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Coolant Temperature Hack. Better MPGs!

Discussion in 'Gen 2 Prius Accessories & Modifications' started by TheForce, Aug 19, 2008.

  1. Flying White Dutchman

    Flying White Dutchman Senior Member

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    when i pres the EV button right after hitting the power button it Will not start warming up
    only after the SOC drops below 45 or something then it starts and begins to warm up
    at that point i can shorten that startup with this mod..
     
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  2. carz89

    carz89 I study nuclear science...

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    You gotta be kidding me! Over what distance, terrain and driving conditions did you achieve that? If one can consistently achieve 200 mpg in a Prius simply by falsifying the engine coolant temperature, then I would presume this would grossly outweigh the environmental advantage of keeping the catalytic converter hot to reduce emissions.

    Thus, I'm skeptical you could consistently achieve even half of that mpg (100mpg) with this mod under typical driving distances and conditions. Perhaps you could significantly boost your MPG this way if your commute was very short. But why go through all the trouble, when an engine block heater would provide the same benefit for a couple pennies on the mile?

    Those engineers at Toyota are a pretty smart bunch, and I'm sure they experimented with different thresholds of temperature control before arriving at the present system.

    I'm very interested in this entire issue of temperature control and modes. My own commute is just 4 miles of flat terrain with about 10 stop signs or traffic lights, speed limit 30mph (which I exceed a bit in order to pulse and glide, when possible). Before my scangauge, I would average about 48mpg. With the scangauge, which provides me better awareness of engine status and modes, I now average about 53 mpg. My coolant temperature doesn't achieve the target 185 degrees until the end of my 4 mile commute. Last night I did a simple experiment --- I drove to work, then turned right around and came back. With the engine completely warmed up and in Stage 4, I achieved 85 mpg on the return trip. Based on that experience there is absolute no way I could achieve even over 100 mpg with either a truly warmed up engine, or a faked-out coolant temperature.
     
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  3. JimboK

    JimboK One owner, low mileage

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    Well, there's a little more to the story. He also recently had installed a plug-in conversion with an additional battery, described in this thread. That's where most of the improvement over the fuel economy achieved by us mere mortals comes from. The hack helps more fully exploit the conversion's capabilities.
     
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  4. DaveinOlyWA

    DaveinOlyWA 3rd Time was Solariffic!!

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    cool mod, but since i did not buy the Prius to reduce my gas bill. i will pass.

    this just makes the Pri pollute like a reg gas car until warmed up.
     
  5. Flying White Dutchman

    Flying White Dutchman Senior Member

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    old cars did not run with higher fuel to warmup faster so maybe this hack/mod is not that bad for the prius engine?
     
  6. DaveinOlyWA

    DaveinOlyWA 3rd Time was Solariffic!!

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    not bad for engine im guessing since engines have run this way for years and still do. just bad for environment. so what is worse? lower gas mileage or slightly more pollution?

    if there are independent sensors in the exhaust stream, it might not be so bad after all, as the car may still be able to sense unburnt fuel and be able to recycle it anyway
     
  7. TheForce

    TheForce Stop War! Lets Rave! Make Love!

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    The past few times I tried to instantly get into WS have failed. There must be some other variable that says its OK for WS besides completing S1 and coolant temp above 157F. I can however get the GPH to drop to .2 or .1GPH which is still good but its still no WS. I will continue to monitor this and see if I can find out whats going on.
     
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  8. TheForce

    TheForce Stop War! Lets Rave! Make Love!

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    Here is something new. The car gave me some codes.

    P0111 Intake Air Temperature Circuit Range/Performance Problem???
    P1600 ECM BATT Malfunction????
    P0000 Null???

    I don't think I did anything to cause it but I'm not sure. Its something that I will continue to look into and to also warn others to look out for.
     
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  9. Flying White Dutchman

    Flying White Dutchman Senior Member

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    sure your not going to contact Hymotion? P1600??
     
  10. TheForce

    TheForce Stop War! Lets Rave! Make Love!

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    From what I read I think it might be referring to the 12v battery.
     
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  11. Flying White Dutchman

    Flying White Dutchman Senior Member

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    ok is the hymotion pack taking more standby current from the 12volkt batt. when the car is turned of?
     
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  12. sandman

    sandman Member

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    Here is a neat video you can see this guys coolant hack and also some neat looking gauges..

    [ame="http://www.youtube.com/watch?v=e-o3qtq3NUs"]YouTube - CNN : Eco Solutions : Hybrid Hackers[/ame]
     
  13. diamondlarry

    diamondlarry EPA MPG #'s killer

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    Those gauges look like the Super MID gauge made by Yoshi. I'm jealous since I see he has 3 strung together and 2 is the maximum for the Scanguage.:(

    My coolant hack is working great so far. Somewhere, the concern was brought up of the engine running lean since the coolant temp is being faked. I have a question about that: Wouldn't the O2 sensors sense the lean condition and call for the injector pulse width to increase?
     
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  14. TheForce

    TheForce Stop War! Lets Rave! Make Love!

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    If you really need more ScanGauges to look at you can always buy a bunch of these OBDII splitter cables.

    OBD2Cables.com

    I use one of these to use my SG and CAN-view at the same time.

    I just wonder how may ScanGauges you can fit on the Prius dash?
     
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  15. diamondlarry

    diamondlarry EPA MPG #'s killer

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    Thanks for the link Jay, I think I'll bookmark it. For the most part, 2 gauges is about right but there are those rare occasions when I want to monitor another parameter or two.

    My guess is you could probably fit 6 or more SG's on the dash if you were creative in how you positioned them. Not that I've measured or anything like that.:p
     
  16. Flying White Dutchman

    Flying White Dutchman Senior Member

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    nice and funny video . like it!
     
  17. JimboK

    JimboK One owner, low mileage

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    Any problems running the two together?
     
  18. TheForce

    TheForce Stop War! Lets Rave! Make Love!

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    They both run fine as far as I can tell.
     
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  19. brick

    brick Active Member

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    When the car is running closed-loop (probably immediately after the S1 warmup) the answer is likely yes. When it first starts, the O2 sensors do nothing so it would not know to adjust the mixture. Maybe you should configure the SG to give you the open loop/closed loop display and only start using the hack after it reads closed? I **think** that you would be good-to-go as far as mixture is concerned.
     
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  20. Flying White Dutchman

    Flying White Dutchman Senior Member

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    and?
    after a while can you tell if your still using it?
    and no problems?