Hybrid Car – More Fun with Less Gas

Stop and go traffic

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Posted by DBLZOOM on September 1, 2005, 12:10 pm
I have a 2001 Prius that I just bought.  This morning I got stuck on
the freeway in stop and go traffic.  Maximum speed was 5 MPH.  Every
time I pressed on the accelerator the ICE would start up and when I
would stop, the engine would shut down.  We were moving about one car
length at a time. My 5 minute interval display showed that I was
getting about 10 miles per gallon for the hour I was in traffic.  I was
under the impression that in stop and go situations that I could run on
just the electric motor and basically not use any gas except when the
battery needed a charge.  My overall miles per gallon went down one MPG
during my one hour in traffic.  Unfortunately, I could not just let my
foot off the accelerator and coast.  I did not have any accessories on
at the time (headlights, AC, etc. all turned off).   Is this normal or
do I need something checked out with my computer?

Posted by Michael Pardee on September 1, 2005, 1:49 pm

The hybrid computer will fire up the ICE if more than 9 kW (IIRC) is
demanded from the battery in the Classic model. That doesn't amount to much
accelerator push. The computer will also fire up the ICE if the catalyst
temperature drops too much, for emissions reasons, or if the battery
state-of-charge drops too much. A few minutes of stop and go traffic has
very little effect on overall fuel consumption, but the longer it drags out
the more those effects matter - especially the catalyst temperature.

However, the effect on your pocketbook is far less than it is in a
conventional car. In terms of the amount of fuel consumed per hour of
creeping through traffic, a conventional 4-cylinder will slurp down about a
liter an hour - regardless whether you are stopped or averaging 5 mph. The
Prius will use a couple ounces per hour keeping the system operating and a
modest amount per mile. If this were your normal commute (and for too many
people it is) it would bring the actual average fuel economy down a lot -
but it would be many times better than any car that idles when stopped.


Posted by Dan on September 13, 2005, 4:56 am
 Sounds like a perfect case for the EV override.


This is a switch removed for the US models because the US regulators
didn't know how to classify the 2004.  The switch turns of the gas
engine and leaves it off until you hit 35mph or your battery starts
running low.  Since it can be a pure Electric Vehicle or a Gas Electric
Hybrid.  Thier forms didn't have a "both" box to check.

But with the EV switch, you could creep along for a good while without
ever spinning up the engine.


Disclaimer: Haven't installed the switch, but plan to when my 06

Posted by DBLZOOM on September 13, 2005, 11:24 am
 Looks like a great fix but this does not help me on my 2001.

Posted by dbs__usenet on September 17, 2005, 11:15 pm
As others said, it is normal.  Keep in mind that if you had maximum
speed of 5 MPH and you were stuck in stop and go for an hour, you only
traveled for 2 miles.  2 miles at 10 mpg is 1/5 of a gallon.  If you
compare that with a conventional car, you may see that they burned a
gallon or more in the same time.

While 10 MPG is attrocious, it's really not too bad for an hour of stop and go
5mph traffic.

To maximize the battery usage, push very gently on the gas pedal to
accelerate, and anticipate the car ahead of you stopping, coasting as
far as you can before hitting the brakes.  You might be able to hit 15,
20 or more MPG in those situations.


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