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

[xcel]

Is it as efficient as the second generation?

Wayne Gerdes - CleanMPG - Oct. 5, 2009

2010 Prius-III - $22,400 to start and 50 mpgUS combined.

Just like the second generation Prius-II, the all-new Prius-III takes some time to understand its idiosyncrasies. In the Prius-II’s case, its maximum city/suburban fuel economy came almost instantly as I was fortunate enough to experience with Dan Kroushl's 2004 Prius-II during the Prius Marathon attempt 4 + years ago. That event showed the world what the Prius-II was worth on an around town course when we ran it from topped off to empty covering 1,397 miles at 110 mpg. Its somewhat poor highway numbers is where the real frustrations came about however.

Back in late 2007, I was offered the opportunity to take a 2006 Prius-II out on a lengthy week long plus, city/highway daily grind drive. It took over 800 frustrating miles before the Prius-II’s higher end highway capabilities, namely SHM with IGN 14/TPS 18, finally revealed itself

Given the Prius-II’s city and highway Hypermiling tools we have at our disposal, would the 2010 Prius-III prove as fuel efficient even with its larger 1.8L atkinsonized Corolla engine? The EPA Fuel Economy figures lead us towards that reality but the nagging questions remained as we experienced in Napa Valley during the 2010 Toyota Prius-III preview launch earlier this year. Namely, the lower highway FE achieved on the 102 mile segment and in particular, the 6 mpg over report of the OEM FCD vs. actual miles traveled and gallons consumed from top off to top off.

Afforded the opportunity to drive from Chicago to NY on a single tank of fuel in both the Prius-II last year and the Prius-III this, how do the two generations of Prius’ compare and which came out on top?

2010 Toyota Prius-III Chicago to NY highway review drive.


A light headwind when leaving Chicago. 70.9 mpg at 53 mph
per the OEM FCD was the result as I stopped in NY for the night.

First fill up...


71.2 mpg at 50 mph average speed and 801.1 miles into NY on a single 12.330 gallon tank of fuel.
This calculated out to an actual 64.97 mpg from top off to near empty and a top off.
I gave Harry Clark a country road and highway hypermiling clinic over the final 250-miles.

And here again the 6 mpg OEM FCD over report vs. actual as experienced in NAPA reared its ugly head again. Working to maintain the 70 + mpg target and to end up so short is more than just a frustrating experience.

Heading back


Even stronger headwinds coming home


72.8 mpg at 44 mph avg. home with a 10 + mph headwind. – 815.9 miles on 12.178 gallons = 67 mpgUS actual.

With the 6-mpg over report now a fact vs. theory, the new yet elusive all-highway OEM FCD target of 76 mpg minimum was just not in the cards with that 10 + mph headwind most of the way home. The overall average was somewhat disappointing at 65.978 mpg although an all-highway drive in a Prius from Chicago to NY and back on a single tank with headwinds in both directions is still an OK drive none the less.

Chicago to NY and back drive. 1617 miles at 72.0 mpg (per the FCD) and 47 mph average speed including hourly rest stops.


66.0 mpg actual with actual average road speed of ~ 53 mph.

There is a still more to learn about the Prius-III’s highway capability as the HSI is more a demand indicator than an actual output. These are Manuel Santos’ words and I wholeheartedly agree with that assessment.

Warp Stealth

There appears to be at least two and possibly three modes of Warp Stealth. One with no fuel consumed at ~ 980 RPM. Another where there is some fuel consumed from 1/3 up the EV side of the HSI to the EV threshold bar. The iFCD holds in the 150 – 220 mpg range while you are pulling off the pack more than just to maintain the engines RPM while the Prius protects MG2 from a minor over rev. Almost like a NICE-On in fact?

SHM

Near the EV threshold and IGN/TPS at 12/18, there is a high FE mode that I have no idea what to do with just yet. I saw it a number of times near transitions but it is not a power addition mode but more like a slightly higher speed glide mode without the drag of WS?

Transitory SHM – IGN 21/TPS 18/RPM 1088/FE 90.0 mpg

And of course a std. SHM using TPS of 18 – 19 and IGN at 21 - 22. SHM is a lot harder to hold in the Prius-III vs. the Prius-II as 1,088 RPM from the 1.8L is just not enough power to hold speed with any impediment be it wind, rain or slight ascent. You really have to pay attention with this to grab as much FE as possible from it as you will be transitioning into and out every few minutes.

SHM – IGN 22/TPS 19/RPM 1088/FE 78.5 mpg

Putting it (P&G, SHM and WS) together in std. heavy Chicago Rush Hour traffic.

For a standard Chicago style stop and crawl, the 2010 Prius-III allowed 87.8 mpg per the OEM FCD which was more like an 81 mpg actual.


