2010 Prius-III P&G, SHM and WS FE techniques rehashed, defined and refined

[royrose]

Originally Posted by FireEngineer

In my Gen III, with over 11,000 miles, having tanks done both on long highway trips and city commutes, I have a consistant 9-10% difference between the FCD and actual.

The 5% error is admitted by Toyota, but doesn't explain why certain early builds are much more.

As Wayne said go stealth until 15MPH, then keep it low for the rpm's. I try to keep mine less than 1,400 rpm. Sitting on a TPS of 21 during acceleration seems to keep the rpm's below 1,400.

Wayne

Thanks Wayne(s)!

Mine is a late July build.

I've done a couple of runs trying to stay within your suggested limits. It definitely takes discipline but I am doing better. I'll probably come back with more questions. I'll reset my trip computer the next time and report back.

[msantos]

Hi Roy;

As Wayne mentioned already, there appears to be a set of somewhat distinct 3G revisions that seem to report the incurred fuel consumption differently.

For instance, prior to buying my 2010 Prius, I had two units for the review period of early to mid July and they consistently reported 5-7 MPG above the calculated consumption. Those two units had been built in early June and like others on the same build batch, they all suffer by the same amplitude.

Now my personal unit was built in late July and like others in my area that were built afterward seems to have a far more accurate accounting of the consumed fuel. needless to say, so far my aFCD has been dead on.

Since Toyota is not known for frequent software updates like Honda does for its hybrids, it is likely that we'll see something from Toyota regarding a possible fix (in whatever form, software or hardware - some clusters have indeed been replaced). At least I can confirm that for some of the earlier units the problem is quite REAL. I can also say that my 2010 Prius along with others (one is a Blizzard pearl Taxi) are reporting no worse than 1 MPG deviation.


Cheers;

MSantos

[royrose]

OK, I said I'd report back. I did a round trip of 53 miles, not perfect conditions due to traffic, weather (52 degrees, windy), etc. I got 78.3 displayed mpg, probably 73 to 75 actual.

Bottom line, a novice can get great milage just by partially applying these techniques. I'm convinced that I can get 80 or over in better conditions.

I won't drive with milage as my absolute priority most of the time, but my everyday milage is improving as well.

I'd post a pic of the HSI, but I couldn't find a way to do it. Maybe I don't have enough posts.

[bestmapman]

Great job Roy

[fuzzy]

I am embarrassed to admit being negligent in not pushing my P-III to its mpg limits, certainly not as far as I pushed the Subaru last summer. But much of last summer's driving was alone, lightly loaded, on a familiar low-traffic route to dad's house, providing much opportunity to experiment. This year's driving was mostly on an extended September vacation in a fully loaded car with DW, who has less patience for lower speeds and experiments. 55 mpg (pump, not MID) before vacation, 51.6 on vacation. Both numbers include many many tens of thousands of vertical feet in screaming B-mode engine compression braking, wasting a lot of gravitational energy that I couldn't use for gliding.

Originally Posted by xcel

___I also did not discuss what you and I have been trying to figure out regarding the 45 mph transition to a Glide vs. a 42 mph to true Glide because that one needs some more work as well. Whenever I was in the position of coming down through 45 mph, I would let off to actually induce regen and than feather to a Glide which would drop my speed to 43 or so but the ICE would shut down. If I feathered in below 45 mph, she would warp stealth until 42 and than a full glide would ensue.

A note I picked up elsewhere is to blip the throttle to push the HSI bar above center, forcing a momentary fuel burn. On release, RPM should go to 0. So far this has worked for me, but has not been tried in enough circumstances to confirm it.

___With that, there is a large and growing contingent in the second batch or Range like yours that are showing a 3-mpg offset. Finally there is even a third batch ... that is showing a dead on match ...

Mine, delivered in mid-June, must belong to the second batch. At 9000+ miles, its accumulated error is 4.95%.

[hobbit]

Has anyone had a chance to match this against some of the ideas
in the HSI article? An awful lot of the uncertainty would go
away with the simple addition of an injection monitor hung off
one of the leads at the engine ECU or something similar like
Yoshi's fuel-pump LED, but nobody's really stepped up yet to
match actual fuel consumption [e.g. injector on-time] vs. what
they see in the HSI. I'm still hoping that once the "new car
paranoia" dies down a bit, some Boston area owner will be willing
to help dig in and do a bit of experimentation.
.
Oh, and the "blip" is definitely a useful Prius technique to force
transition to running or not-running, as there's the annoying
hysteresis that can easily lead the unwary into inefficient
fuel-burning regions. The "foot off and feather back on" technique
is simply a variant of that -- a bit of overshoot to make sure the
receiving end gets the message.
.
_H*

[xcel]

Hi Dean:

___Instead of a short burn with more tip-in, I would bring in regen and than bring it back with an ICE shutdown although there is some loss of momentum in the process.

___The good thing is the Prius-III can be driven to higher highway FE but its around town FE is definitely less than the -II unfortunately.

___Al, The PWR mode when accelerating appears to be to high for high FE in my experience and the WS mode can be extended to about 1/3 up the EV side. For SHM, the HSI as displayed above is just about right. About half way between the threshold and not beyond the leaf above. Right in between is a quasi substitute for IGN but it is to far off to the right to keep your eye on it vs. an SG-II mounted on the dash in line of site on the road. As we have spoken previously, HSI appears to be more of a demand request display rather than actual output display.

___Your comments about HSI being a somewhat poor design for everything other than EV threshold is what I see as well. With Ford's SmartGauge w/ ECOguide and Honda's EcoAssist, HSI was a cost saving addition (subtraction?) harming the overall value of the Prius-III imho.

___Finally, some of the discussions you linked appear to never have reached the 70 mpg highway or 100 mpg local targets? Are you sure you want to have discussions with those that do not walk the walk?

___The local stuff minus the Prius-III's 6, 3 or 0 mpg offset is similar to the Prius-II but not as efficient. On the highway, the SHM band has been decreased and unfortunately or not, a lot more attention needs to be paid to IGN to maintain the 70 + mpg area vs. the Prius-II which you could set and forget for miles and miles. The all-out battle to maintain and handle the transition out of and back into SHM on a long trip with the Prius-III is a lot of work unfortunately

___Good Luck

___Wayne