hobbit
06-29-2006, 10:24 PM
I went out tooling around the backwoods to re-check a couple
of things about injection time, and while out there I came up with
a rather entertaining experiment. As part of the "what can they
do with generic cars" angsting, I realized that maybe I could
do a little simulation on my own. After being out for over half
an hour I had sort of a baseline MPG going in the 5-minute bars --
I didn't try to calculate it, but simply eyeballed the fairly
tall "castle walls" and figured "okay, somewhere near 80". And
then continued driving along similar roads -- for those familiar
with this area, 125 and 97 and 133 and little bits of 1 and
various side roads around the Rowley/Boxford area, which is just
nice territory in general. But now I decided to deliberately
not let the hybrid be a hybrid, and keep the engine running under
all circumstances. I was still driving as I usually do -- fairly
gently, using momentum for long downhill glides but in Neutral
instead of applying a little battery. But I made sure that every
time I stopped, it was with the physical brakes, and stayed
idling during all coasting and sitting at stops -- doing this is
an interesting challenge, and you have to know the hybrid system
really well to *prevent* it from auto-stopping. Kicking over
to neutral disables start/stop, and staying in "B" also keeps
the engine running but then it's a delicate thing to not let
"B" supply heavy regen on slowing down. I found that by keeping
my accelerator foot just above the regen point and left-foot
braking, I could keep the engine idling and go entirely on the
binders [as shown by the pressure indicators and lack of battery
charge current] to stop.
.
So, for a collection of 5-minute intervals roughly equivalent
to the roads I had been on before starting this, and just
eyeballing the held value without trying to get too picky...
.. 40 45 80 70 50 55 50 -- avg= 55.7
a little later, got into some slower town traffic and stopped
off to get a roast-beef at a local drive-thru, and still kept
the ICE idling all the way through just like the Bronco behind
me...
.. 55 35 25 40 52 47 -- avg= 42.3
by which time I was pretty much home. The sharp dip did
coincide with the food stop, and I sat there waiting for my
sandwich and watching the coolant-temp needle climb north of
90 deg C which I almost *never* see. I didn't hear the fans come
on, but I think it takes pretty extreme temps to do that.
.
Nonetheless, the Prius didn't do too badly as a non-hybrid car,
and in fact returned results right in line with what a lot of
drivers get for their *normal* mileage. That's ironic as hell.
.
My driving style for most of this was still pretty much P&G,
using the Prius' throttle strategy of snapping open fairly far
to give the equivalent of DWL or going right back to idle with
very little in between. That alone probably helps a lot. I also
didn't change how I keep back from other traffic and anticipate
lights and all that, so those style elements probably contributed
to decent mileage. And of course my tires are still up at
48/46 or something, so those coasts-in-neutral still had me
rolling like a bicycle. So there you have the two major elements
of that other thread -- tire pressure and long-range planning.
.
I do think this "neutral" thing is severely underrated, though,
and that it's high time for the many states that still have
outdated blue laws on the books against coasting in neutral to
buy a god**** clue and get rid of those. Modern braking systems
make up for any perceived "hazards" of decoupling the drivetrain,
and the FE benefits immediately come clear on the first long
downhill swoop -- even with the engine still ticking over at
1000 rpm and 2 ms injection time. That consumption likely
pales in comparison to what it is under load at higher RPM --
in the case of the Prius, 6 - 7 ms and 1500 rpm or more.
Neutral is trivial with a manual, and I bet it would help the
auto-tranny set by simply not dragging the fluid in the torque
converter around one way or the other. Going between N and D
in an automatic is totally harmless, just like in the Prius,
as long as the engine stays running to keep hydraulic pressure
available to get back into D when needed.
.
With about 160 miles on the tank and just barely down one pip
on the gauge, I probably covered about 40 miles in "stupid mode"
and arrived back home just over 200 miles. That pulled my
average from 67-ish at the peak down to 63.7 at the end.
.
_H*
of things about injection time, and while out there I came up with
a rather entertaining experiment. As part of the "what can they
do with generic cars" angsting, I realized that maybe I could
do a little simulation on my own. After being out for over half
an hour I had sort of a baseline MPG going in the 5-minute bars --
I didn't try to calculate it, but simply eyeballed the fairly
tall "castle walls" and figured "okay, somewhere near 80". And
then continued driving along similar roads -- for those familiar
with this area, 125 and 97 and 133 and little bits of 1 and
various side roads around the Rowley/Boxford area, which is just
nice territory in general. But now I decided to deliberately
not let the hybrid be a hybrid, and keep the engine running under
all circumstances. I was still driving as I usually do -- fairly
gently, using momentum for long downhill glides but in Neutral
instead of applying a little battery. But I made sure that every
time I stopped, it was with the physical brakes, and stayed
idling during all coasting and sitting at stops -- doing this is
an interesting challenge, and you have to know the hybrid system
really well to *prevent* it from auto-stopping. Kicking over
to neutral disables start/stop, and staying in "B" also keeps
the engine running but then it's a delicate thing to not let
"B" supply heavy regen on slowing down. I found that by keeping
my accelerator foot just above the regen point and left-foot
braking, I could keep the engine idling and go entirely on the
binders [as shown by the pressure indicators and lack of battery
charge current] to stop.
.
So, for a collection of 5-minute intervals roughly equivalent
to the roads I had been on before starting this, and just
eyeballing the held value without trying to get too picky...
.. 40 45 80 70 50 55 50 -- avg= 55.7
a little later, got into some slower town traffic and stopped
off to get a roast-beef at a local drive-thru, and still kept
the ICE idling all the way through just like the Bronco behind
me...
.. 55 35 25 40 52 47 -- avg= 42.3
by which time I was pretty much home. The sharp dip did
coincide with the food stop, and I sat there waiting for my
sandwich and watching the coolant-temp needle climb north of
90 deg C which I almost *never* see. I didn't hear the fans come
on, but I think it takes pretty extreme temps to do that.
.
Nonetheless, the Prius didn't do too badly as a non-hybrid car,
and in fact returned results right in line with what a lot of
drivers get for their *normal* mileage. That's ironic as hell.
.
My driving style for most of this was still pretty much P&G,
using the Prius' throttle strategy of snapping open fairly far
to give the equivalent of DWL or going right back to idle with
very little in between. That alone probably helps a lot. I also
didn't change how I keep back from other traffic and anticipate
lights and all that, so those style elements probably contributed
to decent mileage. And of course my tires are still up at
48/46 or something, so those coasts-in-neutral still had me
rolling like a bicycle. So there you have the two major elements
of that other thread -- tire pressure and long-range planning.
.
I do think this "neutral" thing is severely underrated, though,
and that it's high time for the many states that still have
outdated blue laws on the books against coasting in neutral to
buy a god**** clue and get rid of those. Modern braking systems
make up for any perceived "hazards" of decoupling the drivetrain,
and the FE benefits immediately come clear on the first long
downhill swoop -- even with the engine still ticking over at
1000 rpm and 2 ms injection time. That consumption likely
pales in comparison to what it is under load at higher RPM --
in the case of the Prius, 6 - 7 ms and 1500 rpm or more.
Neutral is trivial with a manual, and I bet it would help the
auto-tranny set by simply not dragging the fluid in the torque
converter around one way or the other. Going between N and D
in an automatic is totally harmless, just like in the Prius,
as long as the engine stays running to keep hydraulic pressure
available to get back into D when needed.
.
With about 160 miles on the tank and just barely down one pip
on the gauge, I probably covered about 40 miles in "stupid mode"
and arrived back home just over 200 miles. That pulled my
average from 67-ish at the peak down to 63.7 at the end.
.
_H*