Post Your Prius Stats

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Dardedar
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Post Your Prius Stats

Postby Dardedar » Sat Oct 09, 2010 10:04 pm

My sexy 2004 Prius, purchased October 2009. $10,000.

Image

What follows is my fuel report to see how much fuel, money and CO2 I've saved. [I will now put updates in this one post so they are in one place]

I have found the on board computer to be fairly accurate if a little optimistic. Figuring mileage on the Prius is tricky because instead of a tank it has a gas bladder which can vary in size by as much as 1.5 gallons depending on temperature. This can throw off your calculations on a single tank measurement but should average out okay over the course of a year.

Numbers for the last three months of 2009:

Miles: 3289
Fuel: 69.79
MPG = 47.12

Now 2010, in a couple of batches.

(about) Jan through April:

Miles: 7,812
Fuel: 166.98
MPG = 46.78 (computer average for this period = 53.8 mpg)

June to October:

Miles: 7,270
Fuel: 144.09
MPG = 50.45 (computer average for this period = 51.55 mpg)

First year grand total (Oct 9/09 to Oct 9/10):

Miles: 18,371
Fuel: 380.86
MPG = 48.23 (computer average for the two periods above is 52.67)

So it seems the computer is consistently a little optimistic. Seems there is a hit on mileage in the cold winter (engine runs more to heat the car) and hottest part of summer (Air con).

My previous vehicle ('98 CRV) got about 25 mpg, so to simplify I am going to put the Prius at twice as efficient. This means I saved about 380 gallons of gas this year. At an average of $2.50 a gallon that is:

$950

Since I saved about 380 gallons of gas from being burned, and each gallon produces 20 pounds of CO2 my Prius purchase also saved 7,600 pounds of CO2 from needlessly being emitted into the air.

If gas stays the same price, which is doubtful, my Prius will completely pay for itself in about 10 years. In those ten years it will save about 76,000 pounds of CO2 from being emitted into the air.

Best purchase ever.

***Updates

October 9, 2010 to 2011:

Miles: 3,744
Fuel: 74.69
Fuel cost: $201

MPG = 50.17 (computer average for this period = 51.63 mpg)

Money saved: $201
Pounds of Co2 not released: 1,406

***Update First quarter of 2011:

Miles: 3,917
Fuel: 81.86
Fuel cost: $261

MPG = 47.74 (computer average for this period = 49.27 mpg)

Money saved: $261
Pounds of Co2 not released: 1,555

Total money saved thus: $1,412. Since 10/2009, my Prius is 14% paid for in saved fuel. The higher gas goes, the faster it pays for itself. At this rate I have about 8.5 years to go.

***Update... 2nd quarter 2011

Miles: 4,527
Fuel: 90.29 (gallons)
Fuel cost: $332.26

MPG actual: 50.30 (computer average = 52.2)
Money saved: $332.26
Pounds of CO2 not released: 1,804

Total money saved thus: $1,744
Total pounds of CO2 not released: 12,365

***Update... 3rd quarter 2011

Miles: 5,756
Fuel: 116.01 (gallons)
Fuel cost: $411.83

MPG actual: 49.62 (computer average = 50.8)
Money saved: $411.83
Pounds of CO2 not released: 2,320

Total money saved thus: $2,155
Total pounds of CO2 not released: 14,685

***Update... 4th quarter 2011 stats:

Miles: 3,734
Fuel: 77.33 g
Fuel cost: $242.82

MPG actual: 48.43 (computer average = 49.8)
Money saved: $242.82
Pounds of CO2 not released: 1,547

Total money saved thus (two years): $2,397
Total pounds of CO2 not released: 16,232
Total actual mpg averaged over 9 quarters = 48.83 mpg

***Update... 1st quarter 2012 stats:

Miles: 4,744
Fuel: 100.44 g
Fuel cost: $383.48

MPG actual: 47.39 (computer average = 48.80)
Money saved: $383.48
Pounds of CO2 not released: 2,008.8

Total money saved thus (2.5 years): $2,780
Total pounds of CO2 not released: 18,240

***Update... 2nd quarter 2012 stats:
I was really working at it this quarter, and got my best number yet.

Miles: 4,040
Fuel: 79.44 g
Fuel cost: $273.27

MPG actual: 50.88 (computer average = 52.15)
Money saved: $273.27
Pounds of CO2 not released: 1,588

Total money saved thus (2.7 years): $3,053
Total pounds of CO2 not released: 19,828

Overall average mileage to date, with all ten "quarters" given equal weight (488.88 / 10) = 48.88 mpg (actual)

***
Update... 3rd quarter 2012 stats:


Miles: 3,246
Fuel: 68.74 g
Fuel cost: $239.21

MPG actual: 47.22 (computer average = 48.5)
Money saved: $239.21
Pounds of CO2 not released: 1,374

Total money saved thus (2.7 years): $3,292
Total pounds of CO2 not released: 21,202

Overall mileage to date, with all eleven "quarters" given equal weight (536.1 / 11) = 48.73 mpg (actual)

***
Update... 4th quarter 2012 stats:


Miles: 4,369
Fuel: 92.58 g
Fuel cost: $302.73

MPG actual: 47.03 (computer average = 48.7)
Money saved: $302.73
Pounds of CO2 not released: 1,851

