Hi NASAgineer:

___I was cringing just thinking about your 80 mph run this morning …

___About the pulse … What you want to do is receive 2 - 5X’s the amount of ICE-Off distance as ICE-On distance in the P&G cycle.

___Let’s break it down for a minimum expectation of 100 mpg to start.

1. If you are running a 4:1 ICE-Off vs. ICE-On distance, you need at least a 20 mpg Pulse for 100 mpg.
2. If you are running a 3:1 ICE-Off vs. ICE-On distance, you need at least a 25 mpg Pulse for 100 mpg.
3. If you are running a 2:1 ICE-Off vs. ICE-On distance, you need at least a 33 mpg Pulse for 100 mpg.
4. If you are running a 1:1 ICE-Off vs. ICE-On distance, you need at least a 50 mpg Pulse for 100 mpg.

___The 1:1 and 2:1 stuff are the HS-P&G scenarios as wind resistance really grabs hold of your HCH-II at those speeds … I can accelerate the very well setup Accord at 30 - 35 mpg from ~ 45 mph up to 65 mph and can easily grab a 1:1 and depending on wind, traffic, and terrain, can sometimes glide as far as a 3:1! Temps have to be above 55 degrees F to receive that kind of FE during the HS Pulse in that vehicle … Your HCH-II has to be able to do better then this given the more efficient ICE and it being much lighter weight. The key(s) to find are the minimal to no Assist during the pulse and a steady state SoC after multiple cycles. Since the 03 - 05 and the 06’s IMA appear to be programmed completely different, you are going to have to come up with a better overall solution. 9 -14 mpg during the pulse is way way to low! You have to get off the accelerator for a HS Pulse for sure. That number with a LS P&G, may work but you are going to need a > 6:1 ratio (ICE-Off to ICE-On) and that is an extremely long Glide! Work that FE during the pulse back up into the 35 + range for a HS P&G and maybe 17.5 - 25 mpg for a LS P&G scenario(s). Maybe have your better half come along and she can use a stop watch for actual times as well as watch your odo/trip A/B for actual distances of ICE-Off vs. ICE-On. Let us know what happens because you have the ability to feather the accelerator for HS Glides (above 41 mph) that the Prius, FEH, HCH-I, Insight, and AH do not. The HCH-I and Insight can be FAS’ed but it is a lot of work and I am hoping you will find thje 06’s magic rate/range all on your own.

___I actually wish Tom and I were out there with you so that between the 3 of us, we could put this conundrum to bed with another 2 pair of eyes watching the instruments

___Good Luck

___Wayne R. Gerdes

With all due respect, that didn't answer my question. I have read all 10 or so pages of this post and it sparked my curiosity. I hoped some of you pioneering new owners might have tried it. So, back to my orginal question, will neutral coasting inhibit regen and allow zero fuel flow?

Hi 9G-Man:

___In Neutral, your ICE is idling. This is the killer of wild FE no matter how you look at it. If it comes down to it, you can always FAS your 06 into a full blown P&G but since it has the ability to go Valves Shut in Fuel Cut at 60 + mph on the way down, we are trying to find a way to take advantage of that in heavier traffic and at higher speeds …

___NASAgineer, the reason why you want to lock this down (HS and LS-P&G’s) is not for a one off segment or tank. It is to increase your lmpg over tens of thousands of miles. You would be surprised at how many times a Prius-II’s P&G would work wonders for my daily commute given the traffic I see and some of the local city/suburban type driving I do. It is just another tool in the tool box to be used when it is most effective and you are getting very close to figuring this one out.

___Good Luck

___Wayne R. Gerdes

Wayne and NASAingeer,
I appreciate what you fellows are delving into here with the 06 HCH. I'm glad someone is trying to get a technique figured out and take advantage of the capabilities of this new hybrid. I've been following the different hypermilage techniques since before Wayne and the other wVA guys stunned us all with the benefits of pulse and glide.

So that why I brought up neutral coasting. Now, from what I gathered from the answer to my question, (in Neutral the 06HCH ICE is ideling). How do we know that, and its not in valve-closed fuel-cutoff? Why would it return to idle by just being shifted to neutral?

It would return to idle in that situation because if the engine cuts below a certain RPM, it pumps fuel to prevent a stall. If you put the tranny in neutral (no wheels driving the motor), and fuel is cut off, the engine would drop to 0 RPM. It would be nice if the car were smart enough to induce an "auto-stop" condition if shifted into neutral (meaning low brake pressure, throttle pressure, etc would turn the engine back on), but they probably couldn't put that in the stock car due to safety considerations. There's also not as much gain in fuel economy over sealed-valves mode, and likely much more mechanical wear by re-engaging the transmission.

That's great info, Wayne! Armed with this, I was motivated to go out again for some late night testing. My better half thinks I'm crazy, but is willing to go along and take notes.

I made a significant discovery about how/when the computer (not sure if it's the ECU or PCU?) decides to provide assist when accelerating. Before, I thought it was purely a function of throttle position, but tonight I discovered that it's actually a function of the rate of change of the throttle position. So, while I have to be very gentle on the throttle to avoid assist, I can continually increase that pressure to get increasing acceleration and still avoid assist. With this new technique, I was able to accelerate from 0-25 with no assist, at around 30 MPG! Took about 22 seconds.

