, but you have to do it by hand.

    Cold-climate drivers have reported benefits from block heaters, but I never followed that through to understand whether the gas saved from driving with a warm engine more than offset the electricity used to run the block heater.
     
  5. chogan

    chogan New Member

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    <div class='quotetop'>QUOTE(seasalsa @ Jan 13 2007, 08:45 AM) [snapback]375116[/snapback]</div>
    Well, I learn something every day. I need clarification. Are you suggesting that I would get better winter milage if I run the heat at startup? Or is this just a passenger comfort issue?
     
  6. Beryl Octet

    Beryl Octet New Member

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    <div class='quotetop'>QUOTE(seasalsa @ Jan 13 2007, 08:45 AM) [snapback]375116[/snapback]</div>
    I have the habit of not turning on the heat until 5 minutes or so into a cold-engine trip since I'm used to conventional cars and don't like cold air blowing. Ignoring passenger comfort, does leaving the heat off help or hurt MPG, or hurt the HSD system in any way? It seems like letting the engine warm up before asking for heat would be better, and not using electricity to make cabin heat would help with MPG? Thanks!
     
  7. seasalsa

    seasalsa Active Member

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    <div class='quotetop'>QUOTE(Beryl Octet @ Jan 13 2007, 07:12 AM) [snapback]375125[/snapback]</div>
    The questions you ask depend on the SOC of the battery. The Prius Climate Control System was not designed to ignore passenger comfort. However it was designed for energy efficiency.

    This quote is from the designer DENSO.

    “Concern for the environment spurred automakers to create more efficient engines. But more-efficient engines mean less heat for warming vehicle interiors. Heating units have had to become even more efficient to compensate for lack of the waste heat that conventional systems use.

    We have developed a system for the Prius that gets the same performance as conventional systems despite the lack of engine heat available for the system. Ventilation loss--heat that escapes from the cabin as fresh air comes in--accounts for 60% of the heating load placed on air-conditioning systems. Our two-layer flow air-conditioning system recirculates warm air in the cabin to raise heating efficiency.â€
     
  8. V8Cobrakid

    V8Cobrakid Green Handyman

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    like everyone else said... DRIVE NORMALLY... the car takes care of everything. It won't turn on the fans untill there is heat available.. that's why cars have thermostats in the radiator lines.

    The car likes normal driving conditions. I get 50mpg on my way out because i'm doing a constant 45mph. The car appreciates this constant speed desire and compensates according to engine output and SOC. I don't hit a light untill 3.5 miles. The car is warmed up after 1.5 to 2 miles. There is a "point" in which the car's heater turns on... same point every day.
     
  9. Beryl Octet

    Beryl Octet New Member

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    <div class='quotetop'>QUOTE(V8Cobrakid @ Jan 13 2007, 11:15 AM) [snapback]375138[/snapback]</div>
    Thanks.
     
  10. JimboK

    JimboK One owner, low mileage

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    <div class='quotetop'>QUOTE(seasalsa @ Jan 13 2007, 11:07 AM) [snapback]375136[/snapback]</div>
    Like chogan and Beryl Octet, I am trying to get my head wrapped around this. Please help me understand: This seems to be referring to cabin heating efficiency rather than engine heating efficiency.

    Many of the "experts" (the term sometimes taken with a grain of salt, admittedly) here and on other related forums suggest not running the heat until the engine is warm, assuming occupants can tolerate it. The rationale seems to be that the heater pulls heat from the ICE, requiring a longer ICE warmup time and, therefore, a greater tendency for the ICE to run when it's not needed for motive force (i.e., deceleration, idling, and gliding during Pulse & Glide) before it reaches optimal temperature. It seems counterintuitive to me that running the heater first thing or, for that matter, at any time, increases engine efficiency. Am I missing something?

    If, as you say, the climate control system is designed for energy efficiency, then this logic suggests that running that same system to cool the cabin in the summer would also increase efficiency. Presumably we agree that doesn't happen. And as a system designed for energy efficiency, is it designed to increase overall efficiency, or simply to minimize efficency losses from using it? The energy to run it comes from somewhere, and it has to start from the ICE, correct?

    My own experience seems to bear this out. I can't give you cold-ICE MPG comparisons (cabin heat on vs. off), but I am convinced my engine warms up faster (as monitored by my ScanGauge) and cuts off sooner on cold mornings when I don't run the heat.

    I'm not disagreeing with you. I don't have the technical background of many here, and I'm just trying to understand exactly what my car is doing and why.
     
