Posted by Josepi on January 17, 2010, 4:11 pm
The Camry claim (non-hybrid) was about 80kph tuning for optimum economy.
news:eb5d529d-090b-46a6-b263-> steady 70 mph with The Prius' optimum fuel
efficiency is achieved when running
constantly at about 40-50 mph on a flat surface. The Prius
fuel efficiency should be the same at a fixed speed when
its payload is within its designed load (825 lbs). When the
payload is significantly over the designed limit ( Payload
is > 1000 lbs) - the added weight to the drive train and
the additional rolling friction resistance will most likely
cause some decrease in fuel efficiency even if it only
appears as a fractional increase in energy cost.
Posted by Neo on January 18, 2010, 5:16 pm
> The Camry claim (non-hybrid) was about 80kph tuning for optimum economy.
80 kph would be about 50mph
> news:eb5d529d-090b-46a6-b263->
> The Prius' optimum fuel efficiency is achieved when running
> constantly at about 40-50 mph on a flat surface. The Prius
> fuel efficiency should be the same at a fixed speed when
> its payload is within its designed load (825 lbs). When the
> payload is significantly over the designed limit ( Payload
> is > 1000 lbs) - the added weight to the drive train and
> the additional rolling friction resistance will most likely
> cause some decrease in fuel efficiency even if it only
> appears as a fractional increase in energy cost.
Posted by Bruce Richmond on January 17, 2010, 7:40 pm
> > > > > After 45mph - when driving at a constant speed 50% of all the
> > > > > energy expended by a motor vehicle is used to overcome wind
> > > > > resistance. Your Prius is about 3200lbs so adding 800lbs of
> > > > > payload is is adding about 25% of extra weight to the Prius
> > > > > which should be within its designed performance.
> > > > You're missing the point. The additional weight requires almost no
> > > > additional power to keep moving at a constant speed, especially with
> > > > the tires pumped up to 45 psi.
> > > I agree once you get up to about 55 mph and start moving
> > > at a constant speed, the energy required to move an
> > > the extra 800 pounds should be barely noticable on
> > > Prius which is rated to carry over slightly over 800 lbs of payload.
> > Why do you keep trying to put limiting qualifieres in that don't
> > matter in the real world? You get the same milage at a steady 20 mph
> > with or without the added weight. You get the same mileage at a
> > steady 70 mph with or without the added weight. And since you get the
> > same mileage at a steady speed with or without the maximum rated load
> > it tells you that you would get the same mileage for any load less
> > than the maximum, and probably over it. And physics says this is true
> > for any car, not just the Prius. The place where the Prius might gain
> > some advantage is when the speed is not steady due to it's ability to
> > recover some of the energy used to accelerate when it slows.
> So far I haven't found any information about
> how much additional payload (over the official
> maximum payload specs ) that one can
> safely put on the Prius in the real world
> without destroying it. I'm sure the toyota engineers
> have built in some level of tolerance to make
> the Prius more reliable so that one can go
> over the design limits in the real world by
> a certain degree - but they're mums. When
> I asked that question about two years ago
> I got the same answer that I am essentially
> writing now.
> The Prius' optimum fuel efficiency is achieved when running
> constantly at about 40-50 mph on a flat surface. The Prius
> fuel efficiency should be the same at a fixed speed when
> its payload is within its designed load (825 lbs).
Look up "pulse and glide" sometime.
>When the
> payload is significantly over the designed limit ( Payload
> is > 1000 lbs) - the added weight to the drive train and
> the additional rolling friction resistance will most likely
> cause some decrease in fuel efficiency even if it only
> appears as a fractional increase in energy cost.
> Officially Toyota says that the Prius regenerative
> brakes recaptures 30% of the car's kinetic energy
> but I've read claimed that Prius's brakes can
> recaptures about 50% of the car's kinetic energy
> when certain hypermiler techniques are used.
> The more significant risk is screwing up your car
> ---------------------------------------------------------------------
> When a car is burdened with payload over its
> designed limits the greatest risk to the car's
> future operational integrity is the deforming of
> the cars suspension (springs, shock absorbers, struts)
> wearing the brakes prematurely, and extra tire wear.
> As stated in another post, the Prius drive train
> ( more specifically the CVT) may also fail or be
> at risk if the payload goes over the engineered limits.
> I know I sound like a kill joy - but I think the
> Toyota Highlander Hybrid would be a better
> choice if one needs to haul really heavy payloads
> or tow anything.
