Hybrid Car – More Fun with Less Gas

How to get Better Gas Mileage - Page 5

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Posted by Brian on June 11, 2007, 6:40 pm

I will try to maximize the glide time of the Prius and I've considered
whether rapid or gradual acceleration is best to get back into
gliding.  Intuition suggests that if I rapidly accelerate I can get
back to gliding more quickly,  but the problem arises that I never
have any opportunity to regenerate the battery doing it this way.
Eventually the engine will start during the glide just do maintain

Lately I've been accelerating more slowly from the bottom of a glide.
A rapid acceleration will actually drain the battery further, so I go
for a slower acceleration where I can see the excess energy flowing
into the battery.  This lets me have more uninterrupted glides, with
slightly longer pulses in between.

I've also plotted separate courses to- and from- work.  The route to
work is residential streets when the engine is cooler from the night.
The engine will be running anyway to heat the exhaust system.  I use
that time to charge up the battery.  For the last two miles I have
found a 30mph road that is excellent for gliding.  I head into work
very efficiently and use up the charge I have accumulated.

On the way home the car is usually hot from the daytime sun and so
I'll take the highway.  The car doesn't need to do much to heat the
exhaust system.  I can get gliding quickly before entering the
highway.  The engine won't ever shut down at 60-70mph, but I can still
maintain long stretches of 70+mph because the roads are agreeable (and
apparently downhill).  When the occasional congestion arises, I'm
taking the shortest path home and I'm running all electric on the
highway at 5-20mph.  I usually exit the highway will a high charge and
I can glide the residential streets home, attempting to use that
charge up before I park for the night.

I would like to install an EV button for the ins and outs of the
neighborhood.  I'd like to start  my drive with a low state of charge
since I'm going to be charging it en-route.  If I could just get in/
out of my subdivision on total electric, I think that would really
boost my economy.  I hate starting a drive with a full battery. The
necessary engine operation has nowhere to store all its excess energy
and I suspect that it is wasted.

Brian Herbert Withun

Posted by Tom Ricostronza on June 4, 2007, 6:30 am

On Fri, 01 Jun 2007 21:23:38 -0000, mark b

I remember a hundred years ago in High School that all vehicles were
going to have flywheels to store that energy.  But I was also going to
be flying in a Jetson mobile, so I guess one vision canceled another.

Posted by notaguru on June 4, 2007, 2:27 pm

Tom Ricostronza wrote:

Seems to me that there may be buses on the road today using them
just as the Prius uses a battery. The Prius engine is very
efficient at speed, but has such poor torque that alone it would
provide unacceptable acceleration from zero. The battery just
fills in that gap, hence its limited capacity (a third of a cup
of gasoline). Some flywheel systems work similarly - augmenting
the engine.

But when I was a young engineer in the vacuum tube days, there
was a Swiss bus that ran entirely on a flywheel, which was
re-spun periodically along the route. It drove a generator,
which powered motors, which ran the bus.

Jetson transport is unlikely, since personal transport of that
sort needs an energy equation that is unlikely to be satisfied
with batteries, and carbon-based fuel will probably run out
before the personal air transport is perfected.

Posted by Elmo P. Shagnasty on June 4, 2007, 4:30 pm

The battery does more, actually.

And Toyota did a fabulous job with their Power Split Device to replace
the transmission.

Overall, Toyota's HSD is an amazing piece of technology.  It's more than
just "stick a battery in there" like what Honda did.

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