Total money saved thus (3 years): $3,594
Total pounds of CO2 not released: 23,053

Overall mileage to date, with all 12 "quarters" given equal weight (583.13 / 12) = 48.59 mpg (actual)

***Update... 1st quarter 2013 stats:

Miles: 3,984
Fuel: 84.5 gal
Fuel cost: $285.61

MPG actual: 47.21 (computer average = 48.42)
Money saved: $285.61
Pounds of CO2 not released: 1,690

Total money saved thus (3.25 years): $3,879
Total pounds of CO2 not released: 24,743

Overall mileage to date, with all 13 "quarters" given equal weight (630.34 / 13) = 48.48 mpg (actual, and down .11 this quarter)

***Update... 2nd quarter 2013 stats:

Miles: 2,393
Fuel: 47.7 gal
Fuel cost: $163.13

MPG actual: 50.33 (computer average = 51.86)
Money saved: $163.13
Pounds of CO2 not released: 954

Total money saved thus (3.5 years): $4,042
Total pounds of CO2 not released: 25,697

Overall mileage to date, with all 14 "quarters" given equal weight (680.67 / 14) = 48.61 mpg (actual, and up .13 this quarter)

***
Update... 3rd quarter 2013 stats:

Miles: 4,138
Fuel: 82.9 gal
Fuel cost: $279.37

MPG actual: 49.87 (computer average = 50.8)
Money saved: $279.37
Pounds of CO2 not released: 1,658

Total money saved thus (3.8 years): $4,321
Total pounds of CO2 not released: 27,355

Overall mileage to date, with all 15 "quarters" given equal weight (730.54 / 15) = 48.70 mpg (actual, and up .09 this quarter)
***
Update... 4rd quarter 2013 stats:

Miles: 3,780
Fuel: 76.5 gal
Fuel cost: $225.60

MPG actual: 49.41 (computer average = 50.5)
Money saved: $225.60
Pounds of CO2 not released: 1,530

Total money saved thus (4 years): $4,546
Total pounds of CO2 not released: 28,885

Overall mileage to date, with all 16 "quarters" given equal weight (779.95 / 16) = 48.75 mpg (actual, and up .05 this quarter)

***
Update... 1st quarter 2014 stats:

Miles: 3,521
Fuel: 75.0 gal
Fuel cost: $233.40

MPG actual: 46.95 (computer average = 47.1)
Money saved: $233.40
Pounds of CO2 not released: 1,500

Total money saved thus (4.3 years): $4,779
Total pounds of CO2 not released: 30,385

Overall mileage to date, with all 17 "quarters" given equal weight (826.9 / 17) = 48.64 mpg (actual, and down .11 this quarter)
***
Update... 2nd quarter 2014 stats:

Miles: 4,458
Fuel: 96.76 gal
Fuel cost: $320.20

MPG actual: 46.07 (computer average = 46.5)
Money saved: $320.20
Pounds of CO2 not released: 1,934

Total money saved thus (4.7 years): $5,099
Total pounds of CO2 not released: 32,319

Overall mileage to date, with all 18 "quarters" given equal weight (872.9 / 18) = 48.49 mpg (actual, and down .15 this quarter)

Car total miles: 165k.

***
Update... 3nd quarter 2014 stats:

Miles: 3,806
Fuel: 83.3 gal
Fuel cost: $264.06

MPG actual: 45.69 (computer average = 47.2)
Money saved: $264
Pounds of CO2 not released: 1,666

Total money saved thus (4.8 years): $5,363
Total pounds of CO2 not released: 33,985

Overall mileage to date, with all 19 "quarters" given equal weight (918.59 / 19) = 48.34 (actual, and down .15 this quarter)

***
Update... 4th quarter 2014 stats:

Miles: 4700
Fuel: 104.6 gal
Fuel cost: $254

MPG actual: 44.93 (computer average = 46.5)
Money saved (over previous vehicle): $254
Pounds of CO2 not released: 1,080

Total money saved thus (5.2 years): $5,617
Total pounds of CO2 not released: 35,065

Overall mileage to date, with all 20 "quarters" given equal weight (963.52 / 20) = 48.17 (actual, and down .17 this quarter)

***
Update... 1st quarter 2015 stats:
Miles: 4246
Fuel: 96.25 gal
Fuel cost: $194

MPG actual: 44.11 (computer average = 45.35)
Money saved (over previous vehicle): $194
Pounds of CO2 not released: 1,925

Total money saved thus (5.4 years): $5,811
Total pounds of CO2 not released: 38,002

Overall mileage to date, with all 20 "quarters" given equal weight (1007.63 / 21) = 47.98 (actual, and down .19 this quarter)
***
Update... 2nd quarter 2015 stats:

Miles: 4079
Fuel: 88.6 gal
Fuel cost: $208

MPG actual: 46.03 (computer average = 47.5)
Money saved (over previous vehicle): $208
Pounds of CO2 not released: 1,772

Total money saved thus (5.5 years): $6,019
Total pounds of CO2 not released: 39,774

Overall mileage to date, with all 22 "quarters" given equal weight (1055.13 / 22) = 47.96 (actual, and down .02 this quarter)