The reason for my post about hauling coal in my Prius wasn't to
advocate getting them for that purpose, it was to counter someone's
claim that the reason for US cars getting poor fuel milage was that
they were to heavy. The difference in weight doesn't come close to
accounting for the poorer fuel mileage. We constantly hear fuel
saving tips telling us not to haul anything extra around as if an
extra 50 lbs will make a significat difference in your mileage. If
hauling 800 lbs of coal had for all practical purposes no effect on
mileage then how much effect do you think 50 lbs has?
I tend to think the cause is more due to the minimum power many
consider acceptable, whether they actually ever use that power or
not. If the engine size of the Prius had been increased so that it
was able to accelerate at the same rate that it did without the coal
then it would use more fuel. So weight is a factor but it is not the
primary cause.
> > > Also in extremely low temperatures the Prius
> > > mileage drops from about 50 mpg to about 40 mpg.
> > I haven't noticed much difference due to temps after it has warmed up
> > but there is a big difference during the warm up period. When the
> > engine is cold the fuel injection squirts in more fuel and raises the
> > idle speed. It also will not let the engine shut down till the
> > battery has been charged and the coolent is up to temp. It does make
> > a bit of difference if you turn the heater off. The engine will come
> > on any time the engine coolent drops below some limit just to bring it
> > back up to temp.
> My sister who lives close to the Canadian border
> just purchased a 2010 Prius type III a few weeks
> ago. It pretty cold there now and she reported to
> me she is getting overall about 40 mpg in a mix
> of both city and highway driving.- Hide quoted text -
> - Show quoted text -
Last time I filled the tank I decided to see what I could get for
mileage on the 38 mile ride to home. The first 5 miles were slightly
down hill, dropping at most 200 feet over the five miles, and it
averaged 70 mpg. The next 5 miles climbed to about the same level as
the starting point and the overall average dropped to 60 mpg. For the
remaining 28 miles the mileage went up and down with the changes in
elevation, ending with it at 60 mpg. It was about 10 F degrees at the
time. Since the engine was up to temp and the battery charged when I
filled the tank I don't think the cold was much of a factor. I was
wearing winter clothing so riding with the heater turned off wasn't a
problem. When I went back to normal driving the next day the mileage
dropped into the 50's.
Posted by Neo on January 18, 2010, 6:07 pm
> > > > > > After 45mph - when driving at a constant speed 50% of all the
> > > > > > energy expended by a motor vehicle is used to overcome wind
> > > > > > resistance. Your Prius is about 3200lbs so adding 800lbs of
> > > > > > payload is is adding about 25% of extra weight to the Prius
> > > > > > which should be within its designed performance.
> > > > > You're missing the point. The additional weight requires almost no
> > > > > additional power to keep moving at a constant speed, especially with
> > > > > the tires pumped up to 45 psi.
> > > > I agree once you get up to about 55 mph and start moving
> > > > at a constant speed, the energy required to move an
> > > > the extra 800 pounds should be barely noticable on
> > > > Prius which is rated to carry over slightly over 800 lbs of payload.
> > > Why do you keep trying to put limiting qualifieres in that don't
> > > matter in the real world? You get the same milage at a steady 20 mph
> > > with or without the added weight. You get the same mileage at a
> > > steady 70 mph with or without the added weight. And since you get the
> > > same mileage at a steady speed with or without the maximum rated load
> > > it tells you that you would get the same mileage for any load less
> > > than the maximum, and probably over it. And physics says this is true
> > > for any car, not just the Prius. The place where the Prius might gain
> > > some advantage is when the speed is not steady due to it's ability to
> > > recover some of the energy used to accelerate when it slows.
> > So far I haven't found any information about
> > how much additional payload (over the official
> > maximum payload specs ) that one can
> > safely put on the Prius in the real world
> > without destroying it. I'm sure the toyota engineers
> > have built in some level of tolerance to make
> > the Prius more reliable so that one can go
> > over the design limits in the real world by
> > a certain degree - but they're mums. When
> > I asked that question about two years ago
> > I got the same answer that I am essentially
> > writing now.
> > The Prius' optimum fuel efficiency is achieved when running
> > constantly at about 40-50 mph on a flat surface. The Prius
> > fuel efficiency should be the same at a fixed speed when
> > its payload is within its designed load (825 lbs).
> Look up "pulse and glide" sometime.
If one uses hypermiler techniques like pulse and glide
or stealth warp - one can achieve high FE in other
driving conditions but they require special skills.