I then used this to try some P&G between 30-50. Over 16.1 miles, I averaged 64.6 MPG (personal best). I probably could have done better, but only had a 5 mile stretch of road to try this on so I had to keep turning around at each end and start from 0. The best G ratio I could get was about 2:1 (averaging more like 1.7:1). About .4 miles on the pulse, .6-.8 on the glide. SoC never dropped below 5 blocks (63%).

What exactly do you mean by that? The Prius can't shut down the ICE over 41 mph, even with no throttle input?

Me too, it would be fun. I think one of the reasons I am enjoying this so much is that it reminds me a lot of instrument flying (I'm a private pilot, instrument rated). It's the same kind of game, trying to force a cantakerous gauge to do what you want it to. I've even developed an instrument scan (IFCD -> IMA -> speed -> outside, repeat). And it's a lot cheaper!

I haven't actually tried this, but I'm assuming it would, because of the reasons Double-Trinity pointed out. I'll try it the next time I'm out.

Hi NASAgineer:

___With your new found ability to slowly accelerate w/ no-assist while maintaining a given SoC, you are another step closer to an answer. The throttle position vs. rate of change seems to be the case for the Insight as well IIRC or at least that is they way I drove her? I would never ever punch her into assist but I would slowly but continually increase throttle angle while moving up gear to gear w/ no assist which worked wonders … Second gear was the one I had to be the most gentle in but that is for the Insight forums … The Prius II is similar although it was my forcing of it then its design possibly? I simply hate placing any accelerator pedal to a particular angle from an ICE-Off to ICE-On condition after a FAS as the jerk (4th derivative - perceived or real) is to harsh as to my idea of a 200,000 + mile automobile. I begin with an ICE-Off to ICE-On condition and slowly increase throttle angle in the pulse until I reach my optimum acceleration rate for the road incline/decline I am driving on. Anyway, now that you can achieve ~ 30 mpg in your initial acceleration from 0 to ~ 30 mph, you are very close. Here is something for you to consider. If you were to go into your EV/Glide/Fuel Cut mode at 30 mph and take it all the way down to 0 mph, your ICE-Off Glide distance would be 4, 5 or even 6:1 vs. your ICE-On Pulse distance. Your best ICE-Off distance to ICE-On distance ratios come from these very slow speeds. Aero drag literally disappears vs. tire RR and mechanical drag of bearings, ICE spinning over w/ valves closed, etc. which allows for the ridiculous FE …

___The next time you get the chance on a deserted country road, prove this to yourself. Reset Trip A or B, start up your ICE, take her up from 0 to 30 mph at your 30 + mpg rate and then enter into your ICE-Off Glide mode all the way down to 0 mph again. You should easily be able to peg your averaging FCD to 120.0 + mpg over the distance covered. I have seen this in the Accord at 99.9 mpg, the Insight at 150.0 mpg, the HCH-I at 120.0 mpg, and the FEH at 60.0 mpg. I hope you will see this in your HCH-II as well. With this, you have an understanding of what she can do as you slowly drop down to 0 mph for a turnaround in your 5 mile stretch of road. You should get most of the benefit of EV/Fuel Cut mode when taking her all the way down to 0 mph. There are some kinks to work out at 10 mph and below but I am hoping she will let you drop down to 10 mph and then a std. AS will appear the rest of the way down to 0 mph? I am getting beyond our primary purpose here but it is something for you to think about later on tomorrow …

___So back to a LS and HS P&G. Can you achieve a 30 + mpg acceleration rate at 45 - 65 mph? If you can, you have this just about licked. Your 1.7:1 Glide to ICE-On between 30 and 50 mph seems a bit low and I believe this will improve mightily with a few more miles on your HCH-II, a little bit more pressure in the tires, and once that Moly loaded Dino is replaced. A 30 - 50 mph P&G should give you the 2, 3, or even 4:1 ratio and I sure hope you can find these magic ratios soon.

___In regards to the Prius II and Escape HEV, the ICE is forced to turn over at anything greater then 41 mph for MG1 protection and/or the ability to again restart/spin up the ICE because of the very high MG1 RPM. Since motors lose most of their torque at maximum design RPM, they have little to nothing left to spin up the ICE to re-synch everything for continuing up and beyond 41 mph. In other words, they (Prius II and FEH) are both in Fuel Cut but the electrics are spinning up the ICE to keep MG1 out of harms way. It takes quite a bit of power to spin up and then maintain a spun up ICE from the electrics alone vs. the road speed holding the ICE at RPM via MG2 if that is the way it actually works? The AH cannot be FAS’ed well because of a tranny OD lockout so its capabilities of ICE-Off w/out regen from high speeds to a lower but still significant speed are almost nill To 10 mph or under, they work just like my PZEV. The HCH-I and Insight can simply be FAS’ed but the HCH-I or Insight w/ a CVT are going to be a rough ride if you have to engage from 50 mph or above. The stick versions can simply be rev matched and you are on your way …

___Good Luck

___Wayne R. Gerdes

Well, the average FCD goes up to at least 133, I saw that tonight when coasting down a 1 mile stretch of road Haven't seen it max out yet.

Haven't tried it yet, but I think I can, given the right stretch of road. Tomorrow I'm a slave in the kitchen, but hopefully this weekend...

...and a bit more skill in the driver


Wow, that seems like a pretty good advantage for the HCH-II design?

I verified that shifting into neutral during zero fuel-flow mode will indeed start the ICE firing again.