I am looking for serious feedback on this document: http://techno-fandom.org/~hobbit/cars/warpstealth.html which lays it all out about feathering at higher speeds above 41 mph. I want to try and get this material into widespread knowledge bases once it's confirmed and corrected, so that people understand the advantages and how to play the game. I would also appreciate help in the following areas: . .. if it works in Classics .. if someone with CAN-View can confirm the VVTi stuff . This is along the same lines as "b-mode.html" in the same directory; to inform the folks newer to the Prius about some of the wonderful engineering subtleties in what they're driving. . _H*
whoa, that's some in depth stuff. i'll have to get back to it after tuesday sometime and really go through it. thanks for putting all this info out there.
I think some who have driven bot classics and Gen2 have said that it is easier to glide in a 04+ than a classic.
Yes, warp stealth worked ON THE SAME CONCEPT with Gen 1s (I had two). Graham Davies discussed it. I think he's reachable by e-mail (from his website). I couldn't say that Gen 1s would mirror the graph you've done---I don't imagine so. Two small things from a proofreader's point of view: In the 2nd #, "delightfully" should be "delightedly". If you don't see why, PM me or ask me to explain ongroup. The reference to "stage 4" in the third-from-last # will leave readers not familiar with all the stages nonplussed. Basically, a good description of a little-understood Prius phenomenon. For non-techies, possibly either the very name "warp stealth" should be changed (it is, after all, inaccurate), or a brief explanation of why we call it that should serve as in introduction. Useful!
1)Nice work Hobbit, great detailed explaination. I'm sure Danny would love for you to contribute that article as well as the B-mode article to the PriusChat "articles" section here. 2)Would change the line "
and here i was wondering how i got two 75MPG+ bars in a row yesterday in a 55 MPH construction zone... guess i'm better off than i thought :-p
Okay, some responses... . You're right about "delightedly". Fixed. . I'm assuming *some* prius experience on the part of the reader, in that they know what stage 4 is. But I added a reference. I hope that reference pointing into the "old KB articles" section will remain valid "effectively forever"... . I think the 1 or 2 kw goes to both spinning the engine and lightly pushing the car, but not hard enough to really maintain speed on the flat. The same as you'd get, for example, by drawing 5 or so amps in slower stealth mode. That's about the level I try to use for my "slightly augmented glide" in P&G, so I'm pretty used to finding that level quickly at almost any speed. . I only mention deadband because if someone's looking for no-arrows zero current in this state, they shouldn't bother because that's not where the plateau is. Hmm. "Deadband" doesn't really exist as a "state" anyways, since it's entirely dependent on SOC... someone should maybe write *that* up, too, because people keep asking. . I changed the text to not refer to charge or discharge as "negative" or "positive" at all, leaving it up to how peoples' instrumentation chooses to represent it. There's no standard. I and my li'l meter think of "battery current" as positive when the battery is supplying power, and negative when power is being pushed into it... can-view takes a different view, and that's fine. The graph explains itself. . "Maintained by the motors" is exactly what it means -- it is the COMBINATION of MG1 and MG2 torques [and their relationship to road load] that spins the engine, as it must be. . Anyways, this should bump this thread and maybe some more people will see it and give the updated version a read... . _H*
The article states that fuel is burned when driving in high speed in "N," yet when I do this, the indicator shows the ICE is off and nothing is being charged. It gets really quiet coasting at 80 to 85 mph down the 1/2 mile hill.
