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2010 Prius III fuel efficiency hypermiling results - Page 2

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Posted by Neo on November 25, 2010, 8:41 pm

In the last four weeks the average temperature has dropped
about 20 degrees Fahrenheit and the fuel efficiency of  my
2010 Toyota Prius III has dropped from 62 mpg to 58 mpg.
When the temperature drops from 60 F to 40 F the mpg
drops about 10 mpg  using the same route w/ hypermiling
techniques in approximately the same driving conditions
- the reason it seems is that in stop and go slow urban
driving conditions the 1010 Prius ICE must run more often
to  warmup the coolant/emission devices.  To try to boost
FE - I am implementing the last hypermiling trick I know
- grill blocking. I am blocking the the lower grill by 100%
and I will monitor the coolant temperature via the Scangauge
II. The objective is to make sure the ICE stays warmer and
thus has to run less frequently to keep the coolant
and emission device warm.

While some tires have a max psi rating of 50 psi,
the Yokohama Avid S33 has a maximum tire
pressure of only 44 psi so I've avoided increasing the
tire pressure any further than 44 psi (at least for now)..

2010 Prius III, Blue Ribbon/Dark Grey
Yokohama Avid S33 (44psi front, 42psi rear) <== hypermiler mod #1,
Scangauge II ( RPM, MPG, FWT, AVG) <== hypermiler mod#2
OEM floormats
lower grill blocked 100% <== hypermiler mod#3
upper grill unblocked

DC/MD/VA metro area
worst MPG (550 miles) = 54. mpg
best MPG (300 miles,) =66 mpg
current MPG (fcd) = 58 mpg
Overall estimated MPG = 59 mpg, 6300 miles

Posted by Neo on December 8, 2010, 3:13 am
The temperature in the Washington DC Area has dropped
down to a high of 40 F degrees to a low of 28 F degrees.
Fuel efficiency on my 2010 Toyota Prius III droped down
to an average of 55 mpg for a oneway 12 mile commute
- this is down from an average of 65 mpg for the same
12 mile commute during the summer time.  The problem
is not with the tire's rolling resistance (tire pressures is
44 psi in front and 42 psi in the rear) but with the lower
power performance from both the ICE and MG during
the colder temperatures. Also using the defroster/heater
during the winter lowers the ICE energy efficiency.
Furthermore, It takes more energy for the ICE to keep the
emissions control equipment at the proper temperature
when the outside temperature is near freezing.
To help keep the ICE warm - I've started to block
both the top and bottom grills - during the 12 mile
commute. I am monitoring the coolant temperatures
via ScangaugeII via the FWT gauge. The ICE
water/coolant temperature is peakomg somewhere
between 160 F to 188 F degrees ( If the ScangaugeII
FWT climbs to 200 F degrees I plan start removing  the
top grill blocking ) so far there has been no hint
that the ICE might overheat due to the grill blocking.
I've notice that grill blocking has reduce the number
of time the ICE needs to run inorder to keep the
ICE/emission temperature up...

2010 Prius III, Blue Ribbon/Dark Grey,OEM floormats
Yokohama Avid S33 (44psi front, 42psi rear) <== hypermiler mod #1,
Scangauge II ( RPM, MPG, FWT, AVG) <== hypermiler mod#2
lower grill blocked 100%, upper grill blocked 100% <== hypermiler

DC/MD/VA metro area
 worst MPG (550 miles) = 54. mpg
 best MPG (300 miles,) f mpg
 current MPG (fmd) = 57 mpg (dropping)
Overall estimated MPG = 59 mpg (dropping), +6500 miles

Posted by Bruce Richmond on December 10, 2010, 6:18 am
Temps here in New Hampshire have been in the teens lately and are
dropping.  With lower grill blocked I am still getting about 6 mpg
less than in the summer.  Will be getting a scangage II soon so that I
can tape over the upper grill as well.

On the pulse and glide technique, I'd just like to add a bit to what
you wrote back in Sept.  The idea is to put the engine under more load
part of the time to reduce the losses due to drawing a vacume against
the throttle plates, and then to shut the engine off.  This is an old
trick used in economy runs with normal non-hybrid cars.  The car, with
a manual transmission, would be accelerated at full throttle in high
gear to a fairly low speed to avoid wind drag.  It engine would then
be shut off and the trans slipped into neutral to coast.