  11. KTPhil

    KTPhil Active Member

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    Forcing EV mode when cold seems like a bad idea. I WANT the ICE to run during my initial 1/2 mile downhill drive. I want it to fullly warm up before putting a load on it. Delaying ICE startup until I am on the flat or uphill (or freeway) part of my commute means I am putting full load on a motor that is not warmed and therefore is going to wear prematurely due to toelrances being suboptimum from different thermal expansion rates. You may save ten cents of gas but you will wear out the ICE faster, losing any savings many times over. By letting the ICE run during my downhill start to my commute, it warms without load, which is far less wear-inducing.
     
  12. chogan

    chogan New Member

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    <div class='quotetop'>QUOTE(KTPhil @ Jan 13 2007, 03:18 PM) [snapback]375226[/snapback]</div>
    I'm not disagreeing with the sentiment of this, but I don't (e.g.) turn the ICE on as I'm hitting the freeway onramp either. I turn it on when I'm ready for a long uninterrupted run at speed (35 mph), instead of doding my way through lowspeed 4-way stops. Engine still gets an easy warmup. And the Prius still provides electric power to ease the load after ICE startup. I just don't let it idle along to get warm. It has to work a bit as it gets warm.

    Every car I've owned since, 1990 or so, has said, do not let the engine idle at startup. Start the car up and drive away. Older cars were supposed to get a prolonged warmup. New ones, every time I've bothered to read the manual, they say start it and drive it. That might be more for air quality reasons than anything else, but at any rate I don't think I've killed an engine for excess wear due to no idle warmup.
     
  13. Joe Bernard

    Joe Bernard New Member

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    <div class='quotetop'>QUOTE(chogan @ Jan 13 2007, 04:22 PM) [snapback]375241[/snapback]</div>
    I remember Click and Clack [PBS Radio] talking about this once. They said the start-and-drive technique is recommended for mpg/emissions reasons, but, is still not great for an ICE. Cold oil at the bottom of the sump still needs to become warm oil running through the engine. They recommend idling for at least 30 seconds, which is about how long the ICE runs in the driveway before shutting down. That's what I do. After that it's "drive normal" as others have stated which in a Prius means gentle acceleration and coasting to stops. "Normal" Prius driving is "warm up" driving in most cars. ;)
     
  14. barbaram

    barbaram Active Member

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    I just drive normally but try to not put the heat on for the first 5 minutes or so. Also, inspite of what everyone says, I think the engine parts need time to warm up- the rates of expansion of the various materials are different.

    Obviously, it depends on how cold it is, and it your windsheild is frosting or not.... just do what you need to do to drive SAFELY.
     
  15. donee

    donee New Member

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    Hi All,

    The OP is from Chicago. And while your methods may be prudent above freezing, they are quite dangerous below.

    One needs to run the heat in the Prius to be able to see out of the windows when they are frosted, or fogged. The heat comes on automatically, when one hits the defrost vent button, and turns up the fan. I do this first thing after starting, then turn on the rear defrost. Sometimes I scrape the windows before starting, sometimes after, depending on the amount of scraping to be done. On a heavy snow event it may take 20 minutes or more to get the snow off the car, and scrape the windows clear of underlying ice. Even so, the windows will not be usable at this point. Until they are warmed up, fog will reform on them very quickly. This is the morning ritual. In the evening, the weather is usually dryer, and one might be able to start and go.

    One thing that might be experimented with is the temperature setting. I have mine on 66 F, but hotter might reduce the window clearing time, and allow me to drive away faster. I do not know.

    After clear, then one might set the temp back down to 66.
     
  16. JimboK

    JimboK One owner, low mileage

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    <div class='quotetop'>QUOTE(donee @ Jan 16 2007, 06:18 PM) [snapback]376506[/snapback]</div>
    Not sure which methods you're referring to, but regardless, I certainly run the defroster as needed to clear the windows, whatever the temperature. Sub-freezing temperatures do not guarantee fogging or frost, however.

    I assume that most here realize it's dangerous to drive when they can't see out of the windshield. :)
     
  17. dmckinstry

    dmckinstry New Member

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    <div class='quotetop'>QUOTE(JimboK @ Jan 16 2007, 04:16 PM) [snapback]376531[/snapback]</div>
    On very clear cold (well ~ < 10 F) days, if I weren't breathing, I wouldn't have to use the defroster. Unfortunately I have to breath.

    Dave M.
     
  18. donee

    donee New Member

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    <div class='quotetop'>QUOTE(JimboK @ Jan 16 2007, 09:16 PM) [snapback]376531[/snapback]</div>
    Hi JimboK,

    Of course. My point was that the people suggesting EV'g out of the sub division and not turning on the engine until accellerating on a main street did not realise the Original Poser was in Chicago, and his post was made on January 13 th.