[Diy_efi] Liquid Phase Propane Injectors

[Greg Hermann]

At 11:02 AM 5/31/02, Mazda Ebrahimi wrote:
>Hey all,
>Just wanted to chime in on the fuel quality issue.
>
>Another problem with varrying fuel quality is related to thermo
>properties of the various compounds sold as 'propane'.
>
>It's been a long time since I cracked a thermo book, but from what I
>recall, based on their individual PV diagrams, each component (propane,
>butane, etc...) will achieve equilibrium at a certain volume given
>pressure and temprature.  That means that certain compounds will occupy
>the vapor space in higher relative concentrations than the liquid space.
>
>As you keep refilling each time, you will use less of the compounds that
>have higher vapor concentration.  So over time, the composition of the
>fuel in the tank is actually different than what you're putting in
>(unless you use up almost all the fuel regularly).  This could be
>another explanation for varrying fuel composition.
>
>I don't pretend to be up on my thermodynamics.  Perhaps someone more
>qualified could verify or discount the logic here...
>
>-Mazda

Accurate statements, but not really applicable to propane (gas OR liquid
phase) fueled engines.  Even the gas phase carbys feed the LIQUID fuel from
a dip tube at the bottom of the tank to a "vaporizer" which is heated by
engine coolant. So, because the liquid is constantly "blown down", the
concentration of higher boiling components does not occur.

Greg



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