Re[2]: The Color of Propane -- Final (fwd) (re: engine tin p

[Toby Erkson <Toby_Erkson@ccm.jf.intel.com>]

Text item: Text1


If I may speak on behalf of my interpretation...

I gathered from the text that Bob was talking about the engine compartment tin 
and not the cooling tin that surrounds and connects to the engine.  
Specifically, it would be the firewall tin that separates the engine from the 
tranny (you guys know what I mean) and [on the Type I] the sheet metal that the 
fresh air hoses pass through to go to the heat exchangers (is that the breast 
tin?).  Basically it's all the tinware that surrounds the *entire* engine.

Now, I understand the importance of the color as it relates to cooling and I 
*don't* have a great deal of knowledge about the T1 engine with all its extra 
sheetmetal but at first blush I would think that coloring the compartmental 
sheetmetal some other color would be okay.

My Type 3 cents,
     Toby Erkson, air_cooled_nut@pobox.com
     '72 VW Squareback 1.6L bored and stroked to 2.0L
     '75 Porsche 914 1.8L, ORPCA member
     Portland, Oregon, http://www.geocities.com/MotorCity/8501/

______________________________ Reply Separator _________________________________
Subject: Re: The Color of Propane -- Final (fwd) (re: engine tin pain
Author:  type-3-errors@umich.edu at SMTPGATE_MIME
Date:    12/31/97 12:39 AM


Bob,

This statement of yours got posted to the type 3 list.  I like your
choice of blue for a Propane engine, but I think I would like to take
issue with you on your analysis of the effect of color on the
cooling.  I am posting my response to the T3 list as well as directly
to you.  I will be happy to post any reply you wish to make there as
well.

> To reiterate a point that some still find confusing, those portions
> of the engine that come in contact with the lubricating oil and can
> therefore radiate heat, will be painted flat black.  The tin-ware
> serves to seal the engine compartment and to form the shroud that
> contains the cooling air.  It may be painted any color or even
> plated with chrome without having any effect on the engine's ability
> to cool itself.
>
> -Bob Hoover

The engine cools by both radiation and conduction.  Radiated heat
will be absorbed by the tin itself, but only if the tin is a
good absorber.  Most of this heat will be transferred to the
layer of air that flows next to the tin.  Some of the heat from the
tin will be radiated to the outside of the tin, and some of it
will be re-radiated back inwards.  Still, this is a better situation
that having it all reflected back into the engine.  After all, if
this were not important, then it would not matter what color the
direct radiators of the engine were, because air does not absorb
infra-red and the direct radiators of the engine are almost
completely surrounded by tin, so most of what got radiated would get
reflected right back to the engine.

It is hard to predict what colors or coatings will be good absorbers
in the infra-red, but I don't think chrome plating is one of them.
Choosing a coating that is a poor absorber in the infra-red means
that your engine will only cool by conduction (directly to the
airflow that passes next to it) and this can only result in a net
loss of cooling.

Jim
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       Melissa Kepner                                    Jim Adney
                             Laura Kepner-Adney
                         jadney@vwtype3.org
                             Madison, Wisconsin
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