Pulse and Glide plus Warp Stealth in the Prius II for maximum FE …

Discussion in 'Articles' started by xcel, Jun 22, 2006.

  1. hobbit

    hobbit He who posts articles

    Re: Pulse and Glide plus Warp Stealth in the Prius II for maximum FE

    You've mentioned Rick and his miniscanner experiments before.
    I went looking around a little bit -- found some results at
    Greenhybrid, not IC, and it helps a whole lot to spell his name
    right... so Wayne, please check
    http://www.greenhybrid.com/discuss/showthread.php?t=452 [also t=459]
    and tell me if that's the thread you were thinking of -- and if
    not, I would really appreciate if you could dig up the specific
    reference. I found *nothing* at Insight Central.
    In the meantime, I've asked Graham how he calculates %load. The
    OBDII garbage I have from Alex Peper seems to be calculating
    it way higher than is reasonable, and claims a 23% load during
    *warp stealth* f'krissake when the engine is being DRAGGED.
    So it's becoming really important to me to learn exactly where
    some of those old numbers are landing.
    I don't think you can quite apply the same "throttle setting"
    methodology to an eCVT. The throttle control basically does
    what it needs to, quite decoupled from what your foot is doing.
    I will point out that when the Prius opens the throttle quickly
    like it does, it is not to *full* -- in fact the ballpark opening
    appears to be 20 to 25 percent, as claimed by OBDII and also as
    measured as a fraction of the full voltage swing of the TPS pot.
    So it is quite possible that the Prius is already doing your
    "lower throttle opening" game, and saving the full-throated roar
    for when the driver really punches it. My quest is to optimize
    best use of that "gentle" region.
    One thing that may help with understanding HSD, within certain
    confines, is that pushing harder with your foot has the effect
    of selecting a lower gear ratio. This is totally non-intuitive,
    but given what I see with RPM in relation to wheel speeds in
    a scenario where the throttle opening largely remains UNCHANGED,
    that's got to be how it works. RPM goes up, power [thus hill
    climbing ability] goes up, but all within that narrow range of
    engine *torque*.
    Last edited: Aug 7, 2006
  2. xcel

    xcel PZEV, there's nothing like it :) Staff Member

    Hi Hobbit:

    ___Here you go: OBDII Scanner.
    ___% Load with the SG-II is not a great way to measure ICE load either. Running a max 19 - 20 TP (10 to 89 min/max) at maybe 1,900 RPM in a nice and easy Pulse shows ~ 65% load in the Accord. In other words, pretty useless other then as an instantaneous type load gauge.

    ___When I speak of a throttle setting, I am not speaking of maintaining a particular throttle setting or TP set point but DWL using the iFCD as the guide. I do not really care what the ICE is doing internally if I can instead maintain focus on an iFCD to maximize FE no matter the car. As long as the iFCD is a real world number or at least closely follows the actual iFE, I should be able to maintain it at the highest level for any given speed … Unfortunately, most of my Prius highway driving experiences arose while sitting in the passenger seat watching you or Dan driving your own Prius II’s :(

    ___Good Luck

  3. hobbit

    hobbit He who posts articles

    Okay, thanks; I must have still been using the wrong name to
    search at IC. The greenhybrid post is almost equivalent with fewer
    I'll note that 1300-1400 rpm at 22% or so TPS and upwards of
    75 MPG on the iFCD [only at interstate speeds, it's always lower
    if you're going slower] is at the *low* end of my "sweet spot
    range". Very minimal demand. It also corresponds roughly to
    your "40 mpg pulse rate"...
    This stuff shouldn't be that different between Prius I and Prius II,
    I would think... but I've never actually driven a Classic,
    especially armed with a vacuum gauge...
  4. hobbit

    hobbit He who posts articles

    Is there anyone here with an SG-enabled Prius that could try
    a couple of things for me? Mainly, accelerate from a stop while
    keeping RPM at, say, 1600, and take note of what the SG reports
    as % load during that. It will probably vary a bit but I'd like
    to know the ballpark of what SG thinks your ECU thinks.
    Ideally, I'd be able to get this data for both a Classic and a
    3rd-gen and see if there's any difference.
  5. hobbit

    hobbit He who posts articles

    Okay, I updated http://techno-fandom.org/~hobbit/cars/sweet/
    with a little more explanation, and less of a "do exactly this"
    feel in favor of a "we might be onto something here but more
    research is needed" theme. With more silly pictures. Please
    give it a look and let me know what should be added. What *could*
    be added is a whole book about hypermiling at the bottom, but
    I'll leave that to Wayne!
    In the meantime, I got an answer from Graham about the miniscanner.
    His %load figure is simply grabbed from whatever the ECU says
    about it. However, if a gen-3 Prius is at a claimed "35% load"
    that's completely useless for maintaining any prayer of highway
    speed, so there might be something else going on here that may
    be peculiar to the Classic.
  6. JimboK

