hi Curt!
got a 617.95x? try it yourself and see what happens; what i'm seeing
isn't unusual here amongst the BioD fleet and should be easy to duplicate.
yes, the BTU rating per unit is different, but if we're burning more
of it to get the same power, that difference would seem to be negated.
i've read a bit about the different ways the fuel actually burns,
and think it's more related to that.
again, i've already checked 'stats; i don't have any reason to
believe that there's anything wrong there; there doesn't seem to be an
"problem" to "fix".
as for a higher' stat temp, i don't see how that would make any
difference if the heat available already isn't high enough to open the
one that's in there.
interesting notes about the tractor louvers; i remember having seen
that on diesel trucks as well. good food for thought, but i don't think
i'm going that extreme. ;-)
cheers!
e
Curt Raymond wrote:
Hi Ernest,
This is one of those I've had to keep turning over in my mind to try and get a
handle on. I *think* I finally understand a little of whats going on... I'd
love to see some real testing data on it though.
So we know that bio has fewer BTUs per unit volume than diesel. If combustion
occurs with the same volume of fuel (like in an unmodified engine) it stands to
reason that there will be less power and less waste heat produced. I *think*
the reason for the lowered engine temp is leakage past the thermostat (and slow
thermostat response as its still a mechanical device) which with diesel fuel
wouldn't matter until a much colder temp. It seems like bio folks would
probably want a slightly higher rated thermostat but I can see that causing
problems when switching to diesel...
Somebody else caught what I'd forgotten, not covering the whole swept area of
the fan causes fan fatigure. Big truck fans are massive pieces of kit...
So... Considering all of that the best solution I can think of actually comes
from antique tractors... Back in the day tractors had therosiphon cooling
systems with no thermostat. Temp was controlled with shutters over the radiator
so when it was cold you'd close the shutters and as engine temp rose you'd open
them. It'd be exceptionally slick to rig up something similar that was
thermostatically controlled.
Or you could just put a piece of cardboard over the radiator ;)
-Curt
Date: Thu, 07 Jan 2010 00:21:14 -0800
From: ernest breakfield <erne...@backyardengineering.org>
To: Mercedes Discussion List <mercedes@okiebenz.com>
Subject: Re: [MBZ] running temps in the cold?
Message-ID: <4b45997a.2050...@backyardengineering.org>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
hi Curt!
sorry if i wasn't clear enough for you; let me rehash a few points
(again).
this temp difference only shows when BioD is used; operating temps
are what most of us would agree is normal when using #2.
car will come up to temp on the highway eventually; just takes a
long time, and often never gets quite all the way there when just
running around town.
this isn't an unknown phenomena in the BioD fleet.
all that said, i'll check the oil cooler temps as suggested, but i'm
not really looking for a mechanical problem; it seems unlikely that any
problem would only surface for me (and others in the fleet) when we
switch to BioD.
interesting thoughts about covering the swept area of the fan; i
used to see heavy trucks commonly wearing shrouds across their grills,
and they were often laced only part way up. is there something different
about their fans and/or radiators?
i was thinking of a shroud that was something of a compromise, like
a screen...
cheers!
e
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