***
Update... 3rd quarter 2015 stats:

Miles: 2785
Fuel: 61.7 gal
Fuel cost: $129

MPG actual: 46.03 (computer average = 46.1)
Money saved (over previous vehicle): $129
Pounds of CO2 not released: 1,234

Total money saved thus (5.8 years): $6,147
Total pounds of CO2 not released: 41,008

Overall mileage to date, with all 23 "quarters" given equal weight (1100.26 / 23) = 47.83 (actual, and down .13 this quarter)

***
Update... 4th quarter 2015 stats:

Miles: 3887
Fuel: 86.6 gal
Fuel cost: $148

MPG actual: 44.88 (computer average = 46.13)
Money saved (over previous vehicle): $148
Pounds of CO2 not released: 1,732

Total money saved thus (6 years): $6,295
Total pounds of CO2 not released: 42,740

Overall mileage to date, with all 24 "quarters" given equal weight (1100.26 / 23) = 47.71 (actual, and down .12 this quarter)

***
2016 year update:

Total miles: 13,371
Total fuel: 278 gallons
Fuel cost: $501.70

MPG actual: 48.06
Pounds of CO2 not released (2016): 5,560
Total pounds of CO2 not released: 48,300

Total money saved: $6,796.

***
Update... First half, 2017 stats:

Miles: 6790
Fuel: 146.4
Fuel cost: $295

MPG actual: 46.37
Money saved over previous vehicle: $295
Pounds of CO2 not released: 2928

Total money saved thus (7.5 years): $7,091
Total pounds of CO2 not released: 51,228

Overall mileage to date, with all 24 "quarters" (and half) given equal weight (1146.63 / 24) = 47.77.
"I'm not a skeptic because I want to believe, I'm a skeptic because I want to know." --Michael Shermer

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Re: Post Your Prius Stats

Postby Dardedar » Sun Mar 27, 2011 11:07 am

Had a chat with SAV about the Prius and regenerative braking, thought I would post it here so other Prius owners can learn.

These guys are saying the Prius in "B" operates like a truckers Jake brake. So when you use it, you are wasting energy via combustion engine compression.

***
Using "B" Shift Position
The Prius uses an electronic transmission mode selector, similar to a gear shift on a conventional car. Unlike a conventional vehicle with modes P R N D 2 1 (park, reverse, neutral, drive, 2nd gear, 1st gear) the Prius has a power button, a park button, and a selector for modes R N D and B (reverse, neutral, drive, and engine-Braking).

In the course of normal driving, the driver NEVER needs to use 'B' mode (engine Brake mode). The techniques below are optional. 'B' mode is appropriate when descending long grades (i.e. descending down a mountain road), where if the driver uses the brake pedal to control the vehicle's speed, the vehicle's brake pads will overheat and fail.

In a normal vehicle, the driver handles that condition by slowing to an appropriate speed and shifting to a lower gear (2nd or 1st). This forces the vehicle to spin the engine faster than needed, "wasting" energy through vacuum losses but helping maintain a safe vehicle speed without overheating the brake pads.

In a Prius, the driver handles that condition by selecting "B" mode. This tells the Prius to attempt to emulate "engine braking" in a conventional vehicle. Depending on the vehicle's speed and the battery SOC (state of charge), the Prius will do this using regenerative braking and/or high-RPM zero-fuel-flow engine braking.

Engine braking is inefficient because it uses the engine as an air pump, converting kinetic energy into heat. Unnecessary regenerative braking is also inefficient because of energy conversion losses. (Regenerative braking is good when it replaces friction braking, but it's not as efficient as coasting at a constant speed.) Because of this, "B" mode will not recharge your batteries more efficiently than just braking and is not recommended for general driving.

Above all, it's important to understand that a casual Prius driver needs to understand NONE of the tricks described below. "Just drive it." Just as you might downshift into 2nd gear when going down a long, steep hill to prevent brake damage, you can "downshift" into "B" mode on a Prius. "Shifting" is all electronic, so the system won't let you shift in a harmful way. (Even if you try to shift into reverse when moving quickly forward, you'll just end up in neutral.)

http://en.wikibooks.org/wiki/Toyota_Pri ... ing_tricks

DAR
Also, seems my notion that there was regen going on in the wheels/brakes was wrong. Just do it in the motor, as you say. I had been hearing the whining sound of something, sounding like it was coming from the wheels, but that might be partly in the drive train, probably just in the motor.

Just looked a little, but the above link shows (and I am still quite sure), that there is variable regen going on and there is a difference between gliding and braking in how much energy is recaptured. But the above site stresses that the longer glides are more efficient in capture than shorter harder ones (still pre-physical braking).

Still snooping around...
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Re: Post Your Prius Stats

Postby Savonarola » Sun Mar 27, 2011 3:57 pm

wikibooks wrote:Depending on the vehicle's speed and the battery SOC (state of charge), the Prius will do this using regenerative braking and/or high-RPM zero-fuel-flow engine braking.
I have no qualms with the panning of engine braking, which is an absolute waste of energy, but this says that regenerative braking will engage under some conditions. This is only logical: you have kinetic energy that you want to reduce, so shunt it to the batteries.

