Date: Sat, 1 Apr 2006 17:02:36 -0500
Reply-To: Dennis Haynes <dhaynes@OPTONLINE.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Dennis Haynes <dhaynes@OPTONLINE.NET>
Subject: Re: MPG
In-Reply-To: <20060401201023.37201.qmail@web33506.mail.mud.yahoo.com>
Content-type: text/plain; charset=us-ascii
This is a long shot. Better fuel economy at high altitude may be due to
the fact that you are already on top of the hills and spend more time
going down. Also, the thinner air provides less wind resistance for the
vehicle to travel through requiring less power. As for the effect on
engine efficiency, the O2 sensor does not just measure the amount of O2
in the exhaust. It actually measures the difference in O2 in the exhaust
and outside. The goal is a controlled reduction of O2. The reduced air
charge at altitude lowers the dynamic compression, thus both power and
efficiency suffer. Each 1,000 feet is a 3% loss.
Dennis
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf
Of Robert Keezer
Sent: Saturday, April 01, 2006 3:10 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: MPG
Maggie,
At high elevation there is less oxygen so a fuel
injected engine will compensate with less fuel =
better mileage perhaps but less power .
Like in high desert,relatively level, not going
up mountain grades which demands more fuel.
Most mpg mileage improvement depends on driving
habits and conditions.
Getting lower MPG at low elevation in the summer
couls mean a bad sensor , spark plug/wires/cap
rotor issue as there is more oxygen .
Or you are driving at higher speeds , in wind,
with increased weight, windows open (more drag),
roof rack (drag), etc.
In a carbureted engine, an engine runs rich over
4,000 feet. I went to Lake Tahoe and stayed there
a month years ago and my Bug chugged black smoke,
idled rough and had no power.
I had to change the carburetor main jet to a
smaller size to decrease the fuel and lean it out
.
The fuel injected engine does this automatically
. The oxygen sensor talks to the engine computer
and tells it how much oxygen is exiting the
exhaust.
At higher elevation there is less oxygen, so the
computer will order shorter or less-fuel
injection times to compensate, as the engine
computer is programmed to keep the air/fuel ratio
at a perfect 14:1 under all loads and driving
conditions, including altitude.
Robert
1982 Westfalia Golf 2.0
--- Maggie Dew <wildebus@GMAIL.COM> wrote:
> Regarding mpg issues, there are other factors
> that affect my mpg. One is
> that when I'm at higher elevations during the
> summer, I get between 20-22
> mpg, and when I'm in the flatlands during
> winter I get 16-19 mpg. I assume
> it's an issue of available oxygen. Out here on
> the plains, the winds can be
> devastating and my mileage goes way down
> battling the frequent headwinds.
>
> Another interesting thing I have noticed is
> that when I try to compare my
> speedometer to the speed on my GPS, I don't
> always get the same readings.
> Sometimes when the speedometer reads "60", the
> GPS will say "63", other
> times "65". I have 15" wheels. It's difficult
> to say what my exact mileage
> or mpg is, but I don't think it matters much
> what actual numbers you get -
> as someone said, only in comparison to your own
> vehicle. So if my own
> observations tell me I'm losing mpg in similar
> circumstances, then I start
> checking to see what's up.
>
> Maggie
> '85 Subaru-Westy "Anne Bonney"
>
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