> >When the
> > payload is significantly over the designed limit ( Payload
> > is > 1000 lbs) - the added weight to the drive train and
> > the additional rolling friction resistance will most likely
> > cause some decrease in fuel efficiency even if it only
> > appears as a fractional increase in energy cost.
> > Officially Toyota says that the Prius regenerative
> > brakes recaptures 30% of the car's kinetic energy
> > but I've read claimed that Prius's brakes can
> > recaptures about 50% of the car's kinetic energy
> > when certain hypermiler techniques are used.
> > The more significant risk is screwing up your car
> > ---------------------------------------------------------------------
> > When a car is burdened with payload over its
> > designed limits the greatest risk to the car's
> > future operational integrity is the deforming of
> > the cars suspension (springs, shock absorbers, struts)
> > wearing the brakes prematurely, and extra tire wear.
> > As stated in another post, the Prius drive train
> > ( more specifically the CVT) may also fail or be
> > at risk if the payload goes over the engineered limits.
> > I know I sound like a kill joy - but I think the
> > Toyota Highlander Hybrid would be a better
> > choice if one needs to haul really heavy payloads
> > or tow anything.
> The reason for my post about hauling coal in my Prius wasn't to
> advocate getting them for that purpose, it was to counter someone's
> claim that the reason for US cars getting poor fuel milage was that
> they were to heavy. The difference in weight doesn't come close to
> accounting for the poorer fuel mileage. We constantly hear fuel
> saving tips telling us not to haul anything extra around as if an
> extra 50 lbs will make a significat difference in your mileage. If
> hauling 800 lbs of coal had for all practical purposes no effect on
> mileage then how much effect do you think 50 lbs has?
> I tend to think the cause is more due to the minimum power many
> consider acceptable, whether they actually ever use that power or
> not. If the engine size of the Prius had been increased so that it
> was able to accelerate at the same rate that it did without the coal
> then it would use more fuel. So weight is a factor but it is not the
> primary cause.
The vehicle weight is a factor in fuel efficiency.
But as stated by another, in a conventional ICE
vehicle, it is really the gross-weight-to-power-ratio
which contributes to a vehicle's overall FE (as well
the power-transmission-to-drivetrain efficiency).
This is because a lighter vehicle will allows
a more energy efficient ICE which could
requires less energy to accelerate to its
optimum speed for FE,
Hybrid FE is based on the fact that an
electric motor is more energy efficient than an
equivalent ICE motor. So while a Prius
is much heavier than a Corolla, it has the
ability to use an electric motor which has
the higher FE. However, the energy density
for the fuel for an ICE is over 10x higher
than the energy density for the electric
storage unit/battery needed to run the
electric motor. Thus the electric mode can
only be use for a short time In addition,
the gross weight of a hybrid is a signficant
factor in its FE - the gross weigh being the
sum of the curb weight plus the total
payload (passenger+cargo/payload).
Heavier hybrids like the Camry and Highlander
are less energy efficient than the Prius. As
with most motor vehicles, the payload is
only a fraction of the gross weight so I agree
that most adding an 50lb extra is not
going to effectively change the gas mileage.
However, this makes me wonder what would
happen if a driver had put 800 lbs of coal
in a 2008 Smart Fortwo mini car?
> > > > Also in extremely low temperatures the Prius
> > > > mileage drops from about 50 mpg to about 40 mpg.
> > > I haven't noticed much difference due to temps after it has warmed up
> > > but there is a big difference during the warm up period. When the
> > > engine is cold the fuel injection squirts in more fuel and raises the
> > > idle speed. It also will not let the engine shut down till the
> > > battery has been charged and the coolent is up to temp. It does make
> > > a bit of difference if you turn the heater off. The engine will come
> > > on any time the engine coolent drops below some limit just to bring it
> > > back up to temp.
