Possibly Poor Prius Performance

Discussion in 'Toyota' started by jss, Jan 3, 2009.

  1. donee

    donee Well-Known Member

    Hi mparrish,

    I think you mean S2. S1 is a timed stage, but in cold temperature (< about 20 F ?) it is not enabled at all. And this is because the battery does not have power at colder temperatures to support the S1 function. At least, that is the way it seems to me.
  2. JimboK

    JimboK One owner, low mileage

    Certainly the Prius is capable of much more. The question isn't about its capabilities, but rather whether the OP's results are accurate. Sean summarized nicely why, as I mentioned previously, the effect of cold weather on FE is more exaggerated in the Prius than in other cars. Believe us Prius owners (and, in Skwyre7's case, former owner) when we say that 23 is easy to swallow in his driving conditions. That's not to say there's not substantial room for improvement.

    I think he means S1. S1 is not totally a function of time; it is shortened with EBH preheating.

    I've never seen it described that S1 is disabled due to cold weather. Nor have I ever experienced it, and I've driven the car in single digit (F) temperatures. How would S1 be disabled anyway? What would the behavior be? That implies the car jumps directly into S2, and, again, I've never seen nor heard about that.
  3. JusBringIt

    JusBringIt Be Inspired

    Thanks sean, could you give me a bit more information on warm-up for the prius? or larry, or Jim....or michael... engine rpms and all that. IF there are hills that would damage the trip going into work, then he should be able to get much more over epa on his return trip.
  4. Right Lane Cruiser

    Right Lane Cruiser Penguin of Notagascar

    Ricardo, there is an excellent tabulated summary in Manuel's article HERE.

    For short trips, all it would take to smash FE efforts would be a setup like a section of my route for work. It starts and ends at roughly the same elevation but has a double hill with a dip in between at a lower elevation. There is a light at the bottom that is terribly difficult to time due to brevity. Something like that with sufficient cool down time between trips would give terrible mileage in both directions. Especially if you can't turn the engine off.
  5. JimboK

    JimboK One owner, low mileage

    Ricardo, the warmup process is driven largely by ICE temperature, though time is one component of what we call stage 1 (S1). See this for a thorough description of all five warmup stages. RPM has nothing to do with it except to the extent a higher RPM might warm the ICE faster. Whether it actually does is pure speculation on my part, though it seems intuitive to this relatively uneducated mind. :confused:

    A couple of minor corrections probably should be made in that document (with all due respect to the universally respected authors). The document describes 104F as the threshold between S1 and S2. I and others have observed that it is not strictly temperature-dependent, nor, as I suggested in my previous post, is it totally time-dependent. There is no question that an EBH shortens it, as Marc reports, so obviously there is a temperature component. But without an EBH, it seems to be pretty consistently a little over a minute after a cold startup, irrespective of OAT and ICE temps. Without EBH preheating I've seen it terminate in the winter at ICE temps of <80F, whereas in the summer the ICE can be 120F+ before it transitions to S2; those temperatures just happen to coincide with the one-minute-plus timeframe in those conditions.

    The S2/S3 transition point, on the other hand, is totally dependent on ICE temp: 157F (not 163F as the document states).

    True enough about the hills on Jss' commute, if there is a significant elevation drop from work to home. But assuming no net elevation change, hills will still cause an FE hit.
  6. JusBringIt

    JusBringIt Be Inspired

    THanks for the info and time you guys took to reply.

    I take a huge FE hit going to work in the mornings due to the dramatic elevation changes. I changed my route around as much as possible to take full advantage of both these. That maybe something he could consider. I'll finish reading the links you guys provided. I'm sure they will provide good reads.
  7. mparrish

    mparrish Rosie the Riveter Redux

    JSS, what happens to your "battery bars" during your commute?

    It's a good idea to try to keep them at 6 (~60% SOC) as much as possible. 5 & 7 are acceptable at times. 4 & below are not so good.