Before anybody crucifies me for my conjecture.. as I am speaking out of my own speculation and observation without too much knowledge of the real working parts of the prius. Let me say, this sounds like a kick I was on here while back but finally let go because I didn't have too much foundation to explain it. This article was a nice attempt to put in a nutshell what few seem to talk about and understand. It gets deep into the working of the prius and its hard to defend yourself without adequate knowledge. Most "like myself" know just enough to be dangerous and cause even more confusion as they try to explain themselves. I thought that using the power of the ice to get up to speeds of 60 or 70, then letting go of the pedal briefly and maintaining just enough to barely maintain a deteriating speed so that in about 2 minutes you would loose about 10 - 15 mph on a flat surface... then speed up again and repeat. This almost sounds like a modified pulse and glide technique. I caught alot of arguement becaue many said it was foolish to use the ice to charge during the acceleration phase to then try and use that stored electrical energy to help maintain speed because electrical energy created with the ICE is never as efficient as just maintaining a constant speed? The arguement also indicated that varying speeds was more of a waste of efficiency than maintaining a constant speed. Its funny how we can use the arguement that anytime we use energy created from the ice, its not as efficient as simply using the ice alone and avoiding using the battery unless its from wasted kinetic energy. I know this is going to be hard to follow as I am not explaining myself well... but suffice it to say that Toyota apparently believes using the ICE to make electric energy for later use is sometimes benificial. Its one thing to use the ICE when the battery is "dangerosly" low, but its quite another when the ICE charges the battery when its already in an ok state. After saying all that.... my arguement was that once the ICE is on, it likes to do some work.. might as well make electric energy while it propels the car down the road right? Hence the benifit of the any pulse and glide technique. I've heard Truckers talk about how thier diesels seem to run better pulling a load. The atkinson engine seems to have some similiar properties in that it has a very high compression ratio and likes to work hard once it really gets going. Why not make electric power when the ICE is operating at optimum efficiency so the electric can take the load when the ICE would be a waste to use like in low load situations when its not that efficient. At any rate, the warp stealth seems to be a modified way of saying the electric helps out when the ICE is just kicking back even at high speeds with the throttle feathered, and then the ICE kicks in to regain speed while recharging the batteries. Too bad the electric is not just a little more powerful as it seems you could maintain a speed for quite a distance even at high speeds if it were so. Too bad we don't have the battery the Camry has in it? I think the next generation prius with a bigger battery and higher rpm mg1 could be exciting.
I would like to see the real data how the modified pulse and glide technique is better than CC method. http://priuschat.com/index.php?showtopic=19638&st=8 Ken@Japan
Wind -- in the description, I don't think I really particularly advocate a P&G technique on the highways per se, I just describe a better "glide" side for when it's appropriate. You're pretty much right about heavy use of the battery -- yes, there are conversion losses. The reason P&G works is that it avoids having the engine "loaf" at low RPM and low power output -- have another look at http://techno-fandom.org/~hobbit/cars/prius-curves.gif and note how ICE efficiency falls off until it's torquing good and hard against a load at 15 kW or so. That's what you try to do on a typical pulse -- run it up on top of that curve, and then let it shut down completely, instead of sinking down into that low-efficiency region by continuing to run. Because of the hysteresis in the system, you have to vary what your foot does a little wider to help it make the decision. . But that's really talking about low-speed P&G again. At high speeds the jury's still out on whether actually trying to *pulse* and then warp-stealth glide buys anything -- in my own experience it doesn't, in fact, and as Ken points out it's often better to just set the CC on the interstates and sit back. But we've all noticed that the CC is pretty aggressive uphill to maintain an exact speed, especially if it's fallen behind a little -- which starts getting over toward the *other* side of that curve [which nonetheless is fairly flat anyways, so it doesn't hurt too much] but the higher and harder you run the engine the more heat you're throwing off as well, so going uphill under slightly less power and letting speed bleed off a bit to regain again on the backside probably does save a bit of energy. The debates and wildly differing sets of calculations concerning this have raged for *years*, and can be found sprinkled through the archives of prius_technical_stuff and other forums. . Still, even those not-quite-as-aggessive accelerations [okay, we can call them "pulses"] can bring you up around 60 mph, and if you're on a road with a 50 mph speed limit you might want to back 'er down a little. That's where warp-stealth is really useful, because it provides a don't-loaf-the-engine way of doing that. It also helps to read your upcoming terrain and figure out when it's more appropriate or not. Like if you're pulling and about to hit an uphill, don't go to warp-stealth just because you're 5 over, just hold tight and use the momentum to aid the ascent. Warp-stealth isn't presented as a magic-bullet solution, it's simply a component, a tool in the whole set that you use for high-mileage driving in general. . Have I stuck even close to the topic you were chasing down here??... . For Ken -- there are so many other factors in play that it's really hard to present clean, isolated MPG numbers. I have observed in general that if I use my variety of techniques I can do a bit better than the CC, but not *extremely* better ... and that distinction becomes even narrower at higher speeds. . _H*
Well I do recognize that both of you guys know far more than I do about the system and I'm just throwing in conjecture on the sidelines. The part about the glide technique I see as benificial is that if you can achieve that state, its the most friction free state the prius can achieve and then when you fire up the ICE, you put it in the most effecient state it can acheive as you go ahead an regain the speed lost from gliding..... and the battery gets charged again to help the glide again. True glide without ICE or battery is the most desirable, but good luck on holding that for any length of time.. so in the real world, its about the battery slightly assistiing the glide... but something has to charge the battery back up right?.. its not the glide doing it... or else your gliding wrong as friction kills your kinetic benifit. Its never good to kill needed kinetic speed to charge batteries?... charging batteries is best done with "wasted" kinetic energy or with the ICE under a "like you said" greater than 15kw load. So we are slicing and dicing the two most efficient states of the prius in this process. Some choose to go to neutral to glide, but that seems aweful busy to me.. I would rather learn to feather the throttle. I can see how going to neutral would be far easier, but not near as relaxing and enjoyable a trip. I don't want to have to work to save gas... I want the car to do the work so I can enjoy my trip.
