high tech misfit

The Honda Accord Hybrid's V6 engine works the same way (3 cylinders shut
down). However, I am skeptical that the increase in fuel economy from
cylinder shutdown would be all that significant.

ray o

Various fuel-saving ideas certainly have diminishing returns to scale, and
of course, there is the cost/benefit equation to consider. As the cost of
fuel rises, various fuel-saving measures start to become more feasible. For
example, shutting down half the cylinders might save 25% to 30% in fuel (as
opposed to the 50% loss of output), but if gas is $3.50 or $5.00 per gallon,
that fuel savings starts to become attractive and can still be more
cost-efficient than hybrids.
--
Ray O
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gord beaman

I suppose it's possible but I wouldn't think that it's very
efficient is it Ray?...I'd think that running 8 at 1/8
throttle(?) would be more efficient than running 4 at half
throttle (or whatever's required) because an 8 cylinder engine is
designed to operate 8 cylinders and it'd be horribly rough
running if you actually SHUT OFF four of them.

Hell you can both feel and hear it when you lose ONE sparkplug,
imagine losing FOUR!...
--

-Gord.
(use gordon in email)

gord beaman

How do they get around the rough running HTM?
--

-Gord.
(use gordon in email)

dh

Why would it be particularly rough running? Surely they're not going to
shut unwanted cylinders down this way:

bang-bang-bang-skip-skip-skip

which would be pretty bad but, rather, this way:

bang-skip-bang-skip-bang-skip

??

I suppose the best way to know would be to test-drive and find out. Anyone
done that?

Or get a review. I found this on Edmunds:

http://www.edmunds.com/new/2005/hond...04/review.html
The V6 engine also features a Variable Cylinder Management system (VCM) that
can deactivate three of the engine's six cylinders during cruising and
deceleration with no impact to vehicle performance or passenger comfort.

ray o

DH's explanation is a very good one. Think about a crankshaft turning and
power pulses being applied at even intervals along its rotation, kind of
like lumberjacks on a log in the water. As long as the power pulses are
applied with an even rhythm, the log spins freely. Get out of rhythm and
things get out of balance.
--
Ray O
correct the return address punctuation to reply

kenneth

Howdy,

No expert I, but...

In the situation you describe you still have compression,
but no firing. I am quite certain that with the fuel saving
systems that are being explored in this thread, there would
be no compression in the cylinders that were not firing.

Otherwise, there would be an enormous waste of energy
compressing the charge in those non-firing cylinders with
each cycle.

All the best,
--
Kenneth

If you email... Please remove the "SPAMLESS."

dh

It's not clear how much loss there is if you do compress the air. To some
extent, the compression of the air in the cylinder is sort of like a spring.
Some energy is lost as heat but the compressed air in a non-firing cylinder
will help to push the piston back after the top of the cycle has been
reached.

i.pavlov

Hi,

I'm shopping for a minivan and the choices came
down to Toyota Sienna vs Honda Odyssey.
I'm wondering what are the group's impression of
Sienna. I did a test drive on both and I like both
of them with slight advantage given to Odyssey
due to more confident handling and ease of driving.
I looked in Sunday editions of the local papers
then and noticed that there were some special deals,
rebates and pricing from Toyota dealers including
some very attractive deals on Sienna, but none at
all from Honda. As much as I liked Odyssey, I don't
want to play the tag price.
I'm wondering what is the best Sienna model to go
for? Should I opt for 4w drive and more upscale
module or more basic one? - With Sienna price jumps
quite a bit when optional features are added.

Please share your opinions and driving impressions
of Sienna.

Thanks,
IP.

high tech misfit

You really can't go wrong with either one. They are easily the two best
minivans out there today, and not just because of reliability. Although a
handful of earlier Odysseys had tranny issues, Honda seems to have fixed
that for the current version. I wouldn't bother with 4WD or AWD, whichever
they have. If you do enough winter driving, just get winter tires.