It would be useful to know the conditions under which the Prius engages the regen versus just the engine brake. So I've found:
wikibooks wrote:What happens is that the system will use the engine power when going uphill to charge the battery to normal state. Then, running down hill (with "B" selected) the battery is quickly charged to the maximum before the bottom of the hill. This full charge (battery state shown in green) will then cause the system to use the motor for compressive braking. ....
When using "B" on a long (1 to 2 km) downhill (e.g. over 60 mph, 100 km/h) you may find at higher speeds that the motor is used for braking in addition to the power recovery from the generator. Unless the battery is fully charged (showing green on the monitor), this is wasting excess energy which could be stored. [formatting added]
Thus, it would appear that "B" increases the rate at which the battery is charged (by increasing the field strength of the generator), but that "B" will engage engine braking at high speeds or when the battery is fully charged.

wikibooks wrote:Unnecessary regenerative braking is also inefficient because of energy conversion losses.
Again, no qualms with the statement. Braking just to charge the batteries when you'd only have to re-accelerate is stupid. But when braking is needed, there is no such thing as "unnecessary" regenerative braking.

Darrel wrote:the above link shows (and I am still quite sure), that there is variable regen going on
I think that the above link shows that the only variability in the regen is twofold in only the following ways:
1. "B" increases the field strength of the generator to a higher level than in "D"
2. Regen on (in "D" or "B" while not using accelerator) vs. regen off (using accelerator, in neutral, or at complete stop).

Darrel wrote:and there is a difference between gliding and braking in how much energy is recaptured.
Because of the whole "no such thing as coasting" bit, I'm not sure what you mean by "gliding." Let's set some definitions.
  • Coasting: in neutral with no artificial power being engaged
  • D braking: low level regen braking engaged when the accelerator is released in "D" mode
  • B braking: higher level regen braking engaged when the accelerator is released in "B" mode
  • engine braking: jake-brake style braking using engine compression for no energy recovery
  • mechanical braking: engagement of pads/discs at wheels
Note that it is possible for more than one of these to be engaged at the same time. For example, pressing the brake pedal in "B" at high speed at low SOC engages (1) B braking, (2) engine braking, and (3) mechanical braking.

I see no evidence, experiential or textual, that D braking itself varies in strength based on how "hard" the mechanical brakes are applied.

Darrel wrote:But the above site stresses that the longer glides are more efficient in capture than shorter harder ones (still pre-physical braking).
Here's what I can find on that page regarding this:
wikibooks wrote:By briefly braking to a somewhat slower speed, say 45 to 50 mph (70 to 80 km/h), the motor will not be used to retard the vehicle, all subsequent retarding energy will go to the battery, and a longer time will be spent recovering energy, and so more energy will be recovered.
But this entire section is in the context of using "B" braking. It does not distinguish between amount of time using D braking and amount of time using B braking. I maintain that B braking charges the battery more quickly than D braking. Yes, a longer period of braking in a single mode recovers more energy than a shorter period in that mode, but no information comparing the modes was given.

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Re: Post Your Prius Stats

Postby Savonarola » Sun Mar 27, 2011 4:23 pm

Darrel wrote:First year grand total (Oct 9/09 to Oct 9/10):
MPG = 48.23 (computer average for the two periods above is 52.67)

I started keeping detailed records on January 1, 2011, for my 2007 Prius that I got in June of 2010.
I keep a spreadsheet that records/calculates all sorts of things, like:
  • MPG readout
  • odometer reading
  • gallons of gas added
  • gas usage calculated from computer information
  • MPG per tank
  • computer MPG per tank
  • computer gallons used per tank

Because of variability in the fuel bladder, I don't consider single-tank data based on amount of gas added very reliable. Thus, I keep track of the computer's MPG readout and compare it to long term gas usage such that small variances become insignificant based on the law of large numbers.


For 01-01-11 to 03-25-11:
miles: 1811.1
gas added: 39.56 gal
computer MPG: 45.8 mpg
MPG (based on gas added): 45.8 mpg

During the conversation mentioned in the last two posts, DAR bragged that his mileage was better than mine. But according to the page he posted above,
wikibooks wrote:On the first trip of the day, both the NHW20, 04-current, models and earlier NHW11 will have relatively higher fuel consumption as the ICE and transmission warm-up. By driving the first mile or so at a low speed, these critical lubricants can reach operating temperature with a minimum fuel burn.
I live 1.1 miles from my work. I live 1.0 miles from my local grocery store. Thus, for the vast majority of my driving days, I'm done before my car is ready to start working more efficiently. What does it say that I'm at 95% of DAR's mileage if my driving conditions are so much less favorable?

If we're interested in comparing apples to apples:
Darrel wrote:Numbers for the first three months of 2009:

Miles: 3289
Fuel: 69.79
MPG = 47.12
Or 97+%?

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Re: Post Your Prius Stats

Postby Savonarola » Sun Mar 27, 2011 10:07 pm

Savonarola wrote:
  • B braking: higher level regen braking engaged when the accelerator is released in "B" mode
For the record, my owner's manual doesn't even imply that "B braking" is any different than "D braking,"* and -- during just a little bit of driving today -- I was unable to distinguish with high confidence that a difference exists. Some things that make me think that there is a difference includes:
The high pitched whine (not to be confused with engine revolution noise) that accompanies regen increases in volume when switching from B braking to D braking.
From a low speed with low SOC, coming to a stop in B is significantly more rapid than in D, suggesting that the field is increased to the motor while in D. However, I could not be certain that the engine braking was not engaged.
At a low speed with non-full (blue, not green) SOC and while running on the motor with the engine off, shifting from D to B while pressing neither pedal increases the braking without a noticeable sound that would accompany engine braking. Again, though, I simply don't know whether engine braking was disengaged or engaged but producing very little sound due to the low speed.

