Date: Sun, 25 Mar 2012 09:58:08 -0700
Reply-To: Daryl Christensen <daryl@AATRANSAXLE.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Daryl Christensen <daryl@AATRANSAXLE.COM>
Subject: Re: Fuel consumption in different gears - how does the energy /
fuel work?
In-Reply-To: <4f6ef2ab.8ad6e00a.7676.5742@mx.google.com>
Content-Type: text/plain; charset="US-ASCII"
But I DO have an OBDII system with the Zetec, and there is definitely less
throttle used in say 3rd gear at 40 than 4th gear at 40mph...The LOaD on the
scan gauge is definitely lower at higher rpm in 3rd than it is in 4th at the
same speed.
Have not tried the MPG or average MPG in addition to the LOaD factor with
the scan gauge to see how much difference there is, but it sure seems that
over 3K it requires less fuel..
Cc'ing Jim at Bostig as he is the true guru on this kinda stuff.. Jimminy
????
Daryl of AA Transaxle
425-788-4070
"On the cutting edge of Old technology"
86 Syncro Westy w/Turbo Zetec in the trunk
90 Doka Tristar w/2.5 Subie
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
David Beierl
Sent: Sunday, March 25, 2012 3:26 AM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Fuel consumption in different gears - how does the energy /
fuel work?
At 09:56 PM 3/24/2012, Roland wrote:
>consumed in 3rd gear vs 4th gear? Now the immediate answer is none! It
>takes the same energy to drive at 45 mph in 3rd or 4th. The wind
>resistance is the same, the drive-line loss is the same, other friction
>like tires are the same.
But it takes more energy to run the engine faster. The inertial
losses from reversing the pistons' direction of travel, the
frictional losses from scrubbing the piston rings up and down in
their bores, the energy lost by compressing the fuel/air charge and
operating the valve train, the additional output of the water and oil
pumps - these parasitic losses all increase more-or-less linearly
with increasing rpm.
It would be interesting for someone with an OBDII engine to do some
calculations of no-load operation at various rpm, using the rpm and
engine load numbers to determine the relative amount of fuel required
to merely spin the engine at those rpm. I wish I'd done it while I
still had my Honda.
Yours, David
...My reply...
I was wondering the same a while back with my Syncro Westy with a Bostig
conversion with a Turbo. That motor is a higher revving engine that likes to
run over 3000 rpm.(redline is 7200) It has a scan gauge hooked up and you
can show engine Load as one of its many options. The load is the amount of
injector on time, or fuel consumption basically as I see it.
The efficiency of a particular motor will make a big difference. A diesel
will do better at lower rpm and mine does better at the higher rpm it seems.
On a rural road to town in 3rd gear at 40mph it says 30 load. In 4th it is
about 40 to 50 load with no boost (yet) So at say 50 mph in 3rd gear the
load says 40 or so and in 4th it says 60 or more.. With the turbo at boost,
it always says about 60 to 92 (max). Full 7 lbs boost is max load and at 4
or 5 lbs it is about 60 to 70 at least.
All That tells me the engine should be working harder and getting less MPG
in the taller gears when its loaded more.
Now I may be wrong, but it kinda makes sense with this particular setup.
A stock WBX'er may be totally different in its reality.
