Humidity, Smokey's vapor engine and other ramblings

Robert Harris bob at bobthecomputerguy.com
Tue Sep 23 23:04:06 GMT 1997


Water injection can be very effectively used to increase fuel economy - if the 
engine is built for it.  Vizard in his Part II, Carbs and manifolds - talks 
about lean burn engines.  Using a V-8 test engine, he effectively ran mixtures 
as lean as 28 to 1.  In fact, thru most of the power range, he ran much leaner 
than what people are accustomed to.  Max power occurred at about 12.7 to one 
WOT.

Problem's include  that a super good ignition system is required to fire a lean 
mixture - requiring much higher spark energy, lean mixtures require very good 
atomization, run hotter and stress the octane limits (detonation) of the fuel. 
 A small increase in "humidity" would radically lower the ionization voltage 
needed to fire a very lean mixture.  Such limited injection could also be used 
to "lower" the excessive combustion temp of very lean mixtures.  If you built a 
lean burn engine, with water injection - you could gain significant economy 
improvements - without losing WOT power - and no "magic".  Course, if you are 
using O2 sensors and cats - forget it.  You are stuck at a crap mixture - 
neither rich enuff for max power nor lean enough for reasonable economy - kind 
of the worst of both.

If the first ingredient ain't Habanero, then the rest don't matter.
Other Obsessions: Ferro-Equinary , 1972 "Killer Whale" Mustang
Robert Harris <bob at bobthecomputerguy.com>


-----Original Message-----
From:	Gary Derian [SMTP:gderian at cybergate.net]
Sent:	Tuesday, September 23, 1997 2:51 PM
To:	diy_efi at coulomb.eng.ohio-state.edu
Subject:	Humidity, Smokey's vapor engine and other ramblings

     Water injection cools the combustion process by boiling and absorbing
heat during the combustion process, not necessarily cooling the intake
charge.  Best power is obtained when fuel and water (if water injected) is
taken into the cylinder in liquid form.  Liquids take up much less volume
than the same amount of vapor leaving more room for air.  The fuel mixes and
vaporizes during the compression stroke so it is ready to burn (most of it,
anyway).  The water vaporizes during the combustion phase absorbing heat but
not reducing pressure.  This raises the detonation limit which limits power
and efficiency in a spark ignition engine.

    Humidity in the air is already vaporized and only displaces oxygen.

    Smokey's vapor engine attempted to fully vaporize fuel in the intake
system.  This gives better fuel mixture distribution and prevents some
unvaporized liquid fuel from being wasted.  This achieves the same end as
propane fueled engines but propane does not need high temperature to
vaporize.  The tradeoff is reduced power since the fuel, now in vapor form,
takes up some volume in the cylinder so there is less air.  The high octane
rating of propane allows high compression ratios so some power can be gained
back but there still is a power loss.

    Car manufacturers have (1962 turbocharged Oldsmobile 215 V-8) and would
still install water injection if they thought owners would keep the water
reservoir full and not frozen.

Gary Derian <gderian at cybergate.net>







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