* ETA: This is not to say that B mode does nothing different and D mode, just that "D braking" and "B braking" as defined above might not be different. B mode definitely engages the engine braking under at least some circumstances.

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Re: Post Your Prius Stats

Postby Dardedar » Sun Mar 27, 2011 10:20 pm

Savonarola wrote: for the vast majority of my driving days, I'm done before my car is ready to start working more efficiently.


That is a big minus for sure, so you are doing quite well indeed.

All of the standard stats give the Prius better mileage in city than highway, yet you say you do better on the highway. That's bizarre, because my mileage definitely takes an observable hit every time I go on the highway. I do much better, 50-55 mpg, in city and more like 48 or less on the highway.

It's bizarre how hard it is to find anything detailed about the Prius that isn't written at an extremely introductory level.

Here is why I think the Prius regen's a higher level of voltage depending on how you use your brakes. I can tell when my "physical" brakes kick in. They kick in at 7mph for instance, and if it's rainy they will sometimes be a little sticky or jerky. Now we know coasting produces some regen, and we know gentle braking above 7mph produces more generator braking (because the vehicle slows more), so what are they doing with this extra energy, just throwing it away? I think the Japanese are a little smarter than that. One fellow I was just reading complained that they didn't provide a voltage meter readout option showing how much regen was being created (I think I have seen after market ones for the kit plugin versions). The juice going the batts should be varying all the time depending on how fast you are going, coasting or braking.

Anyway, I'll snoop around some more. Maybe I'll stop by a dealership and chat up a mechanic who hopefully has been trained in this stuff.

D.
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Re: Post Your Prius Stats

Postby Dardedar » Sun Mar 27, 2011 10:37 pm

This site looks pretty good:

http://www.kbtoyota.com/priusmileagetips.html

Excerpt:

"Five of these "hypermileage" enthusiasts recently teamed up and set a record of nearly 110 mpg in a marathon economy run.

Hypermileage techniques are not for everyday driving. They have to be practiced in controlled conditions and then become "second nature" because of the attention that must be paid to the dashboard display at first. Here is a description of how Dan Kroushl, one of the marathoners, adapts hypermileage techniques to daily driving in his Prius:

"On the highway, I just set cruise control to 55 mph and go. In city driving, during acceleration or maintaining speed uphill, I use the deadband technique. This means no flow to or from the battery while accelerating. I glide (no flow at all, engine is stopped) during mild downhill stretches. I apply the brakes (regenerative) on steeper downhill stretches to keep my speed below 42 mph.
"I do this because the motor-generators (MGs) reach their maximum rpm at about 42 mph, which forces the engine to run to prevent damage to the MGs. So at speeds above 42, the engine must run, which creates added friction. This must be compensated for to maintain speed, causing a reduction in fuel economy.

"When coming to a stop I coast (foot off the accelerator) until the stop. While braking and coasting, a small amount of energy is regenerated to maintain the battery level. I use this technique on my daily commute which is 50% highway at 55 mph and 50% city at 35 mph. Depending on environmental variables, during the summer my fuel economy ranges from 67 to 72 mpg."
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Re: Post Your Prius Stats

Postby Savonarola » Sun Mar 27, 2011 11:50 pm

Darrel wrote:That's bizarre, because my mileage definitely takes an observable hit every time I go on the highway. I do much better, 50-55 mpg, in city and more like 48 or less on the highway.
The devil's in the details. Fayetteville is a larger city with lots signal-less or signal-light stretches of 35-40 mph. My town is significantly smaller (and -- incredibly -- just as hilly), so there is only one stretch of 35 mph over 0.3 miles that I ever hit in town, and that's maybe twice a week. Essentially, I'm almost always either on a highway or going from stop sign to stop sign.
What is perhaps more interesting is that my computer readout shows what I'd guesstimated to be an average of 55-60 mpg for highway driving (although my last trip at 55 mph was way over 60 mpg), and the data in my spreadsheet suggest that this is accurate. Let's face it: that's probably not a user-based difference, that's a car-based difference. (Maybe just because mine's newer?) Still, yours seems to be spot on with the predicted mileage while mine is quite different.

one hypermileage enthusiast wrote:"On the highway, I just set cruise control to 55 mph and go.
This works extremely well for me: often over 60 mpg.

one hypermileage enthusiast wrote:I glide (no flow at all, engine is stopped) during mild downhill stretches. I apply the brakes (regenerative) on steeper downhill stretches to keep my speed below 42 mph.
I've been doing this from the get-go, except that I didn't know about the 42 mph bit until today.

one hypermileage enthusiast wrote:the deadband technique. This means no flow to or from the battery while accelerating.
This part seems the most troublesome for me. My Prius will rapidly -- and I do mean rapidly, as in up to three times per second -- change the power distribution while I'm not changing a thing.
I know that there are mode selection buttons in the generation III Priuses that might make "deadbanding" easier, and while it's clear that minimizing conversions is the most efficient, I think that the attention and finicking required to deadband an already finicky synergy drive system isn't feasible in traffic.