    JimboK One owner, low mileage

    Hello, Hobbit. I've been fascinated with your findings regarding this sweet spot ever since I stumbled upon the article on your site. I don't have a mechanical or engineering background (I consider it a major accomplishment just to have changed the oil myself!), so I've read and re-read it to try to absorb it. The take home lesson seems simple enough: At speeds above those where P&G is useful, use “warp stealth” when conditions allow, and when they don’t, in the Prius with no added instrumentation, keep the instantaneous MPG between 35 & 75. I’ve been doing both whenever possible.

    I now have more instrumentation available: I just bought a used ScanGauge I. I've set the SG to display RPM so I can can watch that. But not fully understanding what many of the other SG parameters are, I'm not sure what else to use to help approach Prius high-speed FE utopia. Are you familiar with what it can display? If so, which of the other parameters would be best to monitor in order to achieve and maintain this sweet spot, and what numbers should I aim for?

    Did you get what you need in response to this? If not, I'll offer to test this and anything else you might need with the SG.

    BTW, I posted a similar message on PriusOnline, so if you've responded to one, you may disregard the other unless you think it worthwhile for the masses reading the thread.

  7. hobbit

    hobbit He who posts articles

    In the meantime I've gotten hold of a Vetronix Mastertech MTS3100
    to borrow, i.e. the official Toyota tool, and if *that* lies to
    me then something's very wrong. Under most fairly gentle
    acceleration scenarios I see about 50% calculated load.
    I'd still be interested in what your SG says...
    I rarely hang on priusonline these days; mostly on priuschat,
    well, until it got knocked over AGAIN and I hopped on POL for
    the updates.
  8. JimboK

    JimboK One owner, low mileage

    Hobbit, thanks for the reply. I remember someone else suggesting 50% as a max. I think it was in CleanMPG, but I can't remember. I've searched in so many places, I can't remember what I've read where. :confused:

    Anyway, for your acceleration test, how long/fast do you need me to hold that RPM?

    I knew you were pretty consistent on PriusChat, but it was still down when I posted on POL. There's now a nearly identical post on PC.

    Thanks again!
  9. Yoshi

    Yoshi Active Member

    I would like to hear some comments about Prius fuel injection at downhill coasting on highway.
    Discussing on PriusOnline, they say ScanGauge tells them 110 - 200 MPG instead of 9999.9 above 42 mph.

    Our Japanese Prius clearly shows the fuel cut, but they say some fuel is consuming for CAT.
    Maybe, it is cause by the emission control system difference on the US models.

    I believe the ScanGuage is a kind of macro type of instrument and it sometimes lies. :)
    Can anyone confirm this using oscilloscope or anything?

    Thank you,
  10. brick

    brick Answers to "that guy."

    I wanted to throw my 2 cents in here since I just spent >100 miles on the highway in the closest thing to a HS P&G cycle that I could manage.

    First let me address Yoshi's question about the ScanGauge showing fuel injection while the Prius coasts downhill. In reality I don't think the ScanGauge knows how to deal with fuel cut while the engine spins. While I was watching its iFCD in the Accord it became apparent that the device isn't looking at actual fuel injected. Instead, I think it's basing its calculation on engine displacement, RPM, and manifold absolute pressure. I have never, ever seen 9999mpg without cutting the engine completely. 5MT Insight users will attest to the fact that it can't handle lean-burn, either, which would not be a problem if it had a way to monitor injector pulse width and had some idea of the injector capacity. (Doesn't the SuperMID look at the injectors directly?) I can't confirm that through any instrumentation but this is what the empirical evidence tells me.