Chicago's Circle at the Dan Ryan – Kennedy - Ike Interchanges, to the Kennedy Junction and onto the Eden’s heading home during morning rush hour.

With over 1,600 miles of highway and 150 miles of city behind the Prius-III’s windscreen, let us place all that we have learned and put it to the test... Oh how I was waiting for this day to come

Northern Illinois to Northern Milwaukee, WI highway drive

Last weekend I again had the opportunity to again take a 2010 Prius-III out on the highway on a short trip to Milwaukee for an EBH_install. With a 95% highway commute ahead, was the allusive 70 + mpg highway drive available or not?

Leaving my parents with their 2010 Prius-III showing 40.1 miles and the FCD sitting at 65.1 mpg since the last fill-up, it was time to try again.

Although temperatures were not optimal, 62 – 65 degrees F, and the Prius-III’s tires were sitting at just 34 psi all around, it was going to probably be my final chance of the season with day time temperatures falling almost daily in Northern IL/Southern WI. Winds were absolutely calm so as to not skew the mpg results one way or the other. I hit the Interstate after ~ 5-miles with a warm-up hit and the FCD now sitting at 65.2 mpg.

Accelerating to the std. 50 + mph and using the Prius-III’s brand of SHM at IGN 22/TPS 19 whenever available, I was going to try something a little different regarding Warp Stealth on the descents. The Prius-III unlike the -II uses fuel under a WS like mode (not just the –II’s transition spurt either) whenever you surpass about 1/3 up the EV side of EV threshold on the HSI as described above. What I did was to leave the power demand bar on the HSI set between charging and the bottom of that threshold during any WS event making sure no fuel was used. I would immediately and almost forcefully move to SHM in the trough and DWL while climbing any small hill or overpass ahead. Of course you will fall out of SHM during climbs and at that point, I would not allow the IGN to move no higher than 25 while staying at least 5 mph above the minimums. I arrived at the EBH install with the FCD showing 71.9 mpg and maybe 3-miles of suburban roads off the Interstate to the EBH install garage.

Miles traveled	FCD (mpgUS)	Gallons consumed
40.1 miles	65.2 mpg	.615 gallons
89.1 miles	71.9 mpg	1.239 gallons

Using the above, the 49.0 miles traveled consumed .624 gallons = 78.526 mpgUS (per the FCD). Having experienced the Prius-III’s FCD over reporting of 6 + mpg on my parents and the Review Prius on the trip to NY and back (an ~ 8% over report), the actual FE from IL to Northern Milwaukee during this drive turned out to be 72.24 mpgUS.

Finally, an actual above 70 mpg highway drive including the 8% negative OEM FCD offset. I now believe the Prius-III can achieve the Prius-II’s highway FE numbers unlike my experience earlier this summer on the Chicago to NY review when I was unable to achieve the same. In warmer day time temps, it is possible that the Prius-III could break the 48-Contiguous State WR at 68.5 mpg although it will take one very hardy and experienced team to maintain an ever constant vigil on the Prius-III’s tight SHM band. It is harder to maintain than in the Prius-II but it is there for the taking. Additionally, using a much shallower WS than what we can get away with in the Prius-II appears to be yet another key to the-III’s highway FE prowess. Too bad about the OEM FCD displaying 6 + mpg from actual on so many early Prius-III’s but simply work around it with a 6-mpg offset at any glance

Oak Creek, WI library to home for high FE...

With the highway experience completed in the early morning, I wanted to find out if the 2010 Prius-III was as capable as the Prius-II in a high FE slower speed drive. I pressed up the tires to 60 psi at the EBH install and set out. Coming home, the temperature had risen to 69 degrees so I stopped at the Oak Creek library where the MiHG has its meets. I have driven and ridden in a Prius-II from my home to this library in similar temperatures with little to no wind twice coming in at 99.3 mpg and 101.1 mpg. This course consists of 28 stop signs and 5 stop lights (3 of which I was stuck at being the only person on the non-priority roads ) over 40 miles of very rough frontage roads. Three miles of this drive was on brand new asphalt with one section almost hard gravel as I had to turn around due to this section of Interstate’s frontage road being torn up and closed.