Darrel wrote:I can tell when my "physical" brakes kick in.
I can tell you when your mechanical brakes kick in, too. The mechanical brakes kick in if and only if you step on the brake pedal.

Darrel wrote:and we know gentle braking above 7mph produces more generator braking (because the vehicle slows more),
Hold up. You mean that braking above 7 mph keeps regen engaged, and the longer it is engaged at a constant field strength, the more energy is regenerated. What you haven't shown is that the degree to which the pedal is depressed has any direct effect on the regen rate. (I think that this is what you were claiming previously. If I'm mistaken in my understanding of what you were saying then or what you're saying now, now would be a good time to clear that up.) Gentle braking just means gentle mechanical braking, just like in non-hybrids.

Darrel wrote:so what are they doing with this extra energy, just throwing it away?
Yes! That's what mechanical brakes do!

Darrel wrote:I think the Japanese are a little smarter than that.
I think that they came up with some hellaciously awesome engineering to couple a motor with an ICE that includes the capacity to regenerate at all. I think that it's absurd to say that they must have also come up with a system that ties rapidly variable brake pedal depression distance to generator field strength in an attempt to eke out a tiny bit more regenerated power. It might be that I gave too much credit by presuming that "B" mode increased the field strength -- that is, that two modes is too much to ask for... and you want rheostat-like, continuous-range feedback?

Darrel wrote:The juice going the batts should be varying all the time depending on how fast you are going, coasting or braking.
Hey, I agree that in an ideal world, mechanical brakes should be engaged only when the driver slams on the brake pedal, and variable fields should slow and stop the car otherwise. However, I also think that -- in an ideal world -- the idea of using gasoline would be a joke, the amount of electricity gained by this superfast variable field technology would pale in comparison to the amount of electricity generated by solar panels incorporated into the body of the car, and most of us would be using green public transportation anyway. Alas, here we are in reality, complaining that our cars throw away a couple watt-hours that could theoretically be recovered. In the end, I'm just really wanting to know whether "B braking" is different than "D braking."

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Re: Post Your Prius Stats

Postby Dardedar » Mon Mar 28, 2011 1:18 am

Savonarola wrote:
Darrel wrote:I can tell when my "physical" brakes kick in.


SAV
I can tell you when your mechanical brakes kick in, too. The mechanical brakes kick in if and only if you step on the brake pedal.


DAR
Of course, the mechanical brakes are only activated by the brake pedal, but the vast majority of the time, the mech brakes are not activated at all (other than they are readied for use with a slight increase in hydraulic pressure, but not engaged). Probably about 95% of the time that I am driving and using my brake pedal around town (below 7 mph excluded) the mech brakes are not used at all.

Darrel wrote:and we know gentle braking above 7mph produces more generator braking (because the vehicle slows more),

SAV
Hold up. You mean that braking above 7 mph keeps regen engaged, and the longer it is engaged at a constant field strength, the more energy is regenerated. What you haven't shown is that the degree to which the pedal is depressed has any direct effect on the regen rate. (I think that this is what you were claiming previously. If I'm mistaken in my understanding of what you were saying then or what you're saying now, now would be a good time to clear that up.)


DAR
Yes, that is what I am claiming. The the regen braking generates a variable amount of current depending on the speed and how hard you press on the pedal (this also depends on how charged the batts are since if they are fully charged then the pedals will also, automatically kick into an effective "B" mode of revving up the ICE, causing deceleration and throwing away energy). The last to kick in, always, are the mechanical brakes. This is what I have read over and over on Prius forums where nerds and hypermilers are getting in the details of this, with gauges hooked as they go. The claim/estimates I have read is coasting generating about 10 amps, "B" mode about 15 amps, and firm pedal braking (no extra gain after 42 mph) can generate up to 100 amps. I'll talk to a mechanic and see if they have firm specs on this.

SAV
Gentle braking just means gentle mechanical braking, just like in non-hybrids.


DAR
Positively, categorically, wrong. Gentle braking on a Prius, above 7 mph, is not mechanical braking at all but rather regenerative braking.

Darrel wrote:so what are they doing with this extra energy, just throwing it away?


SAV Yes! That's what mechanical brakes do!


DAR
Again, the mechanical brakes on a Prius, at speeds above 7 mph, are rarely engaged. I can tell when my mechanical brakes kick in, especially on a rainy day. It's quite obvious. I have to hit them quite briskly to get them to activate at a speed above 7 mph. So I am speaking of the range in regenerative deceleration that is obtained by light to medium regen braking. Are they throwing the difference away? No way. They are feeding the batts.

SAV
I think that it's absurd to say that they must have also come up with a system that ties rapidly variable brake pedal depression distance to generator field strength in an attempt to eke out a tiny bit more regenerated power.


It doesn't have to be tiny. I can take 200 yards to slow down or fifty yards. While the 200 probably generates more power, it doesn't mean that 50 yards would only generate 1/4th with the rest being thrown away (which is what you seem to be suggesting).

SAV
and you want rheostat-like, continuous-range feedback?


Not only do I want it, I got it. And you do to.

