Underhood Temperatures

[Garfield Willis]

On Fri, 26 May 2000 09:07:35 +0800 (WST), bernie at innovative.iinet.net.au
wrote:

>> ..rather than get them all the way up to 800degF [no engine
>> compartments live at those temps anyway, at least not more than once :].
>
>Try the exhaust manifold.

You're not serious...well, then again maybe you are. Thanks for the
insight, we might have missed that otherwise. But the engine compartment
(note the words *engine compartment* above?) doesn't EVER reach anything
near the temperature of the exhaust manifold, and nobody with even a few
beers left in their six-pack is gonna mount electronics anywhere near
the exh. manifold. SAE J1128 wire itself is only rated to 125degC. Ya
know, the automotive "good stuff". Think about it.

>> This is how the big-boys do it if they can't shoot the scene with an
>> infrared gun. If you just want a rough idea, and don't wanna do a full
>
>The "big-boys" use a supercomputer to calculate the thermodynamics.
>I won't bore you with the details.

Good idea. I was thinking more of the race car firewall-forward
designer, or the experimental aircraft guys designing their cooling and
FWF installation. Those "big-boys", not the guys with white shirts and
ties doing adverts in Detroit. These techniques are widely used in alot
of industrial design settings as well. Computer simulations still have a
LONG way to go (my field before I retired), especially since the most
costly thing about them isn't so much any more the run-times or the size
of computers required, it's the expense in building the accurate,
detailed models, that often only a mockup or experimental setup and some
tempilsticks or IRguns can ferret out.

Besides, the other reason I mentioned these techniques is because of
their accessibility to most everyone. I hazard to guess that not one
single person on this list is likely to use computer thermal simulation
to work out underhood temp and cooling issues, whereas these techniques
are both industrially robust and available to use, and to use easily.
Altho you can go nuts and spend big bucks on these devices (the IRguns
are getting down there, tho; around $250 gets you pretty good one these
days), the tempilsticks and pellets, if you don't go crazy and order the
complete range all the way up to solar temps, those are quite affordable
and VERY accurate. A bunch of well-placed T-stick crayon marks have
helped many a racing aircraft designer/builder to get his under-cowl
temps under control. Don't knock it till you've tried it!

Gar


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