Heavy rev, reduced mpg

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by williamsoc, Jul 25, 2019.

  1. williamsoc

    williamsoc New Member

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    2010 with about 275k on it. Recently took it to the dealer for the software update. (I can provide more details on this if needed)

    The issue is when accelerating. If it had an old fashioned automatic transmission I'd say it was sluggish switching from first to second gear. The engine keeps working too hard, even after reaching highway speeds.

    Recently we took a short road trip. 300 miles or so total. Got 34mpg. In all the time we've had the car we've never experienced such bad gas mileage.

    I intend to change the transmission oil this weekend. Any additional advice is much appreciated.
     
  2. FuelMiser

    FuelMiser Senior Member

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    Your traction battery is not providing the usual boost to the hybrid drive. There are no gears in the hybrid drive system. The gas engine is always connected to the drive system in top gear. Imagine launching/accelerating from low speed in a traditional car with transmission in top gear. You get very sluggish acceleration because available engine torque is so low. In the Prius with hybrid drive, the electric motors, powered by the traction battery, provide the low-end torque to get the car moving/accelerating at an acceptable rate. Then, once the car is at higher speed, the gas motor can keep the car at speed while also charging back the traction battery. Your traction battery is shot...
     
  3. ThatDudeOrion

    ThatDudeOrion Member

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    Just to clarify, am I inferring correctly that the software update may be the cause of the issues here? How was the car doing before the SW update?
     
  4. bisco

    bisco cookie crumbler

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    is it hot out, battery protection mode will kick in sooner with a weaker hybrid battery
     
  5. williamsoc

    williamsoc New Member

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    This was not an issue before the software update. And yes, it's decently hot (upper 80's). I dont remember this issue in hot weather previous years.

    Thanks for the replies. Fuelmiser, I hope you're wrong!
     
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  6. bisco

    bisco cookie crumbler

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    if you search the update threads, i don't think you're the only one with this complaint. i wonder if the update limits battery output, which affects older batteries more than new.
     
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  7. CR94

    CR94 Senior Member

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    No change in acceleration, or "revving" in hot weather here since the update. Mpg is also normal. Very boring.
     
  8. bisco

    bisco cookie crumbler

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    most don't, but a few claim to
     
  9. ThatDudeOrion

    ThatDudeOrion Member

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    I would be pretty bummed if I get the SW update and my mpg takes a hit, also would be pretty bummed if I don’t get it and my inverter takes a hit... what to do
     
  10. Marco Morel

    Marco Morel Junior Member

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    Every software update Toyota releases for the ECU is to help the IPM's to not overheat and instead of replacing the IPM's with better designed ones they release software updates that make the car more and more reliant on it's gasoline engine and use the hybrid battery as little as possible. (If the hybrid battery isn't being used the IPM's can't overheat) so yes these new updates do hurt fuel economy ALOT. My 2010 Prius drives like its a traditional car with an Auto Start/Stop system now. It shuts down the engine at a stop and if I barely tap the accelerator then IF IM LUCKY the car will CRAWL in EV mode but most times the engine has to kick on because the ECU sends no power from the battery to the wheels. My battery is very aged as well so there's that but it would still go around a parking lot in EV mode now with the new update it cant even reverse in EV...
     
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  11. fuzzy1

    fuzzy1 Senior Member

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    That is a very lousy description of the eCVT transmission. During low speed acceleration, MG2 should be providing most of the wheel torque with power from MG1, in turn driven by the ICE. MG1 never pushes any torque to the wheels (excepting the Prime). MG2 is the only electric motor contributing to wheel torque, and it ought to get the majority of its power from MG1, not the battery.

    I'm not saying that a bad battery doesn't turn the Prius into a dog, only that the mechanics are not as bad as portrayed here.
     
  12. FuelMiser

    FuelMiser Senior Member

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    Sorry, I wasn't paying attention to your mention of the "software update" I don't think our 2014 is involved in the program, so it, and its impact on performance, is not even on our radar. I was simply "doing the math" on your nearly 10-year old car with 275K miles! In my mind, that's end of life for the poor traction battery. Our 2005, Gen 2 battery lost ability to hold charge after our 10 years and 145K miles with the car. The main point in my "lousy" description of the hybrid synergy drive was that the gas motor is connected to the drive in fixed, top gear. Thus, it provides very little torque at low speed...
     
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