Date: Mon, 26 Oct 1998 15:16:02 -0800
Reply-To: Malcolm Holser <mholser@ADOBE.COM>
Sender: Vanagon Mailing List <vanagon@vanagon.com>
From: Malcolm Holser <mholser@ADOBE.COM>
Subject: Re: condensation, knocking was: Uh oh!
In-Reply-To: <01BE0108.321118E0@ip35.raleigh4.nc.pub-ip.psi.net>
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Water in the exhaust is _not_ caused by condensation, rather it is the
normal residue from burning gasoline. The condensation in the oil, as
GMB says, is a real problem and his solution is the proper one. The small
amount of water evaporated from the oil will be sucked into the engine
through the PCV.
Each molecule of gasoline, when burned, produces 8 molecules of water.
This is approximate, because gasoline is a complex mixture of hydrocarbons,
so I am basing this on the "average" gasoline molecule being heptane, which
is C7H16, if I recall ancient college chemistry:
C7H16 + 11 O2 -> 7 CO2 + 8 H20
You can think of this as each litre of gasoline turns into 8 litres of
water in your engine -- mostly as steam. When it is cold out, this steam
condenses into water, which drips out your exhaust. When it's dry or warm
you simply don't see it. (the picky ones among us can figure out, based
on density, just how many litres of water is produced per litre of
gasoline).
This steam combines with any sulphur in the gasoline to produce sulpheric
acid. Mufflers live a very hard life.
Malcolm H.
Non-vanagon:
I once was a steel fitter. Much of the steel that we put together needed
to be heated before welding (so that it would not crack afterwards). We
often used propane torches to heat small areas. I *never* convinced a
welder that the "moisture" was not coming out of the steel. They had
a conviction that steel somehow held moisture in "pores" and released it
when heated by a torch, and that driving this moisture out was the actual
goal of pre-heating the metal. Oh, well. I probably won't do any better
with the list... the propane (C3H8?) turns into quite a bit of water when
it burns -- the flame you see is glowing carbon/carbon dioxide and lots
of water -- so it is essentially a hot stream of steam.
>As far as the water coming out of the exhaust, again, no big. With the
>change in season, your motor is accumulating more condensation inside, and
>it takes some time (15-20 minutes of hard driving) to cook it all off of
>the internal parts/exhaust parts. This condensation can produce a LOT of
>water out the exhaust, enough to dribble out somewhat profusely. My
>air-cooled Westy puts out enough to leave a big wet spot (leave that one
>alone).
>
>By the way, this condensation is the bane of motors. If you only take brief
>trips in the winter, you may think about combining trips or getting a
>beater car for winter service, (to save your Van). Reason: if the
>condensation isn't completely driven off (like 15-20 minutes of hard
>driving will do), it combines with waste produces in your motor and forms a
>very corrosive mixture, primarily Sulfuric Acid.
>
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