SAV
Hey, I agree that in an ideal world, mechanical brakes should be engaged only when the driver slams on the brake pedal, and variable fields should slow and stop the car otherwise.


That's only slightly overstated ("slams on brake"). This is what your Prius does right now. That's why if you are a careful driver, you'll never need to change your mechanical brake pads because they are almost never used (not much wear at 7 mph and less).

Above 7 mph, the mechanical brakes ARE only engaged if your step rather quickly or extra firmly on the brakes, otherwise the variable field "regen" is slowing the car to 7 mph, at which point the mechanical brakes take over to begin their job of coming to a full stop.
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Re: Post Your Prius Stats

Postby Dardedar » Mon Mar 28, 2011 1:43 am

This is just someone yammering on a blog, but I have read enough posts by this fellow to know that he has a lot of knowledge about the Prius. He answers this question in a way that is in line with my understanding of the situation:

Question:
With regard to the amount of regen you can recover, does it make a difference if you brake easily all the way down a long hill, or use a true "no arrow" glide to pick up speed/momentum and then brake smartly near the
end/bottom?


qbee42 responds:

Yes, that is the short answer to the above question. Regenerative braking is a continuum, from max regen to zero. The amount of regeneration is controlled by the accelerator pedal and the brake pedal. When you release the accelerator pedal, the Prius applies a small amount of regenerative braking to simulate engine drag as would occur in a normal car. Pressing lightly on the accelerator pedal causes this simulated drag to reduce. Pressing more removes the simulated drag entirely. Any more pressure after that and you start adding power to the electric motor.

Likewise, when you press the brake pedal it tells the Prius to use more regenerative braking. The harder you press, the more it regenerates. There are limits from the electrical and battery capacities, and traction, but other than that it is entirely related to brake pedal pressure. If you exceed the regenerative limit, the friction brakes take over, just as they do at low speed.

Tom
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Extended answer...

"But yes, to a degree you can control the amount of regen during coasting. For instance, most of the time when you lift your foot off the 'go-pedal' you'll see about 14 amps of regen while you coast with foot off brake and accelerator. you can feather the accelerator gently to reduce the drag in fractional amounts or to a full glide (usually with -3 to -6 amps).

If you google or search this site for "60 Amp Braking" you'll find a detailed and technical discussion of this very question. My answer is that it depends. 60 amps has been found to be the rate of regen, with the prius, that maximizes the regeneration you'll gain. So it's theoretically best to brake such that you'll regen exactly 60 amps from the point brakes are applied until you get to 7mph (where regen drops out). That said, this is a variable thing....if you have to keep your foot on the 'go pedal' an extra 1/4 mile to get to the spot where you'd need to apply the 60 amp ideal braking then you're probably not energy ahead...it would be better to go into a glide earlier and then apply 60 amp braking later and for a shorter time for net energy saved.

I'd say that moderate brake pressure is what you want to shoot for...if you apply firm braking late you risk accidently dropping out of regen completely and you'll be braking less efficiently.


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Re: Post Your Prius Stats

Postby Savonarola » Mon Mar 28, 2011 2:57 am

Darrel wrote:... the vast majority of the time, the mech brakes are not activated at all
I had a very hard time believing this, so I poked around a bit too. Hot damn, you're right. Frankly, this is awesome.

I had noticed a "hitch" when braking to a stop, but I hadn't taken note of a particular speed, and I thought that it was the regen kicking off and letting the mechanical brakes continue alone, not engage alone.

Darrel wrote:The claim/estimates I have read is coasting generating about 10 amps, "B" mode about 15 amps,
So "B braking" does produce more energy than "D braking," but that's probably mostly irrelevant because pedal braking does just as well if not better -- would you agree?

Darrel wrote:and firm pedal braking (no extra gain after 42 mph) can generate up to 100 amps.
"After" isn't clear. You mean that -- above 42 mph -- there is no continued correlation between speed and power generation, not that while braking from above 42 mph, nothing is gained once the speed drops below 42, right? And that means that -- above 42 -- there's still regenerative braking, but only at the same rate as at 42?

Darrel wrote:Positively, categorically, wrong.
Yes, it seems I am was. Damn.

Darrel wrote:While the 200 probably generates more power, it doesn't mean that 50 yards would only generate 1/4th with the rest being thrown away (which is what you seem to be suggesting).
Not what I was suggesting, though apparently irrelevant. My point was that the difference in power generation between the on/off regen plus mechanical brakes system that I thought was in place and a rheostat-like system -- which I didn't think would be powerful enough to do high-speed braking without mechanical assistance -- would be piddly. Clearly, though, MG2 is very powerful.

Darrel wrote:Not only do I want it, I got it. And you do to.
It's worth repeating: Awesome.

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Re: Post Your Prius Stats

Postby Dardedar » Mon Mar 28, 2011 10:13 am

Savonarola wrote:So "B braking" does produce more energy than "D braking," but that's probably mostly irrelevant because pedal braking does just as well if not better -- would you agree?


Yes. I wouldn't mess with "B" braking except for it's apparent use which is long descents where, for some reason Toyota thinks that people aren't detecting enough resistance and might want to have the equivalent of a "downshift." Also, if you are lazy, the "B" braking may be easy way to hold you to that 42 mph range where you are getting maximum regen (take longer to get down the hill, regen more energy). But it seems the brake pedal has the ability to regen more without the tenancy to wind up the ICE and throw away energy (which is an abomination).

