Propane injection (was Nitrus injectors (was Hydrothermal

[Raymond C Drouillard]

On Tue, 16 Jun 1998 23:13:26 -0500 mccabet at mediaone.net writes:
>Raymond C Drouillard wrote:
>
>> I was thinking about injecting it as a liquid.  There would be a lot
of
>> heat absorbed as the liquid vaporizes.  This would cool down the
intake
>> air/fuel mixture.  Very likely, the denser mixture would result in
more
>> power simply because you can stuff more of it into the cylinders.
>
>One question: How would you keep the injectors from freezing?  The
>temperature change would cause condensation (frost/ice) to form on the
>injector tips.  Now this may not be a problem in a hot engine, but what
>about startup?  Another problem, how would you keep the pressure at the
>injector constant?  With a working pressure( liquid) of approximately
>150 PSI, on a hot day it will be higher, and lower on a cold day.  If
>you regulate the liquid to a lower value,  the liquid will convert back
>to a vapor in the fuel rail.  
>
>Just some fuel for discussion.  Several engineering grad students have
>been trying to answer these questions in the LEV/AFV challenge
>contests.  I for one have been contemplating these questions.  
>
>I am no expert in any way, just have experience on LPG conversions.
>
>L8r
>-- 
>Thomas McCabe
>-mccabet at mediaone.net

Truthfully, I have been contemplating the same things.  I first wanted to
do some calculations just to see how fesible such a project would be.

Someone posted a URL about injecting liquid propane.  They didn't give
too many details.  They implied that the propane was injected really
close to the intake valve.  On my AMC 360 engine (Jeep Grand Wagoneer), I
would probablly end up injecting it right under the present throttle
body.  This would give it time to completely evaporate and get well mixed
with the air.

The web page displayed a diagram that indicates that they use an in-tank
fuel pump.  An in-tank pump is used to pressurise the propane to well
above the vapor pressure of warm propane.  They use a return line - just
the same as a gasoline injection system.  It makes a lot of sense to pump
and pressurise the liquid because using the natural pressure of the tank
would probablly allow bubbles to form in the line, causing the injecters
to "spit".

They had a computer that modifies the output of the standard ECM so that
it will work properly with Propane.  I have a Holley Pro-Jection system,
which can be programmed any way I want.  All I will need for the liquid
propane system is the tank, pump, hoses, and injecters.  I would just
reprogram the ECM.  The only real annoyance with this system is that I
would have to load the appropriate program whenever I switch fuels.

The issue of freezing injecters is the only thing that worries me -
especially in cold Michigan winters.  Perhaps the tips would have to be
electrically heated until the engine warms up.

Ray Drouillard

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