Date: Fri, 12 Feb 2010 20:17:44 -0500
Reply-To: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Subject: Re: Friday OT...automatic trannys and driving habits observed
In-Reply-To: <6bc66ccf1002121313q2650af7cpeeaa3b593149b532@mail.gmail.com>
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Modern day automatics do not lose a lot of energy shifting. Since the
adoption of the lock up torque converter there is very little efficiency
gain of a manual versus automatic. On a lot of vehicles the autos even have
an advantage as they can use a higher final drive gear since any need to
accelerate can result in a down shift vs. lugging in the higher gear. These
trannies shift a lot to really keep the engine at the ideal speed for
existing speed and load. Few people really know how to get the best use of a
manual box and this option is gradually disappearing as automatics are more
programmable for economy and emissions.
As for those of us in those 40 foot diesel pushers we as a group are more
aware of what is going on back there than you might imagine.
For starters most of us are enthusiasts and while our spouses love the
Corian counter tops, appliances, and leather seats, us men sit around the
campfire and talk about the equipment. We will tell you all about our Cat
engines coupled to the Allison trannie driving the Dana axle. We know and
can recite our engines serial number on demand. We not only know horsepower
but torque. We will give you the data of all our electrical goodies,
furnaces, etc. As much as the engine is in back, everything these engines do
is transmitted to the front. We know and se it all. In addition to all the
normal engine gauges we also watch the front and rear air pressure. If it is
26,000 pounds or more it air brakes. In most states we have had to have a
license upgrade to drive it. Most of these folks have been with a number of
RV's some starting in tents and pop ups. To most of us the DP is the dream
and many have given up fixed homes to have one. I moved my retirement out
many years for mine.
Most of them have 6 speed transmissions and they need to shift a lot since
real Diesel engines have very limited speed ranges. My Cat runs out at 2,400
rpm. Many larger engines top at as low as 1,800 rpm. Yes we need third gear
to get out of a parking lot. We also downshift going downhill so that the
exhaust brake can do some work. You don't stop 30,000 pounds using friction
brakes any more than needed. Yes, we know how to use the engine for braking.
Diesels have no throttles so they do not slow down just by lifting your
foot.
Yes, we know what is going on back there.
Dennis
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
Don Hanson
Sent: Friday, February 12, 2010 4:14 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Friday OT...automatic trannys and driving habits observed
Someone gave my wife a 2.5 Subaru Forester, automatic, has about 195k
miles on it. It runs really well, the couple who gave it to Marie were
getting a little worried about the miles on it so they got another one..they
are palentologists and travel the back country a lot in remote parts of the
west, a bit aged so anyhow....I've been driving it while we're in the desert
SW. My first encounter with a automatic shift vehicle as a daily
driver...and I don't much care for it. Around the city, I can see how
people might want them but out in the mountains and desert it seems to waste
a lot of energy moving through the gears all the time.
We're camped about a half mile off a highway in the desert, one that's
pretty busy with RVs at certain times of day and days of the week. The
desert quiet sometimes let one hear a vehicle as it negotiates the road for
about 5 miles in the wee hours and I marvel at some of the huge RVs going
by....,.Roaring along up a very slight grade, shifting up and down, sucking
down the diesel fuel while mom and pop sit about 40' away from the motor,
blissfully un-aware of all the activitiy behind in the engine bay. Often
you can hear regular cars and pickups cycling back and forth through a
couple of gears...4 or 5 shifts as they go through the hearing
range..Doesn't that 'bug' the drivers?
I find myself hearing a few WBX Vanagons, too. I glance out when I
hear the distinct Vanagon sound and see them out on the highway...I just
can't help comparing the Vanagons to the Gigantor Mo-Hos...though the ratio
is about 1 vanagon per 500 motorhomes...I often wonder if the dweebs in the
mo-hos are having about 25,000lbs more fun...Prolly not..
Don Hanson
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