    Finally, what I experienced last night. It turns out that the Prius II responds a whole lot better on the highway than I would have expected. Yes, a 1.3L lean burn i-dsi engine with a tall 5-speed would blow this guy out of the water. But coming down the back side of every hill in Warp Stealth gets the job done. My concerns of draining the pack were completely unfounded, as the SoC was completely stable at the top-most blue bar even after a mile+ in the 60mph range. (The only time I have seen a lower SoC so far was after an extended EV at ~30mph around town.)

    However, I do think that I pay some price for gliding down those hills with the engine being spun by MG1 (I think?). It looks like the ECU has figured out my game and likes to keep the battery topped-up in anticipation of my next demand for current. The result is that there were a few times when I would have expected >60mpg at a cruise but it was hanging in the 40s instead. After a minute or two it's back to its old self, especially if I throw in a little regen for speed control and to help it along.

    Barely 300 miles on her and that 105 mile segment came out just north of 56mpg in 43F temps while travelling at an average of 60mph. The Prius II is a joy to drive in this kind of aggressive cycle since it responds so well to fine accelerator input. I'm very much looking forward to seeing what she can do with 5,000+ miles on her and some spring-like daytime temps.
  11. dyoungerman

    dyoungerman New Member

    Hello all,

    I am the proud owner of a new 2007 Prius Touring (Pkg. #3) for 4 whole days and counting. (Yay!) This online community of "Prii People" and technical information is kind of overwhelming, but it's great for newbies like me to have resources to go to.

    I'm averaging 47-50 mpg on my 35 mile each-way commute. It's mostly through small towns, on back roads, and on state routes, but it's hilly. So far, I'm quite pleased and I'm finding this mileage thing quite addictive.

    Here's my question, though. Is my car a Prius II that you speak of? (I was told that my car is the 4th generation of the Prius that Toyota has made?) Can I follow the same rationale/procedures listed in this thread? I've tried coasting techniques down hills and on flat sections of road and I can't get the display to show no energy flow arrows. My Prius has the Hybrid Synergy Drive and the CVT transmission. I think it might be behaving differently than models with prior generation technology, but I dunno.

    Thanks much!
  12. JimboK

    JimboK One owner, low mileage

    Welcome to CleanMPG and congrats on your purchase, dyoungerman! The masters (not me, though I'm working on it) are here to teach you!

    Yes, yours is what many refer to as the Prius II, which began with the 2004 model year. It's actually the third generation, which leads to confusion as you've seen. Here's a good overview of the Prius models' history. To eliminate confusion in discussions where multiple models are discussed, many use the actual Toyota model numbers, NHW10, NHW11, and NHW20. IMHO, just stating your model year is sufficient.

    I don't know all the differences between the Touring model and the basic model, but the hybrid propulsion system is the same. I'm sure the Touring package could affect fuel economy in small ways -- different tires, for example -- but I believe you should still get good hypermiling results if you apply what's taught here and on the Prius forums.

    In particular, keep working on your glides. As long as you're at 40 MPH and below, completely let off the pedal for a second or two, allowing the ICE to shut down and green arrows to appear, and then feather the pedal ever so slightly until the arrows disappear. Once you're able to call that up on demand, you're on your way. If you can't safely stay at those speeds, then at higher speeds "warp stealth" produces mostly the same effect. The technique is the same. The visible difference is that you won't provoke a "no arrows" state, and instead the slight pedal feathering produces orange arrows.

    It takes practice and patience with these and many of the hypermiling techniques described on this site. I suggest you take a couple of them at a time, get good at them, and then progressively add more. I've had my car for over a year, and it's been only recently that I've started even to come close to what the experts have done.
  13. JimboK

    JimboK One owner, low mileage

    About time to bring this thread back to life ....

    I've been wondering something recently: With the experience we Prius drivers now have under our collective belt, is there a consensus on optimal P&G speeds and ranges? And a related question: Are there inefficiencies in the ICE starting and stopping during P&G? It would seem intuitive (to me anyway) that there would be.

    Wayne's experience (described earlier in this thread) suggests wide P&G speed ranges get better results than narrow ones. Inefficiencies in ICE shutdowns and restarts would help explain his results. On the other hand, I remember Diamondlarry suggesting recently that he was experimenting with narrower speed ranges (5 MPH??), but I didn't see any report of his conclusions.