> > My sister who lives close to the Canadian border
> > just purchased a 2010 Prius type III a few weeks
> > ago. It pretty cold there now and she reported to
> > me she is getting overall about 40 mpg in a mix
> > of both city and highway driving.- Hide quoted text -
> > - Show quoted text -
> Last time I filled the tank I decided to see what I could get for
> mileage on the 38 mile ride to home. The first 5 miles were slightly
> down hill, dropping at most 200 feet over the five miles, and it
> averaged 70 mpg. The next 5 miles climbed to about the same level as
> the starting point and the overall average dropped to 60 mpg. For the
> remaining 28 miles the mileage went up and down with the changes in
> elevation, ending with it at 60 mpg. It was about 10 F degrees at the
> time. Since the engine was up to temp and the battery charged when I
> filled the tank I don't think the cold was much of a factor. I was
> wearing winter clothing so riding with the heater turned off wasn't a
> problem. When I went back to normal driving the next day the mileage
> dropped into the 50's.-
Maybe I should get her
a scangauge II for her birthday? (9_9)
Posted by harry on January 18, 2010, 6:27 pm
> > > > > > On Jan 15, 7:55am, Neo <residualselfimage1...@gmail.co=
m> wrote:
> > > > > > > After 45mph - when driving at a constant speed 50% of all the
> > > > > > > energy expended by a motor vehicle is used to overcome wind
> > > > > > > resistance. Your Prius is about 3200lbs so adding 800lbs of
> > > > > > > payload is is adding about 25% of extra weight to the Prius
> > > > > > > which should be within its designed performance.
> > > > > > You're missing the point. The additional weight requires almost no
> > > > > > additional power to keep moving at a constant speed, especially with
> > > > > > the tires pumped up to 45 psi.
> > > > > I agree once you get up to about 55 mph and start moving
> > > > > at a constant speed, the energy required to move an
> > > > > the extra 800 pounds should be barely noticable on
> > > > > Prius which is rated to carry over slightly over 800 lbs of payload.
> > > > Why do you keep trying to put limiting qualifieres in that don't
> > > > matter in the real world? You get the same milage at a steady 20 mph
> > > > with or without the added weight. You get the same mileage at a
> > > > steady 70 mph with or without the added weight. And since you get the
> > > > same mileage at a steady speed with or without the maximum rated load
> > > > it tells you that you would get the same mileage for any load less
> > > > than the maximum, and probably over it. And physics says this is true
> > > > for any car, not just the Prius. The place where the Prius might gain
> > > > some advantage is when the speed is not steady due to it's ability to
> > > > recover some of the energy used to accelerate when it slows.
> > > So far I haven't found any information about
> > > how much additional payload (over the official
> > > maximum payload specs ) that one can
> > > safely put on the Prius in the real world
> > > without destroying it. I'm sure the toyota engineers
> > > have built in some level of tolerance to make
> > > the Prius more reliable so that one can go
> > > over the design limits in the real world by
> > > a certain degree - but they're mums. When
> > > I asked that question about two years ago
> > > I got the same answer that I am essentially
> > > writing now.
> > > The Prius' optimum fuel efficiency is achieved when running
> > > constantly at about 40-50 mph on a flat surface. The Prius
> > > fuel efficiency should be the same at a fixed speed when
> > > its payload is within its designed load (825 lbs).
> > Look up "pulse and glide" sometime.
> If one uses hypermiler techniques like pulse and glide
> or stealth warp - one can achieve high FE in other
> driving conditions but they require special skills.
> > >When the
> > > payload is significantly over the designed limit ( Payload
> > > is > 1000 lbs) - the added weight to the drive train and
> > > the additional rolling friction resistance will most likely
> > > cause some decrease in fuel efficiency even if it only
> > > appears as a fractional increase in energy cost.
> > > Officially Toyota says that the Prius regenerative
> > > brakes recaptures 30% of the car's kinetic energy
> > > but I've read claimed that Prius's brakes can
> > > recaptures about 50% of the car's kinetic energy
> > > when certain hypermiler techniques are used.
> > > The more significant risk is screwing up your car
> > > ---------------------------------------------------------------------
> > > When a car is burdened with payload over its
> > > designed limits the greatest risk to the car's
> > > future operational integrity is the deforming of
> > > the cars suspension (springs, shock absorbers, struts)
> > > wearing the brakes prematurely, and extra tire wear.
> > > As stated in another post, the Prius drive train
> > > ( more specifically the CVT) may also fail or be
> > > at risk if the payload goes over the engineered limits.
> > > I know I sound like a kill joy - but I think the
> > > Toyota Highlander Hybrid would be a better
> > > choice if one needs to haul really heavy payloads
> > > or tow anything.
> > The reason for my post about hauling coal in my Prius wasn't to
> > advocate getting them for that purpose, it was to counter someone's
> > claim that the reason for US cars getting poor fuel milage was that
> > they were to heavy. The difference in weight doesn't come close to
> > accounting for the poorer fuel mileage. We constantly hear fuel
> > saving tips telling us not to haul anything extra around as if an
> > extra 50 lbs will make a significat difference in your mileage. If
> > hauling 800 lbs of coal had for all practical purposes no effect on
> > mileage then how much effect do you think 50 lbs has?