    IF you don't have an EBH (true) and IF you are enduring a long winter-enduced S1 (true) and IF you are aggressively attacking hills while driving during the 60-70 second S1 (maybe true), then you will experience a double whammy:

    (1) Your S1 mpg will be poor by design, as significant fuel is being used to heat up the cat while you significantly deplete the battery down to ~45% (4 bars).
    (2) Your S2 mpg will suffer as well as the ICE utilizes more fuel to both turn the wheels AND restore battery SOC to ~60%.

    Most of us around here limit S1 via the EBH, and then "limp" around in the shortened S1. I'll literally drive @ 15mph for 20-30 seconds or so and refuse to turn the wheels with battery power. When S1 ends, I take off.

    So try that. If you can (route permitting), next time try your best to avoid a yellow arrow from the battery to the electric motor. You'll have to "limp" for a little while, but then S2 will set you free.

    And that's a good general rule for ALL stages. NO WIRE HANGERS EVVVVUUUHHH!!!!...........I mean, NO YELLOW ARROW FROM THE BATTERY EVVVVUUUUHHHHH!!!. :)

    .....until you convert to PHEV. Then yellow arrow is all goodness. :)
  8. donee

    donee Well-Known Member

    Hi JimboK,

    S1 is when the car uses the battery for the first minute of operation, while the engine runs continously at low power and torque. If you hit a hll during this period, its somewhat obvious, as even though the engine is running the car feels like its running on pure EV. Which is nearly what its doing. And the battery SOC will drop quickly.

    In cold temp, the battery map reports low power availability to the ECU connected to the gas peddle. Which then must command the engine to provide the power, rather than the battery. So, S1 in effect, never happens.
  9. JimboK

    JimboK One owner, low mileage

    OK, I see what you're saying. Frankly, I've never noticed at sub-20F temps any tendency for the car to favor ICE power over battery power during S1. But then I've never looked for it.

    I guess the issue is what defines S1: The fact that the ICE shuts off for nothing (behavior that's always present on startup, and how I define S1), or whether power is coming primarily from the battery or the ICE.
  10. mparrish

    mparrish Rosie the Riveter Redux


    That's interesting. It has not been below 20F in Austin, TX since mastodons were swimming in Barton Springs.

    I'm assuming EV mode can not be activated, even though "S1 in effect, never happens". Is that correct?

    It sounds like a modified, cold-weather version of S1 (S0.5? :) ) where iMPG is poor due to cat warmup just like S1, EV mode is disabled just like S1, but the ICE is unleashed to protect the battery.

    Either way, I'm using the EBH. ;)

    Is the new Prius really coming out in 7 days? Hot dog!
  11. Damionk

    Damionk DWL Lover

    Welcome to CleanMPG Jss. Follow the advice of the members here and you will soon find yourself getting better and better.

    On a side note I have an aunt who goes by JSS since those were her initials before she got married. They would be JSL now. Wonder if you are her...
  12. donee

    donee Well-Known Member

    Hi JimboK and mparrish,

    Yep, once the car gets up above 70 C then its into a S2 and will glide and autostop (if the heater/defroster is off). Eventually it gets up to the high 80's C, and then its a normal hybrid mode, as long as you keep it that warm. Which means limited heater usage, unless your on the highway.

    I did about 59 mpg on a Pulse and Glide drive home tonite. Had full grill block. I used the heater a few times towards the end to keep the engine below 90 C where the route is generally uphill. It was 24 F.
  13. JusBringIt

    JusBringIt Be Inspired

    how about just converting the prius to a plug-in? THat would probably help you out due to your log-in and try to keep it using the battery? I know that generally it's more efficient to use the battery as little as possible, but isn't that only with long commutes?
  14. Right Lane Cruiser

    Right Lane Cruiser Penguin of Notagascar

    The inefficiencies of the battery all stem from having to use gasoline to charge it (via regenerative braking with severe conversion losses), so if it is a plug-in, no issue. The two problems with that are expense of the conversion and the fact that it is difficult to get the car keep from starting up the gas engine to get the cat up to temp. It is possible to deal with but not trivial. Check out Jay's thread about his conversion experience here:

    REVIEW: Hymotion Battery Plug-In Prius

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