Re: [Amc-list] overheating, and Smokey Yunick

[adh@xxxxxxxxxxxxxxxxx (Sandwich Maker)]

" From: Wrambler242@xxxxxxxxxxx
" 
" Thinking about it.
" Is there not a finite amount of time per revolution that the "heat" is useful?
" Once that piston has descended past a certain point the push is gone.

i'd guess about the point the exhaust valve begins to have meaningful
opening...  there's still plenty of heat and pressure in the exhaust,
or turbos wouldn't work.

"   I guess that's where the diesel shine as it wants to keep building
" heat to light of the next charge.
" Or is it the squeeze that ignites it?

the squeeze.  pV=nRT...  compression adiabatically heats the air
enough to ignite the fuel when it's injected.

small diesels routinely run higher-than-efficient compressions to
generate enough heat for reliable starting when cold.  the ricardo
comet 5 precombustion geometry gets best efficiency at 17:1 +/-, but
even something as big as the gm 6.5 ran a cr over 20:1.

why is high cr less efficient?  surface-to-volume of the precombustion
chamber [in indirect-injection diesels, unfashionable now] kills heat
retention and increases cooling load.

a big diesel - locomotive size - can run a cr of 12:1 or below [iirc
the also 251 is astoundingly 10.5:1], especially as they are rarely
shut off; an idle diesel earns no money.
________________________________________________________________________
Andrew Hay                                  the genius nature
internet rambler                            is to see what all have seen
adh@xxxxxxxxxxxxxxxxx                       and think what none thought
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