Date:         Wed, 13 Jan 1999 22:04:59 -0800
Reply-To:     Vanman <mckayaa@OIT.EDU>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Vanman <mckayaa@OIT.EDU>
Subject:      Re: ~Flaming DIEsels~ Re: how much interest IS there in
              ...
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-----Original Message-----
From: KENWILFY@AOL.COM <KENWILFY@AOL.COM>
To: vanagon@GERRY.VANAGON.COM <vanagon@GERRY.VANAGON.COM>
Date: Wednesday, January 13, 1999 8:51 PM
Subject: Re: ~Flaming DIEsels~ Re: how much interest IS there in ...


>An intercooler just cools the air before it enters the turbo.

Sorry, unless there is some difference between an intercooler and an
aftercooler, which last time I checked they were the same thing, it is just
the opposite, or VW is more backwards than I have ever imagined.  On all of
the marine diesel engines that I have worked on, from 2.4 L 4 cyl up to 38 L
V-12's, the aftercooler ALWAYS came after the turbo, as the fresh air that
enters the turbo is already plenty cool, however, the air that exits the
turbo can be very hot.  On some Caterpillar engines that I have seen, the
air exiting the turbo was hot enough to change the yellow paint brownish
down to where the aftercooler cooled the air off enough to where it wouldn't
do that any longer.  The longetivity, as far as I know, is unaffected by the
presence, or lack, of an aftercooler.  The only way that it may impact it is
that the extra air supplied to the combustion would drive down exhaust temps
(you should see those temps skyrocket when the engine is over fueling), but
then the engine companies usually add more fuel to make more power anyways,
thus driving exhaust temps back up.  The reason that the air leaving the
turbo is sooo much warmer is that it is compressed, generating heat (I chose
to omit the ideal gas laws, in order to keep things simple), the same
concept that allows a diesel engine to run w/o a spark.  But, as we all
know, warmer air, is also less dense air (what makes a hot air balloon
float) , so the aftercoolers cool the air back down, to make it more dense,
so more air can be packed into the combustion chambers.  The reason that
turbos add horsepower w/o aftercoolers is that the amount that they compress
the air offsets the amount that the heat makes it become less dense.


>This increases
>the air's density thereby allowing more oxygen to be packed into the turbo.
>This increases the amount of fuel that you can burn so therefore you get
more
>power.  It really has nothing whatsoever to do with turbo longevity (sorry
>Chris don't hate me).
>Ken Wilford
>Van-Again
>John 3:16
>

Sorry Ken, but I had to set things straight, and I hope that by the time
that my waterboxer goes out, I will be able to afford you kit, because I
love the concept, and the relative affordability.  Keep up the great work
(waiting for some pics though).  Count me in when the reaper takes my flat 4
away...

BTW, I have heard caught some little words here and there about the Volvo
and Audi engines being similar, is the gas Audi 5 cyl the same block as the
Volvo 5 cyl in their 850 series cars?  Just curious...

-Aaron Mckay
                                 mckayaa@oit.edu
                                 college student in mechanical
                                 engineering at Oregon Institute of
Technology
                                 '85 vanagon GL