Is this normal?

Discussion in 'Gen 2 Prius Technical Discussion' started by Toddwilks, Dec 30, 2020.

  1. mr_guy_mann

    mr_guy_mann Active Member

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    You can swap what parts you want, but I doubt that it will have any affect. The battery resistance values you show on your pic are normal. If you just drive the car (local/highway cruise) then it is perfectly normal for the ecu to maintain the SOC at around 60%.

    I am not sure what else to suggest since you won't do tests that compare functions of your "good" car to the "bad" one. You could have spent not much on a cheap windows laptop for techstream and an android phone or tablet to data log with Dr Prius. If you drive both cars under the SAME conditions you can see if the battery ecu or engine ecu has different data. Are the battery amps and volts the same, does the engine need the same throttle percent to maintain the same speeds, what are MAF readings, and short/long term fuel trims.

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  2. Toddwilks

    Toddwilks Active Member

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    I can do that but no one is telling me what I should be looking at. I have techstream setup on my laptop but I don’t know what to look at to compare the two.


    iPhone ?
     
  3. Skibob

    Skibob Senior Member

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    Looking back I can see you have replaced a lot of parts on this car. Can you get back what you have in if you sell the car?
     
  4. Toddwilks

    Toddwilks Active Member

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    I could but I’d like to figure out what’s wrong. Plus I don’t have plans to sell it. I’m selling the 07 instead since is three owner two accident car with 140k and this is one owner no accident with 84k.


    iPhone ?
     
  5. Skibob

    Skibob Senior Member

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    Unfortunately you may never figure out the problem, or you might tomorrow. No telling. You seem to post a lot of battery stuff. I have said this before if you swap the battery packs and the mileage changes in both cars then you know the problem.
     
  6. Toddwilks

    Toddwilks Active Member

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    I’ve proved the battery isn’t the issue as noted from DR prius report. That’s why I’m thinking to start small with the ECUs.


    iPhone ?
     
  7. Skibob

    Skibob Senior Member

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    Have you checked the readings from the fuel/air and o2 sensors? What if anything is the oil burn rate of both cars?
     
  8. mr_guy_mann

    mr_guy_mann Active Member

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    sigh... Really?

    If you want to figure out what is going on with your car, you have to be able to notice clues and solve puzzles. Things that can reduce MPGs are; ICE problem (weak engine thermostat, restricted exhaust, late ignition or cam timing, fuel control, etc), HV battery, bad wheel alignment, brake drag, damaged aero stuff (undershields, spoilers, etc). Without understanding of how everything works and without having a disciplined test plan, you run the risk of spending more time and money trying to fix your MPG problem than you will ever recoup in fuel savings (if you manage to find something and fix it).

    First I would monitor engine coolant temperature (ECT) from a cold start. I don't know if you can watch data while in maintenance mode or if you have to hold the gas pedal down or just drive the car- you want the engine to run constantly for this test. ECT should start out at ambient, then steadily increase - it should go up to around 180*F then level off as the thermostat opens. If the temperature never gets that high (levels off at lower point and/or drops) then the thermostat is bad (opening early- I often see 150-160* when they fail).

    Now plan these next tests carefully. The idea is to drive both cars on the same route in as close to identical manner as possible. Force charge the HV battery to full. (Safely)Perform a couple of full throttle accelerations followed by heavy decelerations. Then do a gentle accel to a steady highway cruise and hold it for a couple minutes (cruise control?) then coast and gentle braking. You need to repeat these tests several times for both cars, because you want to record all the data for the engine ecu then the battery ecu for each one. The recording time isn't that long, so you may have to do the hard accel test for the engine ecu, save the file (make good notes on it so you can tell later what that particular save file is about), do the cruise test and save that. Repeat for the battery ecu data. THEN do it all again for the second car.

    Afterwards, load a file for each test (example, cruise for car A engine ecu)- Look at MAF (how much air - and therefore, how much fuel is going into the engine), Throttle opening, short and tong term fuel trim (how much the ecu has to correct fuel pulsewidth- should be near "0"), ignition timing (and timing retard), Vehicle Speed Sensor. Then do the same for car B. For the battery ecu look at Voltages, amps, SOC.
    You say that you have a difference of 15-20% mpg- it's gotta show up somewhere in the data. Ideally, the cars should be the doing the same work under the same conditions, so the data should be close (less than 10% difference?)
     
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