B Dike wrote:
So Dieselers,
With many of you folks advocating that our diesels
must be driven *hard*, I decided to look into it a
little. I theorized that diesels differ from gas
motors in that the power loss (per stroke) from
compressing the intake air is relatively constant over
throttle setting. In other words, diesels use a lot
of energy simply compressing the intake air, but the
percent of fuel expended to compress the air goes down
as power setting increases. On the other hand, a
gasser has much less compression, and compression
power loss is proportional with throttle setting due
to their intake air butterfly. So it seems plausible
that one should drive a diesel as hard as possible to
achieve the highest efficiency, as opposed to gassers,
which should be driven with a light foot.
As I have been habitually driving my 300CD like the
miserly gas driver I was brought up to be (light
throttle pedal and all), it was easy to empirically
test my theory. I simply drove the car with the
throttle pedal depressed to the floor, or coasted, as
the situation demanded. I figured a tank of fuel
ought to debunk my theory...I didn't expect the theory
to actually work. The first tank came in at 24 mpg.
Interesting, since I had been recording a steady
22.5-23 mpg with my old style for the last couple
years. Just a coincidence I figured, so I gave it
another tank. 25 mpg!! So at least driving hard
didn't reduce the mileage, and it actually seems to
help. As a side benefit, the car runs better now. I
wonder if engine life is affected, however.
Anyone else have any data to validate the 'drive it
hard' theory?
Bruce
Bruce
82 300CD 333kmi 'His'
85 300CD 234kmi 'Hers'
75 240D 185kmi 'Theirs' (Back in Commission)
77 240D 199kmi 'The Brown Car'
I was surprised when I discovered that winding the engine out didn't
adversely effect economy. Over 38 years of driving diesels, the harder I
push them, the better/smoother/cleaner they run. I have NEVER worn out a
diesel. Very few diesel engines wear out (except in some commercial
applications). Most break!
Marshall
--
Marshall Booth (who doesn't respond to unsigned questions)
"der Dieseling Doktor" [EMAIL PROTECTED]
'87 300TD 181Kmi,'87 190D 2.5 199Kmi, '84 190D 2.2 227Kmi, '85 190D 2.0
159Kmi, '87 190D 2.5 turbo 234kmi
Diesel Technical Advisor MBCA, member GWSection
http://www.dhc.net/~pmhack/mercedes/mbooth1.htm