For the Prius you want to keep the speed down low enough so that when
you let off the gas the engine shuts off and stops turning.  For my
2001 that speed is 41 mph.  Above that speed the engine keeps turning
to keep from over speeding the motor/generator.  When you let off the
gas and the engine shuts down the electric motor starts regenerative
braking.  There are losses when charging and discharging a battery, so
to avoid those losses you gently press on the gas.  You don't want to
step on it so hard as to use the electric motor to propel the car,
because that would drain the battery which would then need to be
recharged.  The trick is to work the gas so that the car is just
coasting, as if it were in neutral.  That is the glide, without
power.  You are basicly doing the same thing as the old car above, but
are able to control everything with just your foot on the gas.

The roads around here are mostly 2 lane, and coasting down to 20 mph
in a 35 zone with traffic behind you isn't really an option.  Under
such circumstances I have found that a modified pulse and glide still
gives better mileage than a steady light throttle.  Let off the gas to
shut the engine down, then step on it lightly to use the electric
motor to maintain your speed.  When the battery gets drained enough,
or the engine cools, it will start up again.  It will have to work
harder to recharge the battery while propelling the car, but the fuel
saved while it was off more than makes up for that used to charge the

Posted by Leftie on December 10, 2010, 12:05 pm
 Bruce Richmond wrote:

    This is essentially the technique I use with my 2010. Since my
commute to work ends with a roughly 7/8 mile low-load (all either
downhill or level, low speed) run, and my commute home ends with a 2.5
mile or so low load run, I'm able to drive those last sections with the
ICE running but the electric motor doing all the driving. This raises my
average about 1.1 MPG going to work, and 2.5 coming home. Since the ICE
is going to have to run a lot to warm up the next time the car is
started, it may as well be charging the battery pack as well. The
battery pack is never below two bars when I shut the car off, and is
usually at 4 or 4.

Posted by Neo on December 29, 2010, 9:40 am
Hypermiling in cold weather

The local ambient driving temperature has dropped to a range
somewhere beteen 37 Fahrenheit to 27 Fahrenheit with the
average about 32 Fahrenheit.  I've increased the tire pressure
to about 48 psi front and 45 psi rear on the Yokohama Avid
S33. The ride is very taut but the Prius tends to coastdown
hill much  easier at this tire pressure setting.  Blocking the
top and bottom grills on the Prius has lessen the need for the
ICE to turn on to heat the emission catalytic converter and has
help keep the fuel efficiency up.  Even with 100% blocking
on the top and bottom, it takes about 45 minutes for the coolant
temperature ( as read by the ScangaugeII FWT gauge)
to get  to the normal operating temperature of 157-188 Fahrenheit.
( For the first five minutes of driving in this kind of cold
weather, the Prius fuel efficiency is between 20 mpg to
30 mpg, After 30 minutes of driving in this kind of cold
weather, the Prius fuel efficiency increases to about 35 mpg
to 45 mpg. After 45 minutes of driving in this kind of cold
weather, the Prius fuel efficency increases to about 45 mpg
to 55 mpg. After 60 minutes of driving in this kind of cold
weather, the Prius fuel efficiency seems to level off
somewhere from about 48 mpg to 60 mpg)  - Short trips
in cold weather can really hurt a Prius' Fuel Efficiency.
Over the last two months that I have been grill blocking,
the coolant temperature has only briefly touched 192
Fahrenheit, the ICE has been operating well within its coolant
operating temperatures ( Note that I have not driven the
car for over 90 minutes during the last two months)
For the last four weeks, the Prius mileage has dropped to
52 miles per gallon -  a new low.   The off brand
anti-fogger that I applied on the interior of  the windshield
has lessen the times I've needed to use the defroster
(which has help keep the Prius fuel efficiency higher)
but at this temperature I still have to use it occasionally
- I am wondering whether I applied enough or whether
I should have stuck with a brand name anti-fog application.
Because using the heater would lessen the Prius's fuel
efficiency, I am not using cabin heat - which makes driving
in this weather - a very cold situation. I am thinking that
maybe I should get a better driving overcoat (9_9) .
It looks like that as long as the *winter formula* gasoline is
being sold --  the Prius MPG is going  to be significantly

2010 Toyota Prius III, Blue Ribbon/Dark Grey, OEM floormats
Yokohama Avid S22 (front 48 psi, rear 45 psi)
ScangaugeII ( RPM, MPG/AVG, FWT, GPH)
lower grill 100% blocked, upper grill 100% blocked

DC/MD/VA metro area
odeometer = +7000 miles
best FE=   66 MPG (approx 300 miles)
worst FE = 52 MPG ( approx 400 miles)

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