My guess is that the thermostat (spring) behaves linearly with
temperature but the loss of energy/temperature due to an
extreme drop in temperature behaves in a non-linear fashion.
Hence, the thermostat cannot easily compensate. Grill blocking
is a very cheap solution ($ of pipe insulation) too. I've seen
school buses and diesel trucks do grill blocking in the past
so it's not a new ideal.
The risk to grill blocking is that the ICE or the MG could overheat
on a long drive. So the maximum internal temperatures need to
be known and monitored. for the 3rd/2nd generation Prius the
max coolant temperature is about 200 F - this is when the thermostat
is opened 100% and coolant flow is operating a peak speed.
When the maximum internal temperatures there is a risk that
the coolant system will not be able to remove the heat from the
ICE fast enough to prevent internal damage. So before that
maximum temperature is reached the grill blocking needs to
come off. While engineering wise grill blocking is not
necessary to run the Prius - it is an inexpensive way to
increase its fuel efficiency by about 10% in extreme cold.
So while the outside temperature is hovering somewhere
between 20 F and 32 F, the Prius is still averaging somewhere
between 52 to 54 mpg in mainly urban driving.conditions
for short distances. The advantages of grill blocking in cold
weather is less clear for highway driving ( > 50 mph) for long
distance ( two or more hours per driving session) because
at high speeds and for long distances - the ICE is running
more often and heat loss is less of a problem.
Elmo's fears and assessments are incorrect in several ways.
Hypermiling actually puts less wear and stress on the car
because acceleration and braking are done more gently.
For example, hypermilers often report extremely low brake
system wear. Hypermiling is generally focused on speeds
between 25 mph to 45 mph (with 55 mph being a niche interest)
inwhich special driving techniques are use to optimizing
one's driving for the current driving environment. Some
organizations like AAA discourage hypermiling due to
one hypermiling technique call drafting. However, I have
not advocated drafting. Rather I am using other easier
and safer hypermiling techniques, traffic light timing-
DWB (driving without brakes), pulse and glide, SHM, etc.
Increase fuel mileage also translates to lower fuel cost.
My thread is not about bragging but about how to maximize
fuel efficiency of a Prius and understand why it works
and when it won't work. In a few years, there
will be other cars whose fuel efficiency will overshadow
the Prius. While the 2010 Prius can't best a 1999
Honda Insight in hypermiling - its easier to drive. My
goal has been to see how close I could get to MPG levels
reported by hypermiler Wayne Gerdes (98 mpg
on a 2010 Prius) and to see what I could learn.
I look like a gearhead?
Engineers must design based on performance and cost
compromises - Many major engineering compromises
are not done by engineers but by the CEO and Marketing types.
For example, those tail fins on cars in the 1950s were never
and engineer decision. Having a solar panel on the 2010
Prius was more of a marketing than an engineering decision.
The life of the tire probably going to be a little over three years
at best - I doubt my experiments will increase or decrease the
life of the current tires. I've read and heard many allegations
that this tire's manufacture products are of poor design
and quality , e.g. claims of tire rot. Sofar I haven't notice
anything unusally bad about these tires though.
The grill blocking is a well know and safe technique;
I am monitoring the coolant temperature and I know what
temperature to look for too.
My hunch is that hypermiling will extend the life of the car.
Reports by 1st Gen Prius owners seem to suggest that
the Prius traction battery has a very low failure rate and
that hypermiling will not prematurely wear it down.
In a way learning can be like a game -- so the analogy that
what I am doing looks like a game has some truth to it.
The question is not whether one might be able to play this game,
but whether one is any good at playing this game
but to be more direct and explicit...
I am incrementally testing and verifying what I've read about
and I am humbly passing on what I have found.
One truth, I would like to pass on is that
one cannot learn hypermiling effectively by reading about it or
watching a video.
its more like a skill or a talent that one acquires
over time through practice .
Youthinks so out of ignorance of the entire picture.
You didn't do the engineering, you didn't do the engineering testing.
You don't *know* what (to you) unintended consequences come about by
blocking the radiator. That's my point. The engineers DO know. If
they could have gotten FREE miles with a simple blocking of the
radiator, they would have done so.
But nothing in this world comes free, and the engineers no doubt
discovered the REAL price the user pays by blocking the radiator. You,
on the other hand, don't know the REAL price. All you know is the
IMMEDIATE benefit. The long term cost? You aren't even considering
that there may be one.