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Cold weather and the Prius skeptic - Page 2

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Posted by Elmo P. Shagnasty on September 21, 2011, 5:11 pm
 
In article


So, what do the FACTS of 35mpg do for YOU?

Oh, that's right--you ignore THOSE facts, because they're inconvenient
for you.

Posted by bwilson4web on September 21, 2011, 10:16 pm
 
wrote:

That is the mileage expected between 75 and 80 mph:
http://hiwaay.net/~bzwilson/prius/epa.jpg


Actually that was one of the earliest observations I made in October
of 2005:
http://www.myhybridcar.com/fuel-economy/toyota-prius/70-nhw11-2003.html

So can you guess what getting 22 MPG means? I've done it deliberately
and have the data:
http://hiwaay.net/~bzwilson/prius/pri_100mph.jpg

This what engineering is all about, facts and data. Apparently you've
failed to read and understand my earlier posting:

Prius cold weather performance has been the straw most often grasped
by hybrid skeptics. The 1.5L Prius take pains to minimize emissions
and engine warm-up and this burns more gas, often inefficiently.
Worse, at high power settings, the 1.5L engine uses fuel enrichment to
avoid burning out the catalytic converter. It didn't take long for
petroleum addicts, petrodicts, to decide this would be their 'hook'
for Prius critical articles.

The first I remember was a Car and Driver article that decided the
middle of winter was the perfect time to do a highway, comparison
drive between a Prius and Jetta diesel. A more blatant effort was the
"Green Human" Portland-to-Portland, 8,000 mile, cross-country USA
drive between a 1.5L Prius and Jetta diesel. But in the end, there was
only a 0.5 MPG difference between the larger, roomier Prius and the
compact Jetta. Even now, hybrid skeptics trot out the 10 F blizzard on
the highway as their metric for Prius performance as if that is the
only metric that counts.

Now the 1.8L Prius introduced two technologies that directly address
cold-weather and high-power performance:
http://hiwaay.net/~bzwilson/prius/pri_2010_060.jpg
This image shows the collant pipe from the exhaust heat exchanger. So
instead of de-tuning the engine to accelerate engine warm-up, the
waste heat downstream of the catalytic converter is captured and sent
to the engine block. A by-product is during winter operation, this
formerly waste heat preserves both the engine block heat and provides
excellent cabin heat.

The second technology is:
http://hiwaay.net/~bzwilson/prius/pri_2010_460.jpg
This image shows the 5th tube on the exhaust manifold that routes
exhaust gas to a cooler before it feeds into the intake manifold.
Cooled, exhaust gas recirculation means at high power settings, this
inert gas cools the exhaust to protect the catalytic converter. The
engine does not have to run an over-rich mixture. Effectively, these
two technologies have eliminated the 10F blizzard from the petrodicts
criticism . . . except for those still thinking the 1.5L Prius is the
only benchmark. But there is one area that the 1.8L Prius needs to
further improve high-speed and cold weather performance.

One of the earliest owner mods is to block the radiator air inlet.
This reduces cooling drag, improves warm-up, and reduces vehicle drag.
The Chevy Cruz Eco uses variable vanes and in Japan, Prius owners can
buy an after-market, variable air inlet kit. With the return of Fall
weather, I've put my duct tape wrapped, pool noodle back in my 1.5L,
2003 Prius to preserve summer mileage. By careful measurements last
winter, there was a 5% improvement in mileage using a whole, air-inlet
block in my wife's 1.8L Prius.

About three years ago, we had a record setting, cold air system come
to Dixie when I needed to drive to South Carolina to buy a failed
traction battery. The high pressure center was over Atlanta, midway in
my trip. I left at 4:00 AM, 15F and by the time I reached Atlanta, it
had not reached freezing. It wasn't until 2:00 PM when the temperature
finally reached 37-38F. I picked up the traction battery and by the
time I returned home at midnight, it was back to 18F.

I kept my speed constant 65 mph on the highway and measured the
mileage over different temperature ranges only to find later that the
mileage followed the air density as a function of temperature. The
highest milege was 49-50 MPG at 37-38F and 65 mph. Other segments were
down as low as 34-35 MPG solely due to the higher air density of cold
air.

The 1.8L Prius could be improved with variable, cooling air inlet
vanes. But compared to the 1.5L Prius, it is substantially improved
with exhaust warmed coolant and cooled exhaust gas recirculation. We
see this in the average mileage owners report for the 1.8L Prius over
the earlier 1.5L Prius. Petrodicts are left with crying over the 1.5L
Prius in a 10F blizzard.

Bob Wilson

Posted by Al Falfa on September 22, 2011, 4:17 am
 "Elmo P. Shagnasty"  wrote in message

In article


So, what do the FACTS of 35mpg do for YOU?

Oh, that's right--you ignore THOSE facts, because they're inconvenient
for you.

You 35 mpg may be fact to you, but it is unsubstantiated hearsay to me.
Call me a skeptic, but I've not seen cold weather mileage like that and I
believe I've driven in some of the coldest weather in the 49 of the 50
states.



Posted by Elmo P. Shagnasty on September 21, 2011, 5:12 pm
 In article


In other words, the fact that people individually report that "cold
weather makes a HUGE hit on mileage" is to be completely ignored by you.

Got it.

Posted by Al Falfa on September 22, 2011, 4:21 am
 "Elmo P. Shagnasty"  wrote in message

In article


In other words, the fact that people individually report that "cold
weather makes a HUGE hit on mileage" is to be completely ignored by you.

Got it.

Again, it makes a small difference, perhaps 5%, in temperature extremes
ranging from 100F to -30F.  I notice that you have taken the headwind out of
your recent statements regarding cold weather performance.   So much for
"fact" Elmo.



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