Welcome to PriusChat

We'd love to have you join our community and participate in the conversation! Sign up for FREE today.

Sign Up

Getting consistent entry into WS at highway speeds

Discussion in 'Gen II Prius Fuel Economy' started by HCHTech, Jul 31, 2010.

Social Buttons

  1. HCHTech

    HCHTech New Member

    Joined:
    Jul 31, 2010
    Messages:
    5
    Likes Received:
    0
    Location:
    Pittsburgh, PA
    Your Vehicle Year:
    2007 Prius
    Model:
    N/A
    Some background. I own a housecall repair service, and put around 24K on a car in a year. Since I go to customer's homes, my typical driving day has between 3 and six cycles of:

    5-10 minutes of residential neighborhood driving, followed by
    15-20 minutes of highway driving followed by
    5-10 minutes of residential neighborhood driving.

    The topography is fairly hilly here in metropolitan Pittsburgh. so there are lots of quick ascents and descents in the residential neighborhoods and lots of long, slow ascents and descents on the highways.

    I purchased a very gently used 2007 package #1 (I think) lease return in March of this year, with 33K on the odo. It has been a ball to watch my own retraining in action. When I started driving the Prius, I managed about 42mpg (only double the average mileage on my previous car, an '03 4-cyl Accord), and have watched this climb steadily to about 52mpg on average over the first 9,000 miles. (MFD numbers only)

    I've been lurking on this board for quite a while, and have read the P&G and SHM articles several times as I got better at driving the Prius-way.

    I've found that there really aren't many opportunities for P&G, save occasional residental stints where there are no other drivers to worry about. I've increased my mileage largely by utilizing the "no arrows" condition while coasting down a long hill on the highway, followed by green arrow, battery-only speed maintaining on the flats. I also use the red arrows, ICE-only-charging-the-battery mode whenever possible. This, combined with more awareness of upcoming traffic flow has earned me my first 10mpg increase.

    So, finally to my questions:

    I've noticed that on some drives, my car just doesn't want to hit the no-arrows condition (is this WS?) when going down a long descent. Feathering the pedal back as gently as possible finds the car moves directly from battery powering the wheels to regeneration mode. Gently increasing acceleration then moves directly from regeneration to power. If there is a no-arrows interval at all, it is split second, and no amount of trying seems to find the sweet spot. It's as if the difference in pedal position between right and wrong is a millimeter's movement - just not maintainable.

    Conversely, on other drives, WS seems absurdly easy to maintain. There must be an entire inch of pedal play in which the car stays in WS. You can keep it there almost by ear.

    The length of descents where I have trouble are long enough that I don't think the problem is coolant moving to the thermos. There also doesn't seem to be any condition that is common (SoC low, engine cold or warm, outside air temp cold or warm or hot, degree of slope, etc.) I usually just resign myself that the car "doesn't want to" at that time and stop trying - I have to pay attention to the road after all!

    I also think that if I could figure this out, I could approach 60mpg, so I'm posting here. Any ideas anyone?

    Thanks!!
  2. 2k1Toaster

    2k1Toaster HID Guru

    Joined:
    Feb 14, 2010
    Messages:
    3,986
    Likes Received:
    1,182
    Location:
    Rocky Mountains
    Your Vehicle Year:
    2006 Prius
    Model:
    Three
    Are the times you cannot glide often shortly after you have started the car, and/or kept below 34mph without stopping for a rather long time since you started?
  3. HCHTech

    HCHTech New Member

    Joined:
    Jul 31, 2010
    Messages:
    5
    Likes Received:
    0
    Location:
    Pittsburgh, PA
    Your Vehicle Year:
    2007 Prius
    Model:
    N/A


    Hmmm, nope, I don't think so, depending on your definition of 'shortly'. It happened this morning, on a long gradual highway decline (about 3 miles). It was a 15-minute trip to the highway, the first 5 minutes was 35mph and the next 10 minutes was 45mph before I got to the highway. No heat or a/c. I tried all the way down that slope to glide, without success.

    Later in the day, after the car had set for about 2.5 hrs, I entered a highway after only about 3 minutes of residential 30mph driving, and entered glide effortlessly on several occasions. It certainly could be environmental or something I'm inadvertantly doing or not doing, but I don't have a handle on what that might be. :eek:hwell:
  4. 2k1Toaster

    2k1Toaster HID Guru

    Joined:
    Feb 14, 2010
    Messages:
    3,986
    Likes Received:
    1,182
    Location:
    Rocky Mountains
    Your Vehicle Year:
    2006 Prius
    Model:
    Three
    What I am referring to is the beginning stages of warmup. When you first start the car, it goes into a warmup cycle. The engine will constantly run no matter what, even if stopped until the engine is up to temperature. However, even if it is at temperature, if you stay below 35mph (1-34mph) and never stop for a couple seconds, it will continue to run. If you go 35mph or more, it should be able to go into the next stage where it will allow gliding. Also if you stop for a few seconds (like > 5) it should transition to the next stage.

    So if your morning commute down that hill doesnt go above 34mph, and doesnt allow you to stop, and you get to it before 51seconds of ontime, before the engine is warmed up, or while in stage 1, the engine will be continuously running
  5. HCHTech

    HCHTech New Member

    Joined:
    Jul 31, 2010
    Messages:
    5
    Likes Received:
    0
    Location:
    Pittsburgh, PA
    Your Vehicle Year:
    2007 Prius
    Model:
    N/A


    Ok, I understand. I don't think this is the situation either. It's certainly possible I haven't stopped for greater than 5 seconds before the glide attempt, but I guarantee I spent several minutes above 34mph before the glide attempt. Looking back over the times this has happened, it just seems random to me. I will be paying greater attention to look for a pattern, and re-read the "stages" article to see if that helps me recognize a pattern.
  6. JimN

    JimN Let the games begin!

    Joined:
    Nov 26, 2006
    Messages:
    5,401
    Likes Received:
    425
    Location:
    South Jersey
    Your Vehicle Year:
    2010 Prius
    Model:
    V
    What is the battery's SOC (State of Charge)? Is it possible that the battery is completely full & the ICE is spinning? In western PA I always want a larger battery because the car can't store all the regenerated energy southbound or eastbound.
  7. HCHTech

    HCHTech New Member

    Joined:
    Jul 31, 2010
    Messages:
    5
    Likes Received:
    0
    Location:
    Pittsburgh, PA
    Your Vehicle Year:
    2007 Prius
    Model:
    N/A


    The problem most always surfaces at highway speeds, and the battery is never fully charged. I know it has happened as low as 4 blue bars, and has high as 1 bar shy of full. I admit I haven't kept careful track of the issue (I'm starting that now). Here I thought it was just a simple technique I didn't know about that was causing the problem - now that I know it's probably expected behavior, I need to flesh out the particulars so I can build a pattern. This should let me figure out the cause and hopefully what to do to prevent the condition.

    I'm guessing it's all about the "stages", so I'll be re-reading that article as I start documenting the issue more carefully. Thanks!
  8. Mike Dimmick

    Mike Dimmick Active Member

    Joined:
    Aug 8, 2008
    Messages:
    965
    Likes Received:
    233
    Location:
    Reading, UK
    Your Vehicle Year:
    Other Hybrid
    Model:
    N/A
    No-arrows glide is nearly impossible to get into at over 42mph, when the engine is spinning. The (relatively) large gap between power-to-wheels and power-to-battery is only there when the engine is stopped.

    Terminology:

    'Stealth' is any use of electric power only to move the car. It's usually used for speeds below 42mph when the engine is stopped.

    'Warp Stealth' is used for travelling over 42mph with the engine spinning (with fuel cut) - i.e. only yellow arrows showing on the MFD Energy screen.

    'Glide' is used for no-arrows.

    'EV Mode' is when you've actually pressed the EV button, if fitted, and the EV indicator is lit up on the dash. In Japan, this is limited to 34mph and the US, which doesn't have a factory EV button, inherits this limit. Over here (UK) the limit is 29mph displayed. I prefer to think of the EV button as 'engine cut'.

    To get into minimal-power 'warp stealth' I back off until the green arrows just appear, then gently apply the power until the green arrows disappear and yellow arrows appear. That's usually the closest it'll come to no-power glide.

    For what it's worth - probably nothing - my suspicion is that it's a case of instrumentation not telling you what you think it is. I think that the yellow arrow indicates that some power is actually driving the wheels, and that the green arrow indicates that some power is actually charging the battery. There is always some electrical demand from accessories and the drive computers (and obviously the MFD itself). The null position is where regen is insufficient to exceed the load from the electronics.

    The faster the car is travelling, the less load is required to generate enough power to power all the electronics, and therefore the 'null' area is smaller. (Power generation is basically load multiplied by speed of rotation.)

    I suspect that the complaint that it's harder to find a null point on the third-generation car is that Toyota have fixed the instrumentation, and it now shows net power use/production by the motors.
    1 person likes this.
  9. HCHTech

    HCHTech New Member

    Joined:
    Jul 31, 2010
    Messages:
    5
    Likes Received:
    0
    Location:
    Pittsburgh, PA
    Your Vehicle Year:
    2007 Prius
    Model:
    N/A
    Yes, I think you've hit the nail on the head. Once I started paying closer attention, my "no glide" incidents all seem to be above 42mph. There were a couple of times where I entered a glide below 42mph (downhill highway entrance ramp) and maintained it to above 42, even above 50. I think that was luck as once it came out of glide, it was impossible to get back.

    Unfortunately, a week of mid 90s temperatures has necessitated A/C and dropped my mileage down to 49 for this last tank. Still WAY better than the days with the Accord.

    I'm going to keep at it, though - this is too much fun.

    Thanks!!
Similar Threads: Getting consistent
Forum Title Date
Gen II Prius Fuel Economy Consistently getting 35-37 mpg, nothing higher Apr 16, 2012
Prius c Main Forum I think I'm getting out of the prius c game..... Sep 5, 2014
Gen III 2010+ Prius Technical Discussion Clunk in the rear end when getting in. Aug 24, 2014
Prius v Main Forum Dashboard "Lens" is getting splotches Aug 23, 2014
Gen II Prius Care, Maintenance and Troubleshooting Getting the Red Exclamation Point when braking on downhills Aug 14, 2014