-- above 42 -- there's still regenerative braking, but only at the same rate as at 42?


That's my understanding. At that point, MG2 speed is topped out.

Clearly, though, MG2 is very powerful.


Prius could brag in their ads: "Now with 100 amps of stopping power!" But few would know what that means.

These cars are truly an engineering marvel. God bless the Japanese.
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Re: Post Your Prius Stats

Postby Savonarola » Mon Mar 28, 2011 10:14 pm

Darrel wrote:I wouldn't mess with "B" braking except for it's apparent use which is long descents where, for some reason Toyota thinks that people aren't detecting enough resistance and might want to have the equivalent of a "downshift."
Now that I understand what's going on, I agree wholeheartedly. The only possibly realistic use for "B" that I can see is to avoid overheating brakes, and that doesn't seem too realistic with MG2 doing most of the braking.

(Also, now that I understand what's going on, I'm going to kick your ass with my boost in "city" mileage. 55 mpg, here I come!)

Darrel wrote:These cars are truly an engineering marvel. God bless the Japanese.
It's a shame that America's love of gasoline and lack of foresight makes us only able to wonder what comparable systems Americans could come up with.

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Re: Post Your Prius Stats

Postby Dardedar » Mon Mar 28, 2011 10:25 pm

Savonarola wrote: ...now that I understand what's going on, I'm going to kick your ass with my boost in "city" mileage. 55 mpg, here I come!)


Yeah, but I'll have a shiny quarter. You don't think I would bet a whole quarter if I wasn't absolutely SURE. (And I did learn a few things in this exchange)

...makes us only able to wonder what comparable systems Americans could come up with.


Actually, I read years ago that some of the patented Prius technology was developed by Ford (with government subsidies) but was sold to Toyota (back when oil was $10 a barrel or so).
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Re: Post Your Prius Stats

Postby Savonarola » Mon Mar 28, 2011 11:00 pm

Darrel wrote:Yeah, but I'll have a shiny quarter.
I'd forgotten. (I was so shocked at being dead wrong, since that happens almost never.) You'll have to harass me until you get said shiny quarter.

Darrel wrote:I read years ago that some of the patented Prius technology was developed by Ford (with government subsidies) but was sold to Toyota (back when oil was $10 a barrel or so).
I shouldn't be surprised. When there is a political push (i.e. monetary incentives) for green technology, Americans work on it. When not, they sell to the highest bidder. Again, it's dirty, rotten capitalism at its finest with the foresight of toddlers and the ethics of rapists.

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Re: Post Your Prius Stats

Postby Doug » Mon Mar 28, 2011 11:11 pm

Savonarola wrote:Again, it's dirty, rotten capitalism at its finest with the foresight of toddlers and the ethics of rapists.


DOUG
Worse, the Republican HATE the thought of helping to keep carbon emissions down. I think it's just part of their anti-intellectualism. The smart people (Democrats) want to save the planet, so the Republicans want to trash it.
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Re: Post Your Prius Stats

Postby Savonarola » Sun Apr 03, 2011 6:17 pm

Well, it's a new quarter, so when refueling yesterday, I recorded the important numbers and then reset my computer counter. Today on the road, I had the idea of taking a picture of my display. The first picture attached shows a sample of my energy consumption during the trip. The second picture was taken when I got to my garage.
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Re: Post Your Prius Stats

Postby Dardedar » Sun Apr 03, 2011 6:59 pm

That's a pretty good run for sure, but I've done it several times too. The truth is in the longer averages. A nice tail wind in a nice hilly area can do this (for instance I can get in the 60's on the way to the airport on 112). Or even on the bypass. Just Friday I noticed I was heading home and humming along at about 75 and getting great numbers. Strong tail wind. It makes a huge difference.

My computer resets each time I refuel my tank so my "computer" average numbers are per tank. I have some new numbers to post soon and hopefully I'll be in the 50's this time.

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Re: Post Your Prius Stats

Postby Doug » Sun Apr 03, 2011 7:07 pm

DOUG
Most of my Prius driving is one the way to NWACC on 540. Until recently, I was getting about 41.5 to 42.5 mpg.

You two started this recent discussion about mileage, and I slowed down a bit from 70mph to about 66mph on the next few trips. Now I'm getting about 48+ mpg!

In town, on the weekends, I usually boost the average close to 49 mpg. When I first got the Prius, I was getting 53-54 mpg almost all the time. I guess I stopped being careful.

It's not just the machine, it's man + machine, to give you the really good mileage.
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Re: Post Your Prius Stats

Postby Dardedar » Sun Apr 03, 2011 7:13 pm

Doug wrote:I slowed down a bit from 70mph to about 66mph on the next few trips. Now I'm getting about 48+ mpg!


I've heard that above 55, each mph your reduce your speed will give you about one more MPG. That seems to be inline with your observation.

Usually having to zip to my next appointment (20 this week) I don't have the luxury. But I do make up for it when I have the time by being quite diligent on the around town stuff. I plan on using 112 more often on the way up to Rogers, as time allows. I can get really good mileage on that road. You might consider taking that route Doug, if you have a few more minutes. Just watch for the speed traps in Elm/Cave Springs.
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