5/12 http://www.wired.com/news/autotech/0,2554,63413,00.html?tw=wn_tophead_1
Honda's Civic Hybrid is rated by the EPA to get 47 miles per gallon
in the city, and 48 mpg on the highway. After nearly 1,000 miles of
mostly city driving, Blackshaw was getting 31.4 mpg. "I feel like a
complete fraud driving around Cincinnati with a license plate that
says MO MILES," says Blackshaw, who claims that after 4,000 miles
his car has never gotten more than 33 mpg on any trip.
(Also, if you check the Prius msg boards linked from the article,
it appears those drivers get 45+ mpg. 2004 Prius >> Civic Hybrid.
But I still think it's easy to hit some poor pedestrian who didn't
hear you coming.)
\_ There's very little difference in road noise at speed between a
hybrid and a standard car.
\_ "at speed" is definitely not the situation I'm imagining.
I am now assuming I don't need to give examples of the situations
I'm actually afraid of.
\_ Toyota is ahead on the hybrid tech, they've done it longer.
\_ That's really sad, I get 33-37 in my regular Honda Civic.
\_ I used to get 38-42 combined in my crappy '87 Ford Escort. Maybe
it's the way he drives. Does electric motor have the same problem
as gas engine where rapid acceleration consumes more energy than
gentle acceleration in order to reach the same final speed?
\_ It's probably something like that. The VW diesels say they
can get over 40 mpg, but you have to shift at like 2000 rpm
to get that kind of mileage. Many people get only around 30
some when driving like they would with a normal car.
\_ Is it correct that they'll use the gas engine to augment the
electric engine during hard acceleration?
\_ The gas engine is the primary means of power. The batteries are
charged *solely* by the brakes storing energy in them. *If* the
batteries have power, the electric will try to take over for the
gas engine, but in a high-horsepower situation both will operate
together.
\_ Just from the brakes? So that means that living in a hilly
place makes a huge difference, right?
\_ Is that true for all hybrids? I thought it was supposed
to be that that gas engine generated electricity, which
moved the car. If it's just based on brakes, unless you
were very careful you'd just be driving a regular car
with too many batteries.
\_ OK, hybrid cars shouldn't be thought of as some
revolutionary new propulsion technology. All they are is
small gasoline-powered cars with an added system that
recaptures energy normally wasted when you hit the brakes.
If you live in a hilly area or have to use the brakes a
lot, a hybrid will save over a conventional car. If you
drive a lot at constant speed or accelerate hard, you
won't save much.
Simply having the gasoline engine generate electricity for
the electric motor will waste power, because every time you
convert forms of energy, you lose. A normal car converts
chemical, to pressure to motion. If you then convert
motion to electricity and then back into motion, you've
wasted energy and had to cary around an electric motor too.
-dgies ( majored in Physics)
\_ dewd, if you checked the Prius web site, you would see
that it said the gas engine would recharge the battery
if the batteries were low. Also, further refinements
include shutting off the gas engine entirely while
the car is stationary. Note that this is linked to
the first statement.
\_ Directly charging the batteries with the gas engine
*is* wasteful of energy. However, since the hybrids
have small engines, it makes sense to keep some
juice in the batteries for when you need some extra
horsepower. -dgies
\_ okay, as long as we know the gas engine does
charge the battery at appropriate times -- it's
not all braking action as asked by a previous
poster -- and one acknowledges the benefit of
having the gas engine turn off completely while
the vehicle is stationary. Finally, the
battery is also charged when going downhill by
applying automatic braking, and the gas engine
may also turn off completely.
\_ You are just wrong dgies. Do you understand
how a diesel electric train engine works? The
hybrids work the same way.
\_ Those dang SCIENTISTS and ENGINEERS!
\_ Actually, this is not quite true. There
is no physical connection (via transm.)
between the diesel engine and to the
locomotives wheel. Prius has CVT as
mentioned below. Prius uses the electric
motor to either supplement energy (from
the batteries) or used as a generator
to capture excess engery (either from
the engine or from the wheels "braking").
Diesel-Electric uses the engine soley
as a power-plant for the electric motor
(which connects to the wheels). The
reason behind this is that the narrow
powerband of the diesel engine would
require a transmission with about 25
gears. BTW, you can use the elec. motor
also to brake a locomotive. Think of
it as a giant hair blow dryer. Instead
of storing the energy in a battery, it
is used to generate heat.
\_ Why doesn't the locomotive also store the
electric energy from braking (or at least
some of it) instead of wasting it?
\_ I guess because freight locomotives
tend to do long haul and not do
quick stop-n-go runs. It probably
doesn't make economical sense (and
much like hybrid doesn't "shine" in
high speed highways).
\_ With CV transmission, you can get "infinite" gear
ratio (versus the traditional 1st gear, 2nd, etc).
This way, the computer can operate the gas engine
at the most efficient RPM without directly
affected by the speed of the car. Any "excess"
energy generated by the engine can be used
to recharge the battery.
\_ Yeah but then you don't get something to mash
about while bombing around the hills. -John
\_ CVT isn't specific to hybrids. MINI's and Audi
A4's have them.
\_ are they something that we should expect to see
on all cars in the near future, or are they too
expensive? (or is there some other reason that
this would be undesirable?)
\_ I imagine they're probably more expensive and
less proven reliability.
\_ Civic HX (a gas-only car) has CVT also.
\_ it's my understanding that the Honda hybrids are primarily
gas and use the electric motor to supplement it whereas the
Toyota Prius is the other way around. |
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