Re: Chip control of auto transmission shift points?


"Vic Smith" <thismailautodeleted@xxxxxxxxxxx> wrote in message
news:q0phe457gkj2us86rab8pj850bhd2ucbgf@xxxxxxxxxx
On Sun, 5 Oct 2008 11:45:18 -0400, "DrollTroll" <fitcat@xxxxxxxxxxxxx>
wrote:

"Mike Romain" <romainm@xxxxxxxxxxxx> wrote in message
news:48e7b668$0$31074$9a6e19ea@xxxxxxxxxxxxxxxxxxxxxxxxxxxx
DrollTroll wrote:
Awl --

Are the shift points of small-car (eg, Honda Fit, 07) auto tranny's
chip
controlled?

If so, I would imagine the shift points, both down and up, can be
readily
changed.
Can I get the dealer to do it?
I feel it shifts *down* too soon on hills, with gas, etc, and would
like
to
delay shifts -- esp. since I can always downshift by hand, if nec.

If not, is there another way to delay downshifting? Something I could
kluge/wire in? A dealer-type job?

Thanks,

I highly doubt any dealer would install an engine blowing chip. Most
engines and trannies for that matter too do not like to be lugged.
Things break when that happens. Gas mileage goes to crap when you lug
it too.

I'm not talking about installing anything additional.
I'm basically asking *how the shift points are controlled*, and if they
can
then be adjusted, particularly in delaying downshifts.

It also depends on what "lug" means. I'm not talking about lugging the
engine until it sputters and smokes.
And, since everything is slower and lower doing this, I think mechanical
wear would not be an issue.

Lastly, mpgs drop drastically when the engine downshifts.
I know this from a scangauge installed on my pickup. The engine certainly
"feels better", say, when going up a hill, and the tranny naturally drops
down a gear, but the mpg's drop 30% as well.

This is one reason mpg's in city driving are so bad.

I looked around a bit about this, but don't have your answer.
Looks like they dropped "manual mode" for the '08 Accord.
Seems like a "manual mode" is the best way to play with best mpg if
you have an auto trans..
Otherwise a manual trans.
An auto trans is a complicated beast and it's not very likely to find
aftermarket mods that are worth while, but I sure could be wrong.
Low rpm torque is part of the picture, and might give the pushrod an
advantage here.
Seems my Lumina 3.1 locks up the torque converter at @30.
My Corsica 2.2 locked it at a bit slower mph - before the converter
failed and I unplugged it. That Corsica got me 34mpg highway the
only time I did a few hundred mile trip with it.
I thing the low rpm torque is why the common pushrod GM mid-size
cars get such good highway mileage.
Recent Vettes put in a switch to bypass lower gears at a certain
mph/rpm to increase CAFE ratings, but there was a lot of torque to
play with on the 350.
The total engine/trans control packages seem pretty darn complicated
nowadays, and as you said "feel" is part of the engineering that goes
into the design. With the "new" emphasis on mileage, I expect some
of the design will go away from "feel" and toward fuel efficiency.
I'd be interested you know what you find.

The Honda Fit gets 46+ mpg highway, 25 in "city" driving -- not anything
like NYC midtown stop and go, either. Quite a disparity.

My pyooter skills rival my auto transmisssion skills, but wiki had an
interesting article http://en.wikipedia.org/wiki/Automatic_transmission

--------------------
As engine computers (ECM) became more capable, much of the logic built into
the transmission's valve body was offloaded to the ECM. (Some manufacturers
use a separate computer dedicated to the transmission but sharing
information with the engine management computer.) In this case, solenoids
turned on and off by the computer control shift patterns and gear ratios,
rather than the spring-loaded valves in the valve body. This allows for more
precise control of shift points, shift quality, lower shift times, and (on
some newer cars) semi-automatic control, where the driver tells the computer
when to shift. The result is an impressive combination of efficiency and
smoothness. Some computers even identify the driver's style and adapt to
best suit it.

------------------------

This is sorta what I thought.

So, if I knew what wires went to what solenoids (and the logic therein), I
could conceivably lock them in/out manually.

And presumably these chips are programmable ito of shift points/patterns.

Also inneresting:

-----------

ZF Friedrichshafen AG and BMW were responsible for introducing the first
six-speed (the ZF 6HP26 in the 2002 BMW E65 7-Series). Mercedes-Benz's
7G-Tronic was the first seven-speed in 2003, with Toyota Motor Company
introducing an 8-speed in 2007 on the Lexus LS 460. Mercedes-Benz unveiled a
conventional automatic transmission with the torque converter replaced with
a lock-up clutch called the AMG SPEEDSHIFT MCT.[2]

-----------------

Go Toyota!!

My friend dragged two small automatic transmissions (junked) over to my
place, and we took one apart. *Unbelievably complicated*.

You become grateful that the price tag shown on the car isn't for the
transmission alone!!

--

DT







--Vic


.

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