Using Pulses that would begin at a min of 20 mph when I could glide to that that low and pulling back into a Glide before 35 mph, I was trying to maintain the 8% offset SG-II's iFCD at 2 to 5 mpg above the current speed. RPM was holding below 1,480 RPM in most cases with any higher R's hurting the aFCD through the next cycle. Climbing as high as 1,700 showed how much fuel the 1.8L would consume with little additional acceleration to shorten the burn and it was very painful to watch

We still need time to hone rates and ranges compared to what most of us have experienced with the Prius-II. All said, it all still works (Pulse_and Glide plus Warp_ Stealth in the Prius II for maximum FE …, A few quick notes on the Prius-II from a non-Prius-II owner … Page 2 and New Prius - "Super Highway Mode" Technique (SHM)) with the Prius-III... Just with a few tweaks

The OEM FCD immediately went to 99.9 mpg and it never dropped. The SG-II with its 8% negative offset inserted however showed a low of 91.8 mpg with much of the drive in the 93 to 96 mpg range. The final result ended at 97.1 mpg with the OEM FCD of course still pegged at 99.9 mpg. What this told me was the 2010 Prius-III’s slower speed capability cannot match the Prius-II’s capability by at least 2 mpg. This was not a side by side but driving both to their max on somewhat poor road conditions, with solid impediments (stoop signs) almost every mile but little traffic to contend with which tells me the 1.8L does not have the same capability as I also experienced at the Prius-III launch in Napa Valley during the many FE challenge courses we drove earlier this year.

Final Oak Creek Library to home. 97.1 mpg actual per the SG-II over 40.3 miles.

There is still more to learn from one of our favorite high fuel economy vehicles and as of last week, I have new found respect for the mighty Prius-III just as the -II before once driven under its own brand of SHM for the very first time.

As far as the question which Prius generation is the best in terms of pure fuel economy, how about I say both are excellent vehicles with the 2010 Prius-III being more the more comfortable of the two. On an all-highway drive over any lengthy distance and knowing what I know today, I would drive the 2010 Prius-III. For a local city or suburban commute, the 2004 – 2009 Prius-II will take on any vehicle on the planet other than a PHEV or BEV. The 2010 Prius-III will be on its heels in hot pursuit however.

I hope you discover what your 2010 Prius-III is actually worth vs. what the EPA tells you it is too

[bestmapman]

Very good article Wayne. Warp stealth is a strange beast in the Gen III. I have noted on several occaisons where it works exactly like the Gen II and then other occaisions where it works as you say above. There must be some combination of items like idel stop in S4 that we don't know exactly what to do yet to tripgger the desired S4 behavior.

But occaisionally, WS works just like Gen II with no fuel flow. I just haven't figured out what combination of events causes it to happen. When it does, the down hill highway segments are great.

[ALS]

Thanks Wayne,
I just installed my Scan Gauge and I had a few questions I was going to ask.
Wayne, as usual you just answered everyone of them.

[royrose]

Wayne,

I am not sure why you consistently get a 6 mpg overstatement on the FCD. I have carefully tracked 6 consecutive fillings, covering 2500 miles on my Gen III. FCD ranged from 50 to 54.7. Actual ranged from 47.6 to 52.8. Average discrepancy was 2.283 mpg. Highest was 2.616.

You would think that this would be pretty accurate, since any filling inconsistencies would average out over 6 tanks.

Prorating to your hypermiling mpgs in the 70s, I would expect an overstatement of about 3.4 mpg, not 6.

Many gen III owners at PriusChat are getting figures similar to mine, about 5% error overall. Some have speculated that hypermiling techniques may somehow result in a bigger error.

Thoughts?

[xcel]

Hi Jud:

___Thank you! WS is indeed a strange one so to remove the inconsistencies; I simply removed any use of power when under it which guarantees no fuel use. Until we have an answer for that one anyway? It works but it would be nice to add some power to extend a WS Glide every once in a while

___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. Frustrating to not be able to do what we want. Since you have driven the FFH with coolant above 141 degrees F, she will shut down from 47 to 46 mph each and every time.

___Al, I am expecting to hear any day now that you will never drive your Volvo again

___Roy, there are three rev’s of Prius-III OEM FCD’s. The original pre-release that the journalists were driving in NAPA that had the 6-mpg offset as did many of the first off-the-boat Prius’. It may also depend on which factories the Prius’ were built (thanks Wayne Mitchell!) as well. The Overflow which is where the US’ early adopters builds were completed are driving the purposely added 6-mpg offset and it has nothing to do with Hypermiling. This is my parent’s car and over 1,736 miles; they have averaged 50.805 mpgUS actual from distance traveled to gallons consumed. Their 2010 Prius’ OEM FCD has averaged 56.9 mpg. An almost dead on 6-mpg offset as seen in the Press Prius I drove to NY and back and the Prius I drove in Napa Valley during the preview.

___I performed their first top off back in early June and their last top off a few days before I took their Prius-III up to Milwaukee and back for the EBH install so the offset is real for them and Hypermiling has nothing to do with it unfortunately

___I do hope Toyota has a fix for those that received the early FCD's is as it is simply wrong that someone high up within Toyota inserted the offset on purpose.

