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Coolant thermos retrofit - humour me

Discussion in 'Gen II Prius Technical Discussion' started by molgrips, Dec 22, 2008.

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  1. molgrips

    molgrips New Member

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    Is it likely to be possible, assuming I can score the relevant parts? I'm annoyed that they don't come with it in the UK. I reckon it'd improve fuel economy not just because the engine starts warmer but also because the engine has to run less in the first 5 mins to deliver cabin heat.

    I'm like to believe that as is the case for the EV switch, the software is already there to operate it, and I should be able to just wire up the pump and level switches in the flask. It would probably be worth finding the contacts and checking for a voltage after startup to see if it's going through the motions.
  2. Patrick Wong

    Patrick Wong DIY Enthusiast

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    If you can obtain the North American engine ECU as well as the other obvious parts then you might be able to retrofit this. You can consult techinfo.toyota.com to obtain North American service and repair info (if that site will accept your UK credit card.)

    However I really doubt the benefit would be worth the trouble and effort involved, and you might have service issues if the engine ECU installed in your car is not UK original. I owned a 2001 as well as 2004 and did not feel that the first 5 minute fuel economy bar on the 2004 is noticeably different from the 2001.

    Good luck with your project should you decide to pursue this.
  3. efusco

    efusco Troll Slayer Staff Member

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    To emphesis Patrick's post, I doubt there is any significant FE impact from the thermos...my impression is that by warming the heads it helps reduce emissions and was necessary for the AT-PZEV emissions rating in the US.
  4. qbee42

    qbee42 My other car is a boat

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    I agree with Evan. I think this is mostly for emissions. You would be better off to install a block heater.

    Tom
  5. David Beale

    David Beale Senior Member

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    Note that the thermos -IS- lossy, and has -NO- effect in the winter here in Edmonton. Well, let me correct myself. The coolant is about 5C warmer when the pump runs according to the Scangauge. So I suppose that's an effect. I'm pretty sure that has no effect on the emissions, as it brings the coolant from -7C to -2C. The block heater brings the coolant from -7C to +30C.
    What the thermos system -DOES- do is add more parts to fail. How about we swap parts? ;)
  6. qbee42

    qbee42 My other car is a boat

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    It has an effect on emissions as tested using the standard EPA procedure. The practical effects are probably small or non-existent with your climate.

    Tom
  7. dogfriend

    dogfriend Human - Animal Hybrid

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    +1

    You would probably get a lot more consistent results with the block heater also.
  8. Stefx

    Stefx Member

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    Also, the thermos won't be a simple installation. I don't know exactly how the whole system works, but I bet there's a few valves involved, and would impact a UK dealer to do service on your car if your Prius is running a different software version.

    I agree with the above, the EBH would bring more benefit and less cost+complexity.
  9. molgrips

    molgrips New Member

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    Do we know for sure if the UK ECU doesn't contain the programming to handle the thermos?

    I've already thought about a block heater - the problem is I don't set off for work every day at the same time, I don't even drive the car every day. So it'd be next to useless. Plus I've heard other reports that the thermos produces a certain amount of cabin heat immediately on starting up, which would surely reduce the amount of running the engine has to do. When I drive from my house, there's quite a bit of stop start driving to do before I hit the open road, and I end up sitting still with the engine running a fair bit. This is what I would hope to reduce.
  10. efusco

    efusco Troll Slayer Staff Member

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    You'll get no cabin heat from the thermos. The US Prius, at least, has 2 400W PTC heaters in the heater circuit that will provide some immediate heat (albeit not a lot).

    And it's a good question about the ECU...it may, indeed be the same as the HV ECU for the US Prius has EV Mode functionality, it just doesn't come enabled. That said, I think even then the speed thresholds are different for EU and US models.
  11. Patrick Wong

    Patrick Wong DIY Enthusiast

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    The NA 2004-2005 Prius has the following engine ECU part numbers:

    89661–47070
    89661–47071
    89661–47100​
    89661–47101

    So, if you can find the engine ECU in your car and determine its part number, you can compare to the above list.
  12. molgrips

    molgrips New Member

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    Now that's interesting. If that provides enough cabin heat at first, it could save the IC from running so much. Anyone got any info on those?
  13. efusco

    efusco Troll Slayer Staff Member

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    http://www.autoshop101.com/forms/Hybrid06.pdf

    Note that they're just 165W heaters...smaller yet.
  14. molgrips

    molgrips New Member

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    Nice. I don't think I have those. When I start off in colder weather, no air comes out of the vents at all, until the engine's warmed up a bit.. That seems like a better retrofit.
  15. David Beale

    David Beale Senior Member

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    I'm pretty sure the UK ECU doesn't have the firmware for the thermos. If it did it would throw codes because it looks for a temp change when it starts the coolant transfer pump. If it sees no change it is supposed to set a code. There may be an escape clause in the programming for that, as if the car sits long enough the coolant in the thermos is the same temp as in the engine. But it may also look for other signals showing the pump system is working, because when it fails you do get codes. Not having it installed would be interpreted as a failure by the firmware (i.e. if you removed all the components you would get codes stored).

    My Prius has the dual 400W heaters. The only time I notice them is in early fall or late spring. They have no effect in winter that I can see, which is understandable. That isn't enough power to provide noticeable heat when it's -20C (or even 0C). They may be in the UK Prius as well. Ask your dealer (good luck with that ;) ).

    Note that the cabin fan won't turn on until the coolant is above about 40C. Unless you have front defrost turned on.
  16. molgrips

    molgrips New Member

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    Hah!

    I've read about the electric heater only being on when the temp is set to max or when there's a big enough temperature differential. I'll give that a try.
  17. Stefx

    Stefx Member

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    *edit: found my answer*
  18. efusco

    efusco Troll Slayer Staff Member

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    I don't, but I assume it's fairly easy to figure out from the diagrams in the linked PDF
  19. Stefx

    Stefx Member

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    Sorry, you replied after I saw that pdf link earlier in the thread ... you're pretty quick on the trigger:)

    http://www.autoshop101.com/forms/Hybrid06.pdf

    It shows the two 165W heating elements in the heater core, therefore all airflows (floor, dash, front windshield) "benefit" from it ("benefit" being a generous word... there isn't much that 330W can do in a real winter).
  20. mybluegt

    mybluegt New Member

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    Can we install a engine heater that connects into the heater lines and warms the whole coolant system, instead of just the engine block? Why not this type instead of the EBH that every one is installing?
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