> > I tend to think the cause is more due to the minimum power many
> > consider acceptable, whether they actually ever use that power or
> > not. If the engine size of the Prius had been increased so that it
> > was able to accelerate at the same rate that it did without the coal
> > then it would use more fuel. So weight is a factor but it is not the
> > primary cause.
> The vehicle weight is a factor in fuel efficiency.
> But as stated by another, in a conventional ICE
> vehicle, it is really the gross-weight-to-power-ratio
> which contributes to a vehicle's overall FE (as well
> the power-transmission-to-drivetrain efficiency).
> This is because a lighter vehicle will allows
> a more energy efficient ICE which could
> requires less energy to accelerate to its
> optimum speed for FE,
> Hybrid FE is based on the fact that an
> electric motor is more energy efficient than an
> equivalent ICE motor. So while a Prius
> is much heavier than a Corolla, it has the
> ability to use an electric motor which has
> the higher FE. However, the energy density
> for the fuel for an ICE is over 10x higher
> than the energy density for the electric
> storage unit/battery needed to run the
> electric motor. Thus the electric mode can
> only be use for a short time In addition,
> the gross weight of a hybrid is a signficant
> factor in its FE - the gross weigh being the
> sum of the curb weight plus the total
> payload (passenger+cargo/payload).
> Heavier hybrids like the Camry and Highlander
> are less energy efficient than the Prius. As
> with most motor vehicles, the payload is
> only a fraction of the gross weight so I agree
> that most adding an 50lb extra is not
> going to effectively change the gas mileage.
> However, this makes me wonder what would
> happen if a driver had put 800 lbs of coal
> in a 2008 Smart Fortwo mini car?
> > > > > Also in extremely low temperatures the Prius
> > > > > mileage drops from about 50 mpg to about 40 mpg.
> > > > I haven't noticed much difference due to temps after it has warmed up
> > > > but there is a big difference during the warm up period. When the
> > > > engine is cold the fuel injection squirts in more fuel and raises the
> > > > idle speed. It also will not let the engine shut down till the
> > > > battery has been charged and the coolent is up to temp. It does make
> > > > a bit of difference if you turn the heater off. The engine will come
> > > > on any time the engine coolent drops below some limit just to bring it
> > > > back up to temp.
> > > My sister who lives close to the Canadian border
> > > just purchased a 2010 Prius type III a few weeks
> > > ago. It pretty cold there now and she reported to
> > > me she is getting overall about 40 mpg in a mix
> > > of both city and highway driving.- Hide quoted text -
> > > - Show quoted text -
> > Last time I filled the tank I decided to see what I could get for
> > mileage on the 38 mile ride to home. The first 5 miles were slightly
> > down hill, dropping at most 200 feet over the five miles, and it
> > averaged 70 mpg. The next 5 miles climbed to about the same level as
> > the starting point and the overall average dropped to 60 mpg. For the
> > remaining 28 miles the mileage went up and down with the changes in
> > elevation, ending with it at 60 mpg. It was about 10 F degrees at the
> > time. Since the engine was up to temp and the battery charged when I
> > filled the tank I don't think the cold was much of a factor. I was
> > wearing winter clothing so riding with the heater turned off wasn't a
> > problem. When I went back to normal driving the next day the mileage
> > dropped into the 50's.-
> Maybe I should get her
> a scangauge II for her birthday? (9_9)- Hide quoted text -
> - Show quoted text -- Hide quoted text -
> - Show quoted text -- Hide quoted text -
> - Show quoted text -
The mass of the car is a major factor in fuel efficiency. If the car
has a ICE then the kinetic energy is wasted when the brakes are
applied.
With electric cars, this energy can be retrieved with "regenerative
braking."
ie, the first pressure on the brake pedal enables the motor to
generate,eg when descending hills. A lot of energy is wasted in the
ICE when the engine is in overrun ie descending hills. In days of yore
some cars were fitted with a "freewheel device" to economise in
fuel. You never see them now. Dangerous in town I should think.
Saab and Rover spring to mind.
The most efficient European cars are built like paper bags. high
tensile steel is the minimum plus lots od plastic eg doors boot, &
bonnet lids. Some are mainly aluminium (glued together) & carbon
fibre.
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