I can certainly attest to the existence of this 'warp stealth' regime. I've noticed this as I've been playing the Prius game when possible/practical, and have noticed the immediate switch from 'battery current only' to the ICE kicking in. The mileage figures I've been getting support this, as I'm ready to post into the 'I beat the EPA' stickie. I've been consistently above 55mpg highway, with my figures at ~58-59 mpg. My driving is mostly (about 90%) highway (as opposed to expressway) driving. I consider myself very lucky when seeing the other posters showing pics of their MFD with 60+ mpg, but also showing a 15 mile trip in an hour! You can have the stop&go, and great that the Prius works as it does in that congested rural setting. That is really helping the cause. No, my normal commute is 12 miles, no stoplights, all highway, no traffic, can drive whatever speed I want. I turn onto the highway from my driveway, and turn off into my parking lot at work. OK, there is a 45mph zone, then 35mph zone as I get into town to my workplace, but that only helps! Anyway, when driving in the 50-60 mph region I've been able to use this technique, as I've been trying to attain the classic pulse & glide at those speeds. Depending on SOC, I've been able to get there at 50+ mph speeds, but for short periods of time. It's a game, for sure, but can be fun & rewarding to get that fuel economy. Thanks for this post and the good information.
<div class='quotetop'>QUOTE(judibob @ Jun 1 2006, 09:45 PM) [snapback]263968[/snapback]</div> Would you please try to measure mileage using the CC method below? http://priuschat.com/index.php?showtopic=19638&st=8 Thank you, Ken@Japan
There is no one more annoying when driving someplace like the NJ turnpike who does not keep a constant speed with cruise. I think at 65+ the cruise cotrol does a pretty good job. Otherwise in more trafficy situations try the pulse- it does seem to work better. Lucky those of you who can play with the road to yourself!!!!! :lol:
The article points out -- and Ken, this may help answer your issue too -- that on downhills the cruise *can* fairly often hop onto the "warp stealth" plateau. And it's often been stated that in general, letting speed bleed off a bit uphill and regaining it on the backside tends to yield better mileage overall than trying to rigidly maintain an exact constant speed regardless of terrain. When you add judicious use of warp stealth *to* that methodology, you should do pretty well. . But at fast highway speeds, the gains aren't going to be all that stunning anyways -- nasty ol' air-resistance. . _H*
I checked the link you included in your comment. I thought this driving style was more or less common sense. In any case, this is usually the way I drive. I drive this way in non-hybrids as well, especially those with automatic transmissions. As you'll notice, many times an AT-equipped car will downshift & actually accelerate when faced with a stiff uphill while in CC. So, over the years, I've gotten into the habit of going off CC in this condition. Now, in the Prius, I also go out of CC going downhill to take advantage of getting the powertrain to do what I prefer. <div class='quotetop'>QUOTE(ken1784 @ Jun 1 2006, 09:34 PM) [snapback]264391[/snapback]</div>