___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 (one of our mods actually owns this Prius-III) that is showing a dead on match between the OEM FCD and the distance driven/gallons consumed actual mpg.

___My parents will make note of the offset to their dealership the next time they take it in as Mike Sirach and Wayne Mitchell have with theirs. We know quite a few clusters are being replaced for some unknown reason and I would like to see my parents fixed so that offset is not staring at them every time they drive the car.

___One more item relating to Prius-III FE has to do with alignment. We have a Prius-III owner that had his alignment checked soon after taking ownership and it was all over the map on three of the four wheels very soon after taking possession of the vehicle. He had them brought back in and saw an immediate improvement in glide distances from his earlier drives. Although pure speculation on my part, I suspect the Chicago Press Prius I drove for the Chicago to NY City and back drive has an alignment issue vs. my parents which could also cause a loss of a few highway mpg’s?

___All said, the 2010 Prius-III is a work in progress and will continue to teach us its secrets over the next year or so... 70 + mpgUS on the highway is available but it is even harder to achieve than the previous gen due to the very narrow range in which SHM-II (IGN 22/TPS 19) works.

___Good Luck

___Wayne

[royrose]

Using Pulses that would begin at a min of 20 mph when I could glide to that that low and pulling back into a Glide before 35 mph, I was trying to maintain the 8% offset SG-II's iFCD at 2 to 5 MPG above the current speed. RPM was holding below 1,480 RPM in most cases with any higher R's hurting the aFCD through the next cycle. Climbing as high as 1,700 showed how much fuel the 1.8L would consume with little additional acceleration to shorten the burn and it was very painful to watch

Wayne,

Thanks so much for your sharing your updated experience. I have a few more questions if you don't mind.

To be clear, you find that gradual acceleration produces better MPG than a shorter burst and then proportionately longer glide? Also, when you are at a stop sign or traffic light (with no traffic behind you), do you try to stay within the 1480 mpg as you go from zero mph to 20 and then up to 35 mpg? Is there a reason why you didn't go above 35 mph before gliding? When you do glide, what settings/positions do you look for on the HSI and the scangauge?

[xcel]

Hi Roy:

___No problem and let us hope we can get the Prius-III owners numbers up before the winter drags us all down

___Any acceleration from 0 mph and you will want to use EV up to about 17 mph. Only about 15 mph in the Prius-II as the ICE trying to pull you up is pulling a horrifically low number from 0 to that low a speed. At ~ 17 mph, I forcefully light off the ICE with a firm step into the pedal and than back off to allow the RPM’s to stay below 1,500 if traffic allows. I was using 35 as a target but solid glides can start at anything below 42. The lower the better of course so work with whatever traffic allows using the traffic techniques you should be very familiar with

___In a Prius-I, II or III, I am always SG-II equipped because without an RPM display, you are never quite sure you are in a glide or not. Failed Glides (NICE-On's) are quite common in every generation of Prius including the -III unfortunately. The -III is better than the -II and -I but its mimic lyes just like the previous (2) generations and the only way to make sure is to see a tach via SG-II.

___Good Luck

___Wayne

[FireEngineer]

Originally Posted by royrose

Wayne,

I am not sure why you consistently get a 6 mpg overstatement on the FCD. I have carefully tracked 6 consecutive fillings, covering 2500 miles on my Gen III. FCD ranged from 50 to 54.7. Actual ranged from 47.6 to 52.8. Average discrepancy was 2.283 mpg. Highest was 2.616.

You would think that this would be pretty accurate, since any filling inconsistencies would average out over 6 tanks.

Prorating to your hypermiling mpgs in the 70s, I would expect an overstatement of about 3.4 mpg, not 6.

Many gen III owners at PriusChat are getting figures similar to mine, about 5% error overall. Some have speculated that hypermiling techniques may somehow result in a bigger error.

Thoughts?

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

[jpleong]

Toyota's computer is not the only one over-reporting FE. Owners of the 2010 Honda Insight report the computer is optimistic by roughly 1-3mpg over actual measured.

JP

[xcel]

Hi Jpleong:

___A bit OT but Honda has played the game as well but stopped the wild offsets with the HCH-I. The Insight-I was dead on, HCH-I's were ~ 4 - 5 over, Prius-I's were ~ 4 - 5 over, Prius-II's were ~ 2 to 3 over (Touring was dead on for the Chicago to NY drive???). The HCH-II's however were the first I have experienced over 10’s of thousands of miles where the FCD reports 2 under actual. And this entire paragraph has little to do with the 2010 Prius-III's capabilities

___Good Luck

___Wayne