    I began some controlled testing last year on various combinations of P&G speeds and ranges:
    • 15-25 MPH
    • 15-30 MPH
    • 15-35 MPH
    • 20-30 MPH
    • 20-35 MPH
    • 25-35 MPH
    The tests were never completed because of the unanticipated need to replace my tires partway through. I plan to begin testing anew sometime this spring, and will include comparisons to steady-state driving. (Results will be posted.) But the incomplete results suggested that range had no effect; instead, results improved as the overall average speed dropped.

    So, what's the current thinking among those of you smarter than me? ;)
  14. bestmapman

    bestmapman Fighting untruth and misinformation

    Hi Jim,

    I think this would be a great study. Maybe I could participate with you. If you give me the parameters you are using (distance, terrain, etc.) I could duplicate your efforts and we could duplicate the data.

    Now that I have a scangauge, we could duplicate things such as tps and ign.
  15. diamondlarry

    diamondlarry Super MPG Man/god :D

    :eek:Oops!:eek: I did mention that didn't I.:eek: I will be doing some driving on Monday and I may be able to test that out. Today, I was experimenting with 25-35 or so on some country roads. I also did a little bit with 30-40 or less. I did notice that the lower end target speeds that were closer to 30 mph seemed to have a higher impg number, ie. going from 30 mph or above to 35 mph or so. I went from my mom's house to a Sunday School class party that was a distance of 13.3 miles and, at ~40F I ended up with 82.2 mpg. Now, if I could just remember exactly what I did...:confused::D

    I have a little story that is slighty off-topic for this thread but is related to mpg. When I got to the party, one of the guys asked me, "What kind of mileage are you getting in your car, 60 mpg?" I just smiled and said, "Maybe on a bad day.:D" Then they looked at me in shock when I told them that I may drive a little slow but I did get 82 mpg coming here. That brought on a short discussion on my P&G techniques; very short.:(
  16. Dan

    Dan KiloTanked in post 153451

    I'm posting from my phone so I've only skimmed the topic revival.

    Now i have done some work this winter on shutoff and ice light losses. all done at lower speeds with am ev button.

    On steady state I think ign14 should stablize around 70 mpg @ 46 mph. i think that will be the best.

    if you test below 45 mph it well need to be done over many miles with start soc = end soc. If you get good numbers by canniblizing soc its invalid.

  17. diamondlarry

    diamondlarry Super MPG Man/god :D

    I have found on my highway trips to Chicagoland and beyond that when the speed drops much below 50 mph that the IMPG numbers usually start to fall. At 50-55 the number will bounce around from 80-85 or greater but will drop to the 70's when below 50 mph.:confused: They really start to drop off when below 45 mph. It must be that when rpm's stay the same that a higher speed will cause a higher calculated FE number. There will, of course, be limits to this because of aerodynamic drag if the speed is too high.
  18. bhchan

    bhchan Newbie

    Re: Pulse and Glide plus Warp Stealth in the Prius II for maximum FE ?

    New Prius owner. thanks for all the info. this is gonna be fun to incorporate.
    Last edited: Sep 11, 2011
  19. lyekka

    lyekka Well-Known Member

    I have been wondering this since I learned about P&G.... Would it vary with the seasons also? I try to extend the P&G and sometimes I think I did too much as the ICE seems to get cold and does not want to glide.
  20. Dan

    Dan KiloTanked in post 153451

    1. Slower is better than faster
    2. Ultra low speed ICE-on is bad.
    3. As few lights as possible is good.
    4. Regen is bad
    5. Assit is bad

    DISCLAIMER: I use metric, so don't freak out.

    OK... culling all that together, here's what I decided (the world according to 11011011). So basically we are asking the pulse entry point (at what speed you light the engine) and your glide entry point (at what speed you cut the engine). So looking at point 1, I decided that a low glide entry point was good. Looking at point 3, I want to have at least a 35 kph (21 mph) delta between my pulse entry and my glide entry velocities. Also looking at point 2 I don't want to dip below 20 kph (12 mph). So my "competition" window is:

    Pulse Entry: 20kph (12 mph)
    Glide Entry: 55kph (34 mph)

    Now to satisfy point 4 and 5, I try to do all my pulse and glide transitions via an instantaneous EV switch (Radio Shack or Factory EV).

    Now based on my SHM research, I really like to see my IGN around 14,15, or 16. So my pulse RPM is usually dialed in at 1600 RPM. Easy.

    Outside of "competition" mode I bump my Pulse entry up to 45 kph (28 mph) or 30 kph (19 mph) if no one is